JP6135985B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus including a compressor constituting a refrigerant circuit and a condenser for condensing refrigerant discharged from the compressor.

  Conventionally, in this type of refrigeration system that supplies refrigerant to showcases (cooling loads) installed in stores such as supermarkets and convenience stores, the refrigerant discharged from the compressor is condensed in a condenser, and the condensed liquid The refrigerant is temporarily stored in the receiver tank and then supplied to each showcase. In each showcase, the liquid refrigerant is depressurized by a throttle valve and then evaporated by an evaporator, thereby cooling the product in the display room.

  In addition, the refrigeration apparatus is provided with an injection circuit for the purpose of cooling the compressor. This injection circuit diverts the liquid refrigerant stored in the receiver tank, depressurizes it with a throttle valve, and then returns it to the intermediate pressure part in the middle of compression of the compressor. And the temperature of the refrigerant | coolant discharged from a compressor was controlled by predetermined | prescribed target discharge temperature by adjusting the valve opening degree of the throttle valve of this injection circuit (for example, refer patent document 1).

JP 2009-25000 A

  Here, it is known that the cooling capacity and efficiency in the showcase can be improved by supercooling the refrigerant directed to the throttle valve of the showcase described above. For this purpose, it is conceivable to provide a supercooling heat exchanger that supercools the mainstream refrigerant from the receiver tank toward the throttle valve of the showcase by the refrigerant flowing through the injection circuit.

  In this case, the sub-cooled heat exchanger is supplied with the diverted refrigerant (injection refrigerant) decompressed by the throttle valve of the injection circuit, and is generated when the diverted refrigerant evaporates in the super-cooling heat exchanger. The refrigerant that flows through the mainstream due to endothermic action and supercools the refrigerant toward the showcase throttle valve. There is a problem in that gas is generated, and even if the shunt refrigerant is evaporated in the supercooling heat exchanger, the supercooling cannot be sufficiently performed.

  Further, since the main refrigerant is supercooled by the supercooling heat exchanger, the temperature of the divided refrigerant for injection is increased as compared with the case where the supercooling is not performed. Therefore, since the ability to cool the compressor decreases, the amount of refrigerant that returns to the compressor through the injection circuit is increased by controlling the throttle valve according to the target discharge temperature. If the amount of refrigerant returning to the compressor increases, the compression work of the compressor will increase. Usually, the efficiency deterioration due to the increase of the compression work and the improvement of the efficiency due to the supercooling in the supercooling heat exchanger Therefore, the control of the throttle valve and the target discharge temperature are set so that the overall COP is improved.

  However, when this target discharge temperature is fixed and controlled, for example, when the refrigerant evaporation temperature in the showcase evaporator is in the refrigeration region, the injection valve throttle valve is fixed at the target discharge temperature at which COP is improved. When controlled, in the case of a showcase where the refrigerant evaporating temperature is in the refrigeration region in order to cool the display room to the refrigeration temperature, the discharge temperature of the compressor also rises, so it is returned to the intermediate pressure part of the compressor via the injection circuit. The amount of refrigerant to be increased.

  If the amount of refrigerant returned to the compressor by the injection circuit increases, the amount of subcooling of the mainstream refrigerant in the supercooling heat exchanger also increases, but the amount of increase in the compression work in the compressor becomes excessive, and overall There was also a problem that the COP would get worse.

  The present invention has been made to solve the conventional technical problems, and a refrigeration apparatus capable of improving the operation efficiency of a refrigerant circuit by effectively supercooling the refrigerant discharged from the condenser. The purpose is to provide.

In order to solve the above-described problems, a refrigeration apparatus according to the present invention is provided in parallel with a compressor that constitutes a refrigerant circuit, a condenser, a receiver tank that stores liquid refrigerant discharged from the compressor, and the condenser. A subcooler that supercools the liquid refrigerant that has flowed out of the receiver tank, an injection circuit that depressurizes the liquid refrigerant in the receiver tank with a throttle valve, and then returns the intermediate refrigerant to the intermediate pressure portion of the compressor; and the throttle valve A subcooling heat exchanger that supercools the mainstream refrigerant that has flowed out of the condenser by evaporating the decompressed refrigerant, and a valve opening of the throttle valve based on a predetermined target discharge temperature of the compressor In the refrigeration apparatus including the control device for controlling the temperature, the control device is based on the first target discharge temperature when the evaporation temperature of the mainstream refrigerant is in the refrigeration region, and the first when the evaporation temperature is in the refrigeration region. Higher than the target discharge temperature And controlling the valve opening degree of the throttle valve based on the second target discharge temperature.

According to a third aspect of the present invention, there is provided the refrigeration apparatus according to the third aspect , wherein the control device is configured to lower the first target discharge temperature in the refrigeration region in a region where the degree of superheat of the mainstream refrigerant is a predetermined small value. The temperature is lowered to the discharge temperature .

A refrigeration apparatus according to a third aspect of the invention is characterized in that, in each of the above inventions, the control device detects an evaporation temperature and / or a superheat degree of the mainstream refrigerant based on a low pressure of the refrigerant circuit .

According to a fourth aspect of the present invention, in the above invention, the control device maintains the first target discharge temperature and prohibits the change to the second target discharge temperature immediately after the compressor is started. It is characterized by that.

The refrigeration apparatus according to a fifth aspect of the invention is characterized in that, in the above invention, the control device sets the minimum valve opening of the throttle valve to a predetermined value larger than the fully closed position .

According to the present invention, the compressor constituting the refrigerant circuit, the compressor constituting the refrigerant circuit, the condenser, the receiver tank storing the liquid refrigerant discharged from the compressor, and the condenser are arranged in parallel. A subcooler that supercools the liquid refrigerant that has flowed out of the receiver tank, an injection circuit that depressurizes the liquid refrigerant in the receiver tank with a throttle valve, and then returns the intermediate refrigerant to the intermediate pressure portion of the compressor; and the throttle valve A subcooling heat exchanger that supercools the mainstream refrigerant that has flowed out of the condenser by evaporating the decompressed refrigerant, and a valve opening of the throttle valve based on a predetermined target discharge temperature of the compressor In the refrigeration apparatus including the control device for controlling the temperature, the control device is based on the first target discharge temperature when the evaporation temperature of the mainstream refrigerant is in the refrigeration region, and the first when the evaporation temperature is in the refrigeration region. Higher than the target discharge temperature Since so as to control the valve opening degree of the throttle valve based on the second target discharge temperature, the mainstream of the refrigerant flowing through the heat exchanger for supercooling, by diverting refrigerant evaporates, which is decompressed by the throttle valve over Since it is possible to cool the liquid refrigerant from the receiver tank after being supercooled by a supercooler arranged in parallel with the condenser, it flows to the supercooling heat exchanger as the main refrigerant. Generation of flash gas after the tank can be eliminated or suppressed.
As a result, the refrigerant exiting the condenser can be effectively subcooled, and the operation efficiency of the refrigerant circuit can be significantly improved. In this case, the refrigerant discharged from the receiver tank is returned to the supercooler arranged in parallel with the condenser.
In this case, a control device for controlling the valve opening degree of the throttle valve based on a predetermined target discharge temperature of the compressor is provided, and the target discharge for controlling the throttle valve based on the evaporation temperature of the mainstream refrigerant by the control device. If the temperature is changed, for example, the control device sets the target discharge temperature as the first target discharge temperature when the evaporation temperature of the mainstream refrigerant is in the refrigeration region, and the first when the evaporation temperature is in the refrigeration region. Is increased to a second target discharge temperature that is higher than the target discharge temperature, thereby preventing an excessive amount of refrigerant from returning from the injection circuit to the intermediate pressure portion of the compressor in the refrigeration region. Instead, an optimum amount of refrigerant is returned to the compressor by the injection circuit from the refrigeration region to the refrigeration region, and high operating efficiency can be realized.

According to a second aspect of the present invention, the controller is configured to lower the first target discharge temperature in the refrigeration region to a lower third target discharge temperature in a region where the degree of superheat of the mainstream refrigerant is a predetermined small value. For example, in a situation where the degree of superheat of the mainstream refrigerant is small and the discharge temperature of the compressor is low, it is possible to maintain the amount of refrigerant flowing in the injection circuit and to ensure overcooling of the refrigerant in the supercooling heat exchanger. become.

In this case, if the control device detects the evaporation temperature and / or superheat degree of the mainstream refrigerant based on the low pressure of the refrigerant circuit as in the invention of claim 3 , the refrigerant is supplied to a cooling load such as a showcase. Even when the information regarding the evaporation temperature cannot be obtained from the cooling load side as in the refrigeration apparatus to be supplied, the control of each of the above inventions can be accurately realized.

Further, if the control device maintains the first target discharge temperature and prohibits the change to the second target discharge temperature immediately after the start of the compressor as in the invention of the fourth aspect , immediately after the start. Thus, it is possible to avoid an abnormal increase in the discharge temperature of the compressor.

Furthermore, the control device as of the invention of claim 5, if the minimum valve opening of the throttle valve to a predetermined value greater than the fully closed position, suppressing an increase in the compression work amount of the such a compressor Even if the control is performed, it is possible to ensure a minimum supercooling effect in the supercooling heat exchanger.

It is a refrigerant circuit figure of the refrigerating device to which the present invention is applied. It is a figure explaining the change control of the target discharge temperature by the control apparatus of FIG. It is another figure explaining the change control of the target discharge temperature by the control apparatus of FIG. It is a figure which shows the relationship between the evaporation temperature of a refrigerant | coolant in the evaporator of FIG. 1, and a superheat degree.

  Hereinafter, embodiments of the present invention will be described in detail. The refrigeration apparatus 1 of the embodiment distributes and supplies refrigerant to a showcase (cooling load) S installed in one or a plurality of stores such as a supermarket or a convenience store. A constant speed compressor 2 (compressor No. 1) and a variable speed compressor 3 (compressor No. 2) controlled by an inverter. In addition, although R-404A is employ | adopted as a refrigerant | coolant of an Example, it is not restricted to it.

  Each of the compressors 2 and 3 of the embodiment is a scroll compressor, and the discharge pipes 4 and 6 are joined by a merger 7 and then connected to an oil separator 8. The oil separator 8 separates the oil in the refrigerant discharged from the compressors 2 and 3, and the separated oil is the service valve 9, the strainer 10, the oil return solenoid valves 11 and 12, and the capillary tube. The oil is returned to the compressors 2 and 3 by oil return circuits 16 and 17 to which 13 and 14 are connected.

  The refrigerant outlet pipe 18 of the oil separator 8 is connected to a condenser 21, and the outlet pipe 22 of the condenser 21 is connected to the inlet of the receiver tank 23. The receiver tank 23 temporarily stores the liquid refrigerant condensed in the condenser 21, and the refrigerant outlet pipe 24 (main flow) connected to the lower part thereof is provided in parallel with the condenser 21 and integrated in the embodiment. Connected to the subcooler 19. In the figure, F is a condenser blower for ventilating the outside air through the condenser 21 and the supercooler 19 and cooling them by air. In the embodiment, two fans are installed. The supercooler 19 is a heat exchanger for supercooling the liquid refrigerant discharged from the receiver tank 23, and is disposed in the same air path as the condenser 21 in order to perform its function, and the condenser blower F Is provided on the upstream side of the condenser 21 in the air flow.

  The refrigerant outlet pipe 25 of the subcooler 19 is branched into a first mainstream pipe 27A and a second mainstream pipe 27B by a branching device 26, and then merged again by a merger 28. 31 and a moisture indicator 32 and are connected to a high-pressure liquid pipe 33 via a valve 35. A throttle valve (electric valve) 34 and an evaporator 36 of each showcase (cooling load) S and an evaporator 36 are connected to the high pressure liquid pipe 33, and an outlet of the evaporator 36 of each showcase S is connected to a low pressure gas pipe 37.

  The low pressure gas pipe 37 is sequentially connected to a strainer 38 and an accumulator 39 via a valve 40. The accumulator 39 separates the non-evaporated liquid refrigerant and gas refrigerant from the evaporator 36, and the gas refrigerant outlet of the accumulator 39 is connected to the suction pipes 41 and 42 of the compressors 2 and 3.

  In addition, injection circuits 46 and 47 are connected to the lower portion of the receiver tank 23. Each injection circuit 46, 47 condenses in the condenser 21, takes out a part of the liquid refrigerant stored in the receiver tank 23 and diverts it, and returns it to the intermediate pressure part in the middle of compression of each compressor 2, 3. Used to cool the compressors 2 and 3 (liquid injection), service valves 48 and 49, strainers 51 and 52, throttle valves (motorized valves) 53 and 54, and solenoid valves 56 and 57 are provided in series, respectively. The compressors 2 and 3 are connected to each other.

  A pipe 58 on the downstream side of the throttle valve 53 of the injection circuit 46 for the compressor 2 is provided in the first supercooling heat exchanger 61 (economizer No. 1) together with the first mainstream pipe 27A. In the first supercooling heat exchanger 61, the refrigerant separated through the pipe 58 and the main refrigerant flowing through the first mainstream pipe 27A are configured to exchange heat. Further, a pipe 59 on the downstream side of the throttle valve 54 of the injection circuit 47 for the compressor 3 is provided in the second supercooling heat exchanger 62 together with the second mainstream pipe 27B. This second subcooling heat exchanger 62 (Economizer No. 2) is configured to exchange heat between the divided refrigerant flowing through the pipe 59 and the mainstream refrigerant flowing through the second mainstream pipe 27B. The refrigerant circuit R of the refrigeration apparatus 1 according to the embodiment is configured as described above.

  In the embodiment, the compressors 2 and 3, the condenser 21 and the supercooler 19, the receiver tank 23, the injection circuits 46 and 47, the supercooling heat exchangers 61 and 62, etc. in FIG. Each device other than the liquid pipe 33 and the low-pressure gas pipe 37 (refrigerant circuit R up to the valves 35 and 40) is installed integrally to constitute the refrigerator 45. The valves 35 and 40 are provided facing the outside from the refrigerator 45 and are connected to a high-pressure liquid pipe 33 and a low-pressure gas pipe 37, respectively. The refrigerator 45 is installed indoors in the store (condenser integrated type).

  Reference numerals 68 and 69 denote float switches for detecting the oil level in the compressors 2 and 3. Further, 63 and 64 are high pressure switches that operate by detecting the high pressure in the compressors 2 and 3, and 66 is a high pressure sensor connected to the refrigerant outlet pipe 18 (high pressure pipe) of the oil separator 8. is there. Reference numeral 67 denotes a low pressure sensor connected to a low pressure pipe on the downstream side of the accumulator 39. Also, discharge temperature sensors (well pipes) 71 and 72 for detecting the discharge temperature of the refrigerant are attached to the compressors 2 and 3. Further, an accumulator temperature sensor 73 for detecting the temperature of the refrigerant in the accumulator 39 is attached to the accumulator 39.

  The output of each switch and sensor is connected to a control device C composed of a general-purpose microcomputer, and the control device C operates each compressor 2 and compressor 3 based on these operations and detection values (the compressor 3 controls the rotation speed). ), And the opening / closing of the solenoid valves 11, 12, 56, 57 and the valve openings of the throttle valves 53, 54 are controlled.

  Next, the operation of the above configuration will be described. The control device C determines the number of operating compressors 2 and 3 based on the low pressure of the refrigerant circuit R detected by the low pressure sensor 67, and executes the rotational speed control of the compressor 3 using an inverter. When the compressors 2 and 3 are operated, the high-temperature and high-pressure gas refrigerant compressed by the compressors 2 and 3 is discharged to the discharge pipes 4 and 6, merges, and flows into the oil separator 8.

  Therefore, the oil is separated as described above, and the refrigerant then flows into the condenser 21 via the refrigerant outlet pipe 18 and the check valve 19. Outside air is passed through the condenser 21 by the condenser blower F, and the refrigerant is cooled in the condenser 21 to be condensed and liquefied. The refrigerant liquefied by the condenser 21 reaches the receiver tank 23 through the outlet pipe 22 and is temporarily stored there.

  The liquid refrigerant (main stream) in the receiver tank 23 exits from the outlet pipe 24 and then enters the subcooler 19. Since the outside air having a low temperature before passing through the condenser 21 is passed through the subcooler 19 by the condenser blower F, the main liquid refrigerant discharged from the receiver tank 23 further flows in the subcooler 19. Air cooled and super cooled. The liquid refrigerant (main flow) supercooled by the subcooler 19 flows out of the refrigerant outlet pipe 25 and flows through the first and second main flow pipes 27A and 27B, and then merges to reach the pipe 29. After passing through the dryer 31 and the moisture indicator 32, the valve 35 leaves the refrigerator 45 and flows into the high-pressure liquid pipe 33.

  The liquid refrigerant flowing into the high-pressure liquid pipe 33 reaches each showcase S, is decompressed by the throttle valve 34, and then flows into the evaporator 36 and evaporates. The display chamber is cooled by the endothermic action at this time. The refrigerant exiting the evaporator 36 enters the refrigerator 45 through the valve 40 through the low-pressure gas pipe 37, and then enters the accumulator 39 through the strainer 38. Therefore, the circulation of only the gas refrigerant from which the gas and liquid are separated is sucked into the compressors 2 and 3 from the suction pipes 41 and 42 is repeated.

  On the other hand, a part of the liquid refrigerant in the receiver tank 23 is taken out and divided and flows into the injection circuits 46 and 47. The diverted refrigerant (injection refrigerant) flowing into the injection 46 reaches the throttle valve 53 through the service valve 48 and the strainer 51. The refrigerant is decompressed and then flows into the pipe 58 of the first supercooling heat exchanger 61 and evaporates. The mainstream liquid refrigerant flowing in the first mainstream pipe 27A is further subcooled by the endothermic action at this time. The refrigerant that has exited the first supercooling heat exchanger 61 is then returned to the intermediate pressure portion of the compressor 2 via the electromagnetic valve 56 (opened) to cool the compressor 2.

  Further, the diverted refrigerant (injection refrigerant) flowing into the injection 47 reaches the throttle valve 54 through the service valve 49 and the strainer 52. Then, after the pressure is reduced, the refrigerant flows into the pipe 59 of the second supercooling heat exchanger 62 and evaporates. The mainstream liquid refrigerant flowing in the second mainstream pipe 27B is further subcooled by the endothermic action at this time. The refrigerant that has exited the second supercooling heat exchanger 62 is then returned to the intermediate pressure portion of the compressor 3 via the electromagnetic valve 57 (opened) to cool the compressor 3.

  Here, particularly in a situation where the amount of refrigerant in the refrigerant circuit R is insufficient, flash gas is generated in the mainstream refrigerant flowing out of the receiver tank 23 and directed to the throttle valve 34 of the showcase S, and the supercooling heat exchanger 61, Even if the diverted refrigerant in the injection circuits 46 and 47 is evaporated in 62, it cannot be sufficiently subcooled, but the refrigerant that has exited the supercooler 19 flows into the supercooling heat exchangers 61 and 62 as the main refrigerant. Since it did in this way, it becomes possible to eliminate or suppress the inconvenience that the refrigerant in which the flash gas is generated after the receiver tank 23 flows into the supercooling heat exchangers 61 and 62.

  As a result, the main-stream liquid refrigerant that does not contain the flash gas flowing through the supercooling heat exchangers 61 and 62 or has a small amount of flash gas is further evaporated by evaporation of the diverted refrigerant depressurized by the throttle valves 53 and 54. It becomes possible to supercool the refrigerant, and the refrigerant discharged from the condenser 21 can be effectively supercooled to significantly improve the operation efficiency of the refrigerant circuit R. In this case, since the refrigerant discharged from the receiver tank 23 returns again to the supercooler 19 provided in parallel with the condenser 21, the compressors 2, 3, the condenser 21, and the receiver tank 23 as in the embodiment. Is particularly effective for the refrigeration apparatus 1 in which the refrigeration unit 45 is installed as a unit.

  Further, since the liquid refrigerant taken out from the receiver tank 23 is caused to flow to the throttle valves 53 and 54, the liquid refrigerant in the receiver tank 23 can be used as a diverted refrigerant flowing into the throttle valves 53 and 54. Thus, the supercooling action of the mainstream refrigerant due to the evaporation of the divided refrigerant can be ensured without any trouble.

  Next, the valve opening control of the throttle valves 53 and 54 of the injection circuits 46 and 47 by the controller C will be described with reference to FIG. The control device C opens the electromagnetic valves 56 and 57 of the injection circuits 46 and 47 when the power is turned on. Based on the refrigerant discharge temperature of the compressors 2 and 3 detected by the discharge temperature sensors 71 and 72 and a predetermined target discharge temperature, which is the target value, each throttle is set so that the discharge temperature becomes the target discharge temperature. The valve openings of the valves 53 and 54 are controlled independently.

  Based on the low pressure of the refrigerant circuit R detected by the low pressure sensor 67, the control device C detects the evaporation temperature of the refrigerant in the evaporator 36 converted from this low pressure, and the evaporation temperature of the refrigerant in the evaporator 36 is For example, in a refrigerated region of −15 ° C. or higher, the control device C sets the target discharge temperature to a first target discharge temperature of, for example, + 95 ° C. to + 100 ° C. (lower limit value + 95 ° C., upper limit value + 100 ° C.) (FIG. 2). . Specifically, when the discharge temperatures of the compressors 2 and 3 detected by the discharge temperature sensors 71 and 72 exceed + 100 ° C., the valve openings of the throttle valves 53 and 54 are increased by a predetermined pulse. That is, the cooling capacity of the compressors 2 and 3 is increased by increasing the amount of refrigerant (injection amount) returned to the intermediate pressure portions of the compressors 2 and 3. Further, when the temperature is between + 95 ° C. and + 100 ° C., the valve opening is not changed. When the discharge temperature falls below + 95 ° C., the valve opening is reduced by a predetermined pulse, and the injection amount is reduced. Thereby, the discharge temperature of the compressors 2 and 3 is controlled within the range of the first target discharge temperature (+ 95 ° C. to + 100 ° C.).

  In addition, the change period of the valve opening degree of the throttle valves 53 and 54 is, for example, 5 seconds. In the present embodiment, the control device C sets the minimum valve opening of the throttle valves 53 and 54 (usually 40 pulses at the fully closed position) to a predetermined value larger than the fully closed position, for example, 100 pulses.

  Further, the control device C changes the target discharge temperature based on the refrigerant evaporation temperature in the evaporator 36. Specifically, when the evaporation temperature of the refrigerant in the evaporator 36 is, for example, a refrigeration region having a temperature of −20 ° C. or lower, the target discharge temperature is higher than the first target discharge temperature, for example, + 110 ° C. to + 115 ° C. (lower limit value +110 The second target discharge temperature is raised (° C., upper limit value + 115 ° C.) (FIG. 2). Specifically, when the discharge temperatures of the compressors 2 and 3 detected by the discharge temperature sensors 71 and 72 exceed + 115 ° C., the valve openings of the throttle valves 53 and 54 are increased by a predetermined pulse. That is, the cooling capacity of the compressors 2 and 3 is increased by increasing the amount of refrigerant (injection amount) returned to the intermediate pressure portions of the compressors 2 and 3. Moreover, when it exists between +110 degreeC-+115 degreeC, a valve opening degree is not changed. When the discharge temperature falls below + 110 ° C., the valve opening is reduced by a predetermined pulse, and the injection amount is reduced. As a result, the discharge temperatures of the compressors 2 and 3 are controlled within the second target discharge temperature range (+ 110 ° C. to + 115 ° C.).

  Incidentally, there is a control hysteresis between the evaporation temperatures of −20 ° C. and −15 ° C., and when the evaporation temperature falls below −15 ° C. to −20 ° C., the second target discharge temperature is changed. When the temperature rises from 20 ° C. to −15 ° C., the control is changed to the first target discharge temperature. Also, the change period in this case is set to 5 seconds, for example.

  Here, when the first target discharge temperature is a target discharge temperature at which COP is improved when the refrigerant evaporation temperature in the evaporator 36 of the showcase S is in the refrigeration region, the display chamber of the showcase S is refrigerated. In the case of the showcase S where the evaporation temperature of the refrigerant is in the refrigeration region in order to cool to the temperature, the discharge temperature of the compressors 2 and 3 also increases, so that the intermediate pressure of the compressors 2 and 3 passes through the injection circuits 46 and 47. The amount of refrigerant returned to the section increases. If the amount of refrigerant returned to the compressors 2 and 3 by the injection circuits 46 and 47 increases, the amount of subcooling of the mainstream refrigerant in the supercooling heat exchangers 61 and 62 also increases. Since the amount of increase in the compression work is excessive, the overall COP is deteriorated.

  However, as described above, the control device C sets the target discharge temperature of the compressors 2 and 3 as the first target discharge temperature when the evaporation temperature of the refrigerant in the evaporator 36 where the main-stream refrigerant evaporates is in the refrigeration region. In the refrigeration region, this target discharge temperature is raised to a second target discharge temperature that is higher than the first target discharge temperature, so that an excessive amount of refrigerant is compressed from the injection circuits 46 and 47 in the refrigeration region. The inconvenience of returning to the intermediate pressure part of the machines 2 and 3 can be prevented. As a result, regardless of the evaporation temperature of the refrigerant in the evaporator 36, the injection circuit 46, 47 has an optimum amount from the situation where the display room of the showcase S is used as the refrigeration area to the situation where it is used as the refrigeration area. It becomes possible to return the refrigerant to the compressors 2 and 3 to achieve high operating efficiency.

  Since the control device C sets the minimum valve opening of the throttle valves 53 and 54 to a value (100 pulses) larger than the fully closed position (40 pulses), the compression work of the compressors 2 and 3 as described above. Even if the control for suppressing the increase is performed, it is possible to ensure the minimum supercooling effect in the supercooling heat exchangers 61 and 62.

  Further, the control device C is based on the difference between the refrigerant temperature in the accumulator 39 detected by the accumulator temperature sensor 73 and the evaporation temperature of the evaporator 36 converted from the low pressure of the refrigerant circuit R detected by the low pressure sensor 67. The degree of superheat of the refrigerant in the evaporator 36 is detected. The control device (not shown) on the showcase S side controls the throttle valve 34 so that the superheat degree becomes the target value based on the superheat degree of the refrigerant in the evaporator 36 detected by itself. Thus, in the superheat degree detected from the refrigerant temperature in the accumulator 39 and the converted evaporation temperature, the evaporating temperature of −20 ° C. or higher becomes the superheat degree variable region (the superheat degree below the line L1 in FIG. 4 is a predetermined small region). In this case, as shown in FIG. 3, the control device C sets the target discharge temperature in the refrigerated region to be lower than the first target discharge temperature, for example, + 85 ° C. to + 90 ° C. (lower limit value + 85 ° C., upper limit value + 90 ° C.) To the third target discharge temperature (FIG. 3).

  Here, when the degree of superheat of the refrigerant in the evaporator 36 decreases, the discharge temperature of the compressors 2 and 3 also decreases. For example, in a situation where the discharge temperature decreases to around 90 ° C., the throttle valves 53 and 54 are controlled. When the target discharge temperature to be performed is the first target discharge temperature, the valve openings of the throttle valves 53 and 54 become small, and the refrigerant hardly flows into the injection circuits 46 and 47. Then, although it becomes almost impossible to supercool the mainstream refrigerant in each of the supercooling heat exchangers 61 and 62, the target discharge temperature is lowered to the third target discharge temperature that is lower than the first target discharge temperature as described above. Therefore, in the situation where the superheat degree of the mainstream refrigerant is small and the discharge temperature of the compressors 2 and 3 is also low, the amount of refrigerant flowing in the injection circuits 46 and 47 is maintained, and the refrigerant flow in the supercooling heat exchangers 61 and 62 is maintained. Supercooling can be secured.

  Further, immediately after the compressor 2 or the compressor 3 is started, the control device C sets the target discharge temperature used for controlling the throttle valves 53 and 54 of the injection circuits 46 and 47 of the compressors 2 and 3 as the first target temperature. The discharge temperature is maintained, and the change to the second target discharge temperature is prohibited. Immediately after the compressors 2 and 3 are started up, the discharge temperature tends to rise. If the target discharge temperature is raised to the second target discharge temperature, the discharge temperature becomes too high and reaches an abnormal value (+ 130 ° C. in FIG. 2). Although maintaining the first target discharge temperature, it is possible to avoid an abnormal increase in the discharge temperature of the compressors 2 and 3 immediately after startup.

  Further, in the embodiment, the control device C detects the evaporation temperature and superheat degree of the mainstream refrigerant based on the low pressure of the refrigerant circuit R, etc., so that the refrigerant is supplied to the store showcase S as in this embodiment. As in the case of the refrigeration apparatus 1, even when information on the evaporation temperature or the like cannot be obtained from the showcase S side, the throttle valves 53 and 54 can be accurately controlled.

  In the above-described embodiment, the present invention is applied to a refrigeration apparatus equipped with two compressors and each having an injection circuit. However, a refrigeration apparatus having one compressor and one injection circuit may be used, and three or more units may be used. The present invention is also effective for a refrigeration apparatus including a compressor and an injection circuit. Moreover, each numerical value demonstrated in the Example is not restricted to it, It should set suitably according to the scale of a freezing apparatus, the number of compressors, etc.

  In the embodiment, the diverted refrigerant is taken out from the receiver tank 23. However, the invention of claim 1 is not limited to this, and it is effective to divert from anywhere in the high-pressure piping from the condenser 21 to the valve 35.

DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 2, 3 Compressor 19 Supercooler 21 Condenser 23 Receiver tank 27A, 27B Mainstream piping 34, 53, 54 Throttle valve 36 Evaporator 45 Refrigerator 46, 47 Injection circuit 61, 62 Supercooling heat exchanger C Control device F Blower for condenser R Refrigerant circuit S Showcase (cooling load)

Claims (5)

A compressor that constitutes a refrigerant circuit, a condenser, a receiver tank that stores liquid refrigerant that has been discharged from the compressor, and supercooling that is provided in parallel with the condenser and that supercools the liquid refrigerant that has been discharged from the receiver tank. And after reducing the pressure of the liquid refrigerant in the receiver tank by the throttle valve, the refrigerant is discharged from the condenser by evaporating the refrigerant reduced in pressure by the throttle valve. A refrigerating apparatus comprising: a supercooling heat exchanger that supercools the mainstream refrigerant; and a control device that controls the valve opening of the throttle valve based on a predetermined target discharge temperature of the compressor.
The control device is configured to control the second target discharge temperature based on the first target discharge temperature when the evaporating temperature of the mainstream refrigerant is in the refrigeration region and higher than the first target discharge temperature when the evaporation temperature is in the refrigeration region. A refrigeration apparatus that controls a valve opening degree of the throttle valve based on temperature . 2. The control device according to claim 1, wherein the first target discharge temperature in the refrigeration region is lowered to a lower third target discharge temperature in a region where the degree of superheat of the mainstream refrigerant is a predetermined small value. The refrigeration apparatus described in 1. The said control apparatus detects the evaporation temperature and / or superheat degree of the said mainstream refrigerant | coolant based on the low pressure of the said refrigerant circuit, The refrigeration apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. The said control apparatus maintains the said 1st target discharge temperature immediately after starting of the said compressor , and prohibits the change to the said 2nd target discharge temperature. The refrigeration apparatus according to any one of the above. The refrigeration apparatus according to any one of claims 1 to 4, wherein the control device sets a minimum valve opening of the throttle valve to a predetermined value larger than a fully closed position .

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