JP2007240040A - Refrigerating system and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating system and its control method capable of preventing frost formation on a heat source-side heat exchanger, improving heating performance and keeping high coefficient of performance. <P>SOLUTION: A refrigerant at high pressure side of a refrigerant circuit 6 for cooling storage equipment is allowed to flow to a cascade heat exchanger 18, and then flow to evaporators 31A, 34A without passing through a condenser 14, and a refrigerant at a low pressure side of a refrigerant circuit 4 for air conditioning is allowed to flow to the cascade heat exchanger 18 without flowing to a heat source-side heat exchanger 25, when an outside air temperature T becomes lower than a low outside air temperature operation mode starting temperature T0 at which frost is formed on the heat source-side heat exchanger 25 in a heating operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration system that controls indoor air conditioning and cooling storage equipment in a store or the like, and a control method thereof.

Conventionally, stores such as convenience stores have been air-conditioned and air-conditioned by air conditioners. In addition, an open showcase for refrigeration or refrigeration for displaying and selling products and a showcase with a door (cooling storage facility) are installed in the store, and these are cooled by a refrigerator. In this type, a system in which a refrigerant circuit for air conditioning and a refrigerant circuit for cooling storage equipment are configured as one system has been devised (for example, Patent Document 1).
JP 2004-360999 A

  By the way, in the heat pump air conditioning that uses indoor air as a heat source, when the outdoor temperature decreases, frost is generated in the outdoor heat exchanger (heat source side heat exchanger) for air conditioning, and the defrosting operation may be repeated. There have been problems such as lowering the coefficient of performance (COP).

  This invention is made | formed in view of the situation mentioned above, provides the refrigeration system which can prevent the frost formation of a heat source side heat exchanger, and can maintain the improvement of heating capability or a high coefficient of performance, and its control method. There is.

In order to solve the above-described problems, the present invention provides an air conditioning refrigerant circuit including a compressor, a heat source side heat exchanger, and a use side heat exchanger, and a cooling storage facility including a cooling compressor, a condenser, and an evaporator. In a refrigeration system comprising: a refrigerant circuit; a cascade heat exchanger that exchanges heat between the low-pressure side refrigerant of the air-conditioning refrigerant circuit and the high-pressure side refrigerant of the refrigeration system unit; and an operation control unit that controls operation. In the heating operation of the air conditioning refrigerant circuit, when the outside air temperature falls below a predetermined start temperature, the operation control unit causes the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility to flow through the cascade heat exchanger. In addition, the refrigerant flows through the evaporator without passing through the condenser, and the refrigerant on the low-pressure side of the air conditioning refrigerant circuit flows through the cascade heat exchanger without flowing through the heat source side heat exchanger.
According to the present invention, during the heating operation of the air conditioning refrigerant circuit, if the outside air temperature falls below a predetermined start temperature, the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility is passed through the cascade heat exchanger, and then the condenser The refrigerant on the low-pressure side of the air conditioning refrigerant circuit flows to the cascade heat exchanger without flowing to the heat source side heat exchanger, preventing frost formation on the heat source side heat exchanger, and , Heating capacity improvement and high coefficient of performance can be maintained.

  In the above configuration, the air-conditioning refrigerant circuit includes a first expansion valve disposed in a path through which the low-pressure side refrigerant of the air-conditioning refrigerant circuit flows to the heat source side heat exchanger; A second expansion valve arranged in a path flowing through the cascade heat exchanger, and the operation control unit, when an outside air temperature falls below a predetermined start temperature during the heating operation of the air conditioning refrigerant circuit, It is preferable to open the second expansion valve and close the first expansion valve.

In the above configuration, the operation control unit opens the second expansion valve and closes the first expansion valve, and then based on the temperature of the refrigerant in the refrigerant circuit for the cooling storage facility, It is preferable to adjust the opening degree of the expansion valve.
Further, in the above configuration, when the air-conditioning refrigerant circuit is in a heating operation, the operation control unit, when the outside air temperature exceeds a predetermined release temperature after falling below a predetermined start temperature, the refrigerant circuit for the cooling storage facility Flowing the high-pressure side refrigerant to the cascade heat exchanger, and then flowing the low-pressure side refrigerant of the air conditioning refrigerant circuit to the heat source side heat exchanger. preferable.

  Further, in the above configuration, the operation control unit is configured such that, during the heating operation of the air conditioning refrigerant circuit, the pressure of the refrigerant on the high-pressure side of the refrigerant circuit for the cooling storage facility is set in advance after the outside air temperature falls below a predetermined start temperature. When the predetermined allowable pressure is exceeded, the refrigerant on the high-pressure side of the refrigerant circuit for the cooling storage facility is flowed to the cascade heat exchanger, and then to the evaporator via the condenser. It is preferable to flow the low-pressure side refrigerant through the heat source side heat exchanger.

  In the above configuration, the cooling storage facility refrigerant circuit may flow the refrigerant on the high-pressure side of the cooling storage facility refrigerant circuit flowing from the cascade heat exchanger to the evaporator without passing through the condenser. It is preferable to have a four-way valve that can switch whether to flow to the evaporator via the condenser.

The present invention also provides a refrigerant circuit for air conditioning comprising a compressor, a heat source side heat exchanger and a utilization side heat exchanger, a refrigerant circuit for cooling storage equipment comprising a cooling compressor, a condenser and an evaporator, and the air conditioning. In the control method of a refrigeration system, comprising the cascade heat exchanger for exchanging heat between the low-pressure side refrigerant of the refrigerant circuit for the refrigerant and the high-pressure side refrigerant of the refrigeration system unit, and an operation control unit for controlling the operation, the operation control When the outside air temperature falls below a predetermined start temperature during the heating operation of the air conditioning refrigerant circuit, the unit causes the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility to flow to the cascade heat exchanger, and then condenses the condensation. The refrigerant is caused to flow through the evaporator without passing through a heater, and the refrigerant on the low-pressure side of the air conditioning refrigerant circuit is allowed to flow through the cascade heat exchanger without flowing through the heat source side heat exchanger.
According to the present invention, when the outside air temperature falls below a predetermined start temperature during the heating operation of the air conditioning refrigerant circuit, the condenser on the high pressure side of the refrigerant circuit for the cooling storage facility is passed through the cascade heat exchanger, and then the condenser The refrigerant on the low-pressure side of the air conditioning refrigerant circuit flows to the cascade heat exchanger without flowing to the heat source side heat exchanger, preventing frost formation on the heat source side heat exchanger, and , Heating capacity improvement and high coefficient of performance can be maintained.

  In the heating operation of the air conditioning refrigerant circuit, when the outside air temperature falls below a predetermined start temperature, the refrigerant on the high-pressure side of the refrigerant circuit for the cooling storage facility is passed through the cascade heat exchanger and then passed through the condenser. The refrigerant on the low-pressure side of the air conditioning refrigerant circuit flows to the cascade heat exchanger without flowing to the heat source side heat exchanger, preventing frost formation on the heat source side heat exchanger and heating. Improve ability and maintain high coefficient of performance.

  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 performs, for example, air conditioning by an air conditioning indoor unit 30 installed in a convenience store, and cooling of the refrigeration case 31 and the refrigeration case 34 as cooling storage facilities installed in the room 2. is there.

  The refrigerated case 31 and the refrigerated case 34 are an open showcase whose front and upper surfaces are open, a closed showcase that can be opened and closed by a glass door, and the like. For example, the inside of the refrigerator case 31 is from about 3 ° C. to about +10. It is cooled to a refrigerated temperature of ℃, and beverages, foods, etc. are displayed, and the inside of the freezing case 34 is cooled to a refrigeration temperature of about -20 ℃ to about -10 ℃, and frozen foods and frozen desserts are displayed. Is.

  The refrigeration system 1 includes an air conditioner 5 having an air conditioning refrigerant circuit 4 and a cooling device 7 having a cooling storage facility refrigerant circuit 6 that cools the inside of the refrigerator case 31 and the refrigeration case 34. The air conditioner 5 includes an indoor unit installed on the ceiling or the like of the room 2 and an outdoor unit 3 installed outside the room, and the air conditioning refrigerant circuit 4 is configured between these units.

  The air conditioning refrigerant circuit 4 includes an accumulator 20 installed in a case of the outdoor unit 3, two compressors 21A and 21B, check valves 22A and 22B, an oil separator 23, a four-way valve 24, Heat source side heat exchanger 25, expansion valves (pressure reducing means comprising electric expansion valves) 26, 27 and 28, cascade heat exchanger 18, check valve 29, and use side heat exchanger installed in room 2 30A or the like. The compressor 21A is a compressor capable of frequency control operation by an inverter, and the compressor 21B is a compressor that performs constant speed operation.

  The compressors 21A and 21B are connected in parallel to each other, and the discharge sides of the compressors 21A and 21B are joined via check valves 22A and 22B, respectively, and connected to the inlet of the oil separator 23. The check valves 22A and 22B have the oil separator 23 in the forward direction. The outlet of the oil separator 23 is connected to one inlet of the four-way valve 24, and one outlet is connected to the inlet of the heat source side heat exchanger 25. The heat source side heat exchanger 25 is composed of an inlet side 25A having a relatively small flow resistance composed of a large number of parallel pipes and an outlet side 25B in which these are aggregated into a small number of parallel pipes or a single pipe. Yes. The outlet side 25B of the heat source side heat exchanger 25 is connected to the inlet of the expansion valve 28 via an expansion valve (first expansion valve) 26, and the outlet of the expansion valve 28 is the inlet of the use side heat exchanger 30A. It is connected to the.

  The outlet of the use side heat exchanger 30A is connected to the other inlet of the four-way valve 24 in the outdoor unit 3, and the other outlet of the four-way valve 24 is connected to the inlet of the accumulator 20 via a check valve 29. The outlet of the accumulator 20 is connected to the suction sides of the compressors 21A and 21B. The check valve 29 has a forward direction in the accumulator 20 direction.

  The piping between the expansion valve 26 and the expansion valve 28 is connected to the inlet of an expansion valve (second expansion valve) 27, and the outlet of the expansion valve 27 is connected to the inlet of the air conditioning side pipe 18 </ b> A of the cascade heat exchanger 18. It is connected. The outlet of the air conditioning side passage 18A of the cascade heat exchanger 18 is connected to the suction sides of the compressors 21A and 21B via the accumulator 20.

  On the other hand, in the cooling device 7, a refrigerant circuit 6 for cooling storage equipment is piped between the outdoor unit 3 and a refrigeration case 31 and a refrigeration case 34 installed indoors. The refrigerant circuit 6 for cooling storage equipment includes a compressor 11 for refrigeration installed in a case of the outdoor unit 3, a condenser 14, three four-way valves 13, 17 and 51, an oil separator 12, and a receiver. Tank 16, check valve 19, refrigeration evaporator 31 </ b> A that cools the inside of refrigeration case 31, refrigeration evaporator 34 </ b> A that cools the inside of refrigeration case 34, expansion valves 32 and 35, electromagnetic It consists of valves 33 and 36, a check valve 40, a compressor 41 for refrigeration amplification, an oil separator 42, and the like.

  The discharge side of the compressor 11 is connected to one inlet of the four-way valve 13 via the oil separator 12, and one outlet of the four-way valve 13 is connected to one inlet of the four-way valve 51. One outlet of the four-way valve 51 is connected to the inlet of the condenser 14. The condenser 14 is composed of an inlet side 14A having a relatively small flow path resistance composed of a large number of parallel pipes and an outlet side 14B in which these are aggregated into a small number of parallel pipes or a single pipe. The outlet side 14 </ b> B of the condenser 14 is connected to the other inlet of the four-way valve 51, and the other outlet of the four-way valve 51 is connected to the inlet of the receiver tank 16. Further, the outlet side 14 </ b> B of the condenser 14 communicates with the receiver tank 16 via the check valve 19 separately from the path via the four-way valve 51 described above. The check valve 19 has the receiver tank 16 in the forward direction.

  One outlet of the four-way valve 17 is connected to the inlet of the case side pipe line 18B of the cascade heat exchanger 18. The cascade heat exchanger 18 exchanges heat between the refrigerants passing through the air conditioning side pipe 18 </ b> A and the case side pipe 18 </ b> B that are arranged inside, and thereby the low pressure of the air conditioning refrigerant circuit 4. The side and the high pressure side of the cooling storage facility refrigerant circuit 6 are thermally coupled.

  The outlet of the case side pipe 18 </ b> B of the cascade heat exchanger 18 is connected to the other inlet of the four-way valve 13. The other outlet of the four-way valve 13 is connected to the other inlet of the four-way valve 17, and the other outlet of the four-way valve 17 exits from the outdoor unit 3 and branches into the room 2.

  One of the branched pipes is connected to the inlet of the refrigeration evaporator 31A via an electromagnetic valve 33 and an expansion valve 32. The other branched pipe is connected to the inlet of the refrigeration evaporator 34A via the electromagnetic valve 36 and the expansion valve 35.

  The outlet of the refrigeration evaporator 34 </ b> A is connected to the suction side of the compressor 41 via a check valve 40. In the check valve 40, the direction of the compressor 41 is the forward direction. This compressor 41 is a compressor having a smaller output than the compressor 11, and its discharge side is connected to the suction side of the compressor 11 via an oil separator 42. That is, the compressor 41 and the compressor 11 are connected in series on the refrigerant circuit. The outlet of the refrigeration evaporator 31 </ b> A is connected to the outlet side of the oil separator 42 on the discharge side of the compressor 41.

  The operation of the refrigeration system 1 will be described with the above configuration. The compressor 11 and the compressor 21A are frequency controlled by an inverter, and the compressor 21B and the compressor 41 are operated at a constant speed. The operation of the entire refrigeration system 1 is controlled by a controller 100 composed of a general-purpose microcomputer. A blower 30B is installed in the vicinity of the use side heat exchanger 30A, a blower 31B is installed in the vicinity of the refrigeration evaporator 31A, and a blower 34B is installed in the vicinity of the refrigeration evaporator 34A. Blowers 50A and 50B are also installed in the vicinity of the heat exchanger 25 and the condenser 14, and air can be blown to these heat exchangers.

  Next, the case where the air conditioner 5 performs the heating operation will be described. When performing the heating operation, the controller 100 acquires the outside air temperature T by the outside air temperature sensor 60, and more specifically, whether or not the outside air temperature T is in a temperature range where frost formation occurs in the heat source side heat exchanger 25, more specifically. Then, it is determined whether or not the low outdoor air operation mode start temperature (start temperature, in this example, −10 degrees) T0 or less, and if the outdoor air temperature T exceeds the low outdoor air operation mode start temperature T0, the outdoor unit 3 The refrigerant circuit shown in FIG.

  As shown in FIG. 2, in the air conditioning refrigerant circuit 4 constituting the air conditioner 5, the controller 100 causes the outlet of the oil separator 23 and the inlet of the use side heat exchanger 30 </ b> A to communicate with each other by a four-way valve 24. The inlet side 25A of the exchanger 25 and the inlet of the check valve 29 are communicated, and the expansion valve 28 is fully opened. And while heating compressor 21A and 21B, heating capacity is adjusted to control the operating frequency of compressor 21A.

  The high-temperature and high-pressure gas refrigerant discharged from the compressors 21A and 21B enters the use side heat exchanger 30A via the oil separator 23 and the four-way valve 24. The air in the room 2 is passed through the use side heat exchanger 30A by the blower 30B, and the refrigerant radiates heat here and heats the room air to condense and liquefy.

  The refrigerant liquefied in the use side heat exchanger 30A flows out of the use side heat exchanger 30A, branches through the expansion valve 28, and after one refrigerant is decompressed in the expansion valve 27, the refrigerant of the cascade heat exchanger 18 is changed. After flowing into the air conditioning side pipe 18A and evaporating and absorbing heat, it is sucked into the compressors 21A and 21B through the accumulator 20, and the other refrigerant is decompressed in the expansion valve 26, and then is supplied to the heat source side heat exchanger 25. After flowing in and evaporating to absorb heat, it is sucked into the compressors 21A and 21B through the accumulator 20.

  The controller 100 adjusts the valve openings of the expansion valves 26 and 27 so that the degree of superheat is appropriate based on the refrigerant temperature at the inlet / outlet of the air conditioning side pipe 18A of the cascade heat exchanger 18 or the temperature of the cascade heat exchanger 18. adjust. Further, the blower 30B is controlled based on the temperature of the use side heat exchanger 30A and the temperature of the air ventilated there.

  Further, the controller 100 causes the outlet of the oil separator 12 and one inlet of the four-way valve 17 to communicate with each other by the four-way valve 13 of the refrigerant circuit 6 for the cooling storage facility of the cooling device 7, and the case-side pipe line of the cascade heat exchanger 18. The outlet of 18B communicates with one inlet of the four-way valve 51. Further, the four-way valve 17 makes one outlet of the four-way valve 13 communicate with the inlet of the case side pipe 18B of the cascade heat exchanger 18, and the outlet of the receiver tank 16 and the electromagnetic valves 33 and 36 communicate with each other. Further, the four-way valve 51 allows one outlet of the four-way valve 13 and the inlet side 14A of the condenser 14 to communicate with each other, and the outlet side 14B of the condenser 14 and the inlet of the receiver tank 16 to communicate with each other.

  Thereby, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 enters the case-side pipe line 18B of the cascade heat exchanger 18 via the four-way valves 13 and 17. Therefore, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 is directly supplied to the case side pipe 18 </ b> B of the cascade heat exchanger 18 before radiating heat with the condenser 14. The refrigerant on the high pressure side of the refrigerant circuit 6 for the cooling storage facility that has flowed into the case side pipe 18B dissipates heat in the cascade heat exchanger 18 and evaporates in the air conditioning side pipe 18A. Cooled by. As a result, the refrigerant of the air conditioning refrigerant circuit 4 can use the exhaust heat of the refrigerant circuit 6 for the cooling storage facility, and the heating capacity can be improved.

  The refrigerant that has passed through the case side pipe 18 </ b> B of the cascade heat exchanger 18 passes through the four-way valves 13 and 51 and enters the inlet side 14 </ b> A of the condenser 14, where it dissipates heat and condenses and liquefies, and passes through the four-way valve 51. The gas refrigerant enters the receiver tank 16 and is separated into gas and liquid. The separated liquid refrigerant flows out of the receiver tank 16, flows into the room 2 through the four-way valve 17, branches, and flows to the inlets of the electromagnetic valves 33 and 36.

By this operation, the waste heat of the high-pressure side refrigerant in the refrigerant circuit 6 for the cooling storage facility can be recovered by the cascade heat exchanger 18 and can be conveyed to the use side heat exchanger 30A of the refrigerant circuit 4 for air conditioning. As a result, it is possible to improve the efficiency of the air-conditioning / refrigeration apparatus 1 that cools the indoor air-conditioning and the refrigerator case 31 and the freezing case 34 as a whole, and energy saving can be achieved.
In particular, since the high-pressure side refrigerant of the refrigerant circuit 6 for the cooling storage facility flows through the cascade heat exchanger 18 before the condenser 14, the waste heat from the high-pressure side refrigerant of the refrigerant circuit 6 for the cooling storage facility can be efficiently recovered. The heating capacity in the use side heat exchanger 30A of the refrigerant circuit 4 for air conditioning can be further improved.

  In addition, when the load of the air conditioner 5 becomes light, the controller 100 reduces the refrigerant flow rate by reducing the valve opening degree of the expansion valve 27. In this case, the amount of heat released from the refrigerant in the refrigerant circuit 6 for the cooling storage facility in the cascade heat exchanger 18 becomes excessive. In the present invention, the high-pressure side refrigerant in the refrigerant circuit 6 for the cooling storage facility is passed through the cascade heat exchanger 18. Since it is made to flow through the condenser 14 later, an excessive amount of heat can be released in the condenser 14 and a stable waste heat recovery operation can be realized.

  Further, the pressure of the refrigerant discharged from the refrigeration evaporator 34A of the refrigerant circuit 6 for the cooling storage facility is lower than the refrigerant discharged from the refrigeration evaporator 31A because its evaporation temperature is lower, but the refrigeration evaporator Since the pressure is increased by compressing by the compressor 41 before joining the refrigerant discharged from 31A, by adjusting the suction side pressure of the compressor 11, the inside cooling of the refrigeration case 31 and the freezing case 34 is appropriately performed. Can be done.

On the other hand, in the cooling operation, as shown in FIG. 1, the controller 100 switches the four-way valve 24 of the air conditioning refrigerant circuit 4 so that the outlet of the oil separator 23 and the inlet side 25A of the heat source side heat exchanger 25 are switched. By connecting, the outlet of the use side heat exchanger 30A and the inlet of the check valve 29 are made to communicate, and the expansion valve 26 is fully opened, whereby the heat source side heat exchanger 25 becomes a condenser and the use side heat exchanger 30A evaporates. Functions as an air conditioner and enters a cooling operation state to cool the room.
In the cooling storage facility refrigerant circuit 6, the refrigerant flows from the condenser 14 through the cascade heat exchanger 18 through the refrigeration case 31 and the refrigeration case 34. By this operation, after condensing by the condenser 14, the supercooling can be increased by the cascade heat exchanger 18, and the refrigeration side cooling capacity can be increased. For this reason, it is possible to improve the efficiency of the air-conditioning / refrigeration apparatus 1 that performs indoor air conditioning and cooling of the refrigerator case 31 and the freezing case 34 to save energy.

By the way, when the outdoor temperature is remarkably lowered, there may occur a case where sufficient heat cannot be pumped by the heat source side heat exchanger 25 in the air conditioning refrigerant circuit 4, and frost is generated in the heat source side heat exchanger 25. As a result, the heating capacity may be reduced.
Therefore, in the present configuration, when the controller 100 falls below the temperature at which the outside air temperature T is lowered and cannot draw sufficient heat during the heating operation (low outside air operation mode start temperature T0), the controller 100 shifts to the low outside air operation mode. The four-way valve 51 is switched from FIG. 2 to FIG. 3, the expansion valve 27 is opened, and the expansion valve 26 is closed.

That is, the controller 100 causes one outlet of the four-way valve 13 and the inlet of the receiver tank 16 to communicate with each other, and causes the inlet side 14 </ b> A and the outlet side 14 </ b> B of the condenser 14 to communicate with each other. For this reason, the refrigerant flowing out from the outlet of the case side pipe line 18B of the cascade heat exchanger 18 does not flow into the condenser 14, and the refrigeration evaporator 31A and the refrigeration case 34 of the refrigeration case 31 are passed through the receiver tank 16. It flows to the freezing evaporator 34A. In other words, after the refrigerant on the high pressure side of the refrigerant circuit 6 for the cooling storage facility flows through the cascade heat exchanger 18, it flows through the evaporators 31 </ b> A and 34 </ b> A without passing through the condenser 14.
In this case, the condenser 14 is independent of the refrigerant circuit 6 for the cooling storage facility, and the refrigerant is stored in the condenser 14, so that the refrigerant circulating in the refrigerant circuit 6 for the cooling storage facility is insufficient or the condenser 14 may increase. Therefore, in the present configuration, the refrigerant is connected from the condenser 14 to the refrigerant circuit 6 for the cooling storage facility by communicating the condenser 14 and the receiver tank 16 through the check valve 19 separately from the path through the four-way valve 51 described above. Has been able to move.

  In addition, since the controller 100 opens the expansion valve 27 and closes the expansion valve 26 in the air conditioning refrigerant circuit 4, the controller 100 converts the refrigerant that has flowed out of the use side heat exchanger 30A and passed through the expansion valve 28 into heat source side heat. Without flowing into the exchanger 25, it passes through the expansion valve 27 and flows into the air conditioning side pipe 18A of the cascade heat exchanger 18, where it is evaporated to absorb heat, and after passing through the accumulator 20, the compressor 21A and 21B is aspirated. That is, the refrigerant on the low pressure side of the air conditioning refrigerant circuit 4 is allowed to flow to the cascade heat exchanger 18 without flowing to the heat source side heat exchanger 25.

  By adopting such a configuration, in the refrigerant circuit 6 for the cooling storage facility, the high-temperature and high-pressure refrigerant discharged from the compressor 11 supplies heat to the refrigerant in the air-conditioning refrigerant circuit 4 in the cascade heat exchanger 18. 14 is directed to the electromagnetic valves 33 and 36 via the receiver tank 16 without radiating heat. Therefore, it is possible to prevent the refrigerant from dissipating excessive heat in the condenser 14, and by collecting the exhaust heat of the refrigerant and transporting it to the use side heat exchanger 30 </ b> A of the air conditioning refrigerant circuit 4, The heating capacity of the conditioner 5 can be improved.

Moreover, in the air conditioning refrigerant circuit 4, the refrigerant does not flow through the heat source side heat exchanger 25 but flows only through the cascade heat exchanger 18 and flows into the use side heat exchanger 30 </ b> A, so that frost is generated in the heat source side heat exchanger 25. Can be avoided. Thereby, when outdoor temperature becomes low at the time of heating operation like the past, it can avoid the situation where frost generate | occur | produces in the heat source side heat exchanger 25, and it repeats defrost operation, the fall of heating capability or a coefficient of performance It is possible to avoid a decrease in (COP).
In this case, the controller 100 opens the expansion valve 27 and closes the expansion valve 26, and then the temperature of the refrigerant in the refrigerant circuit 6 for the cooling storage facility (for example, the outlet of the case side pipe 18 </ b> B of the cascade heat exchanger 18, or Based on the temperature of the inlet, etc., the opening degree of the expansion valve 27 is controlled so as to achieve an appropriate degree of superheat, and if the degree of superheat is not appropriate, the expansion valve 26 is also opened to adjust the degree of superheat. The expansion valve 28 is always fully opened during heating.

  Here, as described above, the heating operation start condition capable of preventing the frost formation is that the outside air temperature T is lower than the low outside air operation mode start temperature (−10 degrees) T0. When the outside air temperature T exceeds a predetermined set temperature (temperature at which frost formation does not occur (release temperature), for example, 0 degrees), or the pressure of the high-pressure side refrigerant in the refrigerant circuit 6 for the cooling storage facility This is a case where the upper limit pressure (for example, 2.3 MPa) is exceeded. When the allowable upper limit pressure is exceeded, the heating in the low outside air operation mode is performed when the pressure of the high-pressure refrigerant falls below a predetermined return pressure (a value lower than the allowable upper limit pressure, for example, 1.0 MPa). It tries to return to driving.

  As described above, according to the present embodiment, when the outside air temperature T becomes equal to or lower than the temperature T0 at which frost formation occurs in the heat source side heat exchanger 25 during the heating operation, the refrigerant on the high pressure side of the refrigerant circuit 6 for the cooling storage facility is changed. After flowing through the cascade heat exchanger 18, the refrigerant flows through the evaporators 31 </ b> A and 34 </ b> A without passing through the condenser 14, and the low-pressure side refrigerant of the air conditioning refrigerant circuit 4 flows through the heat source side heat exchanger 25 without cascade heat. Since it flows to the exchanger 18, frosting of the heat source side heat exchanger 25 can be prevented, and heating capacity can be improved and a high coefficient of performance can be maintained.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, A various change implementation is possible. For example, the refrigeration system installed in a convenience store has been described as an example. However, the present invention is not limited thereto, and can be widely applied to various refrigeration systems that perform indoor air conditioning and cooling of a cooling storage facility.

It is a figure which shows the structure of the refrigeration system which concerns on this embodiment. It is a figure explaining the heating operation of a refrigeration system. It is a figure explaining the heating operation by the low outside air operation mode of a refrigerating system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration system 4 Air conditioning refrigerant circuit 5 Air conditioner 6 Refrigerating circuit for cooling storage equipment 7 Cooling device 11, 21A, 21B, 41 Compressor 13, 17, 24, 51 Four-way valve 14 Condenser 18 Cascade heat exchanger 25 Heat source Side heat exchanger 30A Usage side heat exchanger 31 Refrigerated case 34 Refrigeration case T0 Low outside air operation mode start temperature (start temperature)

Claims (7)

A refrigerant circuit for air conditioning comprising a compressor, a heat source side heat exchanger and a use side heat exchanger, a refrigerant circuit for cooling storage equipment comprising a cooling compressor, a condenser and an evaporator, and a low pressure side of the air conditioning refrigerant circuit In a refrigeration system comprising a cascade heat exchanger that exchanges heat between the refrigerant of the refrigerant and the refrigerant on the high-pressure side of the refrigeration system unit, and an operation control unit that controls operation,
In the heating operation of the air conditioning refrigerant circuit, when the outside air temperature falls below a predetermined start temperature, the operation control unit causes the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility to flow through the cascade heat exchanger. The refrigerant system is configured to flow through the evaporator without passing through the condenser, and to flow the refrigerant on the low-pressure side of the air conditioning refrigerant circuit through the cascade heat exchanger without flowing through the heat source side heat exchanger. . The air conditioning refrigerant circuit includes a first expansion valve arranged in a path for flowing a low-pressure side refrigerant of the air conditioning refrigerant circuit to the heat source side heat exchanger, and the cascade heat exchange branching from the path A second expansion valve disposed in a path flowing through the vessel,
2. The operation control unit opens the second expansion valve and closes the first expansion valve when an outside air temperature falls below a predetermined start temperature during the heating operation of the air conditioning refrigerant circuit. The refrigeration system described in.   The operation control unit opens the second expansion valve and closes the first expansion valve, and then opens the first expansion valve and the second expansion valve based on the temperature of the refrigerant in the refrigerant circuit for the cooling storage facility. The refrigeration system according to claim 2, wherein the degree is adjusted.   In the heating operation of the air conditioning refrigerant circuit, when the outside air temperature exceeds a predetermined release temperature after the outdoor temperature falls below a predetermined start temperature, the operation control unit removes the high-pressure side refrigerant of the refrigerant circuit for the cooling storage facility. 2. After flowing through the cascade heat exchanger, the refrigerant flows through the condenser to the evaporator, and the low-pressure side refrigerant of the air conditioning refrigerant circuit flows through the heat source side heat exchanger. The refrigeration system in any one of thru | or 3.   In the heating operation of the air conditioning refrigerant circuit, the operation control unit is configured so that the pressure of the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility exceeds a predetermined allowable pressure after the outside air temperature falls below a predetermined start temperature. And after flowing the refrigerant on the high-pressure side of the refrigerant circuit for the cooling storage facility to the cascade heat exchanger, the refrigerant on the low-pressure side of the air-conditioning refrigerant circuit is allowed to flow to the evaporator via the condenser. The refrigeration system according to any one of claims 1 to 4, wherein the refrigeration system is passed through a heat source side heat exchanger.   The refrigerant circuit for the cooling storage facility flows the refrigerant on the high-pressure side of the refrigerant circuit for the cooling storage facility that has flowed from the cascade heat exchanger to the evaporator without passing through the condenser, or through the condenser. A refrigeration system according to any one of claims 1 to 5, further comprising a four-way valve capable of switching whether to flow to the evaporator. A refrigerant circuit for air conditioning comprising a compressor, a heat source side heat exchanger and a use side heat exchanger, a refrigerant circuit for cooling storage equipment comprising a cooling compressor, a condenser and an evaporator, and a low pressure side of the air conditioning refrigerant circuit In a control method of a refrigeration system comprising a cascade heat exchanger for exchanging heat between the refrigerant of the refrigerant and the high-pressure side refrigerant of the refrigeration system unit, and an operation control unit for controlling operation,
In the heating operation of the air conditioning refrigerant circuit, when the outside air temperature falls below a predetermined start temperature, the operation control unit causes the refrigerant on the high pressure side of the refrigerant circuit for the cooling storage facility to flow through the cascade heat exchanger. The refrigerant system is configured to flow through the evaporator without passing through the condenser, and to flow the refrigerant on the low-pressure side of the air conditioning refrigerant circuit through the cascade heat exchanger without flowing through the heat source side heat exchanger. Control method.

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