JP2012063120A - Compression refrigerating machine equipped with economizer, and economizer unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compression refrigerating machine easily improved in a coefficient of performance, and an economizer unit which can be mounted to an existing compression refrigerating machine and improve the coefficient of performance.SOLUTION: The compression refrigerating machine includes: an evaporator 40 evaporating refrigerant liquid into refrigerant gas; a main compressor 10 sucking in and compressing the refrigerant gas; a condenser 30 drawing heat from the refrigerant gas compressed by the main compressor 10 to condense the same into the refrigerant liquid; an economizer 20 evaporating the refrigerant liquid condensed by the condenser 30 into the refrigerant gas at an economizer pressure Pm intermediate between the evaporating pressure Pe of the evaporator 40 and the condensing pressure Pc of the condenser 30, cooling the refrigerant liquid with the evaporation heat during the evaporation, and sending the cooled refrigerant liquid to the evaporator 30; and an auxiliary compressor 70 sucking in, compressing the refrigerant gas evaporated in the economizer 20 and sending the same to the condenser 30.

Description

  The present invention relates to a compression refrigerator and an economizer unit. In particular, the present invention relates to a compression refrigerator having an improved coefficient of performance and an economizer unit that can be installed in an existing compression refrigerator to improve the coefficient of performance.

  As shown in the flow sheet of FIG. 8, conventionally, a compression refrigerator having a two-stage compressor 1 uses an economizer 2 to meet the increasing social demand for energy saving. That is, the expansion valve 5 and the economizer 2 are installed on the downstream side of the piping for returning the refrigerant liquid from the condenser 3 to the evaporator 4, and the refrigerant liquid is returned to the evaporator 4 via the expansion valve 6. In the economizer 2, the refrigerant liquid is flushed (partially evaporated), and the evaporated refrigerant gas is sent between the low-pressure side compressor 1 a and the high-pressure side compressor 1 b of the two-stage compressor 1. The sent refrigerant gas is sucked into the high-pressure side compressor 1b together with the gas evaporated by the evaporator 4 and compressed to the intermediate pressure by the low-pressure side compressor 1a, and is discharged to the condenser.

  On the other hand, the refrigerant liquid cooled to a temperature corresponding to the intermediate pressure by the flash is supplied from the economizer 2 to the evaporator. Therefore, the refrigerant liquid having a high refrigeration capacity per unit weight can be supplied to the evaporator 4, and the flushed refrigerant gas only needs to be compressed by the high-pressure compressor 1b. (See, for example, Patent Document 1).

  A conventional economizer cycle will be described with reference to the Mollier diagram of FIG. The condensation pressure is Pc, the evaporation pressure is Pe, and the economizer pressure (intermediate pressure) is Pm. The intersection of Pc and the saturated liquid line is 11; the intersection of Pm and the saturated liquid line is 12; and the intersection of Pe and the saturated vapor line is 14. The enthalpy of point 11 is i11, the enthalpy of point 12 is i12, and the enthalpy of point 14 is i14. In the cycle without the economizer, the refrigerating capacity per unit weight is (i14-i11), whereas in the economizer cycle, the refrigerating capacity per unit weight is (i14-i12). Therefore, the coefficient of performance is improved by 10 to 20%.

Japanese Patent Laid-Open No. 11-337199 (FIGS. 1, 2, and 3)

  However, it is not possible to install an economizer in a single-stage compression type refrigerator. Further, even with a two-stage or more compression type refrigerator, it is difficult to modify the existing compressor itself so that refrigerant gas from the economizer can be sucked. Moreover, even if it updates, the difficulty of construction by carrying in and installing the member for an update can also exceed the effort which newly installs a refrigerator main body. In addition, the refrigerator itself has a long service life, and it is difficult to find the cost merit when considering the cost-effectiveness with and without renewal, and there are many cases where renewal cannot be made.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a compression refrigeration machine having an improved coefficient of performance and an economizer unit that can be mounted on an existing compression refrigeration machine to improve the coefficient of performance.

  In order to solve the above-described problem, a compression refrigerator 101 according to a first aspect of the present invention includes an evaporator 40 that evaporates a refrigerant liquid into a refrigerant gas, for example, as shown in FIG. A main compressor 10 that sucks and compresses the refrigerant; a condenser 30 that takes heat from the refrigerant gas compressed by the main compressor 10 and condenses it into a refrigerant liquid; an evaporation pressure Pe of the evaporator 40 and the condenser 30 The refrigerant liquid condensed in the condenser 30 is evaporated to a refrigerant gas at an economizer pressure Pm intermediate to the condensation pressure Pc, and the refrigerant liquid is cooled by the heat of vaporization during the evaporation, and the cooled refrigerant liquid is evaporated. An economizer 20 that is sent to the condenser 30; and a sub-compressor 70 that sucks and compresses the refrigerant gas evaporated by the economizer 20 and sends it to the condenser 30.

  If comprised like this aspect, since the subcompressor is provided, the refrigerant gas evaporated by the economizer can be compressed and sent to the condenser without going through the main compressor.

  The compression refrigerator 101 according to the second aspect of the present invention is the compression refrigerator according to the first aspect. For example, as shown in FIG. 1, the economizer pressure Pm is calculated from the operating state of the refrigerator 101. And a control device 75 for controlling the sub-compressor so as to achieve the target value.

  If comprised like this aspect, since a control apparatus is provided, an economizer pressure can be controlled to target value.

  In order to solve the above-described problem, an economizer unit 201 according to a third aspect of the present invention includes an evaporator 40 that evaporates a refrigerant liquid into a refrigerant gas and sucks the refrigerant gas, for example, as shown in FIG. An economizer unit 201 attached to a refrigerator 101 having a compressor 10 to be compressed and a condenser 30 that cools and condenses the refrigerant gas compressed by the compressor 10 into a refrigerant liquid; The refrigerant liquid condensed in the condenser 30 is evaporated into a refrigerant gas at an intermediate economizer pressure Pm between the evaporation pressure Pe and the condensation pressure Pc of the condenser 30, and the refrigerant liquid is cooled by the heat of vaporization during the evaporation. An economizer 20 that sends the cooled refrigerant liquid to the evaporator 40; a variable speed sub-compressor 70 that sucks and compresses the refrigerant gas evaporated by the economizer 20 and sends it to the condenser 30; and a sub-compressor 7 A control device 75 for controlling the suction pressure of the sub-compressor 70 to an economizer pressure Pm intermediate between the evaporation pressure Pe of the evaporator 40 and the condensation pressure Pc of the condenser 30 by adjusting the rotational speed of the economizer 20; Is a refrigerant liquid inlet 201-1 for receiving the refrigerant liquid condensed in the condenser 30, a refrigerant liquid outlet 201-2 for sending the refrigerant liquid cooled by the heat of vaporization to the evaporator 40, and evaporation at an economizer pressure Pm. The refrigerant gas outlet 201-3 for sending out the refrigerant gas to the condenser 30 is provided.

  With this configuration, the refrigerant liquid inlet, the refrigerant liquid outlet for sending the refrigerant liquid cooled by the heat of vaporization to the evaporator, and the refrigerant gas feed for sending the refrigerant gas evaporated at the economizer pressure Pm to the condenser are provided. Since it has an outlet, an economizer can be additionally installed in the existing refrigerator, and the coefficient of performance of the existing refrigerator can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the economizer unit which can be mounted in the compression refrigerator which improved the coefficient of performance easily, and the existing compression refrigerator, and can improve a coefficient of performance.

It is a notional flow sheet which shows the composition of the compression refrigerating machine concerning a first embodiment of the present invention. It is a conceptual flow sheet which shows the structure of the compression type refrigerator concerning 2nd embodiment of this invention. It is a Mollier diagram of the compression type refrigerator concerning the 1st and 2nd embodiment of the present invention. It is a conceptual flow sheet which shows the structure of the compression type refrigerator concerning 3rd embodiment of this invention. It is a Mollier diagram of a compression type refrigerator concerning a third embodiment of the present invention. It is a notional flow sheet which shows the composition of the compression refrigerating machine concerning a 4th embodiment of the present invention. It is a Mollier diagram of a compression type refrigerator concerning a 4th embodiment of the present invention. It is a conceptual flow sheet which shows the structure of the conventional compression refrigerator. It is a Mollier diagram of a conventional compression refrigerator.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same or similar reference numerals, and redundant description is omitted.

  With reference to the conceptual flow sheet of FIG. 1, the compression refrigerator 101 which is 1st Embodiment of this invention is demonstrated. The compression type refrigerator 101 sucks heat from, for example, a screw compressor 10 as a main compressor that sucks and compresses refrigerant gas and the refrigerant gas compressed by the screw compressor 10 with cooling water of about 32 ° C., for example. A condenser 30 for condensing into a refrigerant liquid is provided. The refrigerant liquid from the condenser 30 is decompressed and sent to the evaporator 40. An economizer 20 is inserted into the refrigerant liquid flow path from the condenser 30 to the evaporator 40. An expansion mechanism 50 is disposed in the refrigerant liquid flow path between the condenser 30 and the economizer 20, and an expansion mechanism 60 is disposed in the refrigerant liquid flow path between the economizer 20 and the evaporator 40.

  In the evaporator 40, the refrigerant liquid supplied via the economizer is evaporated, and the cold water as the medium to be cooled is cooled to 5 ° C., for example.

  The economizer 20 is configured as a flash tank in which the refrigerant liquid from the condenser 30 is flashed, that is, partially evaporated. In the economizer 20, the entire refrigerant liquid from the condenser 30 is flushed at the economizer pressure Pm. The compression refrigerator 101 includes a scroll compressor 70 as a sub-compressor that sucks and compresses partially evaporated refrigerant gas. The scroll compressor 70 discharges the compressed refrigerant gas to the condenser 30. The refrigerant gas is cooled by the condenser 30 and condensed together with the gas compressed by the screw compressor 10.

  In the economizer 20, the refrigerant liquid is flushed at an economizer pressure Pm that is intermediate between the evaporation pressure Pe of the evaporator 40 and the condensation pressure Pc of the condenser 30. A part of the refrigerant liquid is evaporated by the flash to become a refrigerant gas, and the remaining refrigerant liquid is cooled to a saturation temperature corresponding to the economizer pressure Pm by the heat of vaporization. The cooled refrigerant liquid is decompressed by the expansion mechanism 60 and supplied to the evaporator 40.

  In the first embodiment, since the refrigerant liquid cooled by the economizer is sent to the evaporator 40, it is a so-called open type. The closed economizer is configured as a heat exchanger. The closed type will be described later in detail as a fourth embodiment.

  The compression refrigerator 101 includes a discharge pressure detector 72 on the refrigerant gas discharge side of the scroll compressor 70, a suction pressure detector 73 on the suction side, and an evaporation pressure detector on the downstream side of the expansion mechanism 60. 74. Furthermore, an inverter 71 is provided for supplying electric power (not shown) that drives the scroll compressor 70 to frequency-converted electric power. Each signal representing the pressure detected by the discharge pressure detector 72, the suction pressure detector 73, and the evaporation pressure detector 74 is transmitted to the control device 75. The control device 75 includes a target value calculator 75-1.

  The discharge pressure detector 72 may be seen as detecting the condensation pressure Pc of the condenser 30, and the evaporation pressure detector 74 may be seen as detecting the evaporation pressure Pe of the evaporator 40. When the pressure detector is provided at such a position, unlike the case where the pressure detector is provided in each of the condenser 30 and the evaporator 40, there is an advantage that the pressure detector can be integrated as an economizer unit described later. . Of course, the suction pressure detector 73 detects the economizer pressure Pm.

  The inverter 71 adjusts the rotation speed of the scroll compressor 70 so that the economizer pressure Pm becomes an intermediate pressure between the evaporation pressure Pe and the condensation pressure Pc. If the economizer pressure Pm is higher than the intermediate pressure (target value), the rotational speed is increased, and if it is low, the rotational speed is decreased. The target value calculator 75-1 calculates a target value of the intermediate pressure Pm from the evaporation pressure Pe and the condensation pressure Pc. The control device 75 sends a control signal to the inverter 71 and sends the control signal to the inverter 71 so as to adjust the rotation speed of the sub compressor so that the economizer pressure Pm becomes the target value calculated as described above. Send.

  In the above description, the main compressor is described as a screw compressor, and the sub compressor is described as a scroll compressor. With such a combination, the capacity balance is good. That is, in the case of an air-conditioning refrigerator, in this embodiment, the sub compressor sucks refrigerant gas having a mass flow rate of about 10% of that of the main compressor, so this combination is suitable. However, in a refrigerator having a relatively small capacity, one or both of the main compressor and the sub compressor may be a reciprocating compressor. When the refrigeration capacity is relatively large, the main compressor may be a turbo compressor, and the sub compressor may be a screw compressor or a reciprocating compressor. Such a combination is a balanced combination. The same applies to the following embodiments.

  Although the expansion mechanisms 50 and 60 are illustrated as orifices, they may be capillary tubes. These are simple in structure and are suitable for small refrigerators. Further, the expansion mechanism 50 may be an expansion mechanism that creates a reservoir of the refrigerant liquid condensed by the condenser 30 and whose opening is adjusted so that the liquid level of the reservoir is constant. For example, a float valve (not shown). When the liquid level in the reservoir rises, the float rises and the liquid opening opens. The same applies to the expansion mechanism 60. This is a mechanism that detects the liquid level of the economizer 20 and keeps it constant. For example, a float valve. The liquid level control system is suitable for a relatively large refrigerator because the mechanical structure is somewhat more complicated than that of the orifice, but the liquid is sealed with the refrigerant liquid, so that the refrigerant gas can be prevented from being blown through.

  Further, a portion surrounded by a broken-line frame in the figure, the economizer 20, the upstream expansion mechanism 50, the downstream expansion mechanism 60, the sub compressor 70, the inverter 71, the pressure detectors 72, 73, 74, and these are connected. The unit including the piping and signal wiring to be installed may be mounted on one base plate (not shown) as the economizer unit 201 and configured as a unit for remodeling an existing refrigerator. At this time, the economizer unit 201 sends a refrigerant gas to the condenser 30 between the refrigerant liquid inlet 201-1 between the condenser 30 and the expansion mechanism 50, and between the sub compressor 70 and the condenser 30. Between the outlet 201-3 and the expansion mechanism 60 and the evaporator 40, there is a refrigerant liquid outlet 201-2 for sending the refrigerant liquid to the evaporator 40. At each of these ports, a pipe connection is formed so that the pipe can be connected to an existing machine. The pipe connection may be formed as an open end of the pipe or may be provided with a flange so that it can be connected to the cut pipe of the existing machine by welding. In the case of a flange, the economizer unit 201 can be easily connected to the existing machine by cutting the existing pipe and attaching a companion flange to the end of the pipe.

  As described above, the economizer unit 201 according to the present embodiment includes the economizer 20 pressure detector and the front and rear pressure detectors, and adjusts the rotational speed of the sub-compressor 70 based on the detected value to control the economizer 20 pressure. The control device 75 is provided. Further, instead of the pressure of the economizer itself, a detector for the temperature of the economizer itself and the temperature before and after it may be provided, and the rotational speed of the sub compressor may be adjusted by the detected temperature value.

  With reference to the conceptual flow sheet of FIG. 2, the compression refrigerator 102 which is 2nd Embodiment of this invention is demonstrated. The compression refrigerator 102 of the present embodiment is a modification of the compression refrigerator 101, and the economizer unit 202 is different. Different parts will be described. The economizer unit 202 includes the economizer 20, the expansion mechanism 50, the expansion mechanism 60, the sub compressor 70, and the inverter 71 as in the first embodiment.

  The present embodiment does not include the pressure detectors 72, 73, and 74, but includes a liquid level detector 21 that detects the refrigerant liquid level of the economizer 20 instead. The detection value of the liquid level detector 21 is sent to the inverter 71, and the liquid level of the economizer 20 is controlled by adjusting the rotational speed of the sub compressor 70 by the inverter 71. For this control, a control device (not shown) may be provided, and a detection signal of the liquid level detector 21 may be input thereto, thereby adjusting the rotational speed of the sub compressor 70.

  As in the first embodiment, the portion surrounded by a broken line in the figure, the economizer 20, the upstream expansion mechanism 50, the downstream expansion mechanism 60, the sub compressor 70, the inverter 71, and the liquid level detector 21 and a unit provided with piping and signal wiring for connecting them may be mounted on one base plate (not shown) as an economizer unit 202 and configured as a unit for remodeling an existing refrigerator. . The piping relationship of the economizer unit 202 is the same as that of the first embodiment.

  With reference to the Mollier diagram (Pi diagram (pressure-enthalpy diagram)) in FIG. 3, the operation of the compression refrigerators of the first and second embodiments will be described. In the figure, 10 is a main compressor, 70 is a sub-compressor, 20 is an economizer, 30 is a condenser, 40 is an evaporator, 50 and 60 are expansion mechanisms, which are the same as those in FIGS. Point 11 is the intersection of the condensation pressure Pc and the saturated liquid line, the state of the refrigerant liquid condensed in the condenser 30 (assuming that it is not supercooled), and point 12 is the intersection of the economizer pressure Pm and the saturated liquid line. The state of the refrigerant liquid cooled by the refrigerant flashed and evaporated by the economizer, the point 14 is the intersection of the evaporation pressure Pe and the saturated vapor line, the state of the refrigerant gas evaporated by the evaporator 40, and the point 15 is the economizer The point of intersection of the pressure Pm and the saturated vapor line, the state of the refrigerant gas flashed and evaporated by the economizer, the point 16 is the intersection of the condensation pressure Pc and the saturated vapor line, cooled by the condenser 30 and deprived of sensible heat This is a point indicating the state of the refrigerant gas that is about to be condensed.

  i11 is an enthalpy corresponding to the point 11, i12 is an enthalpy corresponding to the point 12, i14 is an enthalpy corresponding to the point 14, and i15 is an enthalpy corresponding to the point 15.

  In the refrigerant liquid in the state of point 11, the entire amount of the refrigerant liquid condensed by the condenser 30 is expanded via the expansion mechanism 50 and flows into the economizer 20. Here, the (i11-i12) / (i15-i12) portion of the refrigerant liquid that has flowed in evaporates to a state of point 15, and the remaining (i15-i11) / (i15-i12) refrigerant liquid is evaporated by the heat of vaporization. Cooled to point 12.

  The refrigerant liquid in the state of point 12 expands through the expansion mechanism 60 and flows into the evaporator 40. The refrigerant liquid is evaporated by the evaporator 40 to become a refrigerant gas at point 14. Without the economizer 20, the enthalpy of the refrigerant liquid flowing into the evaporator 40 is i11, and the enthalpy difference of the refrigerant liquid that exhibits the refrigerating capacity is (i14-i11). Therefore, the refrigerant liquid cooled by the economizer 20 Since the enthalpy is i12, the enthalpy difference of the refrigerant liquid that exhibits the refrigerating capacity is (i14-i12), and in the case of the refrigerator for air conditioning, the refrigerating capacity per unit weight can be increased by 15 to 25%. .

  The refrigerant gas in the state of point 14 is compressed by the main compressor 10 and sent to the condenser 30. Then, the heat of the sensible heat is taken away by the cooling water and cooled to become the refrigerant gas in the state of point 16, and further the heat of the latent heat is taken away by the cooling water to become the refrigerant liquid in the state of point 11.

  The refrigerant gas in the state of point 15 is compressed by the sub compressor 70 and sent to the condenser 30. The refrigerant gas compressed by the main compressor 10 is mixed in the condenser 30. Then, together with the refrigerant gas compressed by the main compressor 10, the heat of the sensible heat is taken away by the cooling water and cooled to become the refrigerant gas in the state of point 16, and the heat of the latent heat is taken away by the cooling water. The refrigerant liquid is in the state of point 11.

  In this cycle, as described above, since the refrigeration capacity per unit weight of the refrigerant liquid in the evaporator 40 is large, if the total refrigeration capacity is the same, the refrigerant to be compressed by the main compressor 10 Therefore, the power of the main compressor 10 is reduced. Instead, the power of the sub compressor 70 increases, but the head to be generated by the sub compressor 70 is smaller than that of the main compressor 10. Therefore, even when the increase in power is taken into account, the COP (coefficient of performance) of the compression refrigerators 101 and 102 is improved by about 10% even in the case of the air conditioning refrigerator as compared with the case without the economizer 20. .

  As described above, according to the present embodiment, since the sub-compressor 70 is provided, an economizer cycle can be formed even if the main compressor is a single-stage compressor. Further, the economizer unit 201 or the economizer unit 202 can be added to an existing compression refrigerator. In this case, the COP of the existing compression refrigerator can be easily improved without modifying the main compressor.

  It has been described that the economizer pressure Pm is an intermediate pressure between the evaporation pressure Pe of the evaporator 40 and the condensation pressure Pc of the condenser 30. In short, the temperature or pressure of the refrigerant liquid at the economizer outlet is the operating state of the refrigerator. It is better to control so as to be optimal. The pressure and the like are optimal when the specific enthalpy of the outlet refrigerant liquid of the economizer 20 is approximately halfway between the refrigerant liquid of the condenser 30 and the refrigerant liquid of the evaporator 40. Approximately, the temperature of the refrigerant liquid is controlled to be an intermediate temperature between the saturation temperatures of the evaporator 40 and the condenser 30, or the evaporation pressure Pm of the refrigerant liquid in the economizer 20 is The geometric average of the pressure of the condenser 30 may be set. Control of the sub-compressor 70 may be based on rotational speed control, or may be a slide valve when a screw-type compressor is used as the sub-compressor 70. The same applies to the following embodiments. At this time, the sub-compressor has a variable valve timing including a slide valve of the screw compressor, and the sub-compressor is preferably controlled by the variable valve timing.

  The above control may be performed depending on the refrigerant temperature. In this case, the economizer pressure Pm is indirectly controlled to an intermediate pressure between the condensation pressure Pc and the evaporation pressure Pe. Further, the evaporation pressure Pe, the evaporation temperature Te, and the like are generally constant values during stable operation, and may be determined by constant assumption values without actually measuring. If the inverter 71 is used, the economizer pressure Pm can be controlled to an optimum value while operating the sub compressor 70 with high efficiency, but the sub compressor 70 may be operated at a constant speed. In the case of constant speed operation, the economizer pressure Pm does not always become an optimum value, but it can be set to a substantially intermediate pressure with a relatively simple configuration and COP can be improved.

  With reference to the conceptual flow sheet of FIG. 4, the compression refrigerator 103 which is 3rd embodiment of this invention is demonstrated. The compression refrigerator 103 according to the present embodiment includes a supercooler 90 in addition to the economizer 20 according to the first embodiment. At this time, refrigerant vapor may be mixed in the refrigerant liquid exiting the condenser 30. Therefore, a buffer as a gas-liquid separator that temporarily stores the refrigerant exiting the condenser 30 and separates the gas and liquid. A tank 31 may be provided. Here, after gas-liquid separation, it is led to the supercooler 90. A control valve 50a for monitoring the liquid level of the buffer tank 31 with the liquid level detector 32 and controlling the refrigerant flow rate may be used in place of the orifice 50 of the first or second embodiment. A liquid level signal from the liquid level detector 32 is sent to the control valve 50a. A control device (not shown) may be provided, whereby a control signal may be sent to the control valve 50a to control the refrigerant flow rate.

  The subcooler 90 is configured as a heat exchanger that exchanges heat between the refrigerant liquid and the cooling water. Typically, a shell-and-tube heat exchanger is used in the same manner as the condenser 30 and the evaporator 40, cooling water is supplied to the tube side, and refrigerant liquid is supplied to the shell side. The cooling water may flow in parallel with the condenser 30. A flow rate adjustment valve 80 (shown in the cooling water outlet piping) may be provided in the cooling water inlet piping or outlet piping to the supercooler 90. By this adjustment, the degree of supercooling can be adjusted.

  Note that the refrigerant liquid from the condenser 30 may flow directly to the subcooler 90 without providing the buffer tank 31. At this time, the capacity of the refrigerant storage section at the bottom of the condenser 30 is increased so that the refrigerant liquid is stored without containing gas.

  Here, the subcompressor 70 is connected to the economizer 20 as in the first or second embodiment, and the rotation speed is adjusted by the inverter 71 in the same manner. The difference from the first or second embodiment is that an evaporating temperature detector 61 that detects the evaporating temperature Te is provided downstream of the expansion mechanism 60, and an economizer refrigerant liquid temperature detecting that detects the economizer temperature Tm in the economizer 20. The temperature sensor 91 for detecting the supercooled refrigerant liquid temperature Tc ′ is provided in the refrigerant liquid path between the supercooler 90 and the control valve 50a. The temperature signals from these temperature detectors are sent to the inverter 71, and by adjusting the rotational speed of the sub compressor 70, the economizer temperature Tm is an intermediate temperature between the evaporation temperature Te and the supercooled refrigerant liquid temperature Tc ′. To control. Here, the flow rate of the sub-compressor 70 may be adjusted with the arithmetic average temperature of the supercooled refrigerant liquid temperature Tc ′ and the evaporation temperature Te as a target. Although a control device is not shown in FIG. 4, a control device 75 similar to that of the first embodiment is provided, and the calculation is performed by the target value calculator 75-1 to adjust the flow rate of the sub compressor. Good.

  As described above, this also indirectly controls the economizer pressure Pm to an intermediate pressure between the condensation pressure Pc and the evaporation pressure Pe. Of course, as with the first embodiment, control by pressure may be performed.

  Also in this example, these devices can be configured as a set of units. In this case, the outlet pipe of the sub-compressor 70 and the pressure equalizing pipe of the buffer tank 31 in front of the supercooler 90 can be shared, and the engagement with the refrigerator can be minimized.

  With reference to the Mollier diagram (Pi diagram (pressure-enthalpy diagram)) in FIG. 5, the operation of the compression refrigerator 103 of the third embodiment will be described. The difference from the first or second embodiment is that there is supercooling by the supercooler 90. That is, the refrigerant liquid in the state of point 11 enters the left side, that is, the liquid region in the Mollier diagram with respect to the saturated liquid line corresponding to the condensation pressure Pc that is supercooled by the cooling water in the supercooler 90, and is in the state of point 11 ′. It becomes. The enthalpy i11 'at this point is closer to the cooling side than the enthalpy i11 at point 11. Therefore, the amount of the refrigerant gas partially evaporated by the economizer 20 is (i11′-i12) / (i15-i12) of the flowing refrigerant liquid, and (i11−) in the case of the first or second embodiment. It becomes smaller than i12) / (i15-i12). Therefore, the required power of the sub compressor 70 is reduced.

  With reference to the conceptual flow sheet of FIG. 6, the compression refrigerator 104 which is 4th Embodiment of this invention is demonstrated. The compression refrigerator 104 of the present embodiment includes a so-called closed economizer. The economizer unit 204 is different from the previous embodiment. Different parts will be described. The closed economizer is configured as a heat exchanger, and a part of the refrigerant liquid from the condenser 30 and the remaining refrigerant liquid are guided to the cooling side and the cooled side of the heat exchanger, and the part of the refrigerant The liquid is evaporated at an economizer pressure to lower the temperature, and the remaining refrigerant liquid is supercooled by the heat of vaporization caused by the evaporation.

  The point provided with the supercooler by cooling water is the same as that of 3rd embodiment. However, in the present embodiment, the supercooler 90 a is incorporated in the condenser 30. That is, there is a refrigerant liquid pool at the bottom of the condenser 30, and a tube bundle is incorporated therein (not shown). Because it is a built-in condenser, it is difficult to configure as an economizer unit. Since the operation is the same as that of the third embodiment, further explanation is omitted. In addition, you may provide the separate supercooling 90 similar to 3rd Embodiment instead of the supercooling 90a. In that case, since the supercooler 90 can also be configured as an economizer unit, it can be easily dealt with when the existing refrigerator is not equipped with a supercooler.

  In the refrigerator 104 of the present embodiment, the economizer 20a is configured as a shell-and-tube heat exchanger, and the refrigerant liquid from the condenser 30 flows into the tube side via the supercooler 90a. Here, the further subcooled refrigerant liquid expands through the expansion mechanism 60 and flows into the evaporator 40.

  On the other hand, a temperature expansion valve 50b is disposed in a path between the shell side of the economizer 20a and the condenser 30 (in the present embodiment, between the shell side and the subcooler 90a). The refrigerant decompressed and expanded here partially evaporates and flows into the economizer 20a in a mixed state of liquid and gas. Specifically, it flows into the shell side of the economizer 20a. Because of the mixed state of gas and liquid, it is preferable to flow the refrigerant that has passed through the expansion valve 50b to the shell side where the increased volume refrigerant can be easily processed.

  The refrigerant gas evaporated here is sucked into the sub compressor 70. As with the previous embodiment, the rotation speed of the sub compressor 70 is adjusted by the inverter 71. An evaporating temperature detector 61 for detecting the evaporating temperature Te is provided downstream of the expansion mechanism 60, and an evaporating gas detector for detecting the evaporating gas temperature Tm1 at the outlet of the evaporating refrigerant gas on the shell side of the economizer 20a, particularly the outlet pipe At the outlet of the supercooled refrigerant liquid of the economizer 20a, particularly at the outlet pipe, the refrigerant liquid temperature detector 22b for detecting the refrigerant liquid temperature Tm2 is provided between the supercooler 90a and the economizer 20a tube side. The refrigerant liquid path is provided with a temperature detector 91 for detecting the temperature Tc ′ of the refrigerant supercooled by the cooling water. The temperature signals from these temperature detectors are sent to the inverter 71, and by adjusting the rotational speed of the sub compressor 70, the refrigerant liquid temperature Tm2 is intermediate between the evaporation temperature Te and the supercooled refrigerant liquid temperature Tc ′. Control the temperature so that Although a control device is not shown in FIG. 6, the control device 75 is the same as that of the first embodiment, and the calculation is performed by the target value calculator 75-1 to obtain an intermediate temperature. It is better to adjust the flow rate of the sub compressor so that

  The temperature expansion valve 50b receives the temperature signal from the temperature detector 22a, and the flow rate of the refrigerant liquid is prevented so that the refrigerant liquid is not directly sucked into the sub compressor 70 so that the refrigerant gas temperature Tm1 has an appropriate degree of superheat. Adjust. In other words, the temperature expansion valve 50b is controlled so that the degree of superheat of the refrigerant gas at the outlet of the economizer 20a is constant. Alternatively, instead of the temperature detector 22a, a liquid level detector (not shown) that detects the liquid level of the liquid accumulated on the shell side of the economizer 20a is provided, and the liquid level is sufficient in the economizer 20a. The flow rate of the inflowing refrigerant liquid may be adjusted so that the liquid level is maintained at an appropriate level.

  With reference to the Mollier diagram of FIG. 7, the operation of the compression refrigerator 104 of the fourth embodiment will be described. The difference from the first to third embodiments is that the economizer 20a is a closed type, which is shown in the Mollier diagram.

  Point 11 is the state of the refrigerant liquid condensed by the condenser 30 as in the other embodiments. This refrigerant liquid is supercooled by the cooling water as in the refrigerator 103 of the third embodiment and reaches the point 11 '. Here, the flow on the shell side of the economizer 20a will be described first. The refrigerant liquid at this point 11 ′ is depressurized by the temperature expansion valve 50 b and reaches point 13. This is a point of an intermediate pressure Pm1 between the condensation pressure Pc and the evaporation pressure Pe, and the temperature is Tm1. Immediately after expansion by the temperature expansion valve 50b, the refrigerant gas and the refrigerant liquid are mixed. From this state, the refrigerant liquid flowing in the tube is cooled, and it evaporates to reach a point 15 that is the intersection of the pressure Pm1 and the saturated vapor line. Then, it is sucked into the sub compressor 70.

  Next, the flow on the tube side of the economizer 20a will be described. The refrigerant liquid at the point 11 ′ is cooled by the above-described refrigerant that evaporates on the shell side, and reaches a point 11 ″ in the liquid region in the state of Pc. This supercooled refrigerant liquid is expanded via the expansion mechanism 60. Then, this expansion process is an isenthalpy change, and this isoenthalpy line intersects the saturated liquid line at the point 12a, the pressure at the point 12a is Pm2, and the temperature is Tm2. Pm2 is slightly higher than pressure Pm1 and temperature Tm2 is slightly higher than temperature Tm1 Therefore, the refrigerant liquid flowing on the tube side exchanges heat with the refrigerant evaporated on the shell side, and is cooled.

  The economizer 20a of the present embodiment may be called a so-called one-stage expansion economizer that is a combination of a heat exchanger and an expansion valve. In this embodiment, a semi-hermetic screw compressor is used as the main compressor, and a hermetic general-purpose compressor is used as the sub-compressor. In the above description, the refrigerant liquid temperature Tm2 is controlled to be an intermediate temperature between the evaporation temperature Te and the supercooled refrigerant liquid temperature Tc ′. However, the refrigerant evaporation temperature on the shell side in the economizer 20a is controlled. The rotational speed of the sub-compressor 70 may be adjusted so that Tm1 is controlled to be an intermediate temperature between the evaporation temperature Te and the supercooled refrigerant liquid temperature Tc ′.

  If the supercooler 90a is provided, there is an advantage that the refrigeration effect per unit flow rate of the refrigerant can be enhanced. In that case, the apparatus can be simplified.

  Other operations are the same as those of the other embodiments already described. If comprised like this Embodiment, the separation of the gas-liquid in an economizer can be performed reliably.

  As described above, in the embodiment of the present invention, an economizer (intermediate cooler) is provided in the conventional simple cycle, and the refrigerant vapor generated from the economizer is returned to the condenser using the sub compressor and condensed. . If it does in this way, without changing a main compressor, the temperature of the refrigerant | coolant which flows in into an evaporator can be lowered | hung, refrigeration capacity can be increased, and efficiency can be improved further. At this time, power is required to drive the sub-compressor, but the power required by the sub-compressor is theoretically equivalent to the decrease in the power of the main compressor or the increase in the refrigeration output. Small and energy saving as a whole.

  In the present invention, the compression refrigerator is a concept including a compression heat pump. In the heat pump, the heat obtained from the condenser is output. The evaporator obtains heat for evaporating the refrigerant from the heat source fluid.

  The refrigerating machine of the present invention is utilized as a compression type refrigerator with improved coefficient of performance and an economizer unit that can be installed in an existing compression type refrigerator to improve the coefficient of performance.

DESCRIPTION OF SYMBOLS 10 Main compressor 11, 12, 13, 14, 15, 16, Point 20 on Mollier diagram 20 Economizer 20a Economizer 21 Liquid level detector 22, 22a, 22b Temperature detector 30 Condenser 31 Buffer tank 32 Liquid level detector 40 Evaporator 50, 50a, 60 Expansion mechanism 61 Temperature detector 70 Sub compressor 71 Inverter 72, 73, 74 Pressure detector 75 Control device 75-1 Target value calculator 80 Flow rate adjusting valve 90, 90a Subcooler 91 Temperature Detectors 101, 102, 103, 104 Compressive refrigerators 201, 202, 203, 204 Economizer unit 201-1 Refrigerant liquid inlet 201-2 Refrigerant liquid outlet 201-3 Refrigerant gas outlet Pc Condensing pressure Pe Evaporating pressure Pm Intermediate pressure Tc Condensing temperature Te Evaporating temperature Tm Economizer temperature Tm1 Refrigerant gas temperature Tm2 Refrigerant liquid temperature

Claims (3)

An evaporator that evaporates the refrigerant liquid into refrigerant gas;
A main compressor that sucks and compresses the refrigerant gas;
A condenser that takes heat from the refrigerant gas compressed by the main compressor and condenses it into a refrigerant liquid;
The refrigerant liquid condensed in the condenser is evaporated into a refrigerant gas with an economizer pressure intermediate between the evaporation pressure of the evaporator and the condensation pressure of the condenser, and the refrigerant liquid is cooled by the heat of vaporization during the evaporation. An economizer for sending the cooled refrigerant liquid to the evaporator;
A sub-compressor that sucks and compresses the refrigerant gas evaporated by the economizer and sends it to the condenser;
Compression refrigerator.   The compression refrigerator according to claim 1, further comprising a control device that controls the sub-compressor so that the economizer pressure becomes a target value calculated from an operating state of the refrigerator. An evaporator that evaporates the refrigerant liquid to produce a refrigerant gas, a compressor that sucks and compresses the refrigerant gas, and a condenser that cools and condenses the refrigerant gas compressed by the compressor to produce a refrigerant liquid. An economizer unit attached to a refrigerator having;
The refrigerant liquid condensed in the condenser is evaporated into a refrigerant gas with an economizer pressure intermediate between the evaporation pressure of the evaporator and the condensation pressure of the condenser, and the refrigerant liquid is cooled by the heat of vaporization during the evaporation. An economizer for sending the cooled refrigerant liquid to the evaporator;
A variable speed sub-compressor that sucks and compresses the refrigerant gas evaporated by the economizer and sends it to the condenser;
A control device that controls the suction pressure of the sub-compressor to an economizer pressure intermediate between the evaporation pressure of the evaporator and the condensation pressure of the condenser by adjusting the rotational speed of the sub-compressor;
The economizer is configured to receive a refrigerant liquid inlet for receiving the refrigerant liquid condensed by the condenser, a refrigerant liquid outlet for sending the refrigerant liquid cooled by the heat of vaporization to the evaporator, and a refrigerant gas evaporated at the economizer pressure. Having a refrigerant gas outlet for delivery to the condenser;
Economizer unit.

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