JP2007232259A - Turbo refrigerating machine, and its hot gas bypassing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbo refrigerating machine and its hot gas bypassing method capable of avoiding surging of a multistage compressor and reducing power of the multistage compressor. <P>SOLUTION: For example, a composition is comprised by communicating a discharge side of a second stage compressor 23 with intake sides of compressors 22, 23 of two stages via a hot gas bypass valve 44 for the first stage and a hot gas bypass valve 45 for the second stage capable of adjusting openings, and in a controller 55, gas coolant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, the hot gas bypass valve for the second stage and the hot gas bypass valve for the first stage are sequentially opened to send in a gas coolant in order from the second stage compressor every time it is judged that measured values of the gas coolant flow rate have reached a minimum required flow rate in each of the first stage compressor 22 and the second stage compressor 23, or it is judged that refrigerating machine capacities have reached each predetermined value corresponding to the minimum required flow rate, and control is thereby is carried out to secure the minimum required flow rate per compressor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a turbo chiller used for indoor cooling and a hot gas bypass method thereof.

  FIG. 21 is a system configuration diagram of a conventional centrifugal chiller, FIG. 22 is an explanatory diagram showing the relationship between the refrigeration functional force in the turbo chiller and the compressor gas refrigerant flow rate, and FIG. 23 is the refrigeration functional force in the turbo chiller. FIG. 24 is an explanatory view showing the relationship between the hot gas bypass valve opening and FIG. 24 is a view showing the relationship between the refrigeration function force and the compressor required power in the turbo refrigerator.

  The conventional turbo refrigerator shown in FIG. 21 is used for indoor cooling, and is a centrifugal type compressor that compresses the gas refrigerant evaporated in the evaporator 1 by the first stage compressor 2 and the second stage compressor 3. A multistage compressor 4 (two-stage compressor in the illustrated example), a condenser 5 that condenses the gas refrigerant compressed by the multistage compressor 4, and a high stage expansion valve that expands the liquid refrigerant condensed by the condenser 5 6 and a low stage expansion valve 7, an intermediate cooler 8 installed between the high stage expansion valve 6 and the low stage expansion valve 7 as a gas-liquid separator for separating the refrigerant into a gas and liquid, and the intermediate cooler The gas refrigerant separated at 8 bypasses the evaporator 21 and flows into the second stage compressor 3 of the multistage compressor 4, and the evaporator 1 evaporates the refrigerant expanded by the expansion valves 6 and 7. And have. The multistage compressor 4 is rotationally driven by an electric motor 13. In FIG. 21, a refrigerant flow path such as a pipe through which a gas refrigerant flows is indicated by a dotted line, and a refrigerant flow path such as a pipe through which a liquid refrigerant flows is indicated by a solid line.

  The turbo chiller is provided with a hot gas bypass valve 9 to avoid surging of the first stage compressor 2 and the second stage compressor 3 of the multistage compressor 4. The hot gas bypass valve 9 is provided in the bypass refrigerant flow path 12, and the bypass refrigerant flow path 12 is a refrigerant flow that guides the refrigerant discharged from the second stage compressor 2 of the multistage compressor 4 to the condenser 5. The passage 10 communicates with a refrigerant flow path 11 that guides the refrigerant discharged from the evaporator 1 to the first stage compressor 4 of the multistage compressor 4.

  In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 2 and the gas refrigerant flow rate of the second stage compressor 3) decreases as shown in FIG. And when this compressor gas refrigerant flow volume reaches the minimum required flow volume for avoiding the surging of the multistage compressor 4, the hot gas bypass valve 9 is opened and the gas refrigerant flows into the first stage compressor 2. Thus, the necessary minimum flow rate is ensured.

  Therefore, until the compressor gas refrigerant flow rate reaches the necessary minimum flow rate, the compressor gas refrigerant flow rate also decreases as the refrigeration function decreases, so that the required power of the multistage compressor 4 also decreases as shown in FIG. However, after the compressor gas refrigerant flow rate reaches the required minimum flow rate, the hot gas bypass valve 9 is opened to secure the necessary gas refrigerant flow rate, so that the refrigeration function is reduced (the refrigerant flow rate of the evaporator 1). However, the required power of the multistage compressor 4 hardly decreases as shown in FIG.

In addition, as a prior art document disclosed about the technique which avoids the surging of a turbo refrigerator, there exist the following, for example.
JP 2005-180267 A

  The conventional hot gas bypass method as described above can avoid surging of the first stage compressor 2 and the second stage compressor 3, but is not possible from the viewpoint of reducing the necessary power of the multistage compressor 4 as much as possible. It is enough. That is, when the compressor gas refrigerant flow rate gradually decreases as the cooling load decreases, the first stage compressor 2 and the second stage compressor 3 do not reach the surging region at the same time, but the discharge pressures of both Due to the difference or the like, the second stage compressor 3 reaches the surging area first, and then the first stage compressor 2 also reaches the surging area. Therefore, the minimum required flow rate for avoiding surging of the first stage compressor 2 may be smaller than the minimum required flow rate for avoiding surging of the second stage compressor 3.

  However, in the above-described conventional hot gas bypass method, the minimum required flow rate of the first stage compressor 2 and the minimum required flow rate of the second stage compressor 3 are not distinguished, and the compressor gas refrigerant flow rate is simply set to the minimum required flow rate (first flow rate). Since the hot gas bypass valve 9 is simply opened and the gas refrigerant is allowed to flow into the first stage compressor 2 at the time of reaching the required minimum flow rate of the two stage compressor, Will secure the necessary minimum flow rate of the first stage compressor, but will cause the first stage compressor 2 to flow an excess gas refrigerant flow rate than the necessary minimum flow rate of the first stage compressor 2. Therefore, the multistage compressor 4 (electric motor 13) consumes useless power.

  Therefore, in view of the above circumstances, an object of the present invention is to provide a turbo chiller that can avoid surging of a multistage compressor and reduce the power of the multistage compressor, and a hot gas bypass method thereof.

A turbo chiller according to a first aspect of the present invention that solves the above problems includes a multi-stage compressor that sequentially compresses gas refrigerant evaporated by an evaporator using a plurality of compressors, and a condensation that condenses the gas refrigerant compressed by the multi-stage compressor. In a turbo chiller having a compressor, an expansion valve that expands the liquid refrigerant condensed by the condenser, and the evaporator that evaporates the liquid refrigerant expanded by the expansion valve,
It has a hot gas bypass means that can bypass a part of the gas refrigerant discharged from the multi-stage compressor and flow into each of the multi-stage compressors.

The turbo refrigerator of the second invention is the turbo refrigerator of the first invention,
The hot gas bypass means includes a discharge side of the last stage compressor and an intake side of the plurality of stage compressors through the plurality of hot gas bypass valves whose opening degree can be adjusted. It is the structure which connects each of these, It is characterized by the above-mentioned.

Moreover, the turbo refrigerator of the third invention is the turbo refrigerator of the first invention,
The expansion valve comprises a high-stage expansion valve and a low-stage expansion valve, and has a gas-liquid separator that is installed between the high-stage expansion valve and the low-stage expansion valve to separate the refrigerant from gas and liquid,
The hot gas bypass means includes
When the multistage compressor is composed of a two-stage compressor, the discharge side of the latter-stage compressor of the two-stage compressor and the two-stage compressor via a hot gas bypass valve whose opening degree can be adjusted. The other side of the compressor, and the other side of the compressor, and the intake side of the latter compressor through the other hot gas bypass valve whose opening degree can be adjusted. Is a configuration that communicates with
When the multistage compressor is composed of three or more stages of compressors, the discharge side of the last stage compressor among the three or more stages of compressors via a hot gas bypass valve whose opening degree can be adjusted, The gas-liquid separator, which communicates with the intake side of the compressor at the foremost stage of the three or more stage compressors, and through other hot gas bypass valves that can be adjusted in opening degree, Of the three or more stages of compressors, the compressor is configured to communicate with each of the intake sides of the compressors other than the frontmost stage.
It is characterized by that.

The turbo refrigerator of the fourth invention is the turbo refrigerator of the first invention,
The multi-stage compressor is composed of a two-stage compressor,
The hot gas bypass means has a hot gas bypass three-way valve whose opening degree can be adjusted, respectively, on the discharge side of the rear compressor of the two-stage compressor and on the intake side of the two-stage compressor. It is the structure formed by communicating with.

The turbo chiller of the fifth invention is the turbo chiller of the first invention,
The expansion valve comprises a high-stage expansion valve and a low-stage expansion valve, and has a gas-liquid separator that is installed between the high-stage expansion valve and the low-stage expansion valve and separates the refrigerant into gas and liquid, and When the multi-stage compressor is composed of a two-stage compressor, the multi-stage compressor has an orifice through which the gas refrigerant separated by the gas-liquid separator flows into the intake side of the latter-stage compressor of the two-stage compressor. When the multi-stage compressor is composed of three or more stages of compressors, the gas refrigerant separated by the gas-liquid separator is respectively supplied to the intake side of the compressor other than the first stage among the three or more stages of compressors. Having a plurality of inflow orifices;
The hot gas bypass means includes
When the multistage compressor is composed of a two-stage compressor, the discharge side of the latter-stage compressor of the two-stage compressor and the two-stage compressor via a hot gas bypass valve whose opening degree can be adjusted. The gas-liquid separator, and the latter stage through an ON / OFF hot gas bypass valve that communicates with the intake side of the former stage compressor of the compressor and is installed in parallel with the orifice. The structure is made to communicate with the intake side of the compressor of
When the multistage compressor is composed of three or more stages of compressors, the discharge side of the last stage compressor among the three or more stages of compressors via a hot gas bypass valve whose opening degree can be adjusted, Via a plurality of ON / OFF type hot gas bypass valves that communicate with the intake side of the compressor at the foremost stage of the three or more stages of compressors and are installed in parallel with each of the plurality of orifices. The gas-liquid separator is configured to communicate with each of the intake sides of the compressors other than the front stage among the three or more stages of compressors.
It is characterized by that.

The turbo refrigerator of the sixth invention is the turbo refrigerator of the fifth invention,
A plurality of the ON / OFF hot gas bypass valves are installed in parallel to the orifice.

Moreover, the turbo refrigerator of the seventh invention is the turbo refrigerator of the first invention,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the hot gas bypass means sequentially causes the gas refrigerant to flow in from the subsequent stage compressor that reaches the required minimum flow rate first. By ensuring the required minimum flow rate for each of the plurality of stages of compressors,
It has a hot gas bypass control means.

Moreover, the turbo refrigerator of the eighth invention is the turbo refrigerator of the second invention,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is judged that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the opening-adjustable hot gas bypass valve is sequentially opened, and the subsequent stage side compression that reaches the required minimum flow rate first. The required minimum flow rate is ensured for each of the plurality of stages of compressors by flowing gas refrigerant in order from the machine.
It has a hot gas bypass control means.

The turbo chiller of the ninth invention is the turbo chiller of the third invention,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is judged that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the opening-adjustable hot gas bypass valve is sequentially opened, and the subsequent stage side compression that reaches the required minimum flow rate first. Ensuring the required minimum flow rate for each of the multiple stages of compressors by flowing gas refrigerant in order from the machine,
It has a hot gas bypass control means.

Moreover, the turbo refrigerator of the tenth invention is the turbo refrigerator of the fourth invention.
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the compressor in the stage has been reached, the outlet of the hot gas bypass three-way valve whose opening degree can be adjusted is sequentially opened, and the required minimum flow rate is reached first. Ensuring the necessary minimum flow rate for each of the multiple-stage compressors by flowing gas refrigerant in order from the rear-stage compressor;
It has a hot gas bypass control means.

Moreover, the turbo refrigerator of the eleventh invention is the turbo refrigerator of the fifth invention,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the ON / OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening are sequentially opened, Securing the necessary minimum flow rate for each of the plurality of stages of compressors by allowing the gas refrigerant to flow in order from the compressor on the rear stage that reaches the required minimum flow rate first.
It has a hot gas bypass control means.

The turbo chiller of the twelfth invention is the turbo chiller of the sixth invention,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the ON / OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening are sequentially opened, The required minimum flow rate is ensured for each of the multiple-stage compressors by flowing gas refrigerant in order from the subsequent-stage compressor that reaches the required minimum flow rate first.
It has a hot gas bypass control means.

Further, a hot gas bypass method for a turbo chiller according to a thirteenth invention is a hot gas bypass method for a turbo chiller according to the first invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass means sequentially introduces the gas refrigerant from the rear-stage compressor that reaches the required minimum flow rate first, and then compresses the multi-stage compressor. The minimum flow rate is ensured for each machine.

Further, a hot gas bypass method for a turbo chiller according to a fourteenth aspect of the invention is a hot gas bypass method for a turbo chiller according to the second aspect of the invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass valve whose opening degree can be adjusted is sequentially opened in order from the rear-stage compressor that reaches the required minimum flow rate first. The minimum flow rate is ensured for each of the plurality of stages of compressors.

Further, a hot gas bypass method for a turbo chiller according to a fifteenth aspect of the invention is the hot gas bypass method for a turbo chiller according to the third aspect of the invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass valve whose opening degree can be adjusted is sequentially opened in order from the rear-stage compressor that reaches the required minimum flow rate first. The minimum flow rate is ensured for each of the plurality of stages of compressors.

A hot gas bypass method for a turbo chiller according to a sixteenth invention is a hot gas bypass method for a turbo chiller according to the fourth invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
By sequentially opening the outlet of the hot gas bypass three-way valve whose opening degree can be adjusted in order from the downstream compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. Then, a gas refrigerant is introduced to secure the necessary minimum flow rate for each of the plurality of stages of compressors.

A hot gas bypass method for a turbo chiller according to a seventeenth invention is a hot gas bypass method for a turbo chiller according to a fifth invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
The ON / OFF-type hot gas bypass valve and the opening-adjustable hot gas in order from the rear-stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. Gas refrigerant is introduced by sequentially opening the bypass valve, and the necessary minimum flow rate is ensured for each of the plurality of stages of compressors.

Further, a hot gas bypass method for a turbo chiller according to an eighteenth aspect of the invention is the hot gas bypass method for a turbo chiller according to the sixth aspect of the invention,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
The ON / OFF-type hot gas bypass valve and the opening-adjustable hot gas in order from the rear-stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. Gas refrigerant is introduced by sequentially opening the bypass valve, and the necessary minimum flow rate is ensured for each of the plurality of stages of compressors.

  According to the turbo chiller of the first aspect of the present invention, even if the minimum required flow rate for avoiding the surging of the compressors of the plurality of stages is as small as that of the compressor at the front stage, the plurality of the plurality of compressors can be operated by the hot gas bypass means. Since the gas refrigerant can be caused to flow into each of the stage compressors, it is possible to cause the gas refrigerant having a necessary minimum flow rate to flow through the plurality of stage compressors. For this reason, surging can be avoided for any of the plurality of stages of compressors, and the power of the multistage compressor can be reduced as compared with the conventional one.

  According to the turbo chiller of the second aspect of the present invention, even if the necessary minimum flow rate for avoiding the surging of the multiple-stage compressor is as small as the compressor on the front stage side, the multiple-stage compressor can Since the gas refrigerant can be caused to flow into each of the compressors, the necessary minimum flow rate of the gas refrigerant can be caused to flow through the plurality of compressors. Therefore, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced as compared with the conventional one.

  According to the turbo chiller of the third aspect of the present invention, even if the necessary minimum flow rate for avoiding the surging of the multi-stage compressor is as small as that of the front-stage compressor, the hot gas bypass valve causes the multi-stage compressor to Since the gas refrigerant can be caused to flow into each of the compressors, the necessary minimum flow rate of the gas refrigerant can be caused to flow through the plurality of compressors. Therefore, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced as compared with the conventional one. Moreover, since a hot gas bypass valve can be provided using a conventional existing system (bypass refrigerant flow path) without providing a new bypass refrigerant flow path, a new system (bypass refrigerant flow path) can be provided. The system configuration can be simplified as compared with the case of providing.

  According to the turbo refrigerator of the fourth aspect of the present invention, even if the minimum required flow rate for avoiding the surging of the multiple-stage compressor is as small as the previous-stage compressor, the hot gas bypass three-way valve is used to Since the gas refrigerant can be caused to flow into each of the compressors in the stage, it is possible to flow a gas refrigerant having a necessary minimum flow rate to each of the compressors in the plurality of stages. Therefore, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced as compared with the conventional one. Moreover, since one hot gas bypass three-way valve is used, the system configuration can be simplified and the increase in equipment cost can be reduced as compared with the case where two hot gas bypass valves are used.

  According to the turbo chiller of the fifth aspect of the present invention, even if the necessary minimum flow rate for avoiding the surging of the multi-stage compressor is as small as that of the front-stage compressor, the hot gas bypass valve causes the multi-stage compressor to Since the gas refrigerant can be caused to flow into each of the compressors, the necessary minimum flow rate of gas refrigerant can be caused to flow through the plurality of compressors. Therefore, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced as compared with the conventional one. Moreover, since the ON / OFF type hot gas bypass valve is used, the flow rate of the gas refrigerant when the valve is opened is larger than when using a hot gas bypass valve whose opening degree can be adjusted. The increase can be reduced.

  According to the turbo chiller of the sixth invention, the same effect as the turbo chiller of the fifth invention can be obtained, and a plurality of ON / OFF hot gas bypass valves are arranged in parallel to the orifice. Because it is installed, the effect of reducing the increase in equipment cost is reduced compared to the case where one ON / OFF type hot gas bypass valve is installed in parallel to the orifice, but when the valve is opened The fluctuation of the gas refrigerant flow rate can be reduced, and the effect of reducing the power of the multistage compressor is great.

  According to the turbo refrigerator of the seventh aspect of the invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages have decreased, and the measured values of these gas refrigerant flow rates have reached the required minimum flow rate. Every time it is determined that the calculated refrigeration functional force has decreased and has reached each predetermined value corresponding to the required minimum flow rate of the plurality of stages of compressors, the hot gas bypass means In order to control to ensure the necessary minimum flow rate for each of the plurality of compressors by sequentially injecting the gas refrigerant from the downstream compressor that reaches the necessary minimum flow rate to the In any case, surging can be avoided, and the power of the multistage compressor can be reduced as compared with the conventional case.

  According to the turbo refrigerator of the eighth aspect of the invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages have decreased, and the measured values of these gas refrigerant flow rates have reached the necessary minimum flow rate. Each time it is determined that the calculated refrigerating function force has decreased and each predetermined value corresponding to the required minimum flow rate of the plurality of stages of compressors has been reached, In order to control to ensure the required minimum flow rate for each of the multiple stages of compressors by sequentially opening the bypass valve and allowing the gas refrigerant to flow in order from the downstream compressor that reaches the required minimum flow rate first. Surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced compared to the conventional one.

  According to the turbo refrigerator of the ninth aspect of the invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages are reduced, and the measured values of these gas refrigerant flow rates have reached the necessary minimum flow rate. Each time it is determined that the calculated refrigerating function force has decreased and each predetermined value corresponding to the required minimum flow rate of the plurality of stages of compressors has been reached, In order to control to ensure the necessary minimum flow rate for each of the plurality of stages of compressors by sequentially opening the bypass valves and sequentially allowing the gas refrigerant to flow in from the downstream compressor that reaches the required minimum flow rate first. Surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced compared to the conventional one.

  According to the turbo refrigerator of the tenth aspect of the invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages are reduced, and the measured values of these gas refrigerant flow rates have reached the required minimum flow rate. Each time it is determined that the calculated refrigerating function force has decreased and each predetermined value corresponding to the required minimum flow rate of the plurality of stages of compressors has been reached, By sequentially opening the outlet of the bypass three-way valve and injecting the gas refrigerant in order from the latter stage side compressor that reaches the required minimum flow rate first, the required minimum flow rate is ensured for each of the multiple-stage compressors. Therefore, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced as compared with the conventional one.

  According to the turbo refrigerator of the eleventh aspect of the invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages have decreased, and the measured values of these gas refrigerant flow rates have reached the necessary minimum flow rate. Each time, or every time it is determined that the calculated refrigeration function force has reached a predetermined value corresponding to the required minimum flow rate of the compressors of the plurality of stages, the ON / OFF hot gas By opening the bypass valve and the hot gas bypass valve whose opening degree can be adjusted sequentially, the gas refrigerant is introduced in order from the rear stage compressor that reaches the required minimum flow rate first, so that each of the multiple stage compressors. Since the control is performed to ensure the necessary minimum flow rate, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced compared to the conventional one. .

  According to the turbo refrigerator of the twelfth aspect of the present invention, in the hot gas bypass control means, the gas refrigerant flow rates of the compressors in the plurality of stages have decreased, and the measured values of these gas refrigerant flow rates have reached the necessary minimum flow rate. Each time, or every time it is determined that the calculated refrigeration function force has reached a predetermined value corresponding to the required minimum flow rate of the compressors of the plurality of stages, the ON / OFF hot gas Open the bypass valve and the hot gas bypass valve whose opening degree can be adjusted in order, and flow the gas refrigerant in order from the rear side compressor that reaches the required minimum flow rate first, so that each of the multiple stage compressors. Since the control is performed so as to ensure the necessary minimum flow rate, surging can be avoided for any of the multiple-stage compressors, and the power of the multi-stage compressor can be reduced compared to the conventional one.

  According to the hot gas bypass method for a turbo chiller of the thirteenth aspect of the invention, the hot gas in order from the rear stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the plurality of stage compressors decreases. In order to ensure the necessary minimum flow rate for each of the plurality of compressors by flowing gas refrigerant by the bypass means, surging can be avoided for any of the plurality of compressors, and The power of the multistage compressor can be reduced as compared with the prior art.

  According to the hot gas bypass method for a turbo refrigerator of the fourteenth aspect of the present invention, when the gas refrigerant flow rate of the plurality of stages of compressors decreases, the opening degree in order from the rear stage compressor that reaches the required minimum flow rate first. Surging for any of the multiple stage compressors by sequentially opening the adjustable hot gas bypass valve to flow in gas refrigerant and ensure the required minimum flow rate for each of the multiple stage compressors Can be avoided, and the power of the multi-stage compressor can be reduced as compared with the prior art.

  According to the hot gas bypass method for a turbo chiller of the fifteenth aspect of the present invention, when the gas refrigerant flow rate of the plurality of stage compressors decreases, the opening degree in order from the rear stage compressor that reaches the required minimum flow rate first. Surging for any of the multiple stage compressors by sequentially opening the adjustable hot gas bypass valve to flow in gas refrigerant and ensure the required minimum flow rate for each of the multiple stage compressors Can be avoided, and the power of the multi-stage compressor can be reduced as compared with the prior art.

  According to the hot gas bypass method for a turbo refrigerator of the sixteenth aspect of the present invention, the opening degree in order from the rear stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the plurality of stage compressors decreases. By sequentially opening the outlet of the adjustable hot gas bypass three-way valve, gas refrigerant flows in and the required minimum flow rate is ensured for each of the plurality of stages of compressors. In contrast, surging can be avoided and the power of the multi-stage compressor can be reduced as compared with the prior art.

  According to the turbo gas refrigerator hot gas bypass method of the seventeenth aspect of the present invention, the ON / OFF is sequentially performed from the downstream compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the plurality of compressors decreases. In order to ensure the necessary minimum flow rate for each of the plurality of stages of compressors, by sequentially opening an OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening, inflow of gas refrigerant, Surging can be avoided for any of the multistage compressors, and the power of the multistage compressor can be reduced compared to the conventional one.

  According to the hot gas bypass method for a turbo chiller according to an eighteenth aspect of the present invention, when the gas refrigerant flow rate of the plurality of compressors decreases, the ON / In order to ensure the necessary minimum flow rate for each of the plurality of stages of compressors, by sequentially opening an OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening, inflow of gas refrigerant, Surging can be avoided for any of the multistage compressors, and the power of the multistage compressor can be reduced compared to the conventional one.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 is a system configuration diagram of a turbo chiller according to Embodiment 1 of the present invention, FIG. 2 is an explanatory diagram showing a relationship between a refrigeration function force and a compressor gas refrigerant flow rate in the turbo chiller, and FIG. FIG. 4 is an explanatory diagram showing the relationship between the refrigeration functional force and the hot gas bypass valve opening in the turbo chiller, and FIG. 4 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor required power in the turbo chiller.

  The turbo refrigerator of the first embodiment shown in FIG. 1 is used for indoor cooling, and the gas refrigerant evaporated in the evaporator 21 is transferred between the first stage compressor 22 and the second stage compressor 23. A centrifugal multistage compressor 24 (two-stage compressor in the illustrated example) that compresses, a condenser 25 that condenses the gas refrigerant compressed by the multistage compressor 24, and a liquid refrigerant condensed by the condenser 25 are expanded. A high-stage expansion valve 26 and a low-stage expansion valve 27, and an intercooler 28 as a gas-liquid separator that is installed between the high-stage expansion valve 26 and the low-stage expansion valve 27 and separates the refrigerant into a gas-liquid separator. The gas refrigerant separated by the intercooler 28 bypasses the evaporator 21 and flows into the second stage compressor 23 of the multistage compressor 24, and the refrigerant expanded by the expansion valves 26 and 27 is evaporated. And an evaporator 21 to be used. The multistage compressor 24 is rotationally driven by an electric motor 46. In FIG. 1, the refrigerant flow paths 30, 31, 35, 41, 42, and 43 such as pipes through which gas refrigerant flows are indicated by dotted lines, and the refrigerant flow paths 33 such as pipes through which liquid refrigerant flows are indicated by solid lines.

  More specifically, the gear 48 provided on the rotating shaft 47 of the electric motor 46 and the gear 50 provided on the rotating shaft 49 of the multistage compressor 24 are engaged with each other, and the first gear 48 and 50 are used to engage the first gear 48 and 50. The stage compressor 22 and the second stage compressor 23 are rotationally driven by an electric motor 46. At this time, the multistage compressor 24 introduces the gas refrigerant compressed by the first stage compressor 22 of the front stage (low pressure stage) to the second stage compressor 23 of the rear stage (high pressure stage) through the refrigerant flow path 30. This is further compressed by the second stage compressor 23 and discharged to the refrigerant flow path 31.

  In the refrigerant flow path 31, the gas refrigerant discharged from the second stage compressor 23 is guided to the condenser 25. In the condenser 25, the gas refrigerant introduced into the container 56 through the refrigerant flow path 31 is cooled by cooling water that is cooled by an external cooling tower (not shown) and flows through the heat transfer tube group 32 in the container 56. The condensed liquid refrigerant is condensed (liquefied), and the condensed liquid refrigerant is discharged from the bottom of the container 56 to the refrigerant flow path 33. The refrigerant flow path 33 is provided with a high stage expansion valve 26, an intermediate cooler 28, and a low stage expansion valve 27 in order from the upstream side to the downstream side in the refrigerant flow direction. The high stage expansion valve 26 and the low stage expansion valve 27 are valves whose opening degree can be adjusted, such as an electric valve.

  By adjusting the opening degree of the high stage expansion valve 26 so that the liquid refrigerant accumulates at the bottom of the condenser 56 in the container 56, a certain level of refrigerant liquid level 24 is secured in the container 56. Has been. This is because only the liquid refrigerant can be discharged without sucking uncondensed gas refrigerant into the refrigerant flow path 33. In the high stage expansion valve 26, the liquid refrigerant discharged from the container 56 of the condenser 26 is decompressed and expanded. At this time, a part of the liquid refrigerant may become a gas refrigerant, and in order to prevent the gas refrigerant from being supplied to the evaporator 21, the intermediate cooler 28 performs gas-liquid separation of the refrigerant and separates the separated liquid. While only the refrigerant is discharged to the low stage expansion valve 27 side, the separated gas refrigerant is discharged to the bypass refrigerant flow path 35.

  The bypass refrigerant channel 35 communicates the intermediate cooler 28 and the refrigerant channel 30, and an orifice 29 is provided in the middle. Therefore, the gas refrigerant discharged from the intermediate cooler 28 to the bypass refrigerant flow path 35 bypasses the evaporator 21 and is returned to the intake side of the second stage compressor 23 through the orifice 29 to be returned to the second stage compressor. 23 is inhaled.

  A heat transfer tube group 36 is provided in the container 57 of the evaporator 21, and the refrigerant liquid level 37 is adjusted to be positioned above the heat transfer tube group 36 in the container 57. A chilled water flow path 38 such as a pipe is connected to the heat transfer tube group 36. The chilled water flow path 38 is provided with a pump 39 for circulating the chilled water and a fan coil unit 40 having a fan and a coil in the case. ing. Therefore, in the evaporator 21, the liquid refrigerant is cooled by the heat exchange with the cold water supplied by the pump 39 and flowing through the heat transfer tube group 36, and the refrigerant is evaporated to become a gas refrigerant. In the unit 40, the indoor air blown by the fan is cooled by the cold water supplied by the pump 39 and flowing through the coil, thereby cooling the room. The gas refrigerant vaporized by the evaporator 21 is discharged to the refrigerant flow path 41, returned to the intake side of the first stage compressor 22 through the refrigerant flow path 41, and sucked into the first stage compressor 22.

  The turbo chiller includes a first stage hot gas bypass valve 44 as hot gas bypass means for avoiding surging of the first stage compressor 22 and the second stage compressor 23 of the multistage compressor 24, and A second stage hot gas bypass valve 45 is provided.

  The first stage hot gas bypass valve 44 is a valve whose opening degree can be adjusted, such as an electric valve, and is provided in a bypass refrigerant flow path 42 that connects the refrigerant flow path 31 and the refrigerant flow path 41. The second stage hot gas bypass valve 45 is a valve whose opening degree can be adjusted, such as an electric valve, and is provided in a bypass refrigerant flow path 43 that connects the refrigerant flow path 31 and the refrigerant flow path 30. Therefore, when the first stage hot gas bypass valve 44 is opened, a part of the gas refrigerant discharged from the multistage compressor 24 (second stage compressor 23) passes through the first stage hot gas bypass valve 44. (I.e., bypassing the condenser 21) and sucked into the first stage compressor 22. When the second stage hot gas bypass valve 45 is opened, a part of the gas refrigerant discharged from the multistage compressor 24 (second stage compressor 23) passes through the second stage hot gas bypass valve 45 (that is, Bypassing the evaporator 21), the air is sucked into the second stage compressor 23.

  The controller 55 as hot gas bypass control means performs hot gas bypass control based on the measurement result of the gas refrigerant flow rate or the calculation result of the refrigeration function (refrigeration capacity).

  First, a case where hot gas bypass control is performed based on the measurement result of the gas refrigerant flow rate will be described. In this case, the refrigerant flow path 30 is provided with a flow meter 52 for measuring the gas refrigerant flow rate of the first stage compressor 22, and the refrigerant flow path 31 is used for measuring the gas refrigerant flow rate of the second stage compressor 23. The flow meter 54 is provided. The flow measurement signals of these flow meters 52 and 54 are both input to the controller 55.

  The controller 55 includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23 ( The minimum gas refrigerant flow rate necessary to avoid surging of the second stage compressor 23 is set. In this turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases, the second stage compressor 23 is first moved into the surging region ( Since the first stage compressor 22 reaches the surging area (surging area II in FIG. 2) after reaching the surging area I) in FIG. 2, the minimum required flow rate of the first stage compressor 22 is the second stage compressor 23. This is a smaller value than the minimum required flow rate. These necessary minimum flow rates can be set in the design of the multistage compressor 24, the operation test of the multistage compressor 24, and the like.

  Then, in the controller 55, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively set based on the necessary minimum flow rate and the flow rate measurement signals of the flow meters 52 and 54. It is determined whether the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 have been reached, and the minimum necessary flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23. The opening / closing control of the first stage hot gas bypass valve 44 and the opening / closing control of the second stage hot gas bypass valve 45 for ensuring the flow rate are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In FIG. 2, for convenience of explanation, the compressor gas refrigerant flow rate during normal operation (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) is represented by one graph. However, since the gas refrigerant from the intercooler 28 actually flows only into the second stage compressor 23 even during normal operation, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant of the second stage compressor 23 The flow rate is slightly different. This also applies to FIGS. 6, 10, 14 and 18.

  In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is controlled by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG.

  When it is determined that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the minimum required flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23), As shown in FIG. 3, the second stage hot gas bypass valve 45 is opened, and the gas refrigerant is allowed to flow only into the second stage compressor 23, thereby ensuring the necessary minimum flow rate of the second stage compressor 23 and surging. To avoid. That is, as the opening degree of the second stage hot gas bypass valve 45 is gradually increased as shown in FIG. 3, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the second stage hot gas bypass valve 45 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23 and surging is performed. Avoided.

  After that, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22) further decreases, and the measured value of the gas refrigerant flow rate of the first stage compressor 22 by the flow meter 52 becomes the value of the first stage compressor 22. When it is determined that the necessary minimum flow rate (surging region II of the first stage compressor 22) has been reached, the first stage hot gas bypass valve 44 is also opened as shown in FIG. By allowing the refrigerant to flow in, the necessary minimum flow rate of the first stage compressor 22 is secured and surging is avoided. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 3, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided. Note that when the first stage hot gas bypass valve 44 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. The gas bypass valve 45 compensates for the shortage of the increase in the gas refrigerant flow rate of the second stage compressor 23 caused by the first stage hot gas bypass valve 44 to ensure the necessary minimum flow rate of the second stage compressor 23.

  Then, as described above, after the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23, the gas refrigerant flow rate of the first stage compressor 22 becomes the first stage compression. Until the required minimum flow rate (surging region II) of the compressor 22 is reached, only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the minimum required flow rate of the second stage compressor 23, and the first stage compressor 23. Accordingly, the required power of the multistage compressor 24 (electric motor 46) gradually decreases as shown in FIG. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. In addition, after the gas refrigerant flow rate of the first stage compressor 22 reaches the minimum necessary flow rate (surging region II) of the first stage compressor 22, the gas refrigerant flow rate of the first stage compressor 22 is also changed to the first stage compressor. Since the required minimum flow rate of 22 is ensured, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  Next, the case where hot gas bypass control is performed based on the calculation result of the refrigeration functional force is described. Since there is a correlation between the compressor gas refrigerant flow rate and the refrigerating function force as illustrated in FIG. 2, the compressor gas refrigerant flow rate is estimated from the refrigerating function force without directly measuring as described above. be able to. Therefore, in this case, a thermometer 93 for measuring the temperature of the cold water flowing into the evaporator 21 (heat transfer tube group 36) into the cold water flow path 38 in order to obtain the refrigeration function force, and the evaporator 21 (heat transfer tube group). 36), a thermometer 94 for measuring the temperature of the cold water flowing out from 36) and a flow meter 95 for measuring the flow rate of the cold water are provided. These temperature measurement signals from the thermometers 93 and 94 and the flow measurement signal from the flow meter 95 are both input to the controller 55.

  The controller 55 calculates a chilled water temperature difference ΔT (= T1−T2) that is a difference between the chilled water temperature measured value T1 by the thermometer 93 and the chilled water temperature measured value T2 by the thermometer 94, and the chilled water temperature difference ΔT The refrigeration functional force C (= ΔT × F), which is the product of the cold water flow rate measurement value F by the flow meter 95, is calculated. Thus, the refrigeration function C, which is the cooling capacity of the turbo chiller, is required. In general, since the cold water flow rate is constant, a constant value of the cold water flow rate may be used for the calculation of the refrigeration functional force C instead of the measured flow rate F of the cold water.

  The controller 55 also includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23. (Minimum gas refrigerant flow rate necessary for avoiding surging of the second stage compressor 23) and the first stage hot gas bypass valve 44 and the second stage according to the refrigeration function. In order to open each of the hot gas bypass valves 45, data representing the relationship between the refrigeration function force and the opening degree of the first stage hot gas bypass valve 44 as exemplified in FIG. And the data (table data, relational expression, etc.) showing the relationship between the freezing functional force and the opening degree of the second stage hot gas bypass valve 45 are set. As described above, in the turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) is decreased, the second stage compressor 23 is moved first. The surging area (surging area I in FIG. 2) is reached, and then the first stage compressor 22 reaches the surging area (surging area II in FIG. 2). The value is smaller than the necessary minimum flow rate of the stage compressor 23.

  Accordingly, as illustrated in FIG. 3, the refrigeration function force at the time of starting to open the first stage hot gas bypass valve 44 is lower than the refrigeration function force at the time of starting to open the second stage hot gas bypass 45. In addition, data representing the relationship between the refrigeration capacity and the opening of the first stage hot gas bypass valve 44 and data representing the relationship between the refrigeration capacity and the opening of the second stage hot gas bypass valve 45 are provided. , Each is set. The refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44 for ensuring the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23, respectively. And the data representing the relationship between the refrigeration function force and the opening degree of the second stage hot gas bypass valve 45 can be set in the design or operation test of the turbo chiller.

  In the controller 55, data representing the relationship between the refrigeration functional force and the opening degree of the first-stage hot gas bypass valve 44, and the refrigeration functional force and the opening degree of the second-stage hot gas bypass valve 45, , And the calculation result of the refrigeration functional force C, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively those of the first stage compressor 22. Determination of whether or not the necessary minimum flow rate and the necessary minimum flow rate of the second stage compressor 23 have been reached, and the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are ensured. The opening / closing control of the first stage hot gas bypass valve 44 and the opening / closing control of the second stage hot gas bypass valve 45 are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is controlled by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG. At this time, the difference between the temperature of the cold water flowing into the evaporator 21 and the temperature of the cold water flowing out of the evaporator 21 is also reduced. The refrigeration functional force C calculated from the flow rate measurement value F (or a constant value) also decreases.

  Then, the refrigeration functional force C is the first predetermined value (the second stage hot gas bypass valve 45 in the data representing the relationship between the refrigeration functional force and the opening degree of the second stage hot gas bypass valve 45 starts to open. The value of the refrigeration functional force at the time) and the gas refrigerant flow rate of the second stage compressor 23 is determined to have reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). Based on the data representing the relationship between the refrigeration functional force and the opening degree of the second stage hot gas bypass valve 45 and the calculation result of the refrigeration functional force C, as shown in FIG. By opening the valve 45 and allowing the gas refrigerant to flow only into the second stage compressor 23, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. That is, as the opening degree of the second stage hot gas bypass valve 45 is gradually increased as shown in FIG. 3, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the second stage hot gas bypass valve 45 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23 and surging is performed. Avoided.

  Thereafter, the refrigeration functional force C further decreases and a second predetermined value lower than the first predetermined value (first data in the data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44). The value of the refrigeration function force when the first stage hot gas bypass valve 44 begins to open) and the flow rate of the gas refrigerant in the first stage compressor 22 is the minimum required flow rate of the first stage compressor 22 (first stage compressor 22). 3, based on the data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44 and the calculation result of the refrigeration functional force C. As shown, the first stage hot gas bypass valve 44 is also opened and gas refrigerant is allowed to flow into the first stage compressor 22, thereby ensuring the necessary minimum flow rate of the first stage compressor 22 and avoiding surging. To do. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 3, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided. Note that when the first stage hot gas bypass valve 44 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. The gas bypass valve 45 compensates for the shortage of the increase in the gas refrigerant flow rate of the second stage compressor 23 caused by the first stage hot gas bypass valve 44 to ensure the necessary minimum flow rate of the second stage compressor 23.

  Then, as described above, after the refrigeration functional force C reaches the first predetermined value (that is, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23). ) Until the refrigeration functional force C reaches the second predetermined value (i.e., until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). )), Only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the necessary minimum flow rate of the second stage compressor 23, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. As shown in FIG. 4, the required power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. Note that after the refrigeration functional force C reaches the second predetermined value (that is, after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). Since the gas refrigerant flow rate of the first stage compressor 22 is also secured to the necessary minimum flow rate of the first stage compressor 22, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  As described above, according to the turbo chiller of Embodiment 1 of the present invention, the two first-stage hot gas bypass valves 45 and the second-stage hot gas bypass valves 45 that are adjustable in opening degree are used. A configuration in which the discharge side of the second-stage compressor 23, which is the latter-stage compressor of the two-stage compressors 22 and 23, and the intake side of the two-stage compressors 22 and 23 are communicated with each other. As a result, even if the minimum required flow rate for avoiding surging of the first stage compressor 22 is smaller than the minimum required flow rate for avoiding surging of the second stage compressor 23, the first stage compressor 22 Since the gas refrigerant can flow into each of the first stage compressor 22 and the second stage compressor 23 by the hot gas bypass valve 44 and the second stage hot gas bypass valve 45, the first stage compressor 22 Minimum required flow for each second stage compressor 23 It can flow gas refrigerant. Therefore, surging can be avoided for both of the two-stage compressors 22 and 23, and the power of the multistage compressor 24 can be reduced as compared with the conventional one.

  Further, the turbo refrigerator of the first embodiment has a controller 55. In this controller 55, the gas refrigerant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, and these gases are reduced. Every time it is determined that the measured value of the refrigerant flow rate has reached the required minimum flow rate, or the refrigeration functional force C is reduced to the first predetermined value and the second predetermined value corresponding to the required minimum flow rate. Each time it is judged that the second stage hot gas bypass valve 45 and the first stage hot gas bypass valve 44 that can be adjusted in opening degree are sequentially opened, the second stage compression that reaches the required minimum flow rate first is performed. In order to control the required minimum flow rate for each of the two-stage compressors 22 and 23 by sequentially introducing the gas refrigerant from the machine 23, surging is performed for both of the two-stage compressors 22 and 23. Can be avoided And, it is possible to reduce the power of the multi-stage compressor 24 as compared with the prior art.

  In the above description, the case where the multistage compressor 24 is a two-stage compressor has been described. However, the present invention is not limited to this, and the present invention is applied to a turbo refrigerator equipped with a multistage compressor including three or more stages of compressors. Can also be applied. That is, the turbo chiller of the present invention is a last stage compressor (as shown in FIG. 1) among a plurality of stages constituting a multistage compressor through a plurality of hot gas bypass valves whose opening degree can be adjusted. In the case of a two-stage compressor, the discharge side of the second-stage compressor 23) and the plurality of stages of compressors (in the case of a two-stage compressor as shown in FIG. 1, the first-stage compressor 22 and the second-stage compressor). What is necessary is just to make it the structure which connects each of the suction side of the compressor 23). In this case, the controller sets the minimum required flow rate for avoiding the surging of the multi-stage compressors to a smaller value for the front-stage compressor, and the gas refrigerant flow rate of the multi-stage compressors decreases. Each time it is determined that the measured value of the gas refrigerant flow rate has reached the required minimum flow rate, or each of the refrigeration functional forces C decreases and each of the plurality of compressors corresponds to the required minimum flow rate. Each time it is determined that the predetermined value has been reached, the hot gas bypass valve capable of adjusting the opening degree is sequentially opened, and the gas refrigerant is allowed to flow in in order from the compressor on the rear stage that reaches the required minimum flow rate first. What is necessary is just to control so that the said required minimum flow volume may be ensured for every compressor of a several stage.

<Embodiment 2>
FIG. 5 is a system configuration diagram of a turbo chiller according to Embodiment 2 of the present invention, FIG. 6 is an explanatory diagram showing the relationship between the refrigeration function force and the compressor gas refrigerant flow rate in the turbo chiller, and FIG. FIG. 8 is an explanatory diagram showing the relationship between the refrigeration functional force and the hot gas bypass valve opening in the turbo chiller, and FIG. 8 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor required power in the turbo chiller.

  In the system configuration shown in FIG. 5, the same components as those in the system configuration of the first embodiment (FIG. 1) are denoted by the same reference numerals, and detailed description thereof is omitted here.

  As shown in FIG. 5, in the turbo refrigerator of the second embodiment, the second stage hot gas as the hot gas bypass means is connected to the bypass refrigerant flow path 35 that connects the intermediate cooler 28 and the refrigerant flow path 30. A bypass valve 61 is provided. That is, the turbo chiller of the second embodiment is not provided with the orifice 29, the refrigerant flow path 43 and the second stage hot gas bypass valve 45 in the first embodiment (FIG. 1). Instead, a second-stage hot gas bypass valve 61, which is a valve whose opening degree can be adjusted, such as an electric valve, is provided. Therefore, the second stage hot gas bypass valve 61 functions not only for avoiding surging but also as a substitute for the orifice 29. That is, during normal operation (when the cooling load is relatively high and the refrigeration function is high), the second stage hot gas bypass valve 61 is kept at a constant opening, and the second stage hot gas bypass valve 61 is turned on. Then, the gas refrigerant is returned from the intermediate cooler 28 to the intake side of the second stage compressor 23.

  Also in the second embodiment, the controller 55 performs the hot gas bypass control based on the measurement result of the gas refrigerant flow rate or the calculation result of the refrigeration function force (refrigeration capacity).

  First, the case where hot gas bypass control is performed based on the measurement result of the gas refrigerant flow rate will be described. A flow meter 52 is provided, a flow meter 54 for measuring the gas refrigerant flow rate of the second stage compressor 23 is provided in the refrigerant flow path 31, and the flow measurement signals of these flow meters 52 and 54 are both Input to the controller 55.

  As described above, the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are set in the controller 55 in advance. In the controller 55, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively set based on these necessary minimum flow rates and the flow rate measurement signals of the flow meters 52 and 54. It is determined whether the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 have been reached, and the minimum necessary flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23. The opening / closing control of the first stage hot gas bypass valve 44, the opening / closing control of the second stage hot gas bypass valve 45, and the opening / closing control of the high stage expansion valve 26 for ensuring the flow rate are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG.

  When it is determined that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the minimum required flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23), By increasing the opening degree of the high stage expansion valve 26 and lowering the refrigerant liquid level 34 in the container 56 of the condenser 25 as shown in FIG. 5 (that is, by eliminating or making the refrigerant liquid level 34 very low). ), The liquid refrigerant condensed from the bottom of the container 56 is also discharged (suctioned into the refrigerant flow path 33), and the second stage hot gas bypass valve 61 is opened as shown in FIG. By making the gas refrigerant flow only into the second stage compressor 23 (by increasing the opening), the necessary minimum flow rate of the second stage compressor 23 is secured and surging is avoided. That is, as the opening degree of the second stage hot gas bypass valve 61 is gradually increased as shown in FIG. 7, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the second stage hot gas bypass valve 61 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23 and surging is performed. Avoided.

  After that, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22) further decreases, and the measured value of the gas refrigerant flow rate of the first stage compressor 22 by the flow meter 52 becomes the value of the first stage compressor 22. When it is determined that the necessary minimum flow rate (surging region II) has been reached, the first stage hot gas bypass valve 44 is also opened as shown in FIG. The necessary minimum flow rate of the first stage compressor 22 is secured to avoid surging. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 7, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided. Note that when the first stage hot gas bypass valve 44 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. The gas bypass valve 45 compensates for the shortage of the increase in the gas refrigerant flow rate of the second-stage compressor 23 caused by the first-stage hot gas bypass valve 44 to secure the necessary minimum flow rate of the second-stage compressor 23.

  Then, as described above, after the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23, the gas refrigerant flow rate of the first stage compressor 22 becomes the first stage compression. Until the required minimum flow rate (surging region II) of the compressor 22 is reached, only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the minimum required flow rate of the second stage compressor 23, and the first stage compressor 23. Therefore, the required power of the multistage compressor 24 (electric motor 46) gradually decreases as shown in FIG. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor indicated by a one-dot chain line in FIG. In addition, after the gas refrigerant flow rate of the first stage compressor 22 reaches the minimum necessary flow rate (surging region II) of the first stage compressor 22, the gas refrigerant flow rate of the first stage compressor 22 is also changed to the first stage compressor. Since the required minimum flow rate of 22 is maintained, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  Next, the case where hot gas bypass control is performed based on the calculation result of the refrigeration functional force is described. As illustrated in FIG. 6, since there is a correlation between the compressor gas refrigerant flow rate and the refrigeration functional force, the compressor gas refrigerant flow rate is estimated from the refrigeration functional force without directly measuring as described above. be able to. Therefore, in this case, as described above, the thermometer 93 for measuring the temperature of the cold water flowing into the evaporator 21 (heat transfer tube group 36) into the cold water flow path 38 in order to obtain the refrigeration functional force, and the evaporator 21 A thermometer 94 for measuring the temperature of the cold water flowing out of the (heat transfer tube group 36) and a flow meter 95 for measuring the flow rate of the cold water are provided, and the temperature measurement signals of these thermometers 93, 94 and Any flow rate measurement signal of the flow meter 95 is input to the controller 55.

  The controller 55 calculates a chilled water temperature difference ΔT (= T1−T2) that is a difference between the chilled water temperature measured value T1 by the thermometer 93 and the chilled water temperature measured value T2 by the thermometer 94, and the chilled water temperature difference ΔT The refrigeration functional force C (= ΔT × F), which is the product of the cold water flow rate measurement value F by the flow meter 95, is calculated. Thus, the refrigeration function C, which is the cooling capacity of the turbo chiller, is required. In general, since the cold water flow rate is constant, a constant value of the cold water flow rate may be used for the calculation of the refrigeration functional force C instead of the measured flow rate F of the cold water.

  The controller 55 also includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23. (Minimum gas refrigerant flow rate necessary for avoiding surging of the second stage compressor 23) and the first stage hot gas bypass valve 44 and the second stage according to the refrigeration function. In order to open each of the hot gas bypass valves 61, data representing the relationship between the refrigeration function force and the opening degree of the first stage hot gas bypass valve 44 as illustrated in FIG. And the data (table data, relational expression, etc.) showing the relationship between the freezing functional force and the opening degree of the second stage hot gas bypass valve 61 are set.

  In this turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases, the second stage compressor 23 is first moved into the surging region ( Since the first stage compressor 22 reaches the surging area (surging area II in FIG. 6) after reaching the surging area I) in FIG. 6, the second stage hot gas bypass 61 is opened as illustrated in FIG. The refrigerating capacity and the opening degree of the first stage hot gas bypass valve 44 are set so that the refrigeration function capacity when starting the opening of the first stage hot gas bypass valve 44 is lower than the refrigeration function capacity when starting. And data representing the relationship between the refrigerating capacity and the opening degree of the second stage hot gas bypass valve 61 are respectively set. The refrigerating function force and the opening degree of the first stage hot gas bypass valve 44 for ensuring the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23, respectively. And the data representing the relationship between the refrigeration functional force and the opening degree of the second stage hot gas bypass valve 61 can be set in the design or operation test of the turbo chiller.

  In the controller 55, data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44, and the refrigeration functional force and the opening degree of the second stage hot gas bypass valve 61 , And the calculation result of the refrigeration functional force C, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively those of the first stage compressor 22. Determination of whether or not the necessary minimum flow rate and the necessary minimum flow rate of the second stage compressor 23 have been reached, and the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are ensured. The opening / closing control of the first stage hot gas bypass valve 44, the opening / closing control of the second stage hot gas bypass valve 45, and the opening / closing control of the high stage expansion valve 26 are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG. At this time, the difference between the temperature of the cold water flowing into the evaporator 21 and the temperature of the cold water flowing out of the evaporator 21 is also reduced. The refrigeration functional force C calculated from the flow rate measurement value F (or a constant value) also decreases.

  The refrigeration functional force C is a first predetermined value (the opening degree of the second stage hot gas bypass valve 61 in the data representing the relationship between the refrigeration functional force and the opening degree of the second stage hot gas bypass valve 61). The value of the refrigeration functional force when starting to increase), and the gas refrigerant flow rate of the second stage compressor 23 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). Therefore, by increasing the opening of the high stage expansion valve 26 and lowering the refrigerant liquid level 34 in the container 56 of the condenser 25 as shown in FIG. By lowering), the liquid refrigerant condensed from the bottom of the container 56 is also discharged (sucked into the refrigerant flow path 33), and the refrigeration functional force and the second stage hot gas bypass valve 61 are discharged. Data showing the relationship between Based on the calculation result of the functional force C, the second stage hot gas bypass valve 61 is opened as shown in FIG. 7, and the gas refrigerant is allowed to flow only into the second stage compressor 23, whereby the second stage compressor. The necessary minimum flow rate of 23 is secured to avoid surging. That is, as the opening degree of the second stage hot gas bypass valve 61 is gradually increased as shown in FIG. 7, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the second stage hot gas bypass valve 61 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23 and surging is performed. Avoided.

  Thereafter, the refrigeration functional force C further decreases and a second predetermined value lower than the first predetermined value (first data in the data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44). The value of the refrigeration function force when the first stage hot gas bypass valve 44 begins to open) and the flow rate of the gas refrigerant in the first stage compressor 22 is the minimum required flow rate of the first stage compressor 22 (first stage compressor 22). Is determined based on the data representing the relationship between the refrigeration function force and the opening degree of the first stage hot gas bypass valve 44 and the calculation result of the refrigeration function force C. As shown, the first stage hot gas bypass valve 44 is also opened and gas refrigerant is allowed to flow into the first stage compressor 22, thereby ensuring the necessary minimum flow rate of the first stage compressor 22 and avoiding surging. To do. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 7, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided. Note that when the first stage hot gas bypass valve 44 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. In the gas bypass valve 61, the necessary minimum flow rate of the second stage compressor 23 is secured by compensating for the shortage of the increase in the gas refrigerant flow rate of the second stage compressor 23 caused by the first stage hot gas bypass valve 44.

  Then, as described above, after the refrigeration functional force C reaches the first predetermined value (that is, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23). ) Until the refrigeration functional force C reaches the second predetermined value (i.e., until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). )), Only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the necessary minimum flow rate of the second stage compressor 23, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. As shown in FIG. 8, the required power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor indicated by a one-dot chain line in FIG. Note that after the refrigeration functional force C reaches the second predetermined value (that is, after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). Since the gas refrigerant flow rate of the first stage compressor 22 is also secured at the necessary minimum flow rate of the first stage compressor 22, the necessary power of the multistage compressor 24 hardly decreases as shown in FIG.

  As described above, according to the turbo refrigerator of the second embodiment, the rear stage of the two-stage compressors 22 and 23 is arranged via the first-stage hot gas bypass valve 44 whose opening degree can be adjusted. The discharge side of the second-stage compressor 23 that is a compressor communicates with the intake side of the first-stage compressor 22 that is the front-stage compressor of the two-stage compressors 22 and 23, and the opening degree By configuring the intermediate cooler 28 and the intake side of the second stage compressor 23 to communicate with each other via the adjustable second stage hot gas bypass valve 61, the first stage compressor 22 Even if the minimum required flow rate for avoiding surging is smaller than the minimum required flow rate for avoiding surging of the second stage compressor 23, the first stage hot gas bypass valve 44 and the second stage hot The gas bypass valve 61 connects the first stage compressor 22 and the second stage compressor 23 with each other. It is possible to flow the gas refrigerant, respectively, can flow gas refrigerant required minimum flow respectively to the first stage compressor 22 to the second stage compressor 23. Therefore, surging can be avoided for both of the two-stage compressors 22 and 23, and the power of the multistage compressor 24 can be reduced as compared with the conventional one. Moreover, since a hot gas bypass valve can be provided using a conventional existing system (bypass refrigerant flow path) without providing a new bypass refrigerant flow path, a new system (bypass refrigerant flow path) can be provided. The system configuration can be simplified as compared with the case of providing.

  Further, the turbo refrigerator of the second embodiment has a controller 55. In this controller 55, the gas refrigerant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, and these gases are reduced. Every time it is determined that the measured value of the refrigerant flow rate has reached the required minimum flow rate, or the refrigeration functional force C is reduced to the first predetermined value and the second predetermined value corresponding to the required minimum flow rate. Each time it is determined that the second stage compressor has been reached, the second stage hot gas bypass valve 61 and the first stage hot gas bypass valve 44 that are adjustable in opening degree are sequentially opened, and the second stage compressor that reaches the required minimum flow rate first is reached. In order to control the required minimum flow rate for each of the two-stage compressors 22 and 23 by flowing the gas refrigerant in order from 23, surging is applied to both of the two-stage compressors 22 and 23. Can be avoided, One can reduce the power of the multi-stage compressor 24 as compared with the prior art.

  In the above description, the case where the multistage compressor 24 is a two-stage compressor has been described. However, the present invention is not limited to this, and the present invention is applied to a turbo refrigerator equipped with a multistage compressor including three or more stages of compressors. Can also be applied. That is, in this case, the turbo chiller according to the present invention includes a discharge side of the last-stage compressor among the three-stage or more compressors via the hot gas bypass valve whose opening degree can be adjusted, and the 3 The gas-liquid separator and the three-stage through the hot gas bypass valve that communicates with the intake side of the compressor at the foremost stage among the compressors at the stage or higher and that can adjust the opening degree. What is necessary is just to set it as the structure which connects each of the suction side of compressors other than the said front stage among the above compressors. In this case, the controller sets the minimum required flow rate for avoiding the surging of the multiple-stage compressors to a smaller value for the front-stage compressor, and the gas refrigerant flow rate of the multiple-stage compressors decreases. Each time it is determined that the measured value of the flow rate of the gas refrigerant has reached the required minimum flow rate, or the refrigeration functional force C is reduced, and each of the measured values corresponding to the required minimum flow rates of the multiple-stage compressors is reduced. Each time it is determined that the predetermined value has been reached, the hot gas bypass valve capable of adjusting the opening degree is sequentially opened, and the gas refrigerant is allowed to flow in in order from the downstream compressor that reaches the required minimum flow rate first. What is necessary is just to control so that the said required minimum flow volume may be ensured for every compressor of a several stage.

<Embodiment 3>
FIG. 9 is a system configuration diagram of a turbo chiller according to Embodiment 3 of the present invention, FIG. 10 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor gas refrigerant flow rate in the turbo chiller, and FIG. FIG. 12 is an explanatory diagram showing the relationship between the refrigeration functional force and the hot gas bypass valve opening in the turbo chiller, and FIG. 12 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor required power in the turbo chiller.

  In the system configuration shown in FIG. 9, the same parts as those in the system configuration of the first embodiment (FIG. 1) are denoted by the same reference numerals, and detailed description thereof is omitted here.

  As shown in FIG. 9, in the turbo refrigerator of the third embodiment, a hot gas bypass three-way valve 71 as hot gas bypass means is provided in a bypass refrigerant flow path 42 that communicates the refrigerant flow path 31 and the refrigerant flow path 41. Is provided. That is, in the turbo refrigerator of the third embodiment, the first stage hot gas bypass valve 44, the refrigerant flow path 43, and the second stage hot gas bypass valve 45 in the first embodiment (FIG. 1) are provided. Instead, a hot gas bypass three-way valve 71 which is a valve whose opening degree can be adjusted, such as an electric valve, is provided.

  The inlet 72 of the hot gas bypass three-way valve 71 communicates with the refrigerant channel 31 (the discharge side of the second stage compressor 23) via the refrigerant channel 43, and one outlet 73 of the hot gas bypass three-way valve 71 is The refrigerant flow path 43 communicates with the refrigerant flow path 41 (the intake side of the first stage compressor 22). The other outlet 74 of the hot gas bypass three-way valve 71 communicates with the bypass refrigerant channel 35 via a bypass refrigerant channel 75 such as a pipe. That is, the outlet 74 of the hot gas bypass three-way valve 71 communicates with the intake side of the second stage compressor 23 via the refrigerant flow paths 75, 35, and 30.

  Also in the third embodiment, the controller 55 performs the hot gas bypass control based on the measurement result of the gas refrigerant flow rate or the calculation result of the refrigeration function force (refrigeration capacity).

First, the case where hot gas bypass control is performed based on the measurement result of the gas refrigerant flow rate will be described. A flow meter 52 is provided, a flow meter 54 for measuring the gas refrigerant flow rate of the second stage compressor 23 is provided in the refrigerant flow path 31, and the flow measurement signals of these flow meters 52 and 54 are both Input to the controller 55.

  As described above, the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are set in the controller 55 in advance. In the controller 55, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively set based on the necessary minimum flow rate and the flow rate measurement signals of the flow meters 52 and 54. Judgment whether the minimum required flow rate of the stage compressor 22 and the minimum required flow rate of the second stage compressor 23 have been reached, the minimum required flow rate of the first stage compressor 22 and the minimum required flow rate of the second stage compressor 23 The open / close control of the hot gas bypass three-way valve 71 for ensuring the above is performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG.

  Then, if it is determined that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23), As shown in FIG. 11, only one outlet 74 of the hot gas bypass three-way valve 71 is opened, and the gas refrigerant is allowed to flow only into the second stage compressor 23, thereby ensuring the necessary minimum flow rate of the second stage compressor 23. And avoid surging. That is, as the opening degree of the outlet 74 of the hot gas bypass three-way valve 71 is gradually increased as shown in FIG. 11, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the hot gas bypass three-way valve 71 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23 to avoid surging. Is done.

  After that, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22) further decreases, and the measured value of the gas refrigerant flow rate of the first stage compressor 22 by the flow meter 52 becomes the value of the first stage compressor 22. When it is determined that the necessary minimum flow rate (surging region II) has been reached, the other outlet 73 of the hot gas bypass three-way valve 71 is also opened as shown in FIG. Thus, the necessary minimum flow rate of the first stage compressor 22 is ensured and surging is avoided. That is, as the opening degree of the outlet 73 of the hot gas bypass three-way valve 71 is gradually increased as shown in FIG. 11, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the hot gas bypass three-way valve 71 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is avoided. . When the outlet 73 of the hot gas bypass three-way valve 71 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. The outlet 74 of the valve 71 compensates for the shortage of the increase in the gas refrigerant flow rate of the second stage compressor 23 caused by the outlet 73 of the hot gas bypass three-way valve 71 to ensure the necessary minimum flow rate of the second stage compressor 23.

  Then, as described above, after the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23, the gas refrigerant flow rate of the first stage compressor 22 becomes the first stage compression. Until the required minimum flow rate (surging region II) of the compressor is reached, only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the minimum required flow rate, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. Therefore, the required power of the multistage compressor 24 (the electric motor 46) gradually decreases accordingly, as shown in FIG. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by the one-dot chain line in FIG. In addition, after the gas refrigerant flow rate of the first stage compressor 22 reaches the minimum necessary flow rate (surging region II) of the first stage compressor 22, the gas refrigerant flow rate of the first stage compressor 22 is also changed to the first stage compressor. Since the required minimum flow rate of 22 is ensured, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  Next, the case where hot gas bypass control is performed based on the calculation result of the refrigeration functional force is described. As illustrated in FIG. 10, since there is a correlation between the compressor gas refrigerant flow rate and the refrigeration function force, the compressor gas refrigerant flow rate is estimated from the refrigeration function force without directly measuring as described above. be able to. Therefore, in this case, a thermometer 93 for measuring the temperature of the cold water flowing into the evaporator 21 (heat transfer tube group 36) into the cold water flow path 38 in order to obtain the refrigeration function force, and the evaporator 21 (heat transfer tube group). 36), a thermometer 94 for measuring the temperature of the cold water flowing out from 36) and a flow meter 95 for measuring the flow rate of the cold water are provided. These temperature measurement signals from the thermometers 93 and 94 and the flow measurement signal from the flow meter 95 are both input to the controller 55.

  The controller 55 calculates a chilled water temperature difference ΔT (= T1−T2) that is a difference between the chilled water temperature measured value T1 by the thermometer 93 and the chilled water temperature measured value T2 by the thermometer 94, and the chilled water temperature difference ΔT The refrigeration functional force C (= ΔT × F), which is the product of the cold water flow rate measurement value F by the flow meter 95, is calculated. Thus, the refrigeration function C, which is the cooling capacity of the turbo chiller, is required. In general, since the cold water flow rate is constant, a constant value of the cold water flow rate may be used for the calculation of the refrigeration functional force C instead of the measured flow rate F of the cold water.

  The controller 55 also includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23. (The minimum gas refrigerant flow rate necessary for avoiding surging of the second stage compressor 23) and the outlet 73 and the outlet 74 of the hot gas bypass three-way valve 71 according to the refrigeration function. In advance, data (table data, relational expressions, etc.) representing the relationship between the refrigeration function force exemplified in FIG. 11 and the opening degree of one outlet 73 of the hot gas bypass three-way valve 71, and In addition, data (table data, relational expressions, etc.) representing the relationship between the refrigeration functional force and the opening degree of the other outlet 74 of the hot gas bypass three-way valve 71 is set. As described above, in the turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) is decreased, the second stage compressor 23 is moved first. Since the first stage compressor 22 reaches the surging area (surging area II in FIG. 10) after reaching the surging area (surging area I in FIG. 10), the minimum required flow rate of the first stage compressor 22 is The value is smaller than the necessary minimum flow rate of the stage compressor 23.

  Therefore, as illustrated in FIG. 11, the refrigeration functional force at the start of opening the outlet 73 of the hot gas bypass three-way valve 71 is more than the refrigeration functional force at the start of opening the outlet 74 of the hot gas bypass three-way valve 71. Data representing the relationship between the refrigeration capacity and the opening degree of the outlet 73 of the hot gas bypass three-way valve 71 and the relationship between the refrigeration capacity and the opening degree of the outlet 74 of the hot gas bypass three-way valve 71 so as to decrease. Is set for each data. It should be noted that the refrigeration function force and the opening 73 of the hot gas bypass three-way valve 71 for ensuring the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are opened. The data representing the relationship between the temperature and the data representing the relationship between the refrigeration function force and the opening degree of the outlet 74 of the hot gas bypass three-way valve 71 can be set in the design or operation test of the turbo refrigerator. it can.

  In the controller 55, data representing the relationship between the refrigeration functional force and the opening degree of the outlet 73 of the hot gas bypass three-way valve 71, and the opening of the outlet 74 of the refrigeration functional force and the hot gas bypass three-way valve 71 are displayed. The gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively based on the data representing the relationship with the degree and the calculation result of the refrigeration functional force C. Judgment whether the required minimum flow rate of 22 and the required minimum flow rate of the second stage compressor 23 have been reached, and the required minimum flow rate of the first stage compressor 22 and the required minimum flow rate of the second stage compressor 23 are ensured. The hot gas bypass three-way valve 71 for opening and closing is controlled.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG. At this time, the difference between the temperature of the cold water flowing into the evaporator 21 and the temperature of the cold water flowing out of the evaporator 21 is also reduced. The refrigeration functional force C calculated from the flow rate measurement value F (or a constant value) also decreases.

  The refrigeration functional force C is a first predetermined value (the outlet 74 of the hot gas bypass three-way valve 71 in the data representing the relationship between the refrigeration functional force and the opening degree of the outlet 74 of the hot gas bypass three-way valve 71). (The value of the refrigeration function force when starting to open) and the gas refrigerant flow rate of the second stage compressor 23 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). If it judges, based on the data showing the relationship between the said refrigeration functional force and the opening degree of the outflow port 74 of the hot gas bypass three-way valve 71, and the calculation result of the refrigeration functional force C, as shown in FIG. By opening only the outlet 74 of the valve 71 and allowing the gas refrigerant to flow only into the second stage compressor 23, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. That is, as the opening degree of the outlet 74 of the hot gas bypass three-way valve 71 is gradually increased as shown in FIG. However, since the flow rate of the gas refrigerant flowing into the second stage compressor 23 through the outlet 74 of the hot gas bypass three-way valve 71 gradually increases, the necessary minimum flow rate is secured in the second stage compressor 23. Surging is avoided.

  Thereafter, the refrigeration functional force C further decreases and a second predetermined value lower than the first predetermined value (in data representing the relationship between the refrigeration functional force and the opening degree of the outlet 73 of the hot gas bypass three-way valve 71). When the outlet 73 of the hot gas bypass three-way valve 71 starts to open, the flow rate of the gas refrigerant in the first stage compressor 22 reaches the minimum required flow rate (first stage compression). If it is determined that the surging area II) of the machine 22 has been reached, it is based on the data representing the relationship between the refrigeration function force and the opening degree of the outlet 73 of the hot gas bypass three-way valve 71 and the calculation result of the refrigeration function force C. As shown in FIG. 11, the outlet 73 of the hot gas bypass three-way valve 71 is also opened, and gas refrigerant flows into the first stage compressor 22, thereby ensuring the necessary minimum flow rate of the first stage compressor 22. Avoid surging . That is, as the opening degree of the outlet 73 of the hot gas bypass three-way valve 71 is gradually increased as shown in FIG. 11, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the outlet 73 of the hot gas bypass three-way valve 71 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 as well. Surging is avoided. When the outlet 73 of the hot gas bypass three-way valve 71 is opened, not only the gas refrigerant flow rate of the first stage compressor 22 but also the gas refrigerant flow rate of the second stage compressor 23 is increased. The outlet 71 of the valve 71 compensates for the shortage of the increase in the gas refrigerant flow rate of the second stage compressor 23 due to the outlet 73 of the hot gas bypass three-way valve 71 to ensure the necessary minimum flow rate of the second stage compressor 23. .

  Then, as described above, after the refrigeration functional force C reaches the first predetermined value (that is, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23). ) Until the refrigeration functional force C reaches the second predetermined value (i.e., until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). )), Only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the necessary minimum flow rate of the second stage compressor 23, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. As shown in FIG. 12, the required power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by the one-dot chain line in FIG. Note that after the refrigeration functional force C reaches the second predetermined value (that is, after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). Since the gas refrigerant flow rate of the first stage compressor 22 is also secured at the necessary minimum flow rate of the first stage compressor 22, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  As described above, according to the turbo chiller of the third embodiment, the rear compressor of the two-stage compressors 22 and 23 is provided via the hot gas bypass three-way valve 71 whose opening degree can be adjusted. By adopting a configuration in which the discharge side of a certain second-stage compressor 23 and each of the intake sides of the two-stage compressors 22 and 23 are communicated with each other, surging of the first-stage compressor 22 can be avoided. Even if the required minimum flow rate is smaller than the minimum required flow rate for avoiding surging of the second stage compressor 23, the hot gas bypass three-way valve 71 causes the first stage compressor 22 and the second stage compressor 23 to Since the gas refrigerant can be introduced into each of them, the gas refrigerant having the minimum required flow rate can be supplied to the two-stage compressors 22 and 23, respectively. Therefore, surging can be avoided for both of the two-stage compressors 22 and 23, and the power of the multistage compressor 24 can be reduced as compared with the conventional one. Moreover, since one hot gas bypass three-way valve 71 is used, the system configuration can be simplified and the increase in equipment cost can be reduced as compared with the case where two hot gas bypass valves are used.

  Further, the turbo refrigerator of the third embodiment has a controller 55, in which the gas refrigerant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, and these gases are Every time it is determined that the measured value of the refrigerant flow rate has reached the required minimum flow rate, or the refrigeration functional force C is reduced to the first predetermined value and the second predetermined value corresponding to the required minimum flow rate. Each time it is judged that the flow rate has reached, the outlets 74 and 73 of the hot gas bypass three-way valve 71 whose opening degree can be adjusted are sequentially opened, and the gas refrigerant flows in from the second stage compressor 23 that reaches the required minimum flow rate first. By doing so, control is performed so as to ensure the necessary minimum flow rate for each of the two-stage compressors 22, 23, so that surging can be avoided for both of the two-stage compressors 22, 23, and , More than conventional It is possible to reduce the power of the compressor 24.

<Embodiment 4>
FIG. 13 is a system configuration diagram of a turbo chiller according to Embodiment 4 of the present invention, FIG. 14 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor gas refrigerant flow rate in the turbo chiller, and FIG. FIG. 16 is an explanatory diagram showing the relationship between the refrigeration functional force and the hot gas bypass valve opening in the turbo chiller, and FIG. 16 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor required power in the turbo chiller.

  In the system configuration shown in FIG. 13, the same parts as those in the system configuration of the first embodiment (FIG. 1) are denoted by the same reference numerals, and detailed description thereof is omitted here.

  As shown in FIG. 13, in the turbo refrigerator of the fourth embodiment, the second stage hot gas as the hot gas bypass means is connected to the bypass refrigerant flow path 35 communicating the intermediate cooler 28 and the refrigerant flow path 30. A bypass valve 81 is provided. That is, in the turbo refrigerator of the fourth embodiment, the refrigerant flow path 43 and the second stage hot gas bypass valve 45 in the first embodiment (FIG. 1) are not provided. A two-stage hot gas bypass valve 81 is provided. The second stage hot gas bypass valve 81 is an ON / OFF type valve such as an electromagnetic valve (a valve whose degree of opening is not adjustable, and can only be switched between fully open and fully closed), and is in parallel with the orifice 29. is set up.

  Also in the fourth embodiment, the controller 55 performs hot gas bypass control based on the measurement result of the gas refrigerant flow rate or the calculation result of the refrigeration function force (refrigeration capacity).

  First, the case where hot gas bypass control is performed based on the measurement result of the gas refrigerant flow rate will be described. A flow meter 52 is provided, a flow meter 54 for measuring the gas refrigerant flow rate of the second stage compressor 23 is provided in the refrigerant flow path 31, and the flow measurement signals of these flow meters 52 and 54 are both Input to the controller 55.

  As described above, the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are set in the controller 55 in advance. Then, in the controller 55, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively set based on the necessary minimum flow rate and the flow rate measurement signals of the flow meters 52 and 54. Judgment whether or not the minimum required flow rate of the stage compressor 22 and the minimum required flow rate of the second stage compressor 23 have been reached, and the minimum required flow rate of the first stage compressor 22 and the minimum required flow rate of the second stage compressor 23 The opening / closing control of the first stage hot gas bypass valve 44, the opening / closing control of the second stage hot gas bypass valve 81, and the opening / closing control of the high stage expansion valve 26 are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG.

  Then, if it is determined that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23), By increasing the opening degree of the high stage expansion valve 26 and lowering the refrigerant liquid level 34 in the container 56 of the condenser 25 as shown in FIG. 13 (that is, by eliminating or making the refrigerant liquid level 34 very low). ), The liquid refrigerant condensed from the bottom of the container 56 is also discharged (not drawn into the refrigerant flow path 33), and the second stage hot gas bypass valve 81 is opened as shown in FIG.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 via the second stage hot gas bypass valve 81, only the gas refrigerant flow rate of the second stage compressor 23 increases as shown in FIG. To do. For this reason, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration functional force gradually decreases, and the gas refrigerant flow rate of the second stage compressor 23 decreases accordingly, the second The gas refrigerant flow rate of the stage compressor 23 is ensured to be more than the necessary minimum flow rate. That is, even when the minimum cooling load in the capacity control range of the turbo chiller is reached, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. In other words, the capacity of the second stage hot gas bypass valve 81 is set so that the necessary minimum flow rate of the second stage compressor 23 is ensured at this time.

  After that, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22) further decreases, and the measured value of the gas refrigerant flow rate of the first stage compressor 22 by the flow meter 52 becomes the value of the first stage compressor 22. When it is determined that the necessary minimum flow rate (surging region II) has been reached, the first stage hot gas bypass valve 44 is also opened as shown in FIG. The necessary minimum flow rate of the first stage compressor 22 is secured to avoid surging. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 15, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured even in the first stage compressor 22 and surging is avoided. Is done.

  Then, as described above, after the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23, the gas refrigerant flow rate of the first stage compressor 22 becomes the first stage compression. Until the necessary minimum flow rate (surging region II) of the machine 22 is reached, only the gas refrigerant flow rate of the second stage compressor 23 is ensured to be equal to or higher than the necessary minimum flow rate, and the gas refrigerant flow rate of the first stage compressor 23 gradually increases. Therefore, as shown in FIG. 16, the required power of the multistage compressor 24 (the electric motor 46) gradually decreases accordingly. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. Note that after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22, the gas refrigerant flow rate of the first stage compressor 22 is also changed to the first stage compressor. Since the required minimum flow rate of 22 is ensured, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  Next, the case where hot gas bypass control is performed based on the calculation result of the refrigeration functional force is described. Since there is a correlation between the compressor gas refrigerant flow rate and the refrigeration function force as illustrated in FIG. 14, the compressor gas refrigerant flow rate is estimated from the refrigeration function force without directly measuring as described above. be able to. Therefore, in this case, as described above, the thermometer 93 for measuring the temperature of the cold water flowing into the evaporator 21 (heat transfer tube group 36) into the cold water flow path 38 in order to obtain the refrigeration functional force, and the evaporator 21 A thermometer 94 for measuring the temperature of the cold water flowing out of the (heat transfer tube group 36) and a flow meter 95 for measuring the flow rate of the cold water are provided, and the temperature measurement signals of these thermometers 93, 94 and Any flow rate measurement signal of the flow meter 95 is input to the controller 55.

  The controller 55 calculates a chilled water temperature difference ΔT (= T1−T2) that is a difference between the chilled water temperature measured value T1 by the thermometer 93 and the chilled water temperature measured value T2 by the thermometer 94, and the chilled water temperature difference ΔT The refrigeration functional force C (= ΔT × F), which is the product of the cold water flow rate measurement value F by the flow meter 95, is calculated. Thus, the refrigeration function C, which is the cooling capacity of the turbo chiller, is required. In general, since the cold water flow rate is constant, a constant value of the cold water flow rate may be used for the calculation of the refrigeration functional force C instead of the measured flow rate F of the cold water.

  The controller 55 also includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23. (Minimum gas refrigerant flow rate necessary for avoiding surging of the second stage compressor 23) and the first stage hot gas bypass valve 44 and the second stage according to the refrigeration function. In order to open each of the hot gas bypass valves 81, data representing the relationship between the refrigeration function force and the opening degree of the first stage hot gas bypass valve 44 as exemplified in FIG. And the value (1st predetermined value) of the refrigerating functional force when opening the 2nd stage | part hot gas bypass valve 81 which is an ON / OFF type valve is set.

  In this turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases, the second stage compressor 23 is first moved into the surging region ( 14 reaches the surging area I), and then the first stage compressor 22 reaches the surging area (surging area II in FIG. 14), so the second stage hot gas bypass 81 is opened as illustrated in FIG. The refrigeration capacity and the opening degree of the first stage hot gas bypass valve 44 are so set that the refrigeration function power when the first stage hot gas bypass valve 44 starts to open is lower than the refrigeration function power at that time. Data representing the relationship and the value of the refrigeration function force when the second stage hot gas bypass valve 81 is opened are set. The refrigerating function force and the opening degree of the first stage hot gas bypass valve 44 for ensuring the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23, respectively. And the value of the refrigeration function force when the second stage hot gas bypass valve 81 is opened can be set in the design or operation test of the turbo chiller.

  In the controller 55, data representing the relationship between the refrigeration functional force and the opening of the first stage hot gas bypass valve 44, and the value of the refrigeration functional force when the second stage hot gas bypass valve 81 is opened. And the calculation result of the refrigeration functional force C, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are the minimum required flow rate and the first flow rate of the first stage compressor 22, respectively. Determination of whether or not the necessary minimum flow rate of the two-stage compressor 23 has been reached, and the first-stage hot for securing the necessary minimum flow rate of the first-stage compressor 22 and the necessary minimum flow rate of the second-stage compressor 23 The opening / closing control of the gas bypass valve 44, the opening / closing control of the second stage hot gas bypass valve 45, and the opening / closing control of the high stage expansion valve 26 are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is performed by capacity control means (not shown) according to this (for example, by narrowing the vane on the intake side of the multistage compressor 4). In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG. At this time, the difference between the temperature of the cold water flowing into the evaporator 21 and the temperature of the cold water flowing out of the evaporator 21 is also reduced. The refrigeration functional force C calculated from the flow rate measurement value F (or a constant value) also decreases.

  Then, the refrigeration functional force C reaches the first predetermined value, and the gas refrigerant flow rate of the second stage compressor 23 becomes the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). When it is determined that the refrigerant level has reached, the opening degree of the high stage expansion valve 26 is increased and the refrigerant liquid level 34 in the container 56 of the condenser 25 is lowered as shown in FIG. By making it very low), the liquid refrigerant condensed from the bottom of the container 56 also flows out (not sucked into the refrigerant flow path 33), and the second stage hot gas as shown in FIG. The bypass valve 81 is opened.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 via the second stage hot gas bypass valve 81, only the gas refrigerant flow rate of the second stage compressor 23 increases as shown in FIG. To do. For this reason, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration functional force gradually decreases, and the gas refrigerant flow rate of the second stage compressor 23 decreases accordingly, the second The gas refrigerant flow rate of the stage compressor 23 is ensured to be more than the necessary minimum flow rate. That is, even when the minimum cooling load in the capacity control range of the turbo chiller is reached, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. In other words, the capacity of the second stage hot gas bypass valve 81 is set so that the necessary minimum flow rate of the second stage compressor 23 is ensured at this time.

  Thereafter, the refrigeration functional force C further decreases and a second predetermined value lower than the first predetermined value (first data in the data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44). The value of the refrigeration function force when the stage hot gas bypass valve 44 starts to open), and the gas refrigerant flow rate of the first stage compressor 22 reaches the minimum required flow rate of the first stage compressor 22 (surging of the first stage compressor 22). When it is determined that the region II) has been reached, it is shown in FIG. 15 based on the data representing the relationship between the refrigeration function force and the opening degree of the first stage hot gas bypass valve 44 and the calculation result of the refrigeration function force C. As described above, the first stage hot gas bypass valve 44 is also opened and the gas refrigerant is allowed to flow into the first stage compressor 22, thereby ensuring the necessary minimum flow rate of the first stage compressor 22 and avoiding surging. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 15, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided.

  Then, as described above, after the refrigeration functional force C reaches the first predetermined value (that is, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23). Until the refrigeration functional force C reaches the second predetermined value (that is, until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). )), Only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the necessary minimum flow rate of the second stage compressor 23, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. As shown in FIG. 16, the necessary power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. In addition, after the refrigeration functional force C reaches the second predetermined value (that is, after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). Since the gas refrigerant flow rate of the first stage compressor 22 is also secured to the necessary minimum flow rate of the first stage compressor 22, the necessary power of the multistage compressor 24 hardly decreases as shown in FIG.

  As described above, according to the turbo chiller of the fourth embodiment, the rear stage of the two stage compressors 22 and 23 via the first stage hot gas bypass valve 44 whose opening degree can be adjusted. The discharge side of the second stage compressor 23 that is a compressor communicates with the intake side of the first stage compressor 22 that is the front stage compressor of the two stage compressors 22 and 23, and the orifice 29 The intermediate cooler 28 and the intake side of the second-stage compressor 23 are communicated with each other via an ON / OFF-type second-stage hot gas bypass valve 81 installed in parallel. Even if the minimum required flow rate for avoiding surging of the first stage compressor 22 is smaller than the minimum required flow rate for avoiding surging of the second stage compressor 23, the first stage hot gas bypass The valve 44 and the second stage hot gas bypass valve 81 Since the gas refrigerant can flow into each of the compressor 22 and the second stage compressor 23, the necessary minimum flow rate of the gas refrigerant can be made to flow through the first stage compressor 22 and the second stage compressor 23, respectively. it can. Therefore, surging can be avoided for both of the two-stage compressors 22 and 23, and the power of the multistage compressor 24 can be reduced as compared with the conventional one. In addition, since the ON / OFF type second stage hot gas bypass valve 81 is used, the fluctuation of the gas refrigerant flow rate when the valve is opened is smaller than when a hot gas bypass valve with adjustable opening is used. Although large, it is possible to reduce the increase in equipment costs.

  Further, the turbo chiller of the fourth embodiment has a controller 55. In this controller 55, the gas refrigerant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, and these gases are reduced. Each time it is determined that the measured value of the refrigerant flow rate has reached the required minimum flow rate, or the refrigeration functional force C is reduced or the refrigeration functional force C is reduced to correspond to the required minimum flow rate. Each time it is determined that the first predetermined value and the second predetermined value have been reached, every time it is determined that the first predetermined value and the second predetermined value have been reached, the ON / OFF type second stage hot The gas bypass valve 81 and the first-stage hot gas bypass valve 44 whose opening degree can be adjusted are sequentially opened, and gas refrigerant is introduced in order from the second-stage compressor 23 that reaches the required minimum flow rate first. For each compressor 22 and 23 Since control is performed to ensure a low flow rate, surging can be avoided for both of the two-stage compressors 22 and 23, and the power of the multi-stage compressor 24 can be reduced as compared with the conventional one. it can.

  In the above description, the case where the multistage compressor 24 is a two-stage compressor has been described. However, the present invention is not limited to this, and the present invention is applied to a turbo refrigerator equipped with a multistage compressor including three or more stages of compressors. Can also be applied. That is, in this case, the turbo chiller according to the present invention includes a discharge side of the last-stage compressor among the three-stage or more compressors via the hot gas bypass valve whose opening degree can be adjusted, and the 3 Via the plurality of ON / OFF type hot gas bypass valves that communicate with the intake side of the compressor at the foremost stage among the compressors at the stage or more and that are installed in parallel with each of the plurality of orifices, What is necessary is just to set it as the structure formed by connecting the said gas-liquid separator and each of the suction side of compressors other than the said front | former stage among the compressors of the said 3rd or more stage. In this case, the controller sets the minimum required flow rate for avoiding the surging of the multi-stage compressors to a smaller value for the front-stage compressor, and the gas refrigerant flow rate of the multi-stage compressors decreases. Each time it is determined that the measured value of the gas refrigerant flow rate has reached the required minimum flow rate, or each of the refrigeration functional forces C decreases and each of the plurality of compressors corresponds to the required minimum flow rate. Each time it is determined that the predetermined value has been reached, the ON / OFF type hot gas bypass valve and the hot gas bypass valve whose opening degree can be adjusted are sequentially opened, and the downstream compression that reaches the required minimum flow rate first is performed. Control may be performed so as to ensure the necessary minimum flow rate for each of the plurality of stages of compressors by allowing the gas refrigerant to flow in order from the machine.

<Embodiment 5>
FIG. 17 is a system configuration diagram of a turbo chiller according to Embodiment 5 of the present invention, FIG. 18 is an explanatory diagram showing the relationship between the refrigeration functional force and the compressor gas refrigerant flow rate in the turbo chiller, and FIG. FIG. 20 is an explanatory diagram showing the relationship between the refrigeration functional force in the turbo chiller and the hot gas bypass valve opening, and FIG. 20 is an explanatory diagram showing the relationship between the refrigeration functional force in the turbo chiller and the required compressor power.

  In the system configuration shown in FIG. 17, the same components as those in the system configuration of the first embodiment (FIG. 1) are denoted by the same reference numerals, and detailed description thereof is omitted here.

  As shown in FIG. 17, in the turbo chiller of the fifth embodiment, the first second stage as the hot gas bypass means is provided in the bypass refrigerant flow path 35 communicating the intermediate cooler 28 and the refrigerant flow path 30. A hot gas bypass valve 91 and a second second-stage hot gas bypass valve 92 are provided. That is, in the turbo refrigerator of the fifth embodiment, the refrigerant flow path 43 and the second stage hot gas bypass valve 45 in the first embodiment (FIG. 1) are not provided, and instead of these, First and second second stage hot gas bypass valves 91 and 92 are provided. The first and second second-stage hot gas bypass valves 91 and 92 are ON / OFF type valves such as solenoid valves (openable valves are not adjustable and can only be switched between fully open and fully closed). These are all installed in parallel with the orifice 29.

  Also in the fourth embodiment, the controller 55 performs hot gas bypass control based on the measurement result of the gas refrigerant flow rate or the calculation result of the refrigeration function force (refrigeration capacity).

  First, the case where hot gas bypass control is performed based on the measurement result of the gas refrigerant flow rate will be described. A flow meter 52 is provided, a flow meter 54 for measuring the gas refrigerant flow rate of the second stage compressor 23 is provided in the refrigerant flow path 31, and the flow measurement signals of these flow meters 52 and 54 are both Input to the controller 55.

  As described above, the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23 are set in the controller 55 in advance. In the controller 55, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are respectively set based on the necessary minimum flow rate and the flow rate measurement signals of the flow meters 52 and 54. Judgment whether the minimum required flow rate of the stage compressor 22 and the minimum required flow rate of the second stage compressor 23 have been reached, the minimum required flow rate of the first stage compressor 22 and the minimum required flow rate of the second stage compressor 23 Control for opening and closing the first stage hot gas bypass valve 44, opening and closing control for the first and second second stage hot gas bypass valves 91 and 92, and opening and closing control for the high stage expansion valve 26 are performed. .

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is controlled by capacity control means (not shown) (for example, by narrowing the vane on the intake side of the multistage compressor 4) accordingly. In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG.

  Then, if it is determined that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23), By increasing the opening degree of the high stage expansion valve 26 and lowering the refrigerant liquid level 34 in the container 56 of the condenser 25 as shown in FIG. 17 (that is, by eliminating or extremely reducing the refrigerant liquid level 34). ), The liquid refrigerant condensed from the bottom of the container 56 is also discharged (suctioned into the refrigerant flow path 33), and the first second-stage hot gas bypass is first performed as shown in FIG. Open valve 91.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 via the first second stage hot gas bypass valve 91, the gas refrigerant flow rate of the second stage compressor 23 as shown in FIG. Only increase. For this reason, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration function force gradually decreases, and even if the gas refrigerant flow rate of the second-stage compressor 23 decreases accordingly, for a while In the meantime, the gas refrigerant flow rate of the second stage compressor 23 can be maintained above the necessary minimum flow rate.

  Then, it is determined again that the measured value of the gas refrigerant flow rate of the second stage compressor 23 by the flow meter 54 has reached the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). Then, as shown in FIG. 19, the second second stage hot gas bypass valve 92 is now opened.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 through the second second stage hot gas bypass valve 92, the gas refrigerant of the second stage compressor 23 as shown in FIG. Only the flow rate increases again. Therefore, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration function force gradually decreases, and the gas refrigerant flow rate of the second stage compressor 23 decreases accordingly, the second The gas refrigerant flow rate of the stage compressor 23 can be maintained above the required minimum flow rate. That is, even when the minimum cooling load in the capacity control range of the turbo chiller is reached, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. In other words, the capacities of the first and second second stage hot gas bypass valves 91 and 92 are set so that the necessary minimum flow rate of the second stage compressor 23 is ensured at this time.

  After that, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22) further decreases, and the measured value of the gas refrigerant flow rate of the first stage compressor 22 by the flow meter 52 becomes the value of the first stage compressor 22. When it is determined that the necessary minimum flow rate (surging region II) has been reached, the first stage hot gas bypass valve 44 is also opened as shown in FIG. The necessary minimum flow rate of the first stage compressor 22 is secured to avoid surging. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 19, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured even in the first stage compressor 22 and surging is avoided. Is done.

  Then, as described above, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II). During this period, only the gas refrigerant flow rate of the second stage compressor 23 is ensured to be equal to or higher than the necessary minimum flow rate, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. Therefore, as shown in FIG. The necessary power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. Note that after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II), the gas refrigerant flow rate of the first stage compressor 22 also becomes the necessary gas refrigerant flow rate of the first stage compressor 2. Therefore, the necessary power of the multistage compressor 24 hardly decreases as shown in FIG.

  Next, the case where hot gas bypass control is performed based on the calculation result of the refrigeration functional force is described. Since there is a correlation between the compressor gas refrigerant flow rate and the refrigeration function force as illustrated in FIG. 18, the compressor gas refrigerant flow rate is estimated from the refrigeration function force without directly measuring as described above. be able to. Therefore, in this case, as described above, the thermometer 93 for measuring the temperature of the cold water flowing into the evaporator 21 (heat transfer tube group 36) into the cold water flow path 38 in order to obtain the refrigeration functional force, and the evaporator 21 A thermometer 94 for measuring the temperature of the cold water flowing out of the (heat transfer tube group 36) and a flow meter 95 for measuring the flow rate of the cold water are provided, and the temperature measurement signals of these thermometers 93, 94 and Any flow rate measurement signal of the flow meter 95 is input to the controller 55.

  The controller 55 calculates a chilled water temperature difference ΔT (= T1−T2) that is a difference between the chilled water temperature measured value T1 by the thermometer 93 and the chilled water temperature measured value T2 by the thermometer 94, and the chilled water temperature difference ΔT The refrigeration functional force C (= ΔT × F), which is the product of the cold water flow rate measurement value F by the flow meter 95, is calculated. Thus, the refrigeration function C, which is the cooling capacity of the turbo chiller, is required. In general, since the cold water flow rate is constant, a constant value of the cold water flow rate may be used for the calculation of the refrigeration functional force C instead of the measured flow rate F of the cold water.

  The controller 55 also includes a minimum required flow rate of the first stage compressor 22 (a minimum gas refrigerant flow rate necessary to avoid surging of the first compressor 22) and a minimum required flow rate of the second stage compressor 23. (Minimum gas refrigerant flow rate necessary for avoiding surging of the second stage compressor 23) and the first stage hot gas bypass valve 44 and the second stage according to the refrigeration function. In order to open the hot gas bypass valves 91 and 92, data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44 as illustrated in FIG. And the value of the refrigeration function force (first predetermined value and second predetermined value) when the second stage hot gas bypass valves 91 and 92 that are ON / OFF type valves are opened are set. Yes.

  In this turbo chiller, when the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases, the second stage compressor 23 is first moved into the surging region ( Since the first stage compressor 22 reaches the surging area (surging area II in FIG. 18) after reaching the surging area I) in FIG. 18, the second stage hot gas bypasses 91 and 92 are exemplified as shown in FIG. The refrigerating capacity and the opening degree of the first stage hot gas bypass valve 44 are such that the refrigeration function capacity when opening the first stage hot gas bypass valve 44 is lower than the refrigeration function capacity when opening the first stage. And the value of the refrigeration function force when the second stage hot gas bypass valves 91 and 92 are opened are respectively set. The refrigerating function force and the opening degree of the first stage hot gas bypass valve 44 for ensuring the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23, respectively. And the value of the refrigeration function force when the second stage hot gas bypass valves 91 and 92 are opened can be set in the design or operation test of the turbo chiller.

  In the controller 55, data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44, and the refrigeration functional force when the second stage hot gas bypass valves 91 and 92 are opened. And the calculation result of the refrigeration functional force C, the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23 are the minimum required flow rates of the first stage compressor 22, respectively. And determining whether or not the necessary minimum flow rate of the second stage compressor 23 has been reached, and the first stage for securing the necessary minimum flow rate of the first stage compressor 22 and the necessary minimum flow rate of the second stage compressor 23. The open / close control of the hot gas bypass valve 44, the open / close control of the first and second second stage hot gas bypass valves 45, and the open / close control of the high stage expansion valve 26 are performed.

  Hereinafter, the control of the controller 55 in this case will be described in more detail with reference to FIGS. In this turbo chiller, when the cooling load decreases due to a decrease in the outside air temperature or the like, the refrigeration function of the turbo chiller is controlled by capacity control means (not shown) (for example, by narrowing the vane on the intake side of the multistage compressor 4) accordingly. In order to reduce the force, the compressor gas refrigerant flow rate (the gas refrigerant flow rate of the first stage compressor 22 and the gas refrigerant flow rate of the second stage compressor 23) decreases as shown in FIG. At this time, the difference between the temperature of the cold water flowing into the evaporator 21 and the temperature of the cold water flowing out of the evaporator 21 is also reduced. The refrigeration functional force C calculated from the flow rate measurement value F (or a constant value) also decreases.

  Then, the refrigeration functional force C reaches the first predetermined value, and the gas refrigerant flow rate of the second stage compressor 23 becomes the necessary minimum flow rate of the second stage compressor 23 (surging region I of the second stage compressor 23). When it is determined that the refrigerant level has reached, the opening degree of the high stage expansion valve 26 is increased and the refrigerant liquid level 34 in the container 56 of the condenser 25 is lowered as shown in FIG. By making it very low), the liquid refrigerant condensed from the bottom of the container 56 also flows out the uncondensed gas refrigerant (sucked into the refrigerant flow path 33), and the first first as shown in FIG. The two-stage hot gas bypass valve 91 is opened.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 via the first second stage hot gas bypass valve 81, the gas refrigerant flow rate of the second stage compressor 23 as shown in FIG. Only increase. For this reason, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration function force gradually decreases, and even if the gas refrigerant flow rate of the second-stage compressor 23 decreases accordingly, for a while In the meantime, the gas refrigerant flow rate of the second stage compressor 23 is ensured to be more than the necessary minimum flow rate.

  Thereafter, the refrigeration functional force C reaches the second predetermined value, and the gas refrigerant flow rate of the second stage compressor 23 again becomes the necessary minimum flow rate of the second stage compressor 23 (the surging region of the second stage compressor 23). If it is determined that I) has been reached, the second second stage hot gas bypass valve 92 is then opened as shown in FIG.

  As a result, since the gas refrigerant flows only into the second stage compressor 23 through the second second stage hot gas bypass valve 92, the gas refrigerant of the second stage compressor 23 as shown in FIG. Only the flow rate increases again. Therefore, after that, even if the refrigerant flow rate of the evaporator 21 gradually decreases and the refrigeration function force gradually decreases, and the gas refrigerant flow rate of the second stage compressor 23 decreases accordingly, the second The gas refrigerant flow rate of the stage compressor 23 can be maintained above the required minimum flow rate. That is, even when the minimum cooling load in the capacity control range of the turbo chiller is reached, the necessary minimum flow rate of the second stage compressor 23 is ensured and surging is avoided. In other words, the capacities of the first and second second stage hot gas bypass valves 91 and 92 are set so that the necessary minimum flow rate of the second stage compressor 23 is ensured at this time.

  After that, the refrigeration functional force C further decreases to a third predetermined value lower than the first and second predetermined values (data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44). The value of the refrigeration function force when the first stage hot gas bypass valve 44 starts to open) and the gas refrigerant flow rate of the first stage compressor 22 is the minimum required flow rate of the first stage compressor 22 (first stage compressor). 22 surging region II), it is determined based on the data representing the relationship between the refrigeration functional force and the opening degree of the first stage hot gas bypass valve 44 and the calculation result of the refrigeration functional force C. 19, the first stage hot gas bypass valve 44 is also opened and gas refrigerant is allowed to flow into the first stage compressor 22, thereby ensuring the necessary minimum flow rate of the first stage compressor 22 and surging. To avoid. That is, as the opening degree of the first stage hot gas bypass valve 44 is gradually increased as shown in FIG. 19, the refrigerant flow rate of the evaporator 21 is gradually decreased and the refrigeration function force is gradually decreased. However, since the flow rate of the gas refrigerant flowing into the first stage compressor 22 through the first stage hot gas bypass valve 44 gradually increases, the necessary minimum flow rate is secured in the first stage compressor 22 and surging is performed. Avoided.

  Then, as described above, after the refrigeration functional force C reaches the first predetermined value (that is, the gas refrigerant flow rate of the second stage compressor 23 reaches the necessary minimum flow rate (surging region I) of the second stage compressor 23). Until the refrigeration functional force C reaches the second predetermined value (that is, until the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). )), Only the gas refrigerant flow rate of the second stage compressor 23 is ensured to the necessary minimum flow rate of the second stage compressor 23, and the gas refrigerant flow rate of the first stage compressor 23 gradually decreases. As shown in FIG. 20, the necessary power of the multistage compressor 24 (electric motor 46) also gradually decreases. For this reason, in this turbo refrigerator, the required power of the multistage compressor 24 can be reduced more than the required power of the conventional multistage compressor shown by a one-dot chain line in FIG. In addition, after the refrigeration functional force C reaches the third predetermined value (that is, after the gas refrigerant flow rate of the first stage compressor 22 reaches the necessary minimum flow rate (surging region II) of the first stage compressor 22). Since the gas refrigerant flow rate of the first stage compressor 22 is also secured at the necessary minimum flow rate of the first stage compressor 22, the required power of the multistage compressor 24 hardly decreases as shown in FIG.

  As described above, according to the turbo chiller of the fifth embodiment, the rear stage of the two-stage compressors 22 and 23 is arranged via the first-stage hot gas bypass valve 44 whose opening degree can be adjusted. The discharge side of the second stage compressor 23 that is a compressor communicates with the intake side of the first stage compressor 22 that is the front stage compressor of the two stage compressors 22 and 23, and the orifice 29 The intermediate cooler 28 and the intake side of the second stage compressor 23 are communicated with each other via the ON / OFF type second stage hot gas bypass valves 91 and 92 installed in parallel with each other. As a result, the same effect as the turbo chiller of the fourth embodiment is obtained, and two ON / OFF type second-stage hot gas bypass valves 91 and 92 are connected in parallel to the orifice 29. Because it is installed, one ON / OFF type ho Although the effect of reducing the increase in equipment costs is reduced compared to the case where the gas bypass valves are installed in parallel, the fluctuation of the gas refrigerant flow rate when the valves are opened can be reduced, and the power of the multistage compressor 24 can be reduced. The effect of reducing is also great. The number of ON / OFF hot gas bypass valves installed in parallel to the orifice 29 may be three or more.

  Further, the turbo chiller according to the fourth embodiment has a controller 55. In this controller 55, the gas refrigerant flow rates of the first stage compressor 22 and the second stage compressor 23 are reduced, and these gases are reduced. Every time it is determined that the measured value of the refrigerant flow rate has reached the required minimum flow rate, or when the refrigeration functional force C is reduced, the first predetermined value, the second predetermined value corresponding to the required minimum flow rate, and Each time it is determined that the second predetermined value has been reached, the ON / OFF type second stage hot gas bypass valves 91 and 92 and the first stage hot gas bypass valve 44 whose opening degree can be adjusted are sequentially opened, In order to control to ensure the required minimum flow rate for each of the two-stage compressors 22 and 23 by flowing the gas refrigerant in order from the second-stage compressor 23 that reaches the required minimum flow rate first, For either compressor 22 or 23 You can also avoid surging, and can reduce the power of the multi-stage compressor 24 as compared with the prior art.

  In the above description, the case where the multistage compressor 24 is a two-stage compressor has been described. However, the present invention is not limited to this, and the present invention is applied to a turbo refrigerator having a multistage compressor composed of three or more stages of compressors. The same can be applied to the case of the fourth embodiment. Further, the control of the controller in this case is the same as that in the fourth embodiment.

  The present invention relates to a turbo chiller used for indoor cooling and the like and a hot gas bypass method thereof, and is applied to a case where a multistage compressor including a plurality of compressors is used as a compressor of the turbo chiller. It is useful.

1 is a system configuration diagram of a turbo refrigerator according to Embodiment 1 of the present invention. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power. It is a system block diagram of the turbo refrigerator based on Embodiment 2 of this invention. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power. It is a system configuration | structure figure of the turbo refrigerator based on Example 3 of this invention. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power. It is a system configuration | structure figure of the turbo refrigerator based on Embodiment 4 of this invention. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power. It is a system block diagram of the turbo refrigerator based on Embodiment 5 of this invention. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power. It is a system block diagram of the conventional turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor gas refrigerant | coolant flow volume. It is explanatory drawing which shows the relationship between the refrigerating functional force and hot gas bypass valve opening degree in the said turbo refrigerator. It is explanatory drawing which shows the relationship between the refrigerating functional force in the said turbo refrigerator, and compressor required power.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Evaporator 22 1st stage compressor 23 2nd stage compressor 24 Multistage compressor 25 Condenser 26 High stage expansion valve 27 Low stage expansion valve 28 Intermediate cooler 29 Orifice 30, 31 Refrigerant flow path 32 Heat transfer tube group 33 Refrigerant Flow path 34 Refrigerant liquid level 35 Bypass refrigerant flow path 36 Heat transfer tube group 37 Refrigerant liquid level 38 Cold water flow path 39 Pump 40 Fan coil unit 41 Refrigerant flow path 42, 43 Bypass refrigerant flow path 44 First stage hot gas bypass valve 45 Second stage hot gas bypass valve 46 Electric motor 47 Rotating shaft 48 Gear 49 Rotating shaft 50 Gear 52, 54 Flow meter 55 Controller 56, 57 Container 61 Second stage hot gas bypass valve 71 Hot gas bypass three-way valve 72 Inlet 73 74 Outlet 75 Bypass refrigerant flow path 81 Second stage hot gas bypass valve 91 First second stage Tsu preparative gas bypass valve 92 second second-stage hot gas bypass valve 93, 94 thermometer 95 Flowmeter

Claims (18)

A multi-stage compressor that sequentially compresses the gas refrigerant evaporated in the evaporator with a multi-stage compressor, a condenser that condenses the gas refrigerant compressed by the multi-stage compressor, and a liquid refrigerant that is condensed in the condenser is expanded. In a turbo refrigerator having an expansion valve and the evaporator for evaporating liquid refrigerant expanded by the expansion valve,
A turbo comprising hot gas bypass means capable of bypassing the evaporator and allowing a part of gas refrigerant discharged from the multistage compressor to flow into each of the multiple stages of compressors refrigerator. In the turbo refrigerator according to claim 1,
The hot gas bypass means includes a discharge side of the last stage compressor and an intake side of the plurality of stage compressors through the plurality of hot gas bypass valves whose opening degree can be adjusted. A turbo chiller characterized by having a configuration in which each of the above is communicated. In the turbo refrigerator according to claim 1,
The expansion valve comprises a high-stage expansion valve and a low-stage expansion valve, and has a gas-liquid separator that is installed between the high-stage expansion valve and the low-stage expansion valve to separate the refrigerant from gas and liquid,
The hot gas bypass means includes
When the multistage compressor is composed of a two-stage compressor, the discharge side of the latter-stage compressor of the two-stage compressor and the two-stage compressor via a hot gas bypass valve whose opening degree can be adjusted. The other side of the compressor, and the other side of the compressor, and the intake side of the latter compressor through the other hot gas bypass valve whose opening degree can be adjusted. Is a configuration that communicates with
When the multistage compressor is composed of three or more stages of compressors, the discharge side of the last stage compressor among the three or more stages of compressors via a hot gas bypass valve whose opening degree can be adjusted, The gas-liquid separator, which communicates with the intake side of the compressor at the foremost stage of the three or more stage compressors, and through other hot gas bypass valves that can be adjusted in opening degree, Of the three or more stages of compressors, the compressor is configured to communicate with each of the intake sides of the compressors other than the frontmost stage.
A turbo refrigerator characterized by that. In the turbo refrigerator according to claim 1,
The multi-stage compressor is composed of a two-stage compressor,
The hot gas bypass means has a hot gas bypass three-way valve whose opening degree can be adjusted, respectively, on the discharge side of the rear compressor of the two-stage compressor and on the intake side of the two-stage compressor. And a centrifugal chiller characterized by being configured to communicate with each other. In the turbo refrigerator according to claim 1,
The expansion valve comprises a high-stage expansion valve and a low-stage expansion valve, and has a gas-liquid separator that is installed between the high-stage expansion valve and the low-stage expansion valve and separates the refrigerant into gas and liquid, and When the multi-stage compressor is composed of a two-stage compressor, the multi-stage compressor has an orifice through which the gas refrigerant separated by the gas-liquid separator flows into the intake side of the latter-stage compressor of the two-stage compressor. When the multi-stage compressor is composed of three or more stages of compressors, the gas refrigerant separated by the gas-liquid separator is respectively supplied to the intake side of the compressor other than the first stage among the three or more stages of compressors. Having a plurality of inflow orifices;
The hot gas bypass means includes
When the multistage compressor is composed of a two-stage compressor, the discharge side of the latter-stage compressor of the two-stage compressor and the two-stage compressor via a hot gas bypass valve whose opening degree can be adjusted. The gas-liquid separator, and the latter stage through an ON / OFF hot gas bypass valve that communicates with the intake side of the former stage compressor of the compressor and is installed in parallel with the orifice. Is configured to communicate with the intake side of the compressor of
When the multistage compressor is composed of three or more stages of compressors, the discharge side of the last stage compressor among the three or more stages of compressors via a hot gas bypass valve whose opening degree can be adjusted, Via a plurality of ON / OFF type hot gas bypass valves that communicate with the intake side of the compressor at the foremost stage of the three or more stages of compressors and are installed in parallel with each of the plurality of orifices. The gas-liquid separator is configured to communicate with each of the intake sides of the compressors other than the front stage among the three or more stages of compressors.
A turbo refrigerator characterized by that. The turbo refrigerator according to claim 5,
A plurality of the ON / OFF hot gas bypass valves are installed in parallel to the orifice. In the turbo refrigerator according to claim 1,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the hot gas bypass means sequentially causes the gas refrigerant to flow in from the subsequent stage compressor that reaches the required minimum flow rate first. By ensuring the required minimum flow rate for each of the plurality of stages of compressors,
A turbo refrigerator having hot gas bypass control means. In the turbo refrigerator according to claim 2,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is judged that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the opening-adjustable hot gas bypass valve is sequentially opened, and the subsequent stage side compression that reaches the required minimum flow rate first. The required minimum flow rate is ensured for each of the plurality of stages of compressors by flowing gas refrigerant in order from the machine.
A turbo refrigerator having hot gas bypass control means. In the turbo refrigerator according to claim 3,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is judged that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the opening-adjustable hot gas bypass valve is sequentially opened, and the subsequent stage side compression that reaches the required minimum flow rate first. Ensuring the required minimum flow rate for each of the multiple stages of compressors by flowing gas refrigerant in order from the machine,
A turbo refrigerator having hot gas bypass control means. The turbo refrigerator according to claim 4,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the compressor in the stage has been reached, the outlet of the hot gas bypass three-way valve whose opening degree can be adjusted is sequentially opened, and the required minimum flow rate is reached first. Ensuring the necessary minimum flow rate for each of the multiple-stage compressors by flowing gas refrigerant in order from the rear-stage compressor;
A turbo refrigerator having hot gas bypass control means. The turbo refrigerator according to claim 5,
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the ON / OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening are sequentially opened, Securing the necessary minimum flow rate for each of the plurality of stages of compressors by allowing the gas refrigerant to flow in order from the compressor on the rear stage that reaches the required minimum flow rate first.
A turbo refrigerator having hot gas bypass control means. The turbo refrigerator according to claim 6, wherein
The minimum required flow rate for avoiding surging of the multiple-stage compressor is set to a smaller value as the front-stage compressor,
Every time it is judged that the gas refrigerant flow rate of the compressors of the plurality of stages has decreased and the measured value of the gas refrigerant flow rate has reached the necessary minimum flow rate, or the calculated refrigeration functional force is reduced, the plural Each time it is determined that each predetermined value corresponding to the required minimum flow rate of the stage compressor has been reached, the ON / OFF-type hot gas bypass valve and the hot gas bypass valve with adjustable opening are sequentially opened, The required minimum flow rate is ensured for each of the multiple-stage compressors by flowing gas refrigerant in order from the subsequent-stage compressor that reaches the required minimum flow rate first.
A turbo refrigerator having hot gas bypass control means. A hot gas bypass method for a turbo refrigerator according to claim 1,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass means sequentially introduces the gas refrigerant from the rear-stage compressor that reaches the required minimum flow rate first, and then compresses the multi-stage compressor. A hot gas bypass method for a turbo chiller, wherein the required minimum flow rate is ensured for each unit. A hot gas bypass method for a turbo refrigerator according to claim 2,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass valve whose opening degree can be adjusted is sequentially opened in order from the rear-stage compressor that reaches the required minimum flow rate first. A hot gas bypass method for a turbo chiller, wherein the required minimum flow rate is ensured for each of the plurality of stages of compressors. A hot gas bypass method for a turbo refrigerator according to claim 3,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
When the gas refrigerant flow rate of the multi-stage compressor is decreased, the hot gas bypass valve whose opening degree can be adjusted is sequentially opened in order from the rear-stage compressor that reaches the required minimum flow rate first. A hot gas bypass method for a turbo chiller, wherein the required minimum flow rate is ensured for each of the plurality of stages of compressors. A hot gas bypass method for a turbo refrigerator according to claim 4,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
By sequentially opening the outlet of the hot gas bypass three-way valve whose opening degree can be adjusted in order from the downstream compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. A hot gas bypass method for a turbo refrigerator, wherein a gas refrigerant is introduced to secure the necessary minimum flow rate for each of the plurality of stages of compressors. A hot gas bypass method for a turbo refrigerator according to claim 5,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
The ON / OFF-type hot gas bypass valve and the opening-adjustable hot gas in order from the rear-stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. A hot gas bypass method for a turbo chiller, wherein a gas refrigerant is introduced by sequentially opening a bypass valve to ensure the necessary minimum flow rate for each of the plurality of stages of compressors. The hot gas bypass method for a turbo refrigerator according to claim 6,
The minimum required flow rate for avoiding surging of the multi-stage compressor is a smaller value as the front stage compressor,
The ON / OFF-type hot gas bypass valve and the opening-adjustable hot gas in order from the rear-stage compressor that reaches the required minimum flow rate first when the gas refrigerant flow rate of the multiple-stage compressors decreases. A hot gas bypass method for a turbo chiller, wherein a gas refrigerant is introduced by sequentially opening a bypass valve to ensure the necessary minimum flow rate for each of the plurality of stages of compressors.

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