JP4167190B2 - Refrigeration system and operation method thereof - Google Patents

Description

  The present invention relates to a refrigeration system suitable for use in buildings and factory equipment.

Conventionally, there are refrigeration systems that have a plurality of refrigerators in parallel and obtain cold heat from these refrigerators to produce cold water. Cold water obtained by the refrigeration system is supplied to external loads such as air conditioners and fan coils installed in buildings and factory facilities.
In order to increase the efficiency of such a refrigeration system, there is one that controls the temperature difference of the cooling water for cooling the condenser of the refrigerator to be kept constant, as shown in Patent Document 1 below.
Moreover, as shown in the following Patent Document 2, there is one that controls the timing of the increase / decrease stage of each refrigerator in order to quickly stabilize the air conditioning control.

JP 2002-31376 (paragraphs [0070] to [0078] and FIGS. 6 to 7) JP 2000-18683 A (paragraph [0017], FIG. 4)

  However, when the condenser inlet temperature of the cooling water fluctuates due to fluctuations in the outside air temperature, the refrigerating capacity that the refrigerator can output is not fully utilized. For example, the condenser inlet temperature of the cooling water becomes lower than the design specification temperature due to a decrease in the outside air temperature, and the refrigerator may be able to output the refrigeration capacity from the rated load. However, normally, since the refrigerator is operated so as not to exceed the rated refrigeration capacity, the timing of increasing the stage of the refrigerator is performed on the condition that the rated load has been exceeded. In this case, the timing of the stage increase of the refrigerator is accelerated, and the refrigeration accompanying the increase in the power of auxiliary equipment such as the chilled water pump, cooling water pump, cooling tower, etc. accompanying the stage increase or the refrigeration capacity of the chiller per unit is reduced. The total energy consumption of the machine was increased.

  The present invention has been made in view of such circumstances, and provides a refrigeration system that operates with an appropriate number of operating units by utilizing the refrigeration capacity that the refrigerator can output to the maximum, and an operating method thereof. With the goal.

In order to solve the above problems, the refrigeration system of the present invention employs the following means.
That is, a refrigeration system according to the present invention includes a compressor that compresses a refrigerant, a condenser that condenses the compressed refrigerant, an expander that expands the condensed refrigerant, and evaporation that evaporates the expanded refrigerant to obtain cold heat. A chiller provided with a refrigerator, cooling means for supplying cooling water to the condenser, removing exhaust heat in the condenser, and obtaining cold water by the cold heat obtained by the refrigerator, In a refrigeration system comprising a chilled water supply means for supplying to an external load, the chilled water flow rate of the chilled water supply means for the rated load of the refrigerator at the rated exhaust heat temperature in the condenser is stored as a rated chilled water flow rate, wherein when the exhaust heat temperature during operation during operation than the rated exhaust heat temperature is low, the refrigerator further calculates the output possible and increases the refrigeration capacity beyond the rated cooling capacity, this increased cold Characterized in that exceeding the rated cold water flow rate based on the ability Te over-flow and a control means for controlling the coolant flow rate.

When the exhaust heat temperature during operation is different from the rated exhaust heat temperature, the refrigeration capacity that the refrigerator can output varies. For example, when the exhaust heat temperature during operation is lower than the rated exhaust heat temperature, the refrigerator can output more refrigeration capacity than the rated load. On the other hand, when the operating exhaust heat temperature is higher than the rated exhaust heat temperature, the refrigerator outputs only the refrigerating capacity below the rated load.
Necessary and sufficient cold heat can be taken out by changing the flow rate of the cold water in accordance with such a change in the refrigerating capacity.
As the “exhaust heat temperature”, the outside air temperature, the condenser inlet temperature or condenser outlet temperature of the cooling water supplied by the cooling means, the condensed refrigerant temperature in the condenser, the condensed refrigerant pressure representing the condensation temperature, and the like are used. In the absorption refrigerator, in addition to the exhaust heat temperature, the absorber inlet temperature or the absorber outlet temperature of the cooling water, the absorber pressure, and the like are used.
The “rated exhaust heat temperature” means a temperature that is a design specification of the refrigeration system. For example, 32 ° C. is set as the condenser inlet temperature of the cooling water.

  Moreover, according to the refrigeration system of the present invention, the refrigerator includes a centrifugal compressor that compresses the refrigerant.

A refrigerator equipped with a centrifugal compressor has a refrigeration capacity that exceeds the rated load of the refrigerator due to the characteristics of the centrifugal compressor when the exhaust heat temperature during operation is lower than the rated exhaust heat temperature (in the case of a low head). It is possible to drive. Therefore, the flow rate of chilled water can be increased by the amount of heat corresponding to the refrigeration capacity exceeding the rated load, and the required amount of heat of more external loads can be accommodated.
On the other hand, a refrigerator equipped with a centrifugal compressor has a refrigeration capacity that is lower than the rated load of the refrigerator due to the characteristics of the centrifugal compressor when the exhaust heat temperature during operation is higher than the rated exhaust heat temperature (in the case of a high head). Can only output. Therefore, the flow rate of the chilled water is reduced by an amount of heat that is lower than the rated load, so that the power of auxiliary equipment such as a chilled water pump can be reduced and the stability of the chilled water outlet temperature control can be ensured.
As the “centrifugal compressor”, a turbo compressor is suitable.

  Further, according to the refrigeration system according to the present invention, the refrigerator includes a positive displacement compressor that compresses the refrigerant, and the control means has the volume when the operating exhaust heat temperature is lower than a rated exhaust heat temperature. The output of the drive machine which drives a type compressor is increased, and the flow rate of the cold water is increased according to the increased output of the drive machine.

When the exhaust heat temperature during operation is lower than the rated exhaust heat temperature, the head becomes low, so the load on the drive machine is reduced and the drive machine has a surplus power. By increasing the output of the driving machine so as to compensate for this surplus power and increasing the chilled water flow rate corresponding to the refrigerating capacity corresponding to this increased output, it is possible to cope with the required heat quantity of a larger external load.
The power of the driving machine is determined by the product of the head and the refrigerant circulation flow rate. In the present invention, the output is only increased by increasing the output by the amount of the reduced head, and as a result, although the capacity of the entire refrigeration system is increased, the power consumption of the drive unit is not increased.
Examples of the “positive displacement compressor” include compressors such as reciprocating, screw, scroll, and rotary.

  An absorption refrigerator may be used as the refrigerator.

  Further, according to the refrigeration system of the present invention, when an absorption refrigerator is used, a high pressure regenerator that generates a concentrated solution having a high solution concentration by heating with a heat source, and a solution of the concentrated solution supplied from the high pressure regenerator A low pressure regenerator that further increases the concentration, and an absorber that absorbs the refrigerant evaporated in the evaporator with respect to the concentrated solution supplied from the low pressure regenerator to generate a dilute solution having a low solution concentration, and A heat exchanger for exchanging heat between the concentrated solution and the dilute solution is provided between the high pressure regenerator and the low pressure regenerator and the absorber, and bypasses the low pressure regenerator to bypass the high pressure regenerator. A concentrated solution bypass flow rate adjusting valve for adjusting the flow rate of the concentrated solution is provided in a concentrated solution bypass path through which the concentrated solution flows from to the heat exchanger.

In the heat exchanger provided between the high pressure regenerator and the low pressure regenerator, the concentration of the concentrated solution is high and the temperature is low. Therefore, at this position, there is a high possibility that solution crystals that cause the concentrated solution to crystallize are generated. In particular, when the temperature of the cooling water decreases, the pressure of the high pressure regenerator decreases due to the decrease in the condenser pressure, and the pressure difference between the high pressure regenerator and the low pressure regenerator becomes small. If the pressure difference between the high-pressure regenerator and the low-pressure regenerator becomes small, the amount of solution circulation decreases, so that solution crystals are more likely to occur.
Therefore, the present invention employs a concentrated solution bypass flow rate adjustment valve that adjusts the flow rate of the concentrated solution in the concentrated solution bypass path that flows the concentrated solution from the high pressure regenerator to the heat exchanger by bypassing the low pressure regenerator. In a situation where a solution crystal may be generated, the concentrated solution bypass flow rate adjustment valve is opened to increase the amount of concentrated solution from the high pressure regenerator. As a result, the flow rate of the concentrated solution flowing to the heat exchanger is increased, and a solution crystal is obtained by flowing more concentrated solution from the high pressure regenerator having a lower solution concentration than the concentrated solution from the low pressure regenerator to the heat exchanger. prevent. Furthermore, since the solution flow rate of the entire absorption refrigerator is increased by opening the concentrated solution bypass flow rate adjustment valve, the concentrated solution concentration is lowered to prevent solution crystals.

  Further, according to the refrigeration system of the present invention, an absorption refrigerator that generates a concentrated solution by flowing a dilute solution having a low solution concentration into each of the high-pressure regenerator and the low-pressure regenerator, and / or the concentrated solution in the low-pressure regenerator. An absorption refrigerator that generates and further increases the solution concentration in the high-pressure regenerator is provided, and the flow rate of the concentrated solution is adjusted to a path that bypasses the resistance section of the concentrated solution system heat exchanger, riser pipe, etc. at the outlet of the high-pressure regenerator A concentrated solution bypass flow rate adjusting valve is provided.

  According to the refrigeration system of the present invention, the control means increases the chilled water flow rate based on operating state data output from the refrigerator.

Examples of the “operating state data” include an inlet guide vane (IGV) provided at the refrigerant inlet of the centrifugal compressor, an output and input (kW, A) of a driving unit that drives the compressor of the refrigerator.
“Operating state data” is stored, for example, in the control panel of the refrigerator.
The control means obtains such operating state data and determines whether the refrigeration capacity can be further increased. If it is determined that the refrigeration capacity can be increased, the chilled water flow rate is increased by the amount of heat corresponding to the refrigeration capacity that can be increased.

  Further, according to the refrigeration system according to the present invention, a plurality of the refrigerators are installed in parallel with an external load, and the refrigerators include a refrigerator including a centrifugal compressor, and / or a positive displacement type. It is characterized by being either a refrigerator provided with a compressor, an absorption refrigerator, or a combination thereof.

In a refrigeration system in which a plurality of refrigerators are provided in parallel with an external load, each refrigerator is individually operated and stopped with respect to the required heat amount of the external load. According to the refrigeration system of the present invention, depending on the exhaust heat temperature, the chiller flow rate can be increased and the chiller can be operated when the rated load is exceeded. Can be delayed.
As the refrigerator compressor, all may be a refrigerator equipped with a centrifugal compressor, all may be a refrigerator equipped with a positive displacement compressor, or all may be an absorption refrigerator. Moreover, it is good also as a combination of these refrigerator centrifugal compressors and positive displacement compressors.

Further, according to the operation method of the refrigeration system according to the present invention, the compressor that compresses the refrigerant, the condenser that condenses the compressed refrigerant, the expander that expands the condensed refrigerant, and the expanded refrigerant is evaporated. A refrigerator having an evaporator for obtaining cold heat, cooling means for supplying cooling water to the condenser and removing exhaust heat in the condenser, and cold water obtained by the cold heat obtained by the refrigerator A chilled water supply means for supplying the chilled water to an external load, wherein the chilled water flow rate of the chilled water supply means with respect to a rated load of the refrigerator at a rated exhaust heat temperature in the condenser is rated. stores as coolant flow rate, the case exhaust heat temperature during operation during operation than the rated exhaust heat temperature is low, increase refrigerating capacity the refrigerator further exceeds the output possible and rated cooling capacity Calculated, and controls the coolant flow rate Te over-flow rate that is greater than the rated cold water flow rate based on the increased cooling capacity.

According to the present invention, since the flow rate of the chilled water is controlled based on the exhaust heat temperature of the condenser, the maximum refrigeration capacity that the refrigerator can output can be used.
Therefore, when a plurality of refrigerators are installed, even if the required heat amount of the external load increases, the timing of increasing the refrigerator can be delayed, and operation with the optimum number of operating units becomes possible. Thereby, energy saving at the time of refrigeration system operation is realized.

Embodiments of a refrigeration system according to the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 shows the overall configuration of the refrigeration system according to the first embodiment.
The refrigeration system 1 is installed in a building or factory facility. The refrigeration system 1 includes three first to third turbo chillers 11, 12, and 13 that give cold heat to cold water supplied to an external load 3 such as an air conditioner or a fan coil.

  First to third cold water pumps (cold water supply means) 21, 22, and 23 for pumping cold water are installed on the downstream side of the respective centrifugal chillers 11, 12, and 13 as viewed from the cold water flow. The chilled water cooled in the turbo chillers 11, 12, 13 by these chilled water pumps 21, 22, 23 is sent to the supply header 31.

Each of the chilled water pumps 21, 22, and 23 is driven by first to third chilled water pump inverter motors 21 a, 22 a, and 23 a, so that the variable flow rate can be controlled by making the rotation speed variable. Is done.
Further, each of the cold water pumps 21, 22, and 23 can be operated at an excessive flow rate by each of the inverter motors 21a, 22a, and 23a.
Here, “overflow” has the following meaning. The maximum load of the refrigeration system 1 is determined at the time of designing according to the scale of the external load 3. The chilled water flow rate borne by each of the chilled water pumps 21, 22, and 23 at the maximum load is set as the rated chilled water flow rate. A flow rate exceeding the rated cold water flow rate is called an excessive flow rate.

In the supply header 31, cold water obtained in each of the turbo chillers 11, 12, and 13 is collected.
The cold water collected in the supply header 31 is supplied to the external load 3.
The cold water that has been subjected to air conditioning or the like by the external load 3 and raised in temperature is sent to the return header 32. The cold water is branched at the return header 32 and sent to the turbo chillers 11, 12, and 13.

The first to third turbo refrigerators 11, 12, and 13 are installed in parallel to the external load 3.
The turbo refrigerators 11, 12, and 13 are provided with first to third cooling towers (cooling means) 14, 15, and 16, respectively. By the cooling towers 14, 15 and 16, the exhaust heat exhausted from the condenser of the refrigerator is removed. The cooling water flowing through the cooling towers 14, 15, 16 is pumped by first to third cooling water pumps 17, 18, 19. Each cooling water pump 17, 18, 19 is driven by first to third cooling water pump inverter motors 17a, 18a, 19a. Thereby, the discharge flow rate of each cooling water pump 17, 18, 19 can be variably controlled by making the rotation speed variable.

  A bypass circuit 33 is provided between the supply header 31 and the return header 32. The bypass circuit 33 is provided with an open / close valve 34. By adjusting the opening / closing valve 34, the flow rate of cold water flowing from the supply header 31 to the return header 32 is adjusted, and the supply pressure of cold water flowing from the supply header 31 to the external load 3 is adjusted.

A chilled water pipe for connecting the supply header 31 and the external load 3 is provided with a chilled water flow sensor 46 for detecting the chilled water flow rate. The output of the cold water flow sensor 46 is sent to a control unit (control means) 47.
In addition, the installation position of the cold water flow sensor 46 should just be a position which can detect the cold water flow which flows through the external load 3, for example, is good also as a structure provided in the return header 32 side.

The chilled water pipe connecting the external load 3 and the return header 32 is provided with an inflow chilled water temperature sensor 42 for detecting the chilled water temperature. The output of the inflow cold water temperature sensor 42 is sent to the control unit 47.
By this inflow cold water temperature sensor 42, the return temperature of the cold water flowing from the external load 3 to the turbo chillers 11, 12, 13 during operation is obtained.
The chilled water pipes connecting the return header 32 and the turbo chillers 11, 12, 13 are provided with first to third inflow chilled water temperature sensors 43, 44, 45 for detecting the chilled water temperature, respectively. Yes. The output of each inflow cold water temperature sensor 43, 44, 45 is sent to the control unit 47.

  The control unit (control means) 47 obtains outputs of the chilled water flow rate sensor 46, the inflow chilled water temperature sensor 42, and the first to third chilled water temperature sensors 43, 44, 45, and based on predetermined calculation results, The turbo chillers 11, 12, and 13, the cooling water pump inverter motors 17a, 18a, and 19a, the cold water pump inverter motors 21a, 22a, and 23a, the open / close valve 34, and the like are controlled.

In the control unit 47, the return temperature difference (Ti−To) is calculated from the operating return temperature Ti obtained from the inflow cold water temperature sensor 42 and the forward temperature To of cold water flowing out from the supply header 31 to the external load 3. It is like that. Based on this return temperature difference (Ti−To) and the operating cold water flow rate G (m ³ / s) obtained by the cold water flow rate sensor 46, the required refrigeration capacity Qreq of the external load 3 is calculated.
Specifically, it is calculated based on the following equation.
Qreq = (Ti−To) × G × γ × λ (1)
Here, γ means the specific gravity of the cold water at the average temperature of the forward temperature To and the return temperature Ti, and λ means the specific heat of the cold water at the average temperature of the forward temperature To and the return temperature Ti.
In the present embodiment, since the turbo chillers 11, 12, and 13 are controlled so that cold water is supplied at a rated temperature (for example, 7 ° C.), the control unit 47 sets the rated temperature as the forward temperature To. I remember it. However, the supply header 31 may be provided with a temperature sensor so as to detect the forward temperature To.

FIG. 2 shows details of the turbo refrigerators 11, 12 and 13 and the cooling towers 14, 15 and 16. In the figure, for the sake of easy understanding, only the first centrifugal chiller 11 and the first cooling tower 14 out of three turbo chillers and cooling towers provided in parallel are shown.
The turbo refrigerator 11 includes a turbo compressor 60 that compresses the refrigerant, a condenser 62 that condenses the high-temperature and high-pressure gas refrigerant compressed by the turbo compressor 60, and the high-temperature and high-pressure liquid refrigerant condensed by the condenser 62. An expansion valve (expander) 64 that expands and an evaporator 66 that evaporates the liquid refrigerant expanded by the expansion valve 64 are provided.

  The turbo compressor 60 is a centrifugal compressor and is driven by an inverter drive motor 68 under rotation speed control. An inlet guide vane (hereinafter referred to as “IGV”) 60 a for controlling the flow rate of the intake refrigerant is provided at the refrigerant intake port of the turbo compressor 60.

The condenser 62 is provided with a condensed refrigerant pressure sensor 80 for measuring the condensed refrigerant pressure and a condensed refrigerant temperature sensor 82 for measuring the condensed refrigerant temperature. Note that the condensed refrigerant temperature may be a value obtained by calculation in the control unit 47 as the saturated temperature from the condensed refrigerant pressure.
The outputs of these sensors 80 and 82 are transmitted to the control unit 47 (see FIG. 1).

  Cold water having a rated temperature (for example, 7 ° C.) is obtained by absorbing heat in the evaporator 66. That is, the chilled water flowing in the chilled water pipe 70 inserted into the evaporator 66 is cooled by removing heat from the refrigerant. This cold water flow rate is controlled by the first cold water pump 21 (see FIG. 1).

The cooling tower 14 removes the exhaust heat released when the refrigerant condenses in the condenser 62.
The cooling tower 14 includes a cooling water pipe 72 connected to the condenser 62. The cooling water circulates between the cooling tower 14 and the condenser 62 via the cooling water pipe 72. The circulating cooling water absorbs condensation heat (exhaust heat) from the refrigerant in the condenser 62 and dissipates heat in the cooling tower 14. Heat dissipation in the cooling tower 14 is performed by heat exchange with the outside air.
The refrigeration system is designed based on the rated cooling water inlet temperature Tin ^* . In the present embodiment, the rated cooling water inlet temperature (rated exhaust heat temperature) Tin ^* is set to 32 ° C. This rated cooling water inlet temperature Tin ^* is stored in the memory of the control unit 47.
The cooling water inlet temperature Tin during operation is detected by a cooling water inlet temperature sensor 74 provided in the vicinity of the condenser 62 inlet of the cooling water pipe 72. The output of the cooling water inlet temperature sensor 74 (see FIG. 1) is transmitted to the control unit 47 described above.
The coolant outlet temperature Tout during operation is detected by a coolant outlet temperature sensor 76 provided in the vicinity of the condenser 62 inlet of the coolant pipe 72. The output of the coolant outlet temperature sensor 76 is transmitted to the control unit 47 (see FIG. 1).
The cooling water flow rate is controlled by the first cooling water pump 17 and the first cooling water pump inverter motor 17 a installed in the cooling water pipe 72.

The control unit 47 obtains the cooling water inlet temperature Tin and performs the following control.
That is, the control unit 47 compares the cooling water inlet temperature Tin with the rated cooling water inlet temperature Tin ^* stored in the memory, and calculates the increased refrigeration capacity Q (Tin) that the turbo chiller can further output. To do. And the excessive flow volume of the cold water corresponding to this increase freezing capacity Q (Tin) is calculated, and this is reset to the upper limit of a cold water flow volume.
The reason why such control can be performed is as follows.
A centrifugal chiller including a turbo compressor, which is a centrifugal aerodynamic machine, has characteristics as shown in FIG.
In the figure, the horizontal axis represents the refrigeration capacity and the vertical axis represents the cooling water temperature.
The cooling water temperature on the vertical axis means the head, and the higher the temperature, the higher the head.
A curve L1 indicates a characteristic curve at the same rotation speed of the turbo compressor, and a curve L2 indicates a turning stall line indicating the stability limit of the compressor.
The turbo refrigerator is designed to output 100% of the rated refrigeration capacity (rated load) at the rated cooling water temperature (32 ° C.) of the design specification.
However, when the cooling water temperature is lower than the rating (in the case of a low head; for example, at 24 ° C.), the turbo chiller can output a refrigeration capacity exceeding the rated refrigeration capacity (for example, 115%). .
As described above, the turbo chiller can be operated in a region exceeding the rated refrigeration capacity due to the characteristics of the centrifugal chiller, so that the control that effectively uses the characteristics can be performed.

On the other hand, when the cooling water temperature is higher than the rating (in the case of a high head; for example, at 34 ° C.), the turbo chiller can output only a refrigeration capacity (for example, 80%) lower than the rated refrigeration capacity.
In such a case, the control unit 47 instructs the chilled water flow rate according to the refrigeration capacity below the rated refrigeration capacity.

In the present embodiment, since the operation exceeding the rated refrigeration capacity as described above is enabled, the inverter drive motor 68, the cooling tower 14, the cooling water pump 17 and the like of the turbo compressor also have a region exceeding the rated refrigeration capacity. Equipment with specifications that can handle up to is selected.
For example, as shown in FIG. 4, when an inverter drive motor corresponding to a design point is selected, the output of the drive unit cannot catch up with the maximum aerodynamic capacity of the refrigerator in a region exceeding the design point. Therefore, an inverter and an inverter drive motor having an output that can be operated in a region exceeding the rated refrigeration capacity are selected.

Next, an operation method of the refrigeration system 1 configured as described above will be described with reference to FIG.
At the start (S1) when cold extraction is not performed in the external load 3 such as late at night, early morning, holiday, etc., the first to third turbo chillers 11, 12, and 13 are all stopped.
Then, immediately before the time when the cold load is taken out in the external load 3 (the external load 3 is activated), the turbo chillers 11, 12, and 13 are activated to prepare for the required heat quantity of the external load 3. To do.
Specifically, the control unit 47 receives an output from a schedule timer (not shown) (set to be on (ON) in accordance with the start time of the external load 3) (S2), and the first turbo The refrigerator 11, the first cooling tower 14, the first cooling water pump inverter motor 17a, the first cooling water pump 17, the first cold water pump inverter motor 21a, and the first cold water pump 21 are activated (S3).

Immediately after the refrigeration system 1 is started up, the required heat quantity Qreq by the external load 3 is small. Therefore, the control unit 47 performs control to open the on-off valve 34 of the bypass circuit 33 so that the difference between the forward pressure of the supply header 31 and the return pressure of the return header 32 (hereinafter referred to as “pressure difference ΔP”) becomes constant. (S4).
At the time when the operation of the external load 3 is started (S5), the heat extraction by the external load 3 increases, and the required heat quantity Qreq of the external load 3 starts to increase. The control unit 47 performs control to close the open / close valve 34 of the bypass circuit 33 so that the pressure difference ΔP becomes constant (S6).
At this time, the amount of chilled water supplied by each of the chilled water pumps 21, 22, and 23 is a rated chilled water flow rate determined in the design specifications of the refrigeration system 1. Therefore, each inverter motor 21a, 22a, 23a is rotating at a constant rotational speed commensurate with the rated cold water flow rate (hereinafter referred to as “rated rotational speed”).
During such rated operation, the chilled water flow rate is controlled by the opening degree of the open / close valve 34 of the bypass circuit 33.

  When the chilled water return temperature difference (Ti-To) is smaller than the rated return temperature difference, which is a design specification value, the pressure difference Δ in the chilled water flow rate control by the on-off valve 34 while the chilled water flow rate remains at the rated flow rate. It becomes difficult to keep P constant (S7). That is, even if the on-off valve 34 is fully closed, the pressure difference ΔP cannot be kept constant. In the present embodiment, the control unit 47 controls the frequency of the first cold water pump inverter motor 21a without measuring the number of stages of the turbo refrigerator, the cold water pump, the cooling water pump, and the cooling tower in order to maintain ΔP. The overflow control (S8) is entered.

In the overflow control, first, the control unit 47 determines an appropriate upper limit flow rate among the upper limit flow rates of the chilled water prepared in a plurality of stages from the return temperature difference (Ti-To) of the chilled water. And the drive frequency of the inverter motor 21a for the 1st cold water pump is controlled so that it may become less than the determined upper limit cold water flow rate, and may exceed a rated flow rate.
In this way, even when the cold water overflow control is performed and the return temperature difference (Ti-To) is smaller than the rated value, the timing for increasing the stage of the turbo chiller is delayed and the required heat quantity Qreq of the external load is increased. Select the appropriate number of refrigerators that can be operated.

Next, with reference to FIG. 6, a description will be given of the control when the return temperature difference (Ti−To) of the cold water is equal to the rated value and the required heat amount Qreq of the external load 3 is increased.
In this case, even if the chilled water overflow control (S8) described in FIG. 5 is performed, conventionally, if the refrigeration capacity of the first turbo chiller 11 is increased to the rated load, the load is further increased. It is impossible to cope with the increased required heat amount of the external load 3.
However, when the cooling water inlet temperature Tin in the cooling tower 14 is lower than the rated cooling water inlet temperature Tin ^* , the turbo chiller equipped with the turbo compressor outputs more refrigeration capacity at the same rotation speed. It is possible.
Therefore, the control unit 47 according to the present embodiment, even when the rated load of the refrigerator is exceeded (S9), when the cooling water inlet temperature Tin is lower than the rated cooling water inlet temperature Tin ^* (S10). Then, the cooling water inlet temperature Tin and the rated cooling water inlet temperature Tin ^* are compared, and the increased refrigeration capacity Q (Tin) that the turbo chiller can further output is calculated (S11). That is, as described with reference to FIG. 3, the control is performed to increase the refrigerating capacity as the cooling water inlet temperature Tin is lower than the rated cooling water inlet temperature Tin ^* .
And the control part 47 calculates the excessive flow volume of the cold water corresponding to the increase freezing capacity Q (Tin) based on the cooling water inlet temperature Tin, and resets this to the upper limit of a cold water flow volume (S12).
The chilled water flow rate is overflow controlled until the reset upper limit chilled water flow rate is reached, and the required heat amount of the external load 3 is handled.

The stage increase of the refrigerator is performed based on the following equation with respect to the increased refrigeration capacity Q (Tin) determined based on the cooling water inlet temperature Tin (S13).
0.8Q (Tin) <ΣQri (2)
Here, Qri (i = 1 to 3) means the refrigeration capacity at the time of operation of each of the centrifugal chillers 11, 12 and 13. The coefficient of 0.8 is a threshold value suitable for each refrigeration system and varies depending on the system.
Thus, when the sum of the refrigerating capacity at the time of operation of each turbo refrigerator 11, 12, 13 exceeds 80% of the increased refrigerating capacity Q (Tin) determined based on the cooling water inlet temperature (Tin), the freezing is performed. The machine is increased (S15).

On the other hand, if the following equation is satisfied, the refrigerator is further increased.
Tsu <To + dTo (3)
Here, Tsu is the supply upper limit temperature of cold water, and dTo is a safety constant of the cold water temperature.
The above equation is established when the refrigerator has failed and can no longer supply cold water at the specified temperature, thereby determining whether or not the refrigerator has failed (S14).

If the cooling water inlet temperature Tin is higher than the rated cooling water inlet temperature Tin ^* , the turbo chiller can output only a refrigeration capacity that is lower than the rated refrigeration capacity, so that the chilled water flow rate according to this refrigeration capacity is obtained. The inverter motor 21a for cold water pumps is controlled.

Further, the following control may be performed.
An opening degree (operation state data) of the IGV provided in the turbo compressor 60 and an output (operation state data) of the drive motor 68 are transmitted to the control unit 47.
The control unit 47 receives these signals and determines whether the turbo chiller 11 can further output the refrigeration capacity. For example, when receiving a signal that the opening degree of the IGV is 40% and the output of the drive motor 68 is 70%, the control unit 47 determines that the capacity can be increased by about 20%. And the increase of the chilled water flow rate commensurate with the refrigeration capacity of 20% is instructed.

As described above, according to the present embodiment, the following effects are obtained.
Since the chilled water flow rate is increased by the amount of heat corresponding to the refrigeration capacity exceeding the rated refrigeration capacity, and the required amount of heat of the external load 3 is dealt with, the timing for increasing the stage of the refrigerator can be delayed. In this area where the delay can be made, there is no generation of extra chilled water pump, cooling water pump, and cooling tower power, thereby realizing energy saving operation. In particular, even when the difference in the return temperature of the chilled water is the rated value, if the cooling water temperature is low, the adjustment margin for the stage increase timing of the refrigerator is further increased, which is effective.

  On the other hand, when the cooling water temperature is high and the head is high, by reducing the chilled water flow rate by the amount of heat that is lower than the rated refrigeration capacity, it is possible to secure the chilled water pump auxiliary machine power and the stability of the chilled water outlet temperature control.

  In addition, it is determined whether or not the refrigeration capacity can be increased based on the signal from the turbo chiller, and overflow control is performed. It can be set appropriately.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
This embodiment is different from the first embodiment in that the compressor is a turbo chiller but is a positive displacement compressor 100 such as a reciprocator, screw, scroll, or rotary. About another structure, it is the same as that of 1st embodiment. Therefore, the entire configuration of the refrigeration system is the same as that shown in FIG.
However, the drive unit that drives the positive displacement compressor 100 may be an inverter drive motor or a gas engine as in the first embodiment.

FIG. 8 shows an operation method after the overflow control is performed as in the first embodiment (see FIG. 5).
In the positive displacement compressor, there is no characteristic peculiar to the centrifugal aerodynamic machine as described with reference to FIG.
However, when the cooling water inlet temperature is lower than the rated cooling water inlet temperature, the head becomes low, so that the load of the driving device 68 of the positive displacement compressor 100 is reduced and the driving device 68 has a surplus power. The controller 47 calculates the remaining capacity of the drive machine (S17).
The control unit 47 increases the rotation speed of the driving device 68 to increase the refrigerant circulation flow rate so as to compensate for this surplus power. Overflow control is performed by increasing the chilled water flow rate by an amount corresponding to the increased refrigeration capacity Q (Tin) corresponding to the increased refrigerant circulation flow rate (S18). Thereby, it can respond to the demanded amount of heat of more external loads 3.

  The power of the driving machine is determined by the product of the head and the refrigerant circulation flow rate. In the present embodiment, since the coolant circulation flow rate is only increased by increasing the number of revolutions by the amount that the cooling water inlet temperature is decreased and the head is decreased, the maximum output value of the drive unit is not increased as a result.

  About the timing of the stage increase of the refrigerator in this embodiment, the increase refrigerating capacity Q (Tin) according to the cooling water inlet temperature is controlled by the control unit 47 as in the first embodiment described with reference to FIGS. And the timing for increasing the stage is determined according to the increased refrigeration capacity Q (Tin).

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
This embodiment is different in that the refrigerator in the first embodiment is a turbo refrigerator, but the absorption refrigerator 200 is used. About another structure, it is the same as that of 1st embodiment. Therefore, the overall configuration of the refrigeration system is the same as that shown in FIG. 1 except for the difference between the turbo chiller and the absorption chiller.

The absorption refrigerator 200 uses a hygroscopic aqueous solution in which LiBr, ammonia, or the like is dissolved in water used as a refrigerant.
The absorption refrigerator 200 is supplied with a high-pressure regenerator 201 and a low-pressure regenerator 202 that generate a concentrated aqueous solution by evaporating the water in the aqueous solution, and the concentrated solution generated by these regenerators 201 and 202. And an absorber 203 that absorbs moisture from 204 to generate a dilute solution.
The absorption refrigerator 200 is supplied with steam (refrigerant) guided from the high-pressure regenerator 201 and the low-pressure regenerator 202, and condenses the condenser 205 that condenses the steam and the condensed water supplied from the condenser 205. And an evaporator 204.

Steam is supplied to the high pressure regenerator 201 through a regulating valve 206 from a heat source such as a high pressure steam source or a boiler. The aqueous solution is heated by this vapor, and a concentrated solution is produced by evaporating the water in the aqueous solution.
The opening of the adjusting valve 206 is adjusted by the control unit 47.
The vapor (refrigerant) flowing out from the high pressure regenerator 201 is supplied to the low pressure regenerator 202 and then supplied to the condenser 205. Steam generated by the low pressure regenerator 202 is also supplied to the condenser 205.

A high-temperature heat exchanger 207 and a low-temperature heat exchanger 208 are provided between the high-pressure regenerator 201 and the low-pressure regenerator 202 and the absorber 203. These heat exchangers 207 and 208 exchange heat between the dilute solution supplied from the absorber 203 via the solution pump 209 and the concentrated solution supplied from the high pressure regenerator 201 and the low pressure regenerator 202. Is called.
Most of the concentrated solution flowing out of the high temperature heat exchanger 207 is supplied to the low pressure regenerator 202. On the other hand, the other concentrated solution is supplied to the low-temperature heat exchanger 208 through a concentrated solution bypass path 210 that bypasses the low-pressure regenerator 202. The concentrated solution bypass path 210 is provided with a concentrated solution bypass flow rate adjustment valve 211 that adjusts the flow rate of the concentrated solution. Although not shown, the concentrated solution bypass flow rate adjustment valve 211 is configured such that the valve opening is adjusted by the control unit 47.

  A cold water pipe 70 is inserted into the evaporator 204, and cold water is supplied to the external load 3. The cold water flowing in the cold water pipe 70 is cooled by removing heat from the refrigerant in the evaporator 205. The chilled water flow rate is controlled by the first chilled water pump 21 (see FIG. 1). The first cold water pump 21 is inverter-controlled by the control unit 47.

The absorber 203 and the condenser 205 are provided with a cooling water pipe 213, and the internal diluted solution or steam is cooled by the cooling water passing through the cooling water pipe 213. Although not shown, a cooling water pump and a cooling tower are connected to the cooling water pipe 213.
A cooling water inlet temperature sensor 74 is provided at the condenser 205 inlet of the cooling water pipe 213 so that the cooling water inlet temperature Tin is measured. The output of the cooling water inlet temperature sensor 74 is output to the control unit 47.

Next, operation of the absorption refrigerator 200 having the above configuration when the cooling water temperature is lowered will be described.
When the outside air temperature decreases and the cooling water temperature decreases, the logarithm average temperature difference increases, and the amount of refrigerant vapor absorbed in the absorber 203 increases. This increases the absorption capacity, so that the concentration of the dilute solution decreases, thereby increasing the refrigeration capacity.
Further, when the cooling water temperature is lowered, the logarithmic average temperature difference is increased, the amount of refrigerant condensed in the condenser 205 is increased, and the condensation pressure is lowered. When the condensation pressure is lowered, the pressure and temperature of the low pressure regenerator 202 and the high pressure regenerator 201 connected to the condenser 205 are lowered. When the pressure of the high-pressure regenerator 201 is reduced, the load of the heat source steam is reduced, and there is a margin in the operating state.
Further, when the pressure of the high pressure regenerator 201 decreases, the pressure difference between the high pressure regenerator 201 and the low pressure regenerator 202 also decreases. The amount of solution circulation circulating in the absorption refrigerator 200 is determined by the pressure difference between the high pressure regenerator 201 and the low pressure regenerator 202. Therefore, when the cooling water temperature decreases, the pressure difference between the regenerators 201 and 202 becomes small, and the solution circulation amount decreases. When the amount of solution circulation decreases, the amount of heat consumed for solution heating also decreases, so that the amount of heat consumed is not wasted for solution heating not related to the refrigerating capacity, and most of the input heat amount can be used for evaporation of the refrigerant. .

Thus, also in the absorption refrigerator, when the cooling water temperature is lowered, the load of the heat source steam is reduced, the amount of solution circulation is reduced, and a margin is generated in the heat source steam. By increasing the opening degree of the regulating valve 206 by the control unit 47, by further using the surplus heat source steam, the heat source possessed by the refrigeration system can be used to the maximum extent to achieve a refrigeration capacity exceeding the rated refrigeration capacity. Can be output.
Therefore, the stage increase of the absorption refrigerator can be delayed as much as possible, and the energy consumption of the refrigeration system can be suppressed. In particular, the absorption refrigerator has a large COP (coefficient of performance) compared to a turbo refrigerator, and therefore has a large amount of exhaust heat. Therefore, a cooling water pump and a cooling tower having a relatively large capacity are installed. According to this embodiment, since the start-up by the relatively large capacity | capacitance cooling water pump and the stage increase of a cooling tower can be delayed, the merit is large.

When the cooling water temperature is lowered, as will be described below, a problem of a solution crystal that causes a concentrated solution to crystallize occurs.
That is, at the concentrated solution outlet of the low-temperature heat exchanger 208, the concentration of the concentrated solution is high and the temperature is low, so that there is a high possibility that solution crystals are generated. In particular, when the temperature of the cooling water is decreased, the pressure difference between the high pressure regenerator 201 and the low pressure regenerator 202 is reduced, so that the amount of solution circulation is reduced and solution crystals are more likely to be generated.
Therefore, in this embodiment, the concentrated solution bypass flow rate adjustment valve 211 is provided in the concentrated solution bypass path 210 that bypasses the low pressure regenerator 202. In a situation where a solution crystal may be generated, the concentrated solution bypass flow rate adjustment valve 211 is opened to increase the concentration of the concentrated solution from the high pressure regenerator 201. As a result, the flow rate of the concentrated solution flowing to the low-temperature heat exchanger 208 is increased, and the concentrated solution from the high-pressure regenerator 201 having a lower solution concentration than the concentrated solution from the low-pressure regenerator 202 is transferred to the low-temperature heat exchanger 208. A lot of flow prevents solution crystals. Furthermore, since the solution flow rate of the entire absorption refrigerator is increased by opening the concentrated solution bypass flow rate adjustment valve 211, the concentrated solution concentration is lowered to prevent solution crystals.

As described above, when the control by the concentrated solution bypass flow rate adjustment valve 211 is performed, the refrigerating capacity can be further increased as shown in FIG. FIG. 10 shows the refrigerating capacity with respect to the cooling water temperature (horizontal axis). 100% indicates the rated refrigeration capacity.
As shown in the figure, the absorption refrigerator of the present embodiment outputs a rated refrigeration capacity when the cooling water temperature is 32 ° C., and the rated refrigeration capacity is reduced as the cooling water temperature decreases. The refrigeration capacity that exceeds is output.
As described above, even if the refrigeration capacity increases due to a decrease in the cooling water temperature, if the control by the concentrated solution bypass flow rate adjustment valve 211 is not performed, a solution crystal is generated, so that the refrigeration capacity is about 105%. It will end at the top. On the other hand, when the control by the concentrated solution bypass flow rate adjustment valve 211 is performed, no solution crystal is generated, so that it is possible to output a refrigerating capacity corresponding to a low cooling water temperature.

  About the timing of the stage increase of the refrigerator in this embodiment, the increase refrigerating capacity Q (Tin) according to the cooling water inlet temperature is controlled by the control unit 47 as in the first embodiment described with reference to FIGS. And the timing for increasing the stage is determined according to the increased refrigeration capacity Q (Tin).

  An absorption refrigerator that generates a concentrated solution by flowing a dilute solution having a low solution concentration into each of the high-pressure regenerator 201 and the low-pressure regenerator 202, and / or a high-pressure regenerator that generates a concentrated solution in the low-pressure regenerator 202. As an absorption refrigerator that increases the solution concentration in 201, a path for bypassing the resistance unit such as the heat exchanger 207 of the concentrated solution system and the rising pipe at the outlet of the high pressure regenerator 201 is provided, and the flow rate of the concentrated solution is adjusted in this bypass path A concentrated solution bypass flow rate adjustment valve 211 may be provided.

In the first to third embodiments, the cooling water inlet temperature Tin is used as a reference for calculating the increased refrigeration capacity Q (Tin). However, the present invention is not limited to this and represents the exhaust heat temperature of the condenser. Data may be used, and the outside air temperature, the cooling water outlet temperature, the refrigerant condensing temperature, and the refrigerant condensing pressure may be used.
In the first embodiment, a refrigeration system using a turbo refrigerator, in the second embodiment, a refrigeration system using a refrigerator having a positive displacement compressor, and in a third embodiment, a refrigeration system using an absorption refrigerator, respectively. Although demonstrated, it is good also as a refrigeration system which combined suitably the turbo refrigerator, the refrigerator which has a positive displacement compressor, and the absorption refrigerator.
Further, the number of stages of the refrigerator is not limited to three, but may be two or four or more. Of course, it is possible to have only one stage of the refrigeration system according to the present invention and use a conventional refrigeration machine for other refrigeration systems.

It is a block diagram showing the whole refrigeration system composition concerning a first embodiment of the present invention. It is the schematic which showed the detail of the refrigerator of FIG. 1 with the cooling tower. It is the figure which showed the characteristic of the turbo refrigerator. It is the figure which showed the conditions of selection of the drive device of a turbo compressor. It is the flowchart which showed the operating method of the refrigerating system of this invention. It is the flowchart which showed the operating method of the refrigerating system of this invention. It is the block diagram which showed the refrigerator concerning 2nd embodiment of this invention. It is the flowchart which showed the operating method of the refrigerating system concerning 2nd embodiment. It is the block diagram which showed the absorption refrigerator concerning 3rd embodiment of this invention. It is the graph which showed the refrigerating capacity of the absorption refrigerator concerning 3rd embodiment with respect to the cooling water temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration system 3 External load 11, 12, 13 Turbo refrigerator 14, 15, 16 Cooling tower 21, 22, 23 Chilled water pump 47 Control part

Claims (9)

A refrigerator including a compressor that compresses the refrigerant, a condenser that condenses the compressed refrigerant, an expander that expands the condensed refrigerant, and an evaporator that evaporates the expanded refrigerant to obtain cold heat; and
Cooling means for supplying cooling water to the condenser and removing waste heat in the condenser;
In a refrigeration system comprising cold water supply means for obtaining cold water by the cold heat obtained by the refrigerator and supplying the cold water to an external load,
Storing the cold water flow rate of the cold water supply means for the rated load of the refrigerator at the rated exhaust heat temperature in the condenser as a rated cold water flow rate,
When the exhaust heat temperature during operation is lower than the rated exhaust heat temperature , the refrigeration machine calculates the increased refrigeration capacity that can further output and exceeds the rated refrigeration capacity, and the rated refrigeration capacity based on the increased refrigeration capacity refrigeration system, characterized in that more than coolant flow rate Te over-flow and a control means for controlling the coolant flow rate.   The refrigeration system according to claim 1, wherein the refrigerator includes a centrifugal compressor that compresses the refrigerant. The refrigerator includes a positive displacement compressor that compresses a refrigerant,
When the exhaust heat temperature during operation is lower than the rated exhaust heat temperature, the control means increases the output of the drive unit that drives the positive displacement compressor, and
The refrigeration system according to claim 1, wherein the flow rate of the cold water is increased according to the increased output of the driving machine.   The refrigeration system according to claim 1, wherein the refrigerator is an absorption refrigerator. A high-pressure regenerator that generates a concentrated solution having a high solution concentration by heating with a heat source, a low-pressure regenerator that further increases the solution concentration of the concentrated solution supplied from the high-pressure regenerator, and the concentrated solution supplied from the low-pressure regenerator An absorber that absorbs the refrigerant evaporated in the evaporator to generate a dilute solution having a low solution concentration, and
Between the high pressure regenerator and the low pressure regenerator and the absorber, a heat exchanger for exchanging heat between the concentrated solution and the diluted solution is provided,
A concentrated solution bypass flow rate adjusting valve for adjusting the flow rate of the concentrated solution is provided in a concentrated solution bypass path for bypassing the low pressure regenerator and flowing the concentrated solution from the high pressure regenerator to the heat exchanger. The refrigeration system according to claim 4. An absorption refrigerator that generates a concentrated solution by flowing a dilute solution having a low solution concentration into each of the high-pressure regenerator and the low-pressure regenerator, and / or a concentrated solution is generated by the low-pressure regenerator, and the solution concentration is further increased by the high-pressure regenerator. Equipped with absorption refrigerator,
A concentrated solution bypass flow rate adjusting valve for adjusting the flow rate of the concentrated solution is provided in a path that bypasses a resistance unit such as a heat exchanger of a concentrated solution system at the outlet of the high-pressure regenerator or a rising pipe. The refrigeration system according to claim 4. The refrigeration system according to any one of claims 1 to 6, wherein the control means increases the chilled water flow rate based on operating state data output from the refrigerator.
The refrigerator is installed in parallel with the external load,
These refrigerators are the refrigerator described in any one of Claims 2-6, or the combination of the refrigerator described in any one of Claims 2-6. The refrigeration system according to any one of 7. A refrigerator that condenses the refrigerant, a refrigerator equipped with an evaporator that evaporates the refrigerant and obtains cold heat;
Cooling means for supplying cooling water to the condenser and removing waste heat in the condenser;
In a method for operating a refrigeration system comprising: cold water supply means for obtaining cold water by the cold heat obtained by the refrigerator and supplying the cold water to an external load;
Storing the cold water flow rate of the cold water supply means for the rated load of the refrigerator at the rated exhaust heat temperature in the condenser as a rated cold water flow rate,
When the exhaust heat temperature during operation is lower than the rated exhaust heat temperature , the refrigeration machine calculates the increased refrigeration capacity that can further output and exceeds the rated refrigeration capacity, and the rated refrigeration capacity based on the increased refrigeration capacity the method of operating a refrigeration system characterized by greater than coolant flow rate Te over-flow to control the coolant flow rate.

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