JP2005049063A - Refrigeration system and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration system and its control method capable of improving energy consumption efficiency. <P>SOLUTION: This refrigeration system 1 comprises a cascade heat exchanger 21 for heat exchange between a refrigerant at a low-pressure side of a refrigerant circuit 7 for air conditioning and a refrigerant at a high-pressure side of a refrigerant circuit 9 for cooling. A compressor for air conditioning is operated in a case when a compressor for cooling is operated in a state that a cooling thermostat is switched off and the compressor for air conditioning is stopped, to supply the refrigerant at the low-pressure side of the compressor for air conditioning to the cascade heat exchanger 21. Thereby the refrigerant at the high-pressure side of the refrigerant circuit 9 for cooling can be supercooled even when the cooling thermostat is switched off, and the cooling performance and the operation efficiency of a cooling system part 8 can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a refrigeration system that performs indoor air conditioning and cooling of a facility to be cooled, and a control method for the refrigeration system.

In recent years, a refrigeration system has been proposed that includes an air conditioning system that performs indoor air conditioning in a store such as a convenience store, and a cooling system that cools a facility to be cooled (such as a refrigerated case) provided in the store ( For example, Patent Document 1).
JP 2002-174470 A

  By the way, this type of refrigeration system is required to improve the energy consumption efficiency (COP and the like) of the entire system.

  However, this refrigeration system only operates the air conditioning system unit and the cooling system unit independently according to the air conditioning load and the cooling equipment load, respectively. Compared with the case of the device, the energy consumption efficiency was hardly changed.

  This invention is made | formed in view of the situation mentioned above, and it aims at providing the control method of the refrigerating system which can raise energy consumption efficiency, and a refrigerating system.

  In order to solve the above problems, the present invention has an air conditioning refrigerant circuit including an air conditioning compressor, a heat source side heat exchanger, and a usage side heat exchanger in a refrigeration system, and operates and uses the air conditioning compressor. Air-conditioning system that performs indoor air-conditioning with a side heat exchanger and a cooling refrigerant circuit that includes a cooling compressor, a condenser, and an evaporator. The cooling compressor is operated and the equipment to be cooled is cooled by the evaporator. A cooling system section for performing air conditioning, a low-pressure side refrigerant of the air-conditioning refrigerant circuit, and a cascade heat exchanger for exchanging heat between the high-pressure side refrigerant of the cooling refrigerant circuit, When the cooling compressor is operating when the compressor is stopped, the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning compressor to the cascade heat exchanger. According to this configuration, when the cooling compressor is in operation when the air conditioning compressor is stopped, the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning compressor to the cascade heat exchanger. Therefore, the refrigerant on the high pressure side of the cooling refrigerant circuit can be supercooled, and the cooling capacity and operation efficiency of the cooling system can be improved.

  In the refrigeration system, the air conditioning system unit is configured to perform the cooling when the air conditioning compressor is stopped in a cooling thermo-off in which the room temperature is substantially the same as or lower than the preset temperature. When the compressor is in operation, it is preferable that the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning refrigerant circuit to the cascade heat exchanger. Further, when the air conditioning compressor is operated during the cooling thermo-off, it is preferable that the rotation frequency of the air conditioning compressor is controlled within a predetermined frequency range.

  Moreover, in the refrigeration system, the air conditioning system section sets a temperature difference between the inlet temperature and the outlet temperature of the refrigerant on the high-pressure side of the cooling refrigerant circuit that flows to the cascade heat exchanger as a preset temperature difference. A target rotational frequency of the air-conditioning compressor is determined, and when the target rotational frequency is within the predetermined frequency range, the rotational frequency of the air-conditioning compressor is controlled to the target rotational frequency, while the rotational frequency Is substantially coincident with the lower limit frequency of the predetermined frequency, and when the temperature difference is equal to or higher than a predetermined temperature than the set temperature difference, and the rotation frequency substantially coincides with the upper limit frequency of the predetermined frequency, and When the temperature difference is not more than a predetermined temperature from the set temperature difference, it is preferable to stop the operation of the air conditioning compressor.

  Further, in the refrigeration system, the air conditioning system unit adjusts the target rotation frequency so that the outlet temperature of the refrigerant on the high-pressure side of the cooling refrigerant circuit flowing through the cascade heat exchanger is equal to or higher than the outside air temperature. It is preferable. In this configuration, the set temperature difference is preferably changed according to the outside air temperature.

  In the refrigeration system, the air conditioning refrigerant circuit includes a first expansion valve provided between the heat source side heat exchanger and the use side heat exchanger, and the heat source side heat exchanger and the first heat exchanger. A refrigerant pipe between the first expansion valve and the second expansion valve is connected to the cascade heat exchanger via a second expansion valve, and the second expansion valve is connected to the cascade heat exchanger. It is preferable that the valve opening degree is controlled so that the temperature difference between the inlet temperature and the outlet temperature of the refrigerant on the high pressure side of the cooling refrigerant circuit that flows to the heat exchanger becomes the set temperature difference.

  The present invention also relates to a control method for a refrigeration system that performs indoor air conditioning and cooling of a facility to be cooled, wherein the refrigeration system includes an air conditioning compressor, a heat source side heat exchanger, and a use side heat exchanger. An air conditioning system unit that operates a compressor for air conditioning and performs indoor air conditioning by a use-side heat exchanger, and a cooling refrigerant circuit that includes a cooling compressor, a condenser, and an evaporator. Heat exchange is performed between a cooling system unit that operates a compressor and cools a facility to be cooled by an evaporator, a low-pressure side refrigerant of the air-conditioning refrigerant circuit, and a high-pressure side refrigerant of the cooling refrigerant circuit. And a cascade heat exchanger for performing the operation, and when the cooling compressor is in operation when the air conditioning compressor is stopped, the air conditioning compressor is operated to operate the low pressure of the air conditioning compressor. Side refrigerant is supplied to the cascade heat exchanger To. According to this method, when the cooling compressor is operating when the air conditioning compressor is stopped, the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning compressor to the cascade heat exchanger. Therefore, the refrigerant on the high pressure side of the cooling refrigerant circuit can be supercooled, and the cooling capacity and operation efficiency of the cooling system can be improved.

  In the above control method, the cooling compressor is operated when the air conditioning compressor is stopped in a cooling thermo-off state in which the room temperature is substantially the same as or lower than the preset temperature. In operation, it is preferable that the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning refrigerant circuit to the cascade heat exchanger. Further, when the air conditioning compressor is operated during cooling thermo-off, it is preferable to control the rotation frequency of the air conditioning compressor within a predetermined frequency range.

  Further, in the above control method, the air-conditioning for setting the temperature difference between the inlet temperature and the outlet temperature of the refrigerant on the high-pressure side of the cooling refrigerant circuit flowing to the cascade heat exchanger to be a preset set temperature difference. A target rotational frequency of the compressor is obtained, and when the target rotational frequency is within the predetermined frequency range, the rotational frequency of the air conditioning compressor is controlled to the target rotational frequency, while the rotational frequency is the predetermined rotational frequency. When the temperature difference is substantially equal to the lower limit frequency of the frequency, the temperature difference is greater than or equal to a predetermined temperature than the set temperature difference, and the rotation frequency substantially matches the upper limit frequency of the predetermined frequency, and the temperature difference is the setting When the temperature difference is equal to or lower than the predetermined temperature, it is preferable to stop the operation of the air conditioning compressor. In this case, it is preferable to adjust the target rotation frequency so that the outlet temperature of the refrigerant on the high-pressure side of the cooling refrigerant circuit that flows to the cascade heat exchanger is equal to or higher than the outside air temperature, and the set temperature It is preferable to change the difference according to the outside air temperature.

  The refrigeration system of the present invention can increase energy consumption efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a system configuration including a refrigerant circuit of a refrigeration system 1 according to an embodiment of the present invention. The refrigeration system 1 is applied to a store such as a convenience store, for example. The air conditioner in the store 2 and the refrigeration case 3 as a storage facility (cooled facility) installed in the store 2 or the refrigerator cooling of the refrigeration case 4 Is realized. The refrigerated case 3 is a case in which the inside of the refrigerator is cooled to a refrigeration temperature (+ 3 ° C. to + 10 ° C.) and beverages, refrigerated foods, etc. are displayed, and the freezing case 4 has a freezing temperature (−30 ° C.). It is a case where frozen foods or frozen desserts are displayed.

  The refrigeration system 1 includes an air conditioning system unit 6 that performs air conditioning in the store 2 and a cooling system unit 8 that cools the refrigeration case 3 and the refrigeration case 4 in the store 2. The air conditioning system section 6 includes a plurality of indoor units 11 installed in the store 2, an outdoor unit 12 installed outside the store, and an air conditioning refrigerant circuit 7 provided between these units 11 and 12. And.

  The air conditioning refrigerant circuit 7 includes a use side heat exchanger 27 installed in the indoor unit 11, a heat source side heat exchanger 16 installed in the outdoor unit 12, and compressors 13 </ b> A and 13 </ b> B as the compression unit 13. A refrigeration cycle is performed.

  Specifically, the compressor 13A is an inverter compressor, and the compressor 13B is a compressor for constant speed control. These compressors 13A and 13B are connected in parallel, the discharge sides of the compressors 13A and 13B are joined via check valves 5A and 5B, and are connected to one inlet of the four-way valve. One outlet of the four-way valve 14 is connected to the inlet of the heat source side heat exchanger 16. The heat source side heat exchanger 16 includes an inlet side 16A having a relatively small flow resistance composed of a large number of parallel pipes and an outlet side 16B in which these are aggregated into a small number of parallel pipes or a single pipe. Then, the outlet on the outlet side 16B of the heat source side heat exchanger 16 is divided through the expansion valve 17 and the expansion valve 18 and then connected to the inlet of each use side heat exchanger 27 of the indoor unit 11.

  The outlets of the respective use side heat exchangers 27 are joined together and then connected to the other inlet of the four-way valve 14 in the outdoor unit 12, and the other outlet of the four-way valve 14 is connected to the accumulator 23 via the check valve 22. Connected. The outlet of the accumulator 23 is connected to the suction side of the compressors 13A and 13B, so that the refrigerant discharged from the compression unit 13 is compressed via the heat source side heat exchanger 16 and the use side heat exchanger 27. Returned to unit 13.

  In this air conditioning refrigerant circuit 7, the refrigerant pipe between the expansion valve (first expansion valve) 17 and the expansion valve 18 is branched, and this branch pipe passes through the expansion valve (second expansion valve) 19. To the cascade heat exchanger 21. The cascade heat exchanger 21 is formed by laminating a plurality of heat transfer plates, alternately forming refrigerant passages 21A and 21B through which two kinds of refrigerants flow in each heat transfer plate tube, and connecting adjacent refrigerant passages 21A and 21B. A plate heat exchanger is used in which heat exchange is performed via a heat transfer plate while two kinds of refrigerants are circulating. In the cascade heat exchanger 21, the inlet of one refrigerant passage 21 </ b> A is connected to the expansion valve 19, and the outlet thereof is connected to the inlet of the accumulator 23. Thus, the refrigerant whose pressure is reduced by the expansion valve 19 is supplied to the cascade heat exchanger 21 and then returned to the compression unit 13.

  That is, in the refrigeration system 1, a path α passing through the use side heat exchanger 27 and a path β passing through the cascade heat exchanger 21 are formed as the refrigerant circulation paths.

  The outdoor air conditioning controller 26 is configured by a general-purpose microcomputer, and controls the equipment of the air conditioning system unit 6 on the outdoor unit 12 side based on the outside air temperature and the refrigerant pressure. The indoor air conditioning controller 28 is composed of a general-purpose microcomputer, and controls the equipment on the indoor unit 11 side based on a user instruction transmitted from a remote controller (not shown) and input via a receiving unit (not shown). Control or data communication of information in accordance with a user instruction to the outdoor air conditioning controller 26 is performed. The blower 24 is a blower that blows outside air to the heat source side heat exchanger 16, and the blower 15 is a blower that sends room air to the use side heat exchanger 27.

  On the other hand, the cooling system unit 8 includes a refrigeration case 3 and a refrigeration case 4 as storage facilities, and a cooling refrigerant circuit 9 provided between the outdoor unit 12. The cooling refrigerant circuit 9 includes a refrigeration evaporator 43 provided in the refrigeration case 3, a condenser (heat exchanger) 38 installed in the outdoor unit 12, a compressor 37 and a compressor 54 as compression units. A refrigeration cycle is performed.

  More specifically, the discharge side of the compressor 37 is connected to one inlet of the four-way valve 39 via the oil separator 31, and one outlet of the four-way valve 39 is connected to the inlet of the condenser 38. The condenser 38 includes an inlet side 38A having a relatively small flow resistance composed of a large number of parallel pipes and an outlet side 38B in which these are aggregated into a small number of parallel pipes or a single pipe. The outlet on the outlet side 38B of the condenser 38 is connected to the inlet of the receiver tank 36, and the outlet of the receiver tank 36 is connected to one inlet of the four-way valve 41. That is, the receiver tank 36 is connected to the refrigerant downstream side of the condenser 38.

  One outlet of the four-way valve 41 is connected to the inlet of the other refrigerant passage 21 </ b> B of the cascade heat exchanger 21. The outlet of the refrigerant passage 21 </ b> B of the cascade heat exchanger 21 is connected to the other inlet of the four-way valve 39, and the other outlet of the four-way valve 39 is connected to the other inlet of the four-way valve 41. The other outlet of the four-way valve 41 is branched into three, and the first branch pipe is connected to the inlet of one refrigeration evaporator 43 through the solenoid valves 47 and 46 and the expansion valve 44 in sequence. The second branch pipe is connected to the inlet of the other refrigeration evaporator 43 through the solenoid valve 46 and the expansion valve 44 in this order, and the third branch pipe is frozen for freezing through the solenoid valve 52 and the expansion valve 51. Connected to the inlet of the vessel 49. An electromagnetic valve 53 is connected in parallel with the series circuit of the electromagnetic valve 52 and the expansion valve 51.

  The outlet of the refrigeration evaporator 49 is connected to the suction side of the compressor 54 via the check valve 30, and via the check valve 48 between the electromagnetic valves 46 and 47 on the refrigeration evaporator 43 side. Connected. The compressor 54 is a compressor having a smaller output than the compressor 37, and the discharge side thereof is connected to the suction side of the compressor 37 via the oil separator 45. That is, the compressor 37 and the compressor 54 are connected in series on the refrigerant circuit. Further, the oil separator 45 and the compressor 37 are connected after the outlets of the refrigeration evaporators 43 are joined. The suction side of the compressor 37 is connected to the outlet of the oil separator 31 via a check valve 42.

  The outdoor side cooling controller 32 is composed of a general-purpose microcomputer, and controls the equipment of the cooling system unit 8 on the outdoor unit 12 side based on the outside air temperature and the refrigerant pressure. Moreover, the indoor side refrigeration controller 50 is comprised with a general purpose microcomputer, and controls the apparatus of the cooling system part 8 based on the internal temperature of the storage facility for refrigeration (refrigeration case 3). Moreover, the indoor side freezing controller 55 is comprised with a general purpose microcomputer, and controls the apparatus of the cooling system part 8 based on the internal temperature of the storage facility for freezing (refrigeration case 4). The blower 35 is a blower that blows outside air to the condenser 38, the blower 20 is a blower that sends the air in the refrigerator case 3 to the condenser 38, and the blower 25 is frozen to the freezing evaporator 49. This is a blower for sending the air in the case 4.

  Further, the refrigeration system 1 has a main controller 56. The main controller 56 is composed of a general-purpose microcomputer and performs data communication with the outdoor side air conditioning controller 26, the indoor side air conditioning controller 28, the outdoor side cooling controller 32, the indoor side refrigeration controller 50, and the indoor side freezing controller 55, thereby The entire system 1 is controlled. In the refrigeration system 1, different refrigerants are used in the air conditioning refrigerant circuit 7 and the cooling refrigerant circuit 9. For example, R410A is used in the air conditioning refrigerant circuit 7, and R410A is used in the cooling refrigerant circuit 9. R404A having a higher boiling point is used. Thus, since this refrigeration system 1 can use the optimal refrigerant | coolant for each refrigerant circuit, respectively, the freedom degree of circuit design can be made high.

  Next, the operation of the refrigeration system 1 will be described.

  In this refrigeration system 1, the air conditioning system 6 responds to the difference between the set temperature instructed by the outdoor side air conditioning controller 26 and the indoor side air conditioning controller 28 via the remote controller and the temperature in the store (room temperature TA). Then, the cooling operation or the heating operation is performed to air-condition the room temperature to the set temperature. In addition, the cooling system unit 8 sets the internal temperature of the refrigeration case 3 to a preset refrigeration temperature under the control of the outdoor side cooling controller 32, the indoor side refrigeration controller 50, and the indoor side refrigeration controller 55, and the refrigeration case The inside temperature of 4 is set to a preset freezing temperature.

  More specifically, in this refrigeration system 1, the main controller 56 communicates data with each of the controllers 26, 28, 32, 50, 55 to obtain data on the current operating state of the air conditioning system unit 6 and the cooling system unit 8. Based on the received data, an optimum operation pattern at that time, which will be described later, is determined, and data relating to the optimum operation pattern and operation data of each device are transmitted to the controllers 26, 28, 32, 50, 55. Each controller 26, 28, 32, 50, 55 executes a control operation to be described later based on the data received from the main controller 56.

(1) Cooling operation of air conditioning system section First, when the indoor side air conditioning controller 28 determines that the cooling operation of the air conditioning system section 6 is optimal, the indoor side air conditioning controller 28 is directed to the outdoor air conditioning controller 26 and the main controller 56 to perform the cooling operation. The main controller 56 that has received the data transmits the data to the outdoor side cooling controller 32, the indoor side refrigeration controller 50, and the indoor side refrigeration controller 55.

  As shown in FIG. 1, the outdoor air-conditioning controller 26 uses one inlet (a connection port with the oil separator 10) of the four-way valve 14 as one outlet (a connection port with the heat source side heat exchanger 16) based on the received data. And the other inlet (connection port with the use side heat exchanger 27) is communicated with the other outlet (connection port with the accumulator 23). Further, the expansion valve 17 is fully opened, and the compressors 13A and 13B are operated. The outdoor air-conditioning controller 26 controls the capacity of the compressor 13A by inverter-controlling the operation frequency.

  When the compressors 13A and 13B are operated, the high-temperature and high-pressure gas refrigerant discharged from the discharge sides of the compressors 13A and 13B passes through the four-way valve 14 from the oil separator 10 to the inlet side 16A of the heat source side heat exchanger 16. enter. Outside air is ventilated by the air blower 24 to the heat source side heat exchanger 16, and the refrigerant dissipates heat here to be condensed and liquefied. That is, in this case, the heat source side heat exchanger 16 functions as a condenser. The liquid refrigerant is branched after passing through the expansion valve 17 via the heat source side heat exchanger 16. One of the branches reaches the expansion valve 18, where it is throttled to a low pressure (decompression), and then branches into each use side heat exchanger 27 and flows there.

  Indoor air (air in the store) is ventilated by the blower 15 to the use side heat exchanger 27, and the indoor air is cooled by an endothermic action due to evaporation of the refrigerant. Thereby, the room (inside the store) is cooled.

  After the low-temperature gas refrigerant that has exited from the use side heat exchanger 27 is merged, circulation is repeated through the four-way valve 14, the check valve 22, and the accumulator 23 to be supplied to the suction sides of the compressors 13 </ b> A and 13 </ b> B.

  Further, the other refrigerant branched after passing through the expansion valve 17 reaches the expansion valve 19 where it is throttled to a low pressure (decompression), and then flows into the refrigerant passage 21A of the cascade heat exchanger 21 where it evaporates. . The cascade heat exchanger 21 is cooled by the endothermic action due to the evaporation of the refrigerant in the air-conditioning refrigerant circuit 7 and becomes a low temperature. The low-temperature gas refrigerant exiting the cascade heat exchanger 21 repeats circulation supplied to the suction sides of the compressors 13A and 13B via the accumulator 23.

  The indoor side air conditioning controller 28 sets the temperature of the room (inside the store) in advance based on the temperature of the use side heat exchanger 27 detected via a temperature sensor (not shown) and the temperature of the air sucked therein. Then, the blower 15 that ventilates the use side heat exchanger 27 is controlled. Information on the indoor air conditioning controller 28 is transmitted to the outdoor air conditioning controller 26, and the outdoor air conditioning controller 26 controls the operation of the compressors 13A and 13B based on this information.

  The outdoor air-conditioning controller 26 detects the refrigerant temperature at the entrance / exit of the use side heat exchanger 27 or the temperature of the use side heat exchanger 27 detected via a temperature sensor (not shown) and the entrance / exit of the cascade heat exchanger 21. Based on the refrigerant temperature or the temperature of the cascade heat exchanger 21, the valve openings of the expansion valves 18 and 19 are adjusted so as to obtain an appropriate degree of superheat.

  On the other hand, the outdoor side cooling controller 32 supplies one inlet (oil) of the four-way valve 39 of the cooling refrigerant circuit 9 of the cooling system unit 8 in order to supply the high-temperature and high-pressure gas refrigerant discharged from the compressor 37 to the condenser 38. The connection port with the separator 31 is connected to one outlet (connection port with the condenser 38), and the other inlet (connection port with the cascade heat exchanger 21) is connected to the other outlet (connection port with the four-way valve 41). ).

  In addition, the outdoor side cooling controller 32 uses one inlet (a connection port with the four-way valve 39) of the four-way valve 41 as one outlet (refrigeration) in order to supply the gas refrigerant that has passed through the condenser 38 to the cascade heat exchanger 21. Communication with the evaporator 43 and the refrigeration evaporator 49 (connection ports with the electromagnetic valves 46, 47, 52), and the other inlet (connection port with the receiver tank 36) is connected with the other outlet (cascade heat exchanger 21). Communication port). Then, the compressors 37 and 54 are operated.

  As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 37 enters the inlet side 38 </ b> A of the condenser 38 through the four-way valve 39 after the oil is separated by the oil separator 31. Outside air is passed through the condenser 38 by the blower 35, and the refrigerant flowing into the condenser 38 dissipates heat and condenses. The refrigerant discharged from the condenser 38 enters the receiver tank 36 and is temporarily stored therein to separate the gas / liquid. The separated liquid refrigerant exits from the receiver tank 36 and passes through the four-way valve 41, and then enters the refrigerant passage 21B of the cascade heat exchanger 21. The refrigerant in the cooling refrigerant circuit 9 supplied to the cascade heat exchanger 21 is cooled by the cascade heat exchanger 21 that is at a low temperature due to evaporation of the refrigerant in the air conditioning refrigerant circuit 7 as described above, and further subcooled. The Since the receiver tank 36 is disposed immediately after the condenser 38 as described above, heat loss during supercooling can be eliminated and the amount of refrigerant can be adjusted.

  The refrigerant supercooled in the cascade heat exchanger 21 is branched after sequentially passing through the four-way valves 39, 41, one is further branched, and the other is sequentially passed through the electromagnetic valves 47, 46, and then the expansion valve 44. After being throttled by (reduced pressure), it is supplied to one refrigeration evaporator 43, where it evaporates and the other branched through the electromagnetic valve 46 to the expansion valve 44, where it is throttled (reduced pressure), It flows into the other refrigeration evaporator 43 and evaporates there. In each refrigeration evaporator 43, the air in the refrigerator case 3 is ventilated and circulated by the blower 20, and the air in each refrigerator is cooled by the endothermic action due to the evaporation of the refrigerant. Thereby, the inside cooling of the refrigeration case 3 is performed. These low-temperature gas refrigerants exiting the refrigeration evaporator 43 are merged and then reach the outlet side of the oil separator 45 of the compressor 54.

  The other refrigerant that is subcooled and branched in the cascade heat exchanger 21 passes through the electromagnetic valve 52 to reach the expansion valve 51, where it is throttled (decompression) and then supplied to the refrigeration evaporator 49. Where it evaporates. The refrigeration evaporator 49 is circulated and circulated with the air in the refrigeration case 4 by the blower 25, and the refrigeration evaporator 49 is cooled by the endothermic effect of the evaporation of the refrigerant. Thereby, the inside cooling of the freezing case 4 is performed.

  The low-temperature gas refrigerant exiting the freezing evaporator 49 reaches the compressor 54 via the check valve 30, where it is compressed and pressurized to the pressure on the outlet side of the refrigerating evaporator 43 (low pressure side pressure of the refrigerating system). After that, the oil is discharged from the compressor 54 and separated by the oil separator 45, and then merged with the refrigerant from the refrigeration evaporator 43. The merged refrigerant repeats circulation that is sucked into the suction side of the compressor 37.

  The indoor side refrigeration controller 50 detects the internal temperature of the refrigeration case 3 detected through a temperature sensor (not shown), the cold air temperature discharged through the refrigeration evaporator 43 or the cold air temperature sucked into the refrigeration evaporator 43, and the refrigeration. The opening degree of each expansion valve 44 is controlled based on the refrigerant temperature on the outlet side of the evaporator 43 for cooling or the temperature of the evaporator 43 for refrigeration. Thereby, it is set as the appropriate superheat degree (constant superheat degree), maintaining the inside of the refrigerator | coolant case 3 cooling at the refrigeration temperature mentioned above.

  Further, the indoor side refrigeration controller 55 is configured such that the inside temperature of the refrigeration case 4, the temperature of the cold discharged from the refrigeration evaporator 49, or the temperature of the intake chilled air to the refrigeration evaporator 49, and the refrigerant on the outlet side of the refrigeration evaporator 49. The valve opening degree of the expansion valve 51 is controlled based on the temperature or the temperature of the freezing evaporator 49. As a result, while maintaining the inside of the freezing case 4 to be cooled to the above-described freezing temperature, an appropriate degree of superheat (constant superheat) is obtained.

  Further, the outdoor cooling controller 32, when any one of the expansion valves 44, 51 is open, is based on the suction side pressure of the compressor 37 (low pressure of the cooling refrigerant circuit 9). And the operation of the compressor 37 is stopped when all the expansion valves 44 and 51 are fully closed.

  Thus, during the cooling operation, the low-pressure side refrigerant flowing through the air-conditioning refrigerant circuit 7 is supplied to the cascade heat exchanger 21, and the high-pressure side refrigerant flowing through the cooling refrigerant circuit 9 is supercooled, thereby cooling The cooling capacity and operation efficiency of the system part 8 can be improved.

  Note that the pressure of the refrigerant discharged from the refrigeration evaporator 49 of the cooling refrigerant circuit 9 is lower than that of the refrigerant discharged from the refrigeration evaporator 43 because the evaporation temperature thereof is lower, but the refrigerant discharged from the refrigeration evaporator 43 is reduced. Since it is compressed by the compressor 54 before merging with the refrigerant, the compressor 54 compresses the compressor while cooling each case to an appropriate temperature even when controlling to different chamber temperatures such as the refrigeration case 3 and the refrigeration case 4. The pressure of the refrigerant sucked into 37 can be made uniform, and the operation can be performed without any trouble.

(2) Heating operation of the air conditioning system unit Next, the heating operation of the air conditioning system unit will be described with reference to FIG.

  First, when the indoor side air conditioning controller 28 determines that the heating operation of the air conditioning system unit 6 is optimal, the indoor side air conditioning controller 28 transmits predetermined data to the outdoor air conditioning controller 26 and the main controller 56 to perform the heating operation. The main controller 56 that has received the data transmits these data to the outdoor side cooling controller 32, the indoor side refrigeration controller 50, and the indoor side refrigeration controller 55.

  Based on the received data, the outdoor air-conditioning controller 26 connects one inlet (a connection port with the oil separator 10) of the four-way valve 14 to one outlet (the accumulator 23) in order to reverse the refrigerant flow to that during the cooling operation. The other inlet (connection port with the use side heat exchanger 27) is communicated with the other outlet (connection port with the heat source side heat exchanger 16). Further, the expansion valve 17 is fully closed and the expansion valve 18 is fully opened, and the compressors 13A and 13B are operated.

  When the compressors 13A and 13B are operated, the high-temperature and high-pressure gas refrigerant discharged from the discharge sides of the compressors 13A and 13B is supplied to the use-side heat exchanger 27 via the four-way valve 14. The use side heat exchanger 27 is ventilated with room air by the blower 15, and the refrigerant dissipates heat here and heats the room air while condensing. Thereby, the room (inside the store) is heated.

  The refrigerant liquefied by the use side heat exchanger 27 is reduced in pressure through the expansion valve 18 and the expansion valve 19 in order (decompression), and then flows into the refrigerant passage 21A of the cascade heat exchanger 21 where it evaporates. After absorbing heat, the circulation supplied to the suction side of the compressors 13A and 13B through the accumulator 23 is repeated.

  The outdoor side air conditioning controller 26 adjusts the valve opening degree of the expansion valves 18 and 19 so as to achieve an appropriate degree of superheat based on the refrigerant temperature at the entrance and exit of the cascade heat exchanger 21 or the temperature of the cascade heat exchanger 21. . Moreover, the indoor side air conditioning controller 28 uses the use side heat exchanger 27 so that the temperature of the room (inside the store) is set to a preset temperature based on the temperature of the use side heat exchanger 27 and the air temperature sucked therein. The blower 15 that ventilates the air is controlled.

  On the other hand, the outdoor side cooling controller 32 uses one inlet (a connection port with the oil separator 31) of the four-way valve 39 of the cooling refrigerant circuit 9 of the cooling system unit 8 as one outlet (a connection port with the four-way valve 41). The other inlet (connection port with the cascade heat exchanger 21) is communicated with the other outlet (connection port with the condenser 38). In addition, the outdoor side cooling controller 32 uses one inlet (a connection port with the four-way valve 39) of the four-way valve 41 as one outlet (a refrigeration evaporator 43 and a freezing evaporator 49 (solenoid valves 46, 47, 52)). And the other inlet (connection port with the receiver tank 36) is communicated with the other outlet (connection port with the cascade heat exchanger 21). Then, the compressors 37 and 54 are operated.

  Thus, the high-temperature and high-pressure gas refrigerant discharged from the compressor 37 is supplied to the refrigerant passage 21B of the cascade heat exchanger 21 via the four-way valves 39 and 41. That is, the high-temperature and high-pressure gas refrigerant discharged from the compressor 37 is supplied to the cascade heat exchanger 21 after passing through the condenser 38 in the cooling operation, whereas the cascade heat exchange is performed before going to the condenser 38. Is supplied to the vessel 21.

  The refrigerant in the cooling refrigerant circuit 9 supplied to the cascade heat exchanger 21 is cooled by the cascade heat exchanger 21 that is at a low temperature due to evaporation of the refrigerant in the air conditioning refrigerant circuit 7 as described above, and further subcooled. The In other words, the refrigerant in the air conditioning refrigerant circuit 7 can pump up heat from the refrigerant in the cooling refrigerant circuit 9.

  The refrigerant that has passed through the refrigerant passage 21 </ b> B of the cascade heat exchanger 21 enters the inlet side 38 </ b> A of the condenser 38 through the four-way valve 39. Outside air is passed through the condenser 38 by the blower 35, and the refrigerant flowing into the condenser 38 dissipates heat and condenses.

  The refrigerant discharged from the condenser 38 enters the receiver tank 36 and is temporarily stored therein to separate the gas / liquid. The separated liquid refrigerant is branched after leaving the receiver tank 36 and passing through the four-way valve 41, one branching further, one passing through the electromagnetic valves 47 and 46 sequentially, and being throttled by the expansion valve 44 ( Pressure reduction) is supplied to one refrigeration evaporator 43, where it evaporates, and the other branched through the electromagnetic valve 46 reaches the expansion valve 44, where it is throttled (decompression) and the other refrigeration evaporator. 43 where it evaporates. In each refrigeration evaporator 43, the air in the refrigerator case 3 is ventilated and circulated by the blower 20, and the air in each refrigerator is cooled by the endothermic action due to the evaporation of the refrigerant.

  By the above operation, even during the heating operation of the air conditioning refrigerant circuit 7, the low-pressure side refrigerant flowing through the air-conditioning refrigerant circuit 7 is supplied to the cascade heat exchanger 21, and the high-pressure side refrigerant flowing through the cooling refrigerant circuit 9 is excessively passed. By cooling, the cooling capacity of the refrigeration evaporators 43 and 44 of the refrigeration case 3 and the refrigeration case 4 and the operation efficiency of the cooling system unit 8 can be improved.

  Furthermore, during the heating operation, the refrigerant in the air conditioning refrigerant circuit 7 pumps up heat from the refrigerant in the cooling refrigerant circuit 9 in the cascade heat exchanger 21, so that the heating capacity of the air conditioning system unit 6 can be improved. The efficiency of the entire refrigeration system 1 that performs indoor air conditioning and cooling of the refrigeration case 3 and the refrigeration case 4 can be improved to save energy.

  Particularly in this case, the refrigerant on the high-pressure side of the cooling refrigerant circuit 9 is supplied to the cascade heat exchanger 21 before the condenser 38, so that exhaust heat recovery from this refrigerant is efficiently performed, and the air conditioning refrigerant circuit 7 The heating capacity can be further improved.

(3) Operation control at the time of thermo-off at the time of cooling operation of the air conditioning system section By the way, in a general air conditioner (corresponding to the air conditioning system section 6), the room temperature is substantially the same as or lower than the set temperature during the cooling operation. In the state, that is, when the cooling thermo-off is being performed, the operation of the compression unit (corresponding to the compression unit 13) is stopped. On the other hand, the refrigeration system 1 of the present embodiment operates the compression unit 13 of the air conditioning system unit 6 and flows through the cooling system unit 8 when the cooling system unit 8 is operating even when the cooling thermostat is off. The refrigerant is supercooled.
Hereinafter, the operation when the cooling thermostat is off will be described.

  3 and 4 are flowcharts showing the operation during cooling thermo-off.

  First, the main controller 56 determines whether or not the compression unit (the compressors 37 and 54) of the cooling system unit 8 is ON (operating) based on the data received from the outdoor cooling controller 32 (step S1). When the compression unit is OFF (during operation stop), the valve fixing pulse Pv of the expansion valve 19 is set to zero so that the valve opening is zero (fully closed), and the rotation of the compression unit 13 of the air conditioning system unit 6 is rotated. The frequency Fr is set to zero and the compression unit 13 is stopped (step S20).

  On the other hand, when the compression unit of the cooling system unit 8 is ON, the main controller 56 determines whether or not the cooling system unit 8 is defrosting (step S2). On the other hand, if it is not defrosting, it is determined whether or not the compression unit 13 is forcibly stopped based on the data received from the outdoor air conditioning controller 26 (step S3). Here, when the compression unit 13 is forcibly stopped, after the compression unit 13 is completely stopped, the compression unit 13 is held in a stopped state for a predetermined forced stop period (for example, 3 minutes) to protect the compression unit 13. It is a state to do.

  When the compression unit 13 is not forcibly stopped, the outdoor air-conditioning controller 26 sets the valve fixing pulse Pv of the expansion valve 19 to a predetermined initial pulse according to an instruction from the main controller 56, and opens the valve opening of the expansion valve 19. Is controlled from the fully closed state to the initial opening degree (step S4). That is, the expansion valve 19 is opened and fixedly controlled to the initial opening degree when the condition that the compression unit of the cooling system unit 8 is not operating, defrosting, and the compression unit 13 of the air conditioning system unit 6 is not forcibly stopped. .

  Next, the outdoor air conditioning controller 26 sets the target rotation frequency Fr of the compression unit 13 to a predetermined initial target frequency (step S5). In the present embodiment, the setting of the target rotation frequency Fr of the compression unit 13 means the setting of the target rotation frequency of the compressor 13A, and when the compressor 13A is rotated, the compressor 13B is set to a preset steady state. The rotation frequency for rotation is controlled.

  By the operation of the compression unit 13, the refrigerant circulates through the air conditioning refrigerant circuit 7, and the refrigerant whose pressure is reduced by the expansion valve 19 is supplied to the refrigerant passage 21 </ b> A of the cascade heat exchanger 21. Thereby, the cascade heat exchanger 21 is cooled by the endothermic action due to the evaporation of the refrigerant, and the high-pressure side refrigerant of the cooling refrigerant circuit 9 flowing through the refrigerant passage 21B of the cascade heat exchanger 21 can be supercooled.

  Next, the outdoor air conditioning controller 26 sets the temperature difference ΔTE on the basis of the temperature difference ΔTE between the refrigerant outlet temperature TE2 and the inlet temperature TE1 on the air conditioning system unit 6 side in the cascade heat exchanger 21. The SH control (step S6) for setting the correction pulse Δa of the valve fixing pulse Pv for setting the temperature difference SH, the discharge temperature of the compression unit 13 of the air conditioning system unit 6 (discharge temperature TD1 of the compressor 13A, the compressor 13B) Based on the discharge temperature TD2), TD control (step S7) for setting the correction pulse Δb of the valve fixing pulse Pv for protecting the compression unit 13 is performed. The correction pulse Δb is set when the discharge temperature of the compression unit 13 becomes equal to or higher than a predetermined temperature.

  Further, the outdoor air conditioning controller 26 sets the temperature difference ΔSC to a predetermined target temperature based on the temperature difference ΔSC between the refrigerant inlet temperature TC1 and the outlet temperature TC2 on the cooling system unit 8 side in the cascade heat exchanger 21. SC control is performed to set the correction rotation frequency Δc of the compression unit 13 so as to set the difference (set temperature difference) SC and the outlet temperature TC2 to be equal to or higher than the outside air temperature (step S8). Here, the refrigerant outlet temperature TC2 is set to be equal to or higher than the outside air temperature. Usually, a heat insulating material is wound around the refrigerant pipe (indicated by γ in FIG. 1) connecting the cascade heat exchanger 21 and the four-way valve 39. This is because if the refrigerant passing through the refrigerant pipe is lower than the outside air temperature, the refrigerant is warmed and flash gas is generated, resulting in heat loss. However, when the heat insulating material is wound around the refrigerant pipe γ, it is only necessary to set the temperature difference ΔSC to the predetermined target temperature difference SC at the correction frequency ΔFr in step S8, and the refrigerant outlet temperature TC2 is set. Conditions that make the temperature higher than the outside temperature may be excluded.

  The target temperature difference SC is changed according to the outside air temperature. For example, if the outside air temperature is 30 ° C. or higher, the value SC1 is set. If the outside air temperature is 20 ° C. or higher and lower than 30 ° C., the value SC2 is set. If the outside air temperature is lower than 20 ° C., the value SC3 is changed. Here, the target temperature difference SC is set to a value SC1 <value SC2 <value SC3 so that the target temperature difference SC is set to a larger value as the outside air temperature is lower.

  Then, the outdoor air conditioning controller 26 adds the correction pulses Δa and Δb obtained in steps S6 and S7 to the current valve fixing pulse Pv (Pv # old) to obtain the value of the valve fixing pulse Pv to be controlled next. Calculate (step S9), set the valve fixing pulse Pv of the expansion valve 19 within the range of the upper limit pulse (Pv # max) and the lower limit pulse (Pv # min) of the expansion valve 19 and control the valve opening (step S10). ).

  Next, the outdoor air conditioning controller 26 adds the corrected rotation frequency Δc obtained in step S8 to the current target rotation frequency Fr (Fr # old), and calculates the next target rotation frequency Fr of the compression unit 13. (Step S11). If the calculated target rotation frequency Fr is within the range between the upper limit frequency (Fr # max) and the lower limit frequency (Fr # min), the rotation speed of the compression unit 13 is controlled to the target rotation frequency Fr (step S12). .

  Here, the range of the upper limit frequency (Fr # max) and the lower limit frequency (Fr # min) is the upper limit value and lower limit of the frequency range in which the efficiency of the compression unit 13 (compressor 13A) is good (efficiency greater than or equal to a predetermined value). Set to a value. Thereby, it is possible to control the compression unit 13 to an efficient rotation frequency.

  However, even if the rotation frequency of the compression unit 13 is lowered to the lower limit frequency, the refrigerant in the air conditioning system section 6 is excessively cooled, and even if the rotation frequency of the compression unit 13 is raised to the upper limit frequency, the air conditioning system section 6 When any of the conditions when the refrigerant cannot be supercooled is satisfied, the rotation of the compression unit 13 is stopped and the operation of the air conditioning system unit 6 is stopped.

  Specifically, after the process of step S12, the outdoor air conditioning controller 26 determines whether or not the target rotation frequency Fr substantially matches the lower limit frequency (step S13), and the target rotation frequency Fr is set to the upper limit frequency. It is determined whether or not they substantially match (step S14). If it is determined that neither the lower limit frequency nor the upper limit frequency matches, the process proceeds to step S1.

  On the other hand, when the target rotational frequency Fr substantially coincides with the lower limit frequency, the outdoor air conditioning controller 26 determines that the temperature difference ΔSC at the refrigerant inlet / outlet in the cascade heat exchanger 21 is a predetermined temperature than the target temperature difference SH. It is determined whether or not the temperature is higher than (eg, 10 ° C.) (step S15). If the temperature is higher than the temperature, the process proceeds to step S20. As a result, the rotation of the compression unit 13 is stopped, the opening degree of the expansion valve 19 is set to zero, and the operation of the air conditioning system unit 6 is stopped.

  When the target rotational frequency Fr substantially coincides with the upper limit frequency, the outdoor air conditioning controller 26 determines that the temperature difference ΔSC at the refrigerant inlet / outlet of the air conditioning system unit 6 in the cascade heat exchanger 21 is higher than the target temperature difference SH by a predetermined temperature ( For example, it is determined whether or not the temperature is lower than or equal to 5 ° C. (step S16).

  Then, the outdoor air conditioning controller 26 proceeds to the process of step S1 even if any of the above processes is executed, and repeatedly executes the processes of steps S1 to S14 or the processes of steps S1 to S20 while the cooling thermostat is off. Thereby, the cooling thermo-off is being performed, and the rotation control of the compression unit 13 and the valve opening degree control of the expansion valve 19 are executed.

  The above operation is not limited to when the cooling thermo-off is performed, but in a state where the operation of the air-conditioning system unit 6 is stopped by a stop instruction from the remote controller or the like after the cooling operation, that is, in the air-conditioning operation stopped state after the cooling operation. Is also implemented.

  As described above, the refrigeration system 1 includes the compression unit 13 of the air conditioning system unit 6 when the compression unit (the compressors 37 and 54) of the cooling system unit 8 is operating when the compression unit 13 of the air conditioning system unit 6 is stopped. Since the low-pressure side refrigerant flowing through the air-conditioning refrigerant circuit 7 is supplied to the cascade heat exchanger 21, the high-pressure side refrigerant flowing through the cooling refrigerant circuit 9 is always supercooled even during the cooling thermo-off. be able to. As a result, it is possible to avoid a situation in which the cooling capacity of the cooling system unit 8 is lowered during the cooling thermo-off, and it is possible to maintain the cooling capacity and the operation efficiency of the cooling system unit 8 in a high state. In particular, during the cooling thermo-off, the compression unit 13 of the air conditioning system unit 6 is controlled within an efficient rotational frequency range, so that the energy consumption efficiency can be further improved.

  Further, by setting the target temperature difference SC of the temperature difference ΔSC between the refrigerant inlet temperature TC1 and the outlet temperature TC2 of the cooling system section 8 side in the cascade heat exchanger 21 to a larger value as the outside air temperature is lower, the outside air temperature is increased. Accordingly, the supercooling degree of the refrigerant in the cooling system unit 8 can be adjusted appropriately.

  In the above-described embodiment, the expansion valve 19 may use various electric valves as long as the supply / stop of the refrigerant can be switched.

  Moreover, although the said embodiment described the case where this invention is applied to the refrigeration system applied to stores, such as a convenience store, air conditioning and cooling of to-be-cooled facilities other than the refrigeration case 3 and the refrigeration case 4 are performed. Can be widely applied to refrigeration system. Furthermore, the piping configuration shown in the above embodiment is not limited thereto, and can be appropriately changed without departing from the gist of the present invention.

It is a figure which shows the system configuration | structure containing the refrigerant circuit of the refrigerating system which concerns on embodiment of this invention. It is a figure for demonstrating the heating operation of the air-conditioning system part of the refrigeration system which concerns on embodiment of this invention. It is a flowchart which shows the operation | movement during air_conditioning | cooling thermo-off. It is a flowchart which shows the operation | movement during air_conditioning | cooling thermo-off.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration system 3 Refrigeration case 4 Refrigeration case 6 Air-conditioning system part 7 Air-conditioning system part 7 Air-conditioning refrigerant circuit 8 Cooling system part 9 Cooling refrigerant circuit 10 Oil separator 11 Indoor unit 12 Outdoor unit 13 Compression unit 13A, 13B, 37, 54 Compressor 17, 18, 19 Expansion valve 21 Cascade heat exchanger

Claims (13)

An air conditioning system unit having an air conditioning refrigerant circuit including an air conditioning compressor, a heat source side heat exchanger, and a usage side heat exchanger, and operating the air conditioning compressor to perform indoor air conditioning by the usage side heat exchanger;
A cooling system having a cooling refrigerant circuit including a cooling compressor, a condenser and an evaporator, operating the cooling compressor and cooling the cooled equipment by the evaporator; and
A cascade heat exchanger for performing heat exchange between the low-pressure side refrigerant of the air-conditioning refrigerant circuit and the high-pressure side refrigerant of the cooling refrigerant circuit;
When the cooling compressor is in operation when the air conditioning compressor is stopped, the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning refrigerant circuit to the cascade heat exchanger. Refrigeration system. The air-conditioning system unit is operating when the air-conditioning compressor is stopped while the air-conditioning compressor is in a cooling thermo-off state where the room temperature is substantially the same as or lower than the preset temperature. In this case, the air-conditioning compressor is operated to supply the refrigerant on the low-pressure side of the air-conditioning refrigerant circuit to the cascade heat exchanger. 3. The refrigeration system according to claim 1, wherein when the air conditioning compressor is operated during cooling thermo-off, a rotation frequency of the air conditioning compressor is controlled within a predetermined frequency range. The air-conditioning system section is configured such that the air-conditioning compressor is configured to set a temperature difference between an inlet temperature and an outlet temperature of a refrigerant on a high-pressure side of the cooling refrigerant circuit flowing through the cascade heat exchanger as a preset temperature difference. The target rotation frequency of
When this target rotational frequency is within the predetermined frequency range, the rotational frequency of the air conditioning compressor is controlled to the target rotational frequency, while the rotational frequency substantially matches the lower limit frequency of the predetermined frequency. When the temperature difference is equal to or higher than the preset temperature difference and the rotation frequency is substantially equal to the upper limit frequency of the predetermined frequency, and the temperature difference is equal to or less than the preset temperature difference from the preset temperature difference The refrigeration system according to claim 3, wherein the operation of the air conditioning compressor is stopped. The air conditioning system unit adjusts the target rotation frequency so that an outlet temperature of a refrigerant on a high-pressure side of the cooling refrigerant circuit that is passed through the cascade heat exchanger is equal to or higher than an outside air temperature. 4. The refrigeration system according to 4. The refrigeration system according to claim 4 or 5, wherein the set temperature difference is changed according to an outside air temperature. In the refrigerant circuit for air conditioning, a first expansion valve is provided between the heat source side heat exchanger and the use side heat exchanger, and between the heat source side heat exchanger and the first expansion valve. The refrigerant pipe is branched, and this branch pipe is connected to the cascade heat exchanger via a second expansion valve,
The refrigeration system according to any one of claims 4 to 6, wherein a valve opening degree of the second expansion valve is controlled so that the temperature difference becomes the set temperature difference. In the control method of the refrigeration system that performs indoor air conditioning and cooling of the equipment to be cooled,
The refrigeration system includes an air conditioning refrigerant circuit including an air conditioning compressor, a heat source side heat exchanger, and a usage side heat exchanger, and operates the air conditioning compressor to perform indoor air conditioning by the usage side heat exchanger. A cooling system including a system part, a cooling refrigerant circuit including a cooling compressor, a condenser, and an evaporator; and operating the cooling compressor to cool the cooled equipment by the evaporator; and A cascade heat exchanger for performing heat exchange between the low-pressure side refrigerant of the refrigerant circuit and the high-pressure side refrigerant of the cooling refrigerant circuit,
When the cooling compressor is in operation when the air conditioning compressor is stopped, the air conditioning compressor is operated to supply the refrigerant on the low pressure side of the air conditioning refrigerant circuit to the cascade heat exchanger. A control method of the refrigeration system. When the cooling compressor is in operation when the air conditioning compressor is stopped in the cooling thermo-off state where the indoor temperature is substantially the same as or lower than the preset temperature, the air conditioning 9. The method for controlling a refrigeration system according to claim 8, wherein a compressor is operated to supply a refrigerant on a low-pressure side of the air conditioning refrigerant circuit to the cascade heat exchanger. The control of the refrigeration system according to claim 8 or 9, wherein when the air conditioning compressor is operated during a cooling thermo-off, a rotation frequency of the air conditioning compressor is controlled within a predetermined frequency range. Method. A target rotational frequency of the air conditioning compressor for obtaining a preset temperature difference between the inlet temperature and the outlet temperature of the refrigerant on the high-pressure side of the cooling refrigerant circuit flowing through the cascade heat exchanger is obtained. ,
When this target rotational frequency is within the predetermined frequency range, the rotational frequency of the air conditioning compressor is controlled to the target rotational frequency, while the rotational frequency substantially matches the lower limit frequency of the predetermined frequency. When the temperature difference is equal to or higher than the preset temperature difference and the rotation frequency is substantially equal to the upper limit frequency of the predetermined frequency, and the temperature difference is equal to or less than the preset temperature difference from the preset temperature difference The method for controlling the refrigeration system according to claim 10, wherein the operation of the compressor for air conditioning is stopped. 12. The refrigeration system according to claim 11, wherein the target rotation frequency is adjusted such that an outlet temperature of a refrigerant on a high-pressure side of the cooling refrigerant circuit that flows to the cascade heat exchanger is equal to or higher than an outside air temperature. Control method. The method for controlling a refrigeration system according to claim 11 or 12, wherein the set temperature difference is changed according to an outside air temperature.

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