JP2018204812A - Heat exchange system and method of controlling the same - Google Patents

Abstract

To provide a heat exchange system that can be placed in defrosting operation while heat exchange loss of the heat exchange system having a plurality of outdoor heat exchangers is suppressed, and a method of controlling the same.SOLUTION: An air conditioner 10 comprises a low stage-side compressor 3a, a high stage-side compressor 3b further compressing a refrigerant compressed by the low stage-side compressor 3a, and a plurality of outdoor heat exchangers 6 and an indoor heat exchangers 5, and is equipped with: a four-way valve 7 which is connected to the indoor heat exchanger 5 and one end side of the respective outdoor heat exchangers 6, a discharge side of the high stage-side compressor 3b, and a connection point between the low stage-side compressor 3a and high stage-side compressor 3b, and switches a flow passage of a refrigerant to be circulated; a three-way valve 8 which is provided between the four-way valve 7 and the respective outdoor heat exchangers 6, and switches a flow passage of a refrigerant to be circulated to the four-way valve 7, the respective outdoor heat exchangers 6, and a suction side of the low stage-side compressor 3a; and a control part which controls the switching of the flow passages by the four-way valve 7 and three-way valve 8.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a heat exchange system and a control method thereof.

For example, when the air conditioner is operating in a heating state, if the blown air of a heat exchanger operating as an evaporator falls below 0 ° C., the heat exchanger forms frost and the evaporation capacity decreases. Will occur. Therefore, by switching the four-way valve that switches the refrigerant flow direction in the refrigerant circuit of the air conditioner and temporarily operating in the cooling cycle, the role of operating the heat exchanger that was operating as an evaporator as a condenser An operation (defrosting operation) is performed in which a reverse cycle operation is performed by inverting the heat exchanger, and the frosted heat exchanger is defrosted.
In addition, in the case of equipment with a high heating temperature such as a heat pump type heating / water heater, the difference between the low pressure and the high pressure is large, so the capacity of one compressor is insufficient, and two compressors are connected in series to increase the pressure. In some cases, the multi-stage compression system is configured (see, for example, Patent Document 1).

  At the time of defrost operation in the reverse cycle, the refrigerant flow in the refrigerant circuit during heating operation is reversed, and the heat exchanger on the outdoor unit side is heated to defrost and the heat exchanger on the indoor unit side is cooled to defrost. For this reason, the heating capacity is reduced. In order to prevent such a decrease in the capacity of the indoor unit, in Patent Document 2 below, two evaporators are provided in the outdoor unit, a cycle in which the use side heat exchanger 33 and the heat source side heat exchanger 52 are heated, and a heat source The technology which comprises two cycles of the cycle which defrosts the side heat exchanger 51 and the heat source side heat exchanger 52, and defrosts the frosted heat exchanger is disclosed.

JP 2004-85047 A JP 2014-224644 A

  However, in the method of Patent Document 2, a plurality of evaporators provided in an outdoor unit are connected to the same compressor during heating operation in a multistage compression air conditioner, and the evaporation temperatures of the respective evaporators. Are different from each other, the evaporator with a high evaporation temperature is controlled to match the evaporation temperature with the evaporator with a low evaporation temperature. If it does so, there existed a problem that the driving | running capability of the evaporator which can be drive | operated with high evaporation temperature was suppressed, and a loss produced. Moreover, in the method of patent document 2, since it presupposes that two or more evaporators are functioning simultaneously in the outdoor unit, for example, when there is no one heat source of the heat exchanger of the outdoor unit, defrosting is performed. I can't. Moreover, in the method of patent document 1, since only one outdoor heat exchanger is provided, the case where there are a plurality of evaporators in the multistage compression method is not considered.

  The present invention has been made in view of such circumstances, and heat capable of performing a defrosting operation of the heat exchange system while suppressing a heat exchange loss of the heat exchange system having a plurality of outdoor heat exchangers. An object is to provide an exchange system and a control method thereof.

In order to solve the above problems, the present invention employs the following means.
The present invention includes a low-stage compressor, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, a plurality of heat source-side heat exchangers, and a use-side heat exchanger. A heat exchange system comprising: the use side heat exchanger; one end side of each heat source side heat exchanger; the discharge side of the high stage compressor; the low stage side compressor and the high stage side. A first flow path switching means that is connected to a connection point between the compressor and switches the flow path of the refrigerant to be circulated; the first flow path switching means; and the heat source side heat exchangers. A second flow path switching means for switching between the first flow path switching means, each of the heat source side heat exchangers, and the flow path of the refrigerant flowing to the suction side of the low stage compressor; A heat exchange system comprising control means for controlling flow path switching between the first flow path switching means and the second flow path switching means. To provide.

According to the configuration of the present invention, the refrigerant discharged from the heat source side heat exchanger flows to the low-stage compressor and to the first channel switching unit by switching the channel of the second channel switching unit. The refrigerant discharged from the high-stage compressor by the switching of the first flow path switching unit is divided into a path, the use-side heat exchanger side through the first flow path switching unit, the low-stage side compressor, The flow path is switched between a flow path connected to a connection point with the high stage compressor and one end side on each heat source side heat exchanger side.
According to the configuration of the present invention, the refrigerant discharged from the plurality of heat source side heat exchangers circulates through the low stage compressor via the path through which the refrigerant flows to the input side of the low stage compressor and the first flow path switching unit. Without being divided, it can be divided into a route that circulates to the input side of the high-stage compressor. In this way, the refrigerant from the plurality of heat source side heat exchangers can be individually introduced into the low stage side compressor and the high stage side compressor, so the heat source side heat exchanger is used as an evaporator. In this case, the plurality of heat source side heat exchangers can be operated at different evaporation temperatures, and can be operated more efficiently than when the plurality of heat source side heat exchangers are operated at the same evaporation temperature.

  In the heat exchange system, the second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other than the one heat source side heat exchanger, the other The second flow path switching means connected to the heat source side heat exchanger is used as a second second flow path switching means, and during the heating operation, the control means is connected via the first second flow path switching means. The refrigerant may be caused to flow into the low-stage compressor, and the refrigerant may be caused to flow into the high-stage compressor via the second second flow path switching unit.

  Thereby, the refrigerant output from the heat source side heat exchanger with a low evaporation temperature is compressed by the low stage side compressor and the high stage side compressor, and the refrigerant output from the heat source side heat exchanger with a high evaporation temperature is Since it can compress with a high stage side compressor, even if there is a heat source side heat exchanger of different evaporation temperature, it can be operated without loss.

  In the heat exchange system, the second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other than the one heat source side heat exchanger, the other The second flow path switching means connected to the heat source side heat exchanger is used as a second second flow path switching means, and one of the heat source side heat exchangers is frosted. In this case, the control means causes one of the heat source side heat exchangers to operate as a condenser, causes the other heat source side heat exchanger to operate as an evaporator, and the first second flow path switching means includes the The refrigerant from the high stage side compressor is circulated through the one heat source side heat exchanger, and the second second switching means passes the refrigerant from the other heat source side heat exchanger to the low stage side compressor. It may be distributed.

  Thus, by providing a plurality of heat source side heat exchangers, when one of the heat source side heat exchangers is frosted, the frosted heat source side heat exchanger is operated as a condenser and frosted. By operating the heat source side heat exchanger that is not used as an evaporator, the defrosting (defrost) operation can be performed only with the heat source side heat exchanger. Thereby, a low temperature refrigerant | coolant does not distribute | circulate to a utilization side heat exchanger, and it can suppress the temperature fall of the refrigerant | coolant in a utilization side.

  The present invention includes a low-stage compressor, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, a plurality of heat source-side heat exchangers, and a use-side heat exchanger. A heat exchange system comprising: the use side heat exchanger; one end side of each heat source side heat exchanger; the discharge side of the high stage compressor; and the suction side of the low stage compressor And provided between the first flow path switching means for switching the flow path of the refrigerant to be circulated, the first flow path switching means, and each heat source side heat exchanger, and the first flow path switching means. Each of the heat source side heat exchangers, a second flow path switching means for switching a flow path of the refrigerant to be circulated to a connection point between the low stage side compressor and the high stage side compressor, and the first flow path Provided is a heat exchange system comprising a switching means and a control means for controlling switching of the flow path between the second flow path switching means. .

According to the configuration of the present invention, the refrigerant discharged from the heat source side heat exchanger flows to the high-stage compressor and to the first channel switching unit by switching the channel of the second channel switching unit. The refrigerant discharged from the high-stage compressor by the switching of the first flow path switching means is divided into the use side heat exchanger side and the low-stage compressor side via the first flow path switching means. The flow path is switched between a flow path connected to the one end side and one end side on each heat source side heat exchanger side.
According to the configuration of the present invention, the refrigerant discharged from the plurality of heat source side heat exchangers is circulated to the input side of the high stage compressor, and the input side of the low stage compressor via the first flow path switching unit. It is possible to divide it into a route for distribution to As described above, since the refrigerants from the plurality of heat source side heat exchangers can be individually flowed into the low stage side compressor and the high stage side compressor, the plurality of heat source side heat exchangers are differently evaporated. It can be operated at temperature.

  In the heat exchange system, the second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other than the one heat source side heat exchanger, the other The second flow path switching means connected to the heat source side heat exchanger is used as a second second flow path switching means, and one of the heat source side heat exchangers is frosted. The frosted heat source side heat exchanger is operated as a condenser, the non-frosted heat source side heat exchanger is operated as an evaporator, and the control means discharges from the high stage compressor. The first second flow path switching means is controlled so as to distribute the refrigerant to the heat source side heat exchanger operated as the condenser, and the refrigerant is operated as the evaporator after distribution through the condenser. The refrigerant is circulated through the high stage compressor through the heat source side heat exchanger. Sea urchin may control the second of the second flow path switching unit.

During the defrosting operation, the refrigerant compression difference between the low-stage compressor and the high-stage compressor tends to be small. Therefore, during the defrosting operation, the refrigerant output from the evaporator is sucked into the high-stage compressor. By adopting single-stage compression, a reduction in refrigerant compression efficiency is prevented.
When one of the heat source side heat exchangers is frosted by providing a plurality of heat source side heat exchangers, the frosted heat source side heat exchanger is operated as a condenser, and the heat source side that is not frosted By operating the heat exchanger as an evaporator, the defrosting operation can be performed only with the heat exchanger on the heat source side. Thereby, a low temperature refrigerant | coolant does not distribute | circulate to a utilization side heat exchanger, and it can suppress the temperature fall of the refrigerant | coolant in a utilization side.

  The heat exchange system includes a liquid gas heat exchanger for exchanging heat between the liquid refrigerant at the outlet of the use-side heat exchanger and a two-phase refrigerant obtained by expanding a part of the liquid refrigerant during heating operation. The latter two-phase refrigerant may flow into the low-stage compressor or the high-stage compressor.

  Heat exchange is performed between the liquid refrigerant at the outlet of the use-side heat exchanger and the two-phase refrigerant obtained by expanding a part of the liquid refrigerant, and the two-phase refrigerant after heat exchange flows into the compressor side to circulate in the refrigerant circuit. Since the refrigerant circulation amount can be reduced and the input can be reduced, the performance is improved.

  In the heat exchange system, a defrost path may be provided by returning a bypass of the refrigerant discharged from the high-stage compressor to the heat source side heat exchanger.

  According to such a structure, since it becomes a circuit comprised with the compressor and the heat source side heat exchanger, control for defrosting becomes easy.

  The present invention includes a low-stage compressor, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, a plurality of heat source-side heat exchangers, and a use-side heat exchanger. A heat exchange system control method comprising: the use side heat exchanger; one end side of each heat source side heat exchanger; the discharge side of the high stage side compressor; the low stage side compressor; A first step of switching a flow path of the refrigerant to be circulated in a first flow path switching means connected to a connection point between the high stage side compressor, the first flow path switching means, and each heat source side A second flow path switching means provided between the heat exchanger and connected to the first flow path switching means, the heat source side heat exchangers, and the suction side of the low stage compressor; A second step of switching a flow path of the refrigerant to be circulated; a flow of the first flow path switching means and the second flow path switching means; A control method of the heat exchange system and a third step of controlling the switching of.

  The present invention includes a low-stage compressor, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, a plurality of heat source-side heat exchangers, and a use-side heat exchanger. A heat exchange system control method comprising: the use side heat exchanger; one end side of each heat source side heat exchanger; the discharge side of the high stage side compressor; and the suction of the low stage side compressor A first step of switching the flow path of the refrigerant to be circulated to the first flow path switching means connected to the side, provided between the first flow path switching means and each of the heat source side heat exchangers, The refrigerant to be circulated through the first flow path switching means, each of the heat source side heat exchangers, and the second flow path switching means connected to a connection point of the low-stage compressor and the high-stage compressor. A second step of switching the flow path, and a first step of controlling flow path switching between the first flow path switching means and the second flow path switching means. A control method of the heat exchange system and a process.

  The present invention has an effect that a defrosting operation of a heat exchange system can be performed while suppressing heat exchange loss of a heat exchange system having a plurality of outdoor heat exchangers.

It is a refrigerant | coolant system | strain diagram of the air conditioner which concerns on 1st Embodiment of this invention. It is a functional block diagram of the control apparatus of the air conditioner which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the flow of the refrigerant | coolant at the time of the 2nd heating operation of the air conditioner which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the flow of the refrigerant | coolant at the time of the defrost driving | operation of the air conditioner which concerns on 1st Embodiment of this invention. It is a refrigerant | coolant system | strain diagram of the air conditioner which concerns on 2nd Embodiment of this invention, and is the figure which showed the refrigerant | coolant flow at the time of a defrost driving | operation. It is a refrigerant | coolant system | strain diagram of the air conditioner which concerns on 3rd Embodiment of this invention. It is a refrigerant | coolant system | strain diagram of the air conditioner which concerns on 4th Embodiment of this invention.

  Hereinafter, an embodiment of a heat exchange system and a control method thereof according to the present invention will be described with reference to the drawings. The heat exchange system of the present invention heats and outputs a heat medium. For example, a heat pump including an air conditioner, a water heater, and the like can be given as an example. The heat medium may be gas or liquid. Moreover, the heat exchange system may have only the function of heating the heat medium, or may have both functions of heating and cooling. In the following description, an air conditioner will be described as an example of the heat exchange system.

[First Embodiment]
FIG. 1 is a refrigerant system diagram of an air conditioner 10 according to the present embodiment. The air conditioner 10 includes a compressor 3 that compresses refrigerant, an indoor heat exchanger (use side heat exchanger) 5 that exchanges heat between indoor air and refrigerant, and an outdoor heat exchanger that exchanges heat between outside air and refrigerant. (Heat source side heat exchanger) 6, receiver 4, four-way valve (first flow path switching means) 7, three-way valve (second flow path switching means) 8, and temperature detector 2. The refrigerant pipe between the receiver 4 and the indoor heat exchanger 5 is provided with a first expansion valve 9, and the refrigerant pipe between the receiver 4 and the outdoor heat exchanger 6 is provided with a second expansion valve 11. ing. In the above configuration, for example, the compressor 3, the receiver 4, the outdoor heat exchanger 6, the four-way valve 7, the three-way valve 8, and the second expansion valve 11 are provided in the outdoor unit, and the indoor heat exchanger 5 and the first expansion valve are provided. The valve 9 is provided in the indoor unit.

In the present embodiment, description will be made assuming that there are two outdoor heat exchangers 6 as the outdoor heat exchangers 6a and 6b, but the number of outdoor heat exchangers is not particularly limited.
In the present embodiment, it is assumed that the size (heat exchange amount) of each evaporator (outdoor heat exchanger 6a, 6b) is smaller than that of the condenser (indoor heat exchanger 5). If a single evaporator can supply sufficient heat, it is not necessary to use an evaporator that is not operated. However, if the required amount of heat cannot be supplied by a single evaporator, an evaporator that is not operated is not used. Use to make up for the shortage.
The temperature detector 2, the three-way valve 8, and the second expansion valve 11 are provided corresponding to each outdoor heat exchanger 6, and in this embodiment, the temperature detectors 2a and 2b are used to distinguish each of them. The three-way valves 8a and 8b and the second expansion valves 11a and 11b are shown with the symbols a and b omitted when not particularly distinguished.

The compressor 3 is a two-stage compressor including a low-stage compressor 3a and a high-stage compressor 3b. The intermediate pressure refrigerant compressed by the low stage compressor 3a is further compressed by the high stage compressor 3b and discharged as a high pressure. As the low-stage compressor 3a and the high-stage compressor 3b, a known type of compression mechanism such as a rolling piston type or a swing type rotary compression mechanism and a scroll compression mechanism can be applied.
The low-stage compressor 3a is connected to the high-stage compressor 3b from the discharge side via a refrigerant pipe, and the high-stage compressor 3b is an intermediate-pressure refrigerant compressed by the low-stage compressor 3a. Inhaled gas and compressed in two stages.
The air conditioner 10 includes a pressure sensor (not shown) that measures the pressure (high pressure: condensation pressure) of the refrigerant that is discharged from the compressor 3 and flows to the four-way valve 7, and the refrigerant that is returned from the four-way valve 7 to the compressor 3. A pressure sensor (not shown) for measuring the pressure (low pressure: evaporation pressure) is provided.

  The air conditioner 10 includes a pipe L1 that connects the low-stage compressor 3a and the high-stage compressor 3b, a pipe L2 that connects the high-stage compressor 3b and the four-way valve 7, and a four-way valve 7 and indoor heat exchange. A pipe L3 for connecting the vessel 5, a pipe L4 for connecting the indoor heat exchanger 5 and the receiver 4 via the first expansion valve 9, and a receiver 4 and the outdoor heat exchanger 6a via the second expansion valves 11a and 11b. , 6b, a pipe L5 connecting the outdoor heat exchanger 6a and the three-way valve 8a, a pipe L7 connecting the outdoor heat exchanger 6b and the three-way valve 8b, the three-way valve 8a and the low-stage compressor Between the pipe L12 connecting the 3a, the pipe L11 connecting the three-way valve 8b and the low-stage compressor 3a, and the discharge side of the low-stage compressor 3a and the suction side of the high-stage compressor 3b A pipe L8 that connects the provided connection point X and the four-way valve 7 is connected to the four-way valve 7 and the three-way valve 8a. A pipe L9 which, and a pipe L10 connecting the four-way valve 7 and a three-way valve 8b, constituting the refrigerant circuit in which the refrigerant circulates.

The receiver 4 performs gas-liquid separation of the refrigerant and adjusts the circulating refrigerant amount.
The four-way valve 7 includes an indoor heat exchanger 5, three-way valves 8a and 8b (one end side of the outdoor heat exchangers 6a and 6b), a discharge side of the high-stage compressor 3b, and a discharge of the low-stage compressor 3a. Is connected to a connection point X provided between the suction side of the high-stage compressor 3b and the flow path of the refrigerant to be circulated.
The three-way valve 8a is provided between a connection point Y on the path where the four-way valve 7 and the outdoor heat exchanger 6b are connected to the outdoor heat exchanger 6a, and the four-way valve 7, the outdoor heat exchanger 6a, The flow path of the refrigerant to be circulated to the suction side of the low-stage compressor 3a is switched. That is, the three-way valve 8a switches the refrigerant flow paths of the pipe L6, the pipe L9, and the pipe L12.
The three-way valve 8b is provided between a connection point Y on the path where the four-way valve 7 and the three-way valve 8a are connected and the outdoor heat exchanger 6b, and the four-way valve 7, the outdoor heat exchanger 6b, The flow path of the refrigerant circulated to the suction side of the side compressor 3a is switched. That is, the three-way valve 8b switches the refrigerant flow paths of the pipe L7, the pipe L10, and the pipe L11.

  The temperature detectors 2 a and 2 b are sensors, for example, and detect the temperatures of the outdoor heat exchangers 6 a and 6 b operating as evaporators (hereinafter also referred to as “evaporator temperatures”) and output them to the control device 20. In the present embodiment, the case where the temperature of the evaporator is determined by detecting the pipe temperature of the evaporator, that is, the pipe temperature of the outdoor heat exchangers 6a and 6b during the heating operation will be described as an example. The method for detecting the temperature of the vessel is not limited to this. The temperature of the evaporator may be obtained, for example, by detecting the heat source temperature of the evaporator, that is, the heat source temperature of the outdoor heat exchangers 6a and 6b during heating operation. If the heat source is air, the temperature detector 2 Detects the outside air temperature, and if the heat source is water, the temperature detector 2 detects the temperature of the water. The temperature information of the evaporators of the outdoor heat exchangers 6a and 6b detected by the temperature detectors 2a and 2b is output to the control device 20.

In such an air conditioner 10, the control of the compressor 3, the switching of the four-way valve 7, the switching of the three-way valves 8a and 8b, the opening control of the first expansion valve 9 and the second expansion valves 11a and 11b, etc. are controlled. This is done by the device 20 (see FIG. 2).
The control device 20 is, for example, a microprocessor, and various functions realized by each unit described later are realized by the CPU reading a program stored in a recording medium such as a ROM into a memory such as a RAM and executing it. The Specifically, the control device 20 includes a control unit (control means) 21, an evaporation temperature calculation unit 22, and a determination unit 23 as main components.

The evaporation temperature calculation unit 22 acquires the temperature information of the evaporator (each outdoor heat exchanger 6a, 6b) detected by the temperature detection unit 2, calculates the evaporation temperature based on the temperature information of the evaporator, Information on the evaporation temperature of the heat exchangers 6 a and 6 b is output to the determination unit 23. Alternatively, a pressure detector (not shown) may be provided in the refrigerant pipe, and the evaporation temperature calculator 22 may obtain pressure information by the pressure detector and calculate the evaporation temperature based on the saturation temperature.
The determination unit 23 compares the difference in evaporation temperature between the outdoor heat exchangers 6a and 6b with a predetermined temperature difference (threshold temperature) of the evaporator stored in the storage unit (not shown). As a result of the comparison, the determination unit 23 outputs the first heating operation command when the difference in evaporation temperature between the outdoor heat exchangers 6a and 6b is less than the predetermined temperature difference, and outputs the second heating operation when the difference is equal to or greater than the predetermined temperature difference. Outputs the operation command.
The determination unit 23 determines whether or not the outdoor heat exchangers 6a and 6b have formed frost. If the frost is detected, the determination unit 23 outputs a defrost (defrost) operation command to the control unit 21.

  For example, when the air conditioner 10 is in the heating operation, the determination unit 23 determines whether or not the evaporation temperature difference between the two outdoor heat exchangers 6a and 6b is equal to or greater than a predetermined temperature difference (for example, 20 ° C.). When the temperature difference is smaller than a predetermined temperature (for example, 20 ° C.), the first heating operation command is output. When the evaporator temperature difference is equal to or greater than the predetermined temperature (for example, 20 ° C.), the second heating operation command is output. Output.

  The control unit 21 performs switching of the four-way valve 7, switching of the three-way valves 8a and 8b, and opening control based on the acquired command. For example, a three-way valve 8 connected to one outdoor heat exchanger 6 is a first three-way valve, and a three-way valve 8 connected to another outdoor heat exchanger 6 other than one outdoor heat exchanger 6 is a second three-way valve. When the valve is used, the control unit 21 causes the refrigerant to flow into the low-stage compressor 3a through the first three-way valve and the refrigerant to the high-stage compressor 3b through the second three-way valve during the second heating operation. Let it flow.

Specifically, when acquiring the cooling operation command, the control unit 21 controls opening and closing of the three-way valves 8a and 8b and the four-way valve 7 according to the cooling operation.
For example, the three-way valve 8b opens the flow paths on the four-way valve 7 side and the outdoor heat exchanger 6b side, and closes the flow path on the low-stage compressor 3a side, and the three-way valve 8a includes the four-way valve 7b. The flow path on the side and the outdoor heat exchanger 6a side is opened, and the flow path on the low-stage compressor 3a side is closed. As a result, the refrigerant discharged from the high-stage compressor 3b flows into the outdoor heat exchanger 6b via the three-way valve 8b, and flows into the outdoor heat exchanger 6a via the three-way valve 8a. It becomes a path | route which distribute | circulates with the heat exchanger 5 and flows in into the high stage side compressor 3b via the four-way valve 7. FIG.

During the first heating operation, the control unit 21 controls the three-way valves 8a and 8b to close the flow path on the four-way valve 7 side and open the flow path on the low-stage compressor 3a side, The inflow destination of the refrigerant discharged from the outdoor heat exchangers 6a and 6b is a low-stage compressor 3a.
During the second heating operation, for example, the three-way valve 8a (first three-way valve) connected to the outdoor heat exchanger 6a having a low evaporator temperature closes the flow path on the four-way valve 7 side. The three-way valve 8b (second three-way valve) connected to the outdoor heat exchanger 6b having a high evaporator temperature is controlled so as to open the flow path on the low-stage compressor 3a side. Control is performed so that the flow path is opened and the flow path on the low-stage compressor 3a side is closed, and the compressor to which the refrigerant flowing out of the outdoor heat exchangers 6a and 6b flows is made different. Thereby, the refrigerant output from the outdoor heat exchanger 6 having a low evaporator temperature is compressed by the low-stage compressor 3a and the high-stage compressor 3b, and output from the outdoor heat exchanger 6 having a high evaporator temperature. Since the refrigerant can be compressed by the high-stage compressor 3b, even if there are outdoor heat exchangers 6 having different evaporator temperatures, the refrigerant can be operated without waste.

  Moreover, if the control part 21 acquires a defrost operation instruction | command, it will drive | operate the outdoor heat exchanger 6 determined that there exists a possibility of frost formation among several outdoor heat exchangers 6 as a condenser, and there exists a possibility of frost formation. The outdoor heat exchanger 6 that has not been determined to be present is operated as an evaporator. For example, the control unit 21 is configured such that the three-way valve 8b (first three-way valve) is closed by closing the flow path on the low-stage compressor 3a side and opening the flow path on the outdoor heat exchanger 6b side. The refrigerant from the stage side compressor 3b is circulated to the outdoor heat exchanger 6b, the three-way valve 8a (second three-way valve) closes the flow path on the four-way valve 7 side, and the flow path on the low-stage compressor 3a side. Is opened to allow the refrigerant from the outdoor heat exchanger 6a to flow to the low-stage compressor 3a. The defrost operation may be performed by a well-known reverse cycle operation.

  As described above, by providing a plurality of outdoor heat exchangers 6a and 6b, even if one of the outdoor heat exchangers 6a and 6b is frosted, the frosted outdoor heat exchangers 6a and 6b are condensed. By operating the outdoor heat exchangers 6a and 6b that are not frosted as evaporators, the defrosting operation can be performed only by the heat exchanger on the outdoor unit side. Thereby, a low temperature refrigerant | coolant does not distribute | circulate through the indoor heat exchanger 5, and it can suppress the temperature fall of the refrigerant | coolant in a utilization side.

Here, the flow of the refrigerant during the cooling operation and the heating operation of the air conditioner 10 will be described.
During the cooling operation of the air conditioner 10 according to the present embodiment, the refrigerant discharged from the indoor heat exchanger 5 is sent to the high-stage compressor 3b via the four-way valve 7. The refrigerant compressed in the high-stage compressor 3b is sent to the outdoor heat exchangers 6a and 6b via the four-way valve 7 and the three-way valves 8a and 8b, where it is condensed and liquefied by exchanging heat with the outside air. It becomes a liquid refrigerant. The refrigerant that has become liquid refrigerant is adjusted to an intermediate pressure by the second expansion valve 11 and sent to the receiver 4. In the receiver 4, the refrigerant is separated into gas and liquid, and the liquid refrigerant undergoes adiabatic expansion in the process of passing through the first expansion valve 9, and then is sent to the indoor heat exchanger 5 where it evaporates and vaporizes by cooling the indoor air. . In the indoor heat exchanger 5, the refrigerant that has absorbed heat into gas is sent to the high-stage compressor 3 b via the four-way valve 7. The refrigerant compressed by the high stage side compressor 3 b is sent to the four-way valve 7. Thus, during the cooling operation of the air conditioner 10, the outdoor heat exchanger 6 functions as a condenser, and the indoor heat exchanger 5 functions as an evaporator.

  On the other hand, in the case of the heating operation, in the present embodiment, the two heating operation methods of the first heating operation and the second heating operation can be switched. The first heating operation is selected when the difference in evaporation temperature between the outdoor heat exchangers 6a and 6b is less than a predetermined temperature difference, and the second heating operation is performed when the difference in evaporation temperature between the outdoor heat exchangers 6a and 6b is equal to or higher than a predetermined temperature. It is selected in the case of.

Below, the heating operation which concerns on this embodiment is demonstrated. Here, the amount of heat required to operate the plurality of outdoor heat exchangers 6a and 6b is required, and the case where the plurality of outdoor heat exchangers 6a and 6b are operated as an evaporator will be described as an example. .
During the first heating operation of the air conditioner 10, the refrigerant flowing out of the outdoor heat exchangers 6a and 6b flows into the low stage compressor 3a via the three-way valves 8a and 8b and is discharged from the high stage compressor 3b. Then, the air flows into the indoor heat exchanger 5 from the four-way valve 7. The indoor heat exchanger 5 radiates heat to the room air to condense and liquefy it to become a high-pressure and low-temperature liquid refrigerant. This liquid refrigerant is adjusted to an intermediate pressure by the first expansion valve 9 and sent to the receiver 4. The intermediate-pressure refrigerant is separated into gas and liquid in the receiver 4 and adiabatically expanded in the process of passing through the second expansion valve, and then sent to the outdoor heat exchangers 6a and 6b, where it evaporates and vaporizes by cooling the outside air. The refrigerant that has absorbed heat in the outdoor heat exchangers 6a and 6b and turned into gas is sent to the compressor through the three-way valve 8a, the four-way valve 7 and the like.

  If the evaporating temperature difference is detected and it is determined whether the evaporating temperature difference is equal to or greater than the predetermined temperature difference. Can be switched. Here, the evaporation temperature calculated based on the temperature of the evaporator of the outdoor heat exchanger 6a is the first temperature (for example, 20 ° C.), and the evaporation calculated based on the temperature of the evaporator of the outdoor heat exchanger 6b is used. A case where the temperature is the second temperature (for example, 0 ° C.) will be described as an example.

  For example, during the second heating operation of the air conditioner 10, the refrigerant flowing out of the outdoor heat exchanger 6b whose evaporator temperature is lower than that of the outdoor heat exchanger 6a is, for example, the three-way valve 8b as shown by the dotted line arrow in FIG. And then sent to the low-stage compressor 3a. As shown by the solid arrow in FIG. 3, the refrigerant that has come out of the outdoor heat exchanger 6a, whose evaporator temperature is higher than that of the outdoor heat exchanger 6b, joins at the connection point X via the three-way valve 8a and the four-way valve 7. Then, it is sent to the high stage side compressor 3b. The refrigerant discharged from the high-stage compressor 3b is sent to the indoor heat exchanger 5, and is sent in the order of the first expansion valve 9, the receiver 4, the second expansion valve 11, and the outdoor heat exchangers 6a and 6b.

  Here, the three-way valve 8a closes the flow path on the low-stage compressor 3a side and opens the flow path on the four-way valve 7 side, and the three-way valve 8b opens the flow path on the low-stage compressor 3a side. Although it has been described that the flow path on the four-way valve 7 side is closed in a state, it is not limited to this. For example, the three-way valve 8a opens the flow path on the low-stage compressor 3a side and closes the flow path on the four-way valve 7 side, and the three-way valve 8b closes the flow path on the low-stage compressor 3a side. Thus, the heating operation may be performed by opening the flow path on the four-way valve 7 side. In this embodiment, depending on the respective evaporation temperatures when the outdoor heat exchangers 6a and 6b to which the three-way valves 8a and 8b are connected operate as evaporators, the four-way valve 7 side is opened or low. Whether to open the flow path of the stage side compressor 3a is determined.

The refrigerant compressed in the low-stage compressor 3a merges with the refrigerant from the outdoor heat exchanger 6 that has circulated through the pipe L8 at the connection point X, and is sucked into the high-stage compressor 3b. Then, the refrigerant further compressed is sent to the four-way valve 7.
Thus, during the heating operation of the air conditioner 10, the indoor heat exchanger 5 functions as a condenser, and the outdoor heat exchangers 6a and 6b function as an evaporator.
In the present embodiment, both the indoor heat exchanger 5 and the outdoor heat exchanger 6 are heat exchanges with gas. However, the heat exchange is not limited to this and may be heat exchange with a liquid (for example, water).

  In addition, it is determined whether or not the outdoor heat exchangers 6a and 6b operating as evaporators have been frosted (frosted) during the heating operation. For example, when the frost is detected by the outdoor heat exchanger 6b In this case, the refrigerant is allowed to flow as shown by the solid line in FIG. That is, the four-way valve 7 closes the flow path on the indoor heat exchanger 5 side and the flow path to the connection point X, and the three-way valve 8b closes the flow path on the low-stage compressor 3a side, The flow path on the outdoor heat exchanger 6b side is opened, the three-way valve 8a closes the flow path on the four-way valve 7 side, opens the flow path on the low-stage compressor 3a side, and the outdoor heat exchanger The flow path on the 6a side is opened.

  Then, the outdoor heat exchanger 6b is operated as a condenser and the outdoor heat exchanger 6a is operated as an evaporator, whereby the refrigerant discharged from the high-stage compressor 3b is passed through the three-way valve 8b to the outdoor heat exchanger. 6b, the refrigerant discharged from the outdoor heat exchanger 6b flows into the outdoor heat exchanger 6a, and the refrigerant discharged from the outdoor heat exchanger 6a flows into the low-stage compressor 3a and the high-stage compressor 3b. . In this way, the outdoor unit is provided with a plurality of outdoor heat exchangers 6, and the plurality of outdoor heat exchangers 6 are operated as a condenser and an evaporator, so that the refrigerant is not circulated through the indoor unit, and the outdoor unit side. With defrost operation becomes possible. At this time, since the heating is stopped, cold air does not blow out into the space (indoor) where the indoor unit is placed. Therefore, the air conditioner 10 is defrosted while maintaining the sensible temperature inside the room. it can.

As described above, according to the air conditioner 10 and the control method thereof according to the present embodiment, the refrigerant discharged from the outdoor heat exchangers 6a and 6b is low-stage by switching the flow paths of the three-way valves 8a and 8b. The refrigerant discharged from the high-stage compressor 3b by the switching of the four-way valve 7 is divided into a flow path to the side compressor 3a and a flow path to the four-way valve 7, and the indoor heat exchanger passes through the four-way valve 7 5 side, a flow path connected to a connection point X between the low-stage compressor 3a and the high-stage compressor 3b, and three-way valves 8a and 8b (connected to one end of each of the outdoor heat exchangers 6a and 6b) The three-way valve) is switched.
According to the configuration of the present embodiment, the refrigerant discharged from the plurality of outdoor heat exchangers 6a and 6b passes through the path to the input side of the low-stage compressor 3a and the four-way valve 7, and the low-stage compressor 3a. Without being distributed (bypassed), and can be divided into a path for distributing to the input side of the high-stage compressor 3b.

Thus, since the refrigerant | coolant which came out from the several outdoor heat exchangers 6a and 6b can be separately made to flow in into the low stage side compressor 3a and the high stage side compressor 3b, a some outdoor heat exchanger 6a and 6b can be operated at different evaporation temperatures.
In the past, when using a plurality of evaporators with different evaporation temperatures, it was necessary to match the evaporator with a high evaporation temperature to the evaporator with a low evaporation temperature, so the capacity of the evaporator with a high evaporation temperature has decreased. It was. According to this embodiment, the refrigerant output from the outdoor heat exchanger 6 having a low evaporation temperature is compressed by the low-stage compressor 3a and the high-stage compressor 3b, and from the outdoor heat exchanger 6 having a high evaporation temperature. The outputted refrigerant can be compressed by the high stage compressor 3b. Thus, since the single-stage compression or the two-stage compression can be selected for the refrigerant that has left the evaporator, it is not necessary to match the evaporator with a low evaporation temperature, and there is an outdoor heat exchanger 6 with a different evaporation temperature. , You can drive without waste.

Moreover, when one of the outdoor heat exchangers 6 is frosted by providing a plurality of outdoor heat exchangers 6, the frosted outdoor heat exchanger 6 is operated as a condenser and is not frosted. By operating the outdoor heat exchanger 6 as an evaporator, the defrosting (defrost) operation can be performed only by the heat exchanger on the heat source side. Thereby, a low temperature refrigerant | coolant does not distribute | circulate through the indoor heat exchanger 5, the temperature fall of the refrigerant | coolant in a utilization side (for example, indoor) can be suppressed, and the indoor temperature fall is prevented.
In the present embodiment, the first flow path switching unit is a four-way valve and the second flow path switching unit is a three-way valve. However, the present invention is not limited to this. For example, the second flow path switching unit may be a valve (for example, electric or manual) that can switch the refrigerant direction.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. The positions where the four-way valve (first flow path switching means) and the three-way valve (second flow path switching means) of the refrigerant circuit of the air conditioner 10 of the present embodiment are different from the first embodiment. About the heat exchange system of this embodiment, description is abbreviate | omitted about the point which is common in 1st Embodiment, and a different point is mainly demonstrated using FIG.

The four-way valve 7 includes an indoor heat exchanger 5, three-way valves 8a and 8b (connected to one end side of the outdoor heat exchangers 6a and 6b), a discharge side of the high-stage compressor 3b, and a low-stage compression. The refrigerant flow path connected to the machine 3a and circulated is switched.
The three-way valve 8a is provided between a connection point Y on the path where the four-way valve 7 and the outdoor heat exchanger 6b are connected and the outdoor heat exchanger 6a, and is connected to the discharge side and the high stage of the low-stage compressor 3a. The flow path of the refrigerant | coolant distribute | circulated to the connection point Q provided between the suction sides of the side compressor 3b, the four-way valve 7, and the outdoor heat exchanger 6a is switched.
The three-way valve 8b is provided between a connection point Y on the path where the four-way valve 7 and the three-way valve 8a are connected and the outdoor heat exchanger 6b, and the four-way valve 7, the outdoor heat exchanger 6b, The flow path of the refrigerant circulated to the connection point P connected between the discharge side of the side compressor 3a and the suction side of the high stage compressor 3b is switched.

In the case of the second heating operation, as in the case of the first embodiment, when the difference in evaporation temperature between the outdoor heat exchangers 6a and 6b exceeds a predetermined temperature difference, the open / close state of the three-way valves 8a and 8b is changed. The refrigerant from the outdoor heat exchangers 6a and 6b is caused to flow into different compressors.
In the case of the defrost operation according to the present embodiment, the three-way valves 8a and 8b and the four-way valve 7 are controlled as follows. Here, the case where the outdoor heat exchanger 6b is frosted will be described as an example.
The four-way valve 7 closes the flow path on the indoor heat exchanger 5 side and the flow path on the low-stage compressor 3a side, and opens the flow path on the outdoor heat exchanger 6 side. The three-way valve 8a opens the flow path on the outdoor heat exchanger 6a side, closes the flow path on the four-way valve 7 side, and connects the low-stage compressor 3a and the high-stage compressor 3b. Open the flow path to Q.

  The three-way valve 8b opens the flow path on the four-way valve 7 side, opens the flow path on the outdoor heat exchanger 6b side, and is a connection point between the low-stage compressor 3a and the high-stage compressor 3b. Close the flow path to Q. Then, the outdoor heat exchanger 6a is operated as an evaporator, the outdoor heat exchanger 6b that has detected the frosting is operated as a condenser, and the refrigerant discharged from the high stage side compressor 3b is passed through the four-way valve 7 to the three-way valve. After passing through 8b, it flows into the outdoor heat exchanger 6b that operates as a condenser. The refrigerant discharged from the outdoor heat exchanger 6b flows into the outdoor heat exchanger 6a, and is sucked into the high stage compressor 3b through the three-way valve 8a.

In this way, the frosted evaporator (for example, outdoor heat exchanger 6b) is operated as a condenser, and defrosting is performed by flowing warm refrigerant.
As described above, according to the air conditioner 10 and the control method thereof according to the present embodiment, a plurality of outdoor heat exchangers 6 are provided, and when one of the outdoor heat exchangers 6 is frosted, By operating the frosted outdoor heat exchanger 6 as a condenser and operating the non-frosted outdoor heat exchanger 6 as an evaporator, a defrosting operation is performed only with the heat source side heat exchanger. be able to. Thereby, a low temperature refrigerant | coolant does not distribute | circulate through the indoor heat exchanger 5, and it can suppress the temperature fall of the refrigerant | coolant in a utilization side. In addition, during the defrosting operation, the refrigerant compression difference between the low-stage compressor 3a and the high-stage compressor 3b tends to be small. Therefore, during the defrosting operation, the refrigerant after the output of the evaporator is compressed to the high stage. By reducing the efficiency of refrigerant compression, compared with the case of two-stage compression, the refrigerant is sucked into the machine and single-stage compression is performed.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described. The air conditioner 10 of this embodiment differs from 1st Embodiment and 2nd Embodiment by the point which provides a liquid gas heat exchanger. About the heat exchange system of this embodiment, description is abbreviate | omitted about the point which is common in 1st Embodiment, 2nd Embodiment, and a different point is mainly demonstrated using FIG.

6 includes a liquid gas heat exchanger 30 and a third expansion valve 31 in the outdoor unit in addition to the configuration of FIG.
The liquid gas heat exchanger 30 diverts the liquid refrigerant at the outlet of the indoor heat exchanger 5 and the liquid refrigerant, and partially exchanges heat between the two refrigerants expanded by the third expansion valve 31. The liquid gas heat exchanger 30 may be a counter flow or a parallel flow, and is not particularly limited.

  The indoor heat exchanger 5 condenses and liquefies by releasing heat to the indoor air, and the pressure of the high-pressure and low-temperature liquid refrigerant is adjusted by the first expansion valve 9, and a part of the liquid refrigerant flows into the liquid-gas heat exchanger 30. . In the liquid gas heat exchanger 30, the liquid refrigerant at the outlet of the indoor heat exchanger 5 and a part of the two-phase refrigerant expanded by the third expansion valve 31 are heat-exchanged, and the gas refrigerant is sucked into the high stage compressor 3b. (Refer to piping L20). Here, the connecting portion of the pipe L20 is the suction side of the high stage compressor 3b, but the present invention is not limited to this, and may be, for example, the suction side of the low stage compressor 3a.

Moreover, in FIG. 6, although the liquid gas heat exchanger 30 is provided between the indoor heat exchanger 5 and the receiver 4, the position of the liquid gas heat exchanger 30 is not limited to this, For example, You may provide between the receiver 4 and the outdoor heat exchanger 6. FIG.
Thus, by providing the liquid gas heat exchanger 30, the liquid gas heat exchanger 30 plays the role of injection, so that the amount of refrigerant circulating to the low-stage compressor 3a can be reduced, and the input can be reduced. Can be achieved. Thereby, the further improvement of heating operation performance can be expected.

[Fourth Embodiment]
The fourth embodiment of the present invention will be described below. The air conditioner 10 of the present embodiment is different from the first embodiment, the second embodiment, and the third embodiment in that a bypass path is provided in the section of the outdoor heat exchanger from the discharge side of the high stage compressor. About the heat exchange system of this embodiment, description is abbreviate | omitted about the point which is common in 1st Embodiment, 2nd Embodiment, and 3rd Embodiment, and a different point is mainly demonstrated using FIG.

FIG. 7 shows the connection points A and B between the second expansion valves 11a and 11b and the outdoor heat exchangers 6a and 6b and the connection points provided on the discharge side of the high stage compressor 3b in addition to the configuration of FIG. A bypass path L40 connecting Z is provided. For example, the bypass path L40 is used when the outdoor heat exchanger 6 operating as an evaporator has frosted.
For example, when the outdoor heat exchanger 6a is frosted, as shown by the solid line arrow in FIG. 7, the entire amount of refrigerant is transferred to the outdoor heat exchanger 6a, the three-way valve 8a, the low-stage compressor 3a, and the high-stage compressor. 3b, the bypass path L40, and the outdoor heat exchanger 6a are circulated in this order. For example, when the outdoor heat exchanger 6b is frosted, the outdoor heat exchanger 6b, the three-way valve 8b, the low-stage compressor 3a, the high-stage compressor 3b, the bypass path L40, and the outdoor heat exchanger 6b You may circulate in order.
Furthermore, for example, when all of the plurality of outdoor heat exchangers 6a and 6b are frosted, the plurality of outdoor heat exchangers 6a and 6b, the three-way valves 8a and 8b, the low-stage compressor 3a, and the high-stage compressor 3b. The refrigerant may be circulated through the plurality of outdoor heat exchangers 6 such as the bypass path L40 and the outdoor heat exchangers 6a and 6b.

  The three-way valves 8a and 8b use the bypass path L40, and when the flow path on the outdoor heat exchangers 6a and 6b side and the flow path on the low-stage compressor 3a side are opened, the four-way valve 7 side The flow path is closed. The four-way valve 7 closes the discharge-side flow path of the high-stage compressor 3b. As a result, the refrigerant discharged from the outdoor heat exchangers 6a and 6b flows into the low-stage compressor 3a, further flows into the high-stage compressor 3b, passes through the bypass path L40, and the outdoor heat exchangers 6a and 6b. Return to.

The three-way valves 8a and 8b use the bypass path L40, and when the flow path on the outdoor heat exchangers 6a and 6b side and the flow path on the four-way valve 7 side are opened, the low-stage compressor 3a Close the flow path on the side. The four-way valve 7 opens the flow path on the side of the three-way valves 8a and 8b and the flow path to the connection point X, and closes the flow path on the discharge side of the high-stage compressor 3b. Thereby, the refrigerant | coolant which came out of the outdoor heat exchangers 6a and 6b flows into the high stage side compressor 3b, returns to the outdoor heat exchangers 6a and 6b through the bypass path L40.
As described above, the refrigerant discharged from the outdoor heat exchangers 6a and 6b may flow into the low-stage compressor 3a or may flow into the high-stage compressor 3b.

When the bypass path L40 is used, the outdoor heat exchangers 6a and 6b are not operated as an evaporator or a condenser, but are used when circulating hot gas. Call it.
In FIG. 7, the bypass path L40 is a section from the discharge side of the high-stage compressor 3b to the connection points A and B, but the arrangement position of the bypass path L40 is not limited to this. For example, a connection point may be provided on the discharge side of the low-stage compressor 3a and the connection points A and B may be connected from the discharge-side connection point of the low-stage compressor 3a.

  Even if it is a case where the conventional defrost driving | operation cannot be implemented by such a structure, the defrost of the outdoor heat exchanger 6 is carried out by making the refrigerant | coolant discharged from a compressor flow in into the outdoor heat exchanger 6 directly. Can be implemented. This eliminates the need for a condenser during defrosting. Moreover, since it becomes a circuit only of the compressor 3 and the outdoor heat exchanger 6, defrost control is easy compared with another Example.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

2a, 2b Temperature detector 3a Low stage compressor 3b High stage compressor 5 Indoor heat exchanger (use side heat exchanger)
6a, 6b Outdoor heat exchanger (heat source side heat exchanger)
7 Four-way valve (first flow path switching means)
8a, 8b Three-way valve (second flow path switching means)
10 Air conditioner X, Y, Z, A, B Connection point

Claims (9)

A heat exchange system comprising: a low stage compressor; a high stage compressor that further compresses the refrigerant compressed by the low stage compressor; a plurality of heat source side heat exchangers; and a use side heat exchanger. Because
The use side heat exchanger, one end side of each heat source side heat exchanger, the discharge side of the high stage compressor, and a connection point between the low stage compressor and the high stage compressor And a first flow path switching means for switching the flow path of the refrigerant to be circulated.
Provided between the first flow path switching means and the heat source side heat exchangers, respectively, the first flow path switching means, the heat source side heat exchangers, and the suction of the low stage compressor Second flow path switching means for switching the flow path of the refrigerant to be circulated to the side,
A heat exchange system comprising a control means for controlling the switching of the flow path between the first flow path switching means and the second flow path switching means. The second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other heat source side heat exchangers other than the one heat source side heat exchanger The second flow path switching means to be connected is a second second flow path switching means,
During the heating operation, the control means causes the refrigerant to flow into the low-stage compressor via the first second flow path switching means, and the high pressure via the second second flow path switching means. The heat exchange system according to claim 1, wherein the refrigerant flows into the stage-side compressor. The second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other heat source side heat exchangers other than the one heat source side heat exchanger When the second flow path switching means to be connected is a second second flow path switching means, and one of the heat source side heat exchangers is frosted,
The control means operates one heat source side heat exchanger as a condenser, operates the other heat source side heat exchanger as an evaporator, and the first second flow path switching means is the high stage side. The refrigerant from the compressor is circulated to the one heat source side heat exchanger, and the second second flow path switching unit passes the refrigerant from the other heat source side heat exchanger to the low stage compressor. The heat exchange system according to claim 1 or 2, wherein the heat exchange system is distributed. A heat exchange system comprising: a low stage compressor; a high stage compressor that further compresses the refrigerant compressed by the low stage compressor; a plurality of heat source side heat exchangers; and a use side heat exchanger. Because
The flow of the refrigerant to be circulated connected to the use side heat exchanger, one end side of each heat source side heat exchanger, the discharge side of the high stage compressor, and the suction side of the low stage compressor First flow path switching means for switching the path;
Provided between the first flow path switching means and the heat source side heat exchangers, respectively, the first flow path switching means, the heat source side heat exchangers, the low stage compressor, and the Second flow path switching means for switching the flow path of the refrigerant to be circulated to the connection point of the high stage compressor;
A heat exchange system comprising a control means for controlling the switching of the flow path between the first flow path switching means and the second flow path switching means. The second flow path switching means connected to one heat source side heat exchanger is a first second flow path switching means, and other heat source side heat exchangers other than the one heat source side heat exchanger When the second flow path switching means to be connected is a second second flow path switching means, and one of the heat source side heat exchangers is frosted,
The frosted heat source side heat exchanger is operated as a condenser, the heat source side heat exchanger not frosted is operated as an evaporator,
The control means controls the first second flow path switching means so that the refrigerant discharged from the high stage side compressor flows to the heat source side heat exchanger operated as the condenser, The second second flow path switching unit is controlled so that the refrigerant flows through the high-stage compressor via the heat source side heat exchanger operated as the evaporator after flowing through the condenser. The heat exchange system according to claim 4.   A liquid gas heat exchanger that exchanges heat between the liquid refrigerant at the outlet of the use side heat exchanger and the two-phase refrigerant obtained by expanding a part of the liquid refrigerant during heating operation, and the two-phase refrigerant after heat exchange The heat exchange system according to any one of claims 1 to 5, wherein the refrigerant flows into the low-stage compressor or the high-stage compressor.   The heat exchange system according to any one of claims 1 to 6, wherein a defrost path is provided to return the refrigerant discharged from the high stage side compressor to the heat source side heat exchanger. A heat exchange system comprising: a low stage compressor; a high stage compressor that further compresses the refrigerant compressed by the low stage compressor; a plurality of heat source side heat exchangers; and a use side heat exchanger. Control method,
The use side heat exchanger, one end side of each heat source side heat exchanger, the discharge side of the high stage compressor, and a connection point between the low stage compressor and the high stage compressor A first step of switching the flow path of the refrigerant to be circulated in the first flow path switching means connected to
Provided between the first flow path switching means and the heat source side heat exchangers, respectively, the first flow path switching means, the heat source side heat exchangers, and the suction of the low stage compressor A second step of switching the flow path of the refrigerant to be circulated in the second flow path switching means connected to the side;
A control method for a heat exchange system, comprising: a third step of controlling switching of the flow path between the first flow path switching means and the second flow path switching means. A heat exchange system comprising: a low stage compressor; a high stage compressor that further compresses the refrigerant compressed by the low stage compressor; a plurality of heat source side heat exchangers; and a use side heat exchanger. Control method,
First flow path switching means connected to the use side heat exchanger, one end side of each heat source side heat exchanger, the discharge side of the high stage compressor, and the suction side of the low stage compressor A first step of switching the flow path of the refrigerant to be circulated to
Provided between the first flow path switching means and the heat source side heat exchangers, respectively, the first flow path switching means, the heat source side heat exchangers, the low stage compressor, and the A second step of switching the flow path of the refrigerant flowing through the second flow path switching means connected to the connection point of the high stage compressor;
A control method for a heat exchange system, comprising: a third step of controlling switching of the flow path between the first flow path switching means and the second flow path switching means.

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