JP2014016079A - Heat pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct an injection passage that can control both a discharge temperature of a high stage side compression mechanism and an intermediate pressure of a refrigeration cycle.SOLUTION: A heat pump (1) includes a refrigerant circuit (10) in which a low stage side compression mechanism (11) and a high stage side compression mechanism (12), a radiator (13), and a vaporizer (15) are connected in turn, and which performs a two-stage compression type refrigeration cycle. The refrigerant circuit (10) includes: an overcooling heat exchanger (21) that provides heat exchange between an output refrigerant of the radiator (13) and a first branch refrigerant of the output refrigerant to turn the first branch refrigerant to an overheat gas refrigerant; and an injection passage (22) that mixes the first branch refrigerant turned to the overheat gas refrigerant with a second branch refrigerant of the output refrigerant of the radiator (13) to supply it to a part between both of the compression mechanisms (11 and 12). On the injection passage (22), two flow regulating valves (25 and 26) are provided which regulate the sum of flow rates and flow ratios of the first branch refrigerant and the second branch refrigerant.

Description

    The present invention relates to a heat pump that performs a two-stage compression refrigeration cycle.

    Conventionally, as disclosed in Patent Document 1, for example, a heat pump that performs a two-stage compression refrigeration cycle is known. The heat pump of Patent Document 1 includes a refrigerant circuit that performs a refrigeration cycle by connecting a two-stage compressor (a low-stage compression mechanism and a high-stage compression mechanism), a radiator, an expansion mechanism, and an evaporator. The refrigerant circuit is provided with an injection circuit that decompresses a part of the liquid refrigerant condensed by the radiator and supplies it between the low-stage compression mechanism and the high-stage compression mechanism. In the heat pump of Patent Document 1, by adjusting the opening of the expansion valve provided in the injection circuit and adjusting the temperature of the intermediate pressure refrigerant supplied between the low-stage compression mechanism and the high-stage compression mechanism, The discharge temperature of the two-stage compressor is kept below the upper limit value.

JP 2007-278686 A

    By the way, in the heat pump described above, the expansion valve of the injection circuit is adjusted to change not only the temperature of the refrigerant but also the flow rate of the refrigerant, so that the intermediate pressure of the refrigeration cycle (that is, the low-stage compression mechanism and the high-stage compression mechanism). (Pressure between the side compression mechanisms) fluctuates and there is a problem that it is difficult to set the compression ratio of each compression mechanism to an appropriate value. In a heat pump that performs a two-stage compression refrigeration cycle, each of the low-stage compression mechanism and the high-stage compression mechanism has an optimum compression ratio. If this compression ratio deviates from the optimum value, the operating efficiency of the compression mechanism decreases, and as a result, the COP (coefficient of performance) of the heat pump decreases.

    The present invention has been made in view of the above points, and an object of the present invention is to provide a high-stage compression in a heat pump including a passage for injecting intermediate pressure refrigerant between a low-stage compression mechanism and a high-stage compression mechanism. The object is to construct an injection passage that can control both the discharge temperature of the mechanism and the intermediate pressure of the refrigeration cycle.

    The first invention is a two-stage compression refrigeration cycle in which a low-stage compression mechanism (11), a high-stage compression mechanism (12), a radiator (13), and an evaporator (15) are sequentially connected. It is intended for heat pumps equipped with a refrigerant circuit (10) that performs the above. The refrigerant circuit (10) allows liquid refrigerant and gas refrigerant flowing downstream from the radiator (13) to pass between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). Injection passage (22, 32) to be supplied, and injection for adjusting the state and total flow rate of the liquid refrigerant and gas refrigerant supplied between the compression passages (11, 12) from the injection passage (22, 32) And an adjustment mechanism.

    In the first aspect of the invention, the state (dryness, superheat degree) of the liquid refrigerant and gas refrigerant supplied between the compression mechanisms (11, 12) from the injection passage (22, 32) is adjusted. The discharge temperature of the stage side compression mechanism (12) is adjusted. Further, the discharge flow rate of the low-stage compression mechanism (11) (by adjusting the total flow rate of liquid refrigerant and gas refrigerant supplied between the compression mechanisms (11, 12) from the injection passage (22, 32) ( The suction pressure of the high stage compression mechanism (12) is adjusted.

    In a second aspect based on the first aspect, the refrigerant circuit (10) exchanges heat between the outlet liquid refrigerant of the radiator (13) and the first branch refrigerant of the outlet liquid refrigerant. A subcooling heat exchanger (21) for the outlet liquid refrigerant in which the branch refrigerant becomes a superheated gas refrigerant is provided. Further, the injection passage (22) passes the first branch refrigerant that has become superheated gas refrigerant in the supercooling heat exchanger (21) and the second branch refrigerant that is the outlet liquid refrigerant of the radiator (13). It is configured to supply between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). The injection adjusting mechanism adjusts a total flow rate of the first branch refrigerant and the second branch refrigerant flowing through the injection passage (22) and adjusts a flow rate ratio between the first branch refrigerant and the second branch refrigerant. And a flow rate adjusting mechanism (25, 26).

    In the second aspect of the invention, in the supercooling heat exchanger (21), the outlet liquid refrigerant of the radiator (13) and its first branch refrigerant exchange heat, and the outlet liquid refrigerant is supercooled, while the first branch The refrigerant evaporates and becomes a superheated gas refrigerant. In the injection passage (22), the first branch refrigerant that is a superheated gas refrigerant and the second branch refrigerant that is a liquid refrigerant are supplied between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). .

    Then, by adjusting the flow rate ratio between the first branch refrigerant and the second branch refrigerant supplied between the two compression mechanisms (11, 12), the state of the suction refrigerant (dry) of the high-stage compression mechanism (12) And the degree of superheat) are adjusted, whereby the discharge temperature of the high-stage compression mechanism (12) is adjusted. Further, the total flow rate of the first branch refrigerant and the second branch refrigerant supplied between the compression mechanisms (11, 12) is adjusted, so that the discharge pressure (high stage side) of the low stage side compression mechanism (11) is adjusted. The suction pressure of the compression mechanism (12) is adjusted.

    In a third aspect based on the second aspect, the flow rate adjusting mechanism (25, 26) is configured such that the first branch refrigerant is discharged when a discharge temperature of the high-stage compression mechanism (12) is lower than a target value. When the discharge temperature of the high-stage compression mechanism (12) is higher than its target value, the first branch refrigerant and the second branch refrigerant are increased so that the flow ratio of the two branch refrigerants increases. While adjusting the flow ratio of the two-branch refrigerant, when the discharge pressure of the low-stage compression mechanism (11) is lower than its target value, increase the total flow of the first branch refrigerant and the second branch refrigerant, When the discharge pressure of the low stage side compression mechanism (11) is higher than the target value, the total flow rate of the first branch refrigerant and the second branch refrigerant is decreased.

    In the third aspect of the present invention, when the flow rate ratio of the first branch refrigerant increases, the dryness or superheat degree of the suction refrigerant of the high stage compression mechanism (12) increases. As a result, the discharge temperature of the high stage compression mechanism (12) increases. When the flow rate ratio of the second branch refrigerant increases, the dryness or superheat degree of the suction refrigerant of the high-stage compression mechanism (12) also decreases. As a result, the discharge temperature of the high stage compression mechanism (12) decreases.

    Further, when the total flow rate of the first branch refrigerant and the second branch refrigerant increases, the discharge pressure of the low-stage compression mechanism (11) (the suction pressure of the high-stage compression mechanism (12)) increases, and the first branch refrigerant When the total flow rate of the second branch refrigerant decreases, the discharge pressure of the low-stage compression mechanism (11) (the suction pressure of the high-stage compression mechanism (12)) decreases.

    According to a fourth aspect of the present invention based on the second aspect, the injection passage (22) branches off from an outlet side passage of the radiator (13) and passes through the supercooling heat exchanger (21). A main passage (23) connected between the compression mechanism (11) and the high stage compression mechanism (12), and a bypass passage (24 of the supercooling heat exchanger (21) provided in the main passage (23) ). The flow rate adjustment mechanism includes a first flow rate adjustment valve (1) for the first branch refrigerant provided between the inlet side of the supercooling heat exchanger (21) in the main passage (23) and the bypass passage (24). 25) and a second flow rate adjustment valve (26) for the second branch refrigerant provided in the bypass passage (24).

    In the fourth aspect of the invention, the flow rate of the first branch refrigerant is adjusted by adjusting the opening of the first flow rate adjustment valve (25) in the injection passage (22), and the second flow rate adjustment valve (26) is opened. The flow rate of the second branch refrigerant is adjusted by adjusting the degree. Therefore, by adjusting the opening degree of one or both of the two flow rate adjustment valves (25, 26), the total flow rate of the first branch refrigerant and the second branch refrigerant and the flow rate ratio of the first branch refrigerant and the second branch refrigerant. Is adjusted.

    In a fifth aspect based on the first aspect, the refrigerant circuit (10) includes an intermediate-pressure gas-liquid separator (31) provided between the radiator (13) and the evaporator (15). It has. The injection passage (32) supplies the liquid refrigerant and gas refrigerant of the gas-liquid separator (31) between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). It is configured. The injection adjusting mechanism includes a flow rate adjusting mechanism (36, 37) for adjusting a total flow rate of the liquid refrigerant and gas refrigerant flowing through the injection passage (32), and the liquid refrigerant and gas refrigerant flowing through the injection passage (32). And a heating heat exchanger (38) for heating the refrigerant by the outlet refrigerant of the radiator (13).

    In the fifth aspect, the liquid refrigerant and gas refrigerant of the gas-liquid separator (31) are supplied between the compression mechanisms (11, 12). Then, by adjusting the total flow rate of the first branch refrigerant and the second branch refrigerant supplied between the compression mechanisms (11, 12), the discharge pressure (high stage side) of the low stage compression mechanism (11) is adjusted. The suction pressure of the compression mechanism (12) is adjusted. In addition, by adjusting the heating capacity of the heating heat exchanger (38), the state (dryness, superheat degree) of the suction refrigerant of the high stage compression mechanism (12) is adjusted, and thereby, the high stage compression mechanism The discharge temperature of (12) is adjusted.

    In a sixth aspect based on the fifth aspect, the flow rate adjusting mechanism (36, 37) is configured such that the liquid refrigerant and the gas are discharged when the discharge pressure of the low-stage compression mechanism (11) is lower than the target value. The total flow rate of the refrigerant is increased, and when the discharge pressure of the low-stage compression mechanism (11) is higher than the target value, the total flow rate of the liquid refrigerant and the gas refrigerant is decreased. On the other hand, the heating heat exchanger (38) is configured so that the temperature of the liquid refrigerant and the gas refrigerant rises when the discharge temperature of the high-stage compression mechanism (12) is lower than the target value. When the discharge temperature of the side compression mechanism (12) is higher than the target value, the heating capacity is adjusted so that the temperatures of the liquid refrigerant and the gas refrigerant are lowered.

    In the sixth aspect of the invention, when the total flow rate of the liquid refrigerant and the gas refrigerant supplied between the both compression mechanisms (11, 12) increases, the discharge pressure (high-stage compression mechanism) of the low-stage compression mechanism (11) When the suction pressure of (12) rises and the total flow rate of the liquid refrigerant and gas refrigerant supplied between both compression mechanisms (11, 12) decreases, the discharge pressure (high) of the low-stage compression mechanism (11) The suction pressure of the stage side compression mechanism (12) decreases. In addition, when the heating capacity of the heating heat exchanger (38) increases, the enthalpy of liquid refrigerant and gas refrigerant supplied between both compression mechanisms (11, 12) increases, and as a result, high-stage compression The degree of dryness or superheat of the suction refrigerant in the mechanism (12) increases, and as a result, the discharge temperature of the high-stage compression mechanism (12) increases. When the heating capacity of the heating heat exchanger (38) decreases, the enthalpy of the liquid refrigerant and gas refrigerant supplied between the two compression mechanisms (11, 12) decreases, and accordingly, the high-stage compression mechanism ( The dryness or superheat of the suction refrigerant in 12) is lowered, and as a result, the discharge temperature of the high-stage compression mechanism (12) is lowered.

    According to a seventh invention, in the second or fifth invention, a dryness adjustment unit that performs a refrigeration cycle so that an outlet refrigerant of the evaporator (15) is less than 1 in the refrigerant circuit (10). (52).

    In the seventh aspect of the invention, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the evaporator (15) is compared with the case where the outlet refrigerant of the evaporator (15) is overheated. ) Is suppressed. Superheated gas refrigerant has a larger specific volume and higher flow rate than wet refrigerant, so in an evaporator with multiple passes, if superheated gas refrigerant is generated in some passes, that pass is more pressure than other passes. Loss increases. Therefore, it becomes difficult for the refrigerant to flow into the path where the superheated gas refrigerant is generated, and a drift occurs in which the refrigerant flows in the other path. However, in this embodiment, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), no superheated gas refrigerant is generated in the evaporator (15). Therefore, the refrigerant drift in the evaporator (15) is suppressed.

    As described above, according to the present invention, the liquid refrigerant and the gas refrigerant that flow downstream from the radiator (13) are placed between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). And the state of the liquid refrigerant and gas refrigerant (dryness, superheat degree) supplied between the compression passages (11, 12) from the injection passage (22, 32) and the injection passage (22, 32) ) And an injection adjustment mechanism for adjusting the total flow rate. Therefore, it is possible to adjust both the discharge temperature of the high-stage compression mechanism (12) and the discharge pressure of the low-stage compression mechanism (11) (that is, the intermediate pressure in the refrigeration cycle). Since the discharge temperature of the high-stage compression mechanism (12) can be controlled, the required heating capacity can be exhibited in the heat pump (1). In addition, since the intermediate pressure can be controlled, the compression ratio of each compression mechanism (11, 12) can be set to an optimum value, thereby improving the operation efficiency of the compression mechanism (11, 12). As described above, it is possible to operate with a high COP (coefficient of performance) while sufficiently satisfying the heating capacity.

    According to the second invention, as the injection adjusting mechanism, a flow rate adjusting mechanism that adjusts the total flow rate and flow rate ratio of the superheated gas refrigerant (first branch refrigerant) and the liquid refrigerant (second branch refrigerant) flowing through the injection passage (22). Since (25, 26) is provided, both the discharge temperature of the high-stage compression mechanism (12) and the intermediate pressure of the refrigeration cycle can be controlled with a simple configuration.

    According to the fourth invention, the injection passage (22) branches off from the outlet side passage of the radiator (13) and is connected to the low stage compression mechanism (11) and the high stage side via the supercooling heat exchanger (21). A main passage (23) connected between the compression mechanisms (12), and a bypass passage (24) of the supercooling heat exchanger (21) provided in the main passage (23). The first flow rate adjustment valve (25) is provided between the inlet side of the supercooling heat exchanger (21) and the bypass passage (24) in 23), and the second flow rate adjustment valve (26) is provided in the bypass passage (24). I tried to provide it. For this reason, it is possible to easily adjust the total flow rate and flow rate ratio of the superheated gas refrigerant and the liquid refrigerant only by adjusting the opening degree of the two flow rate adjustment valves (25, 26).

    According to the fifth aspect of the invention, the injection passage (32) for supplying the liquid refrigerant and the gas refrigerant of the gas-liquid separator (31) between the compression mechanisms (11, 12) and the injection passage (32) flow. A flow rate adjusting mechanism (36, 37) for adjusting the total flow rate of the liquid refrigerant and the gas refrigerant, and a heating heat exchanger (38) for heating the liquid refrigerant and the gas refrigerant flowing through the injection passage (32) are provided. Generally, in a heat pump (1) that performs a two-stage compression refrigeration cycle, an intermediate-pressure gas-liquid separator (31) is provided. Therefore, in the present invention, the gas-liquid separator (31) is used to Both the discharge temperature of the side compression mechanism (12) and the intermediate pressure of the refrigeration cycle can be controlled.

    According to the seventh invention, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the evaporator (15) has an evaporator (15) as compared with the case where the outlet refrigerant is overheated. The drift of the refrigerant in 15) can be suppressed. Superheated gas refrigerant has a larger specific volume and higher flow rate than wet refrigerant, so in an evaporator with multiple passes, if superheated gas refrigerant is generated in some passes, that pass is more pressure than other passes. Loss increases. Therefore, it becomes difficult for the refrigerant to flow into the path where the superheated gas refrigerant is generated, and a drift occurs in which the refrigerant flows in the other path. However, in this embodiment, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), no superheated gas refrigerant is generated in the evaporator (15). Therefore, the refrigerant drift in the evaporator (15) can be suppressed.

FIG. 1 is a piping diagram illustrating a configuration of a heat pump according to the first embodiment. FIG. 2 is a piping diagram illustrating the configuration of the heat pump according to the second embodiment.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

Embodiment 1 of the Invention
A first embodiment of the present invention will be described. The heat pump (1) of the present embodiment is used for industrial purposes, and heats a fluid to be heated (target fluid) to 100 ° C. or higher. As shown in FIG. 1, the heat pump (1) includes a refrigerant circuit (10) and a controller (50).

    The refrigerant circuit (10) performs a two-stage compression refrigeration cycle by circulating the refrigerant. The refrigerant circuit (10) includes a low-stage compressor (11) and a high-stage compressor (12), a radiator (13), an expansion valve (expansion mechanism) (14), and an evaporator (15). Are sequentially connected by refrigerant piping. In the present embodiment, a single refrigerant of R245fa (critical temperature is 154 ° C.) is used as the refrigerant.

    Although not shown, the low-stage compressor (11) and the high-stage compressor (12) are configured in a completely sealed manner, and the inside of the casing that houses the compression section and the motor that rotationally drives the compression section is the suction pressure. It has a so-called low-pressure dome shape. That is, in each compressor (11, 12), the suction refrigerant flows into the casing, and the refrigerant compressed by the compression unit is directly discharged out of the casing without flowing into the casing. Each of the compressors (11, 12) is configured to have a variable operating rotational speed. Both compressors (11, 12) are connected in series with each other and compress the refrigerant in two stages by both compressors (11, 12), and constitute a refrigerant compression mechanism.

    The radiator (13) has a low temperature channel (13a) and a high temperature channel (13b). The high temperature flow path (13b) has an inflow end connected to the discharge side of the high stage compressor (12) and an outflow end connected to a subcooling heat exchanger (21) described later. On the other hand, the low-temperature flow path (13a) of the radiator (13) is connected to the heat medium circuit (100). In the radiator (13), the high-pressure refrigerant flowing through the high-temperature channel (13b) and the heat medium (oil in this embodiment) of the heat medium circuit (100) flowing through the low-temperature channel (13a) exchange heat to The medium is heated. That is, in the present embodiment, the heat medium of the heat medium circuit (100) is the fluid to be heated (target fluid) of the radiator (13). The heat medium circuit (100) has a heating heat exchanger (102) provided in a constant temperature bath (103) of hot water, and is a closed circuit in which the heat medium is circulated by a pump (101). The pump (101) is provided between the outlet side of the constant temperature bath (103) and the low temperature flow path (13a) of the radiator (13). In the heat medium circuit (100), the heat medium heated by the radiator (13) exchanges heat with the water in the thermostat (103) by the heating heat exchanger (102), and the water in the thermostat (103) is exchanged. Heated to a constant temperature. The heat medium circuit (100) is provided with a water temperature sensor (104) for measuring the water temperature in the constant temperature bath (103).

    The expansion valve (14) is an electronic expansion valve whose opening degree can be adjusted.

    The evaporator (15) has a low temperature channel (15a) and a high temperature channel (15b). The low temperature flow path (15a) has an inflow end connected to the expansion valve (14) and an outflow end connected to the suction side of the low stage compressor (11). On the other hand, the high-temperature channel (15b) of the evaporator (15) is connected to the heat source circuit (110). In the evaporator (15), the low pressure refrigerant flowing through the low temperature flow path (15a) and the heat source medium of the heat source circuit (110) flowing through the high temperature flow path (15b) exchange heat, and the low pressure refrigerant is heated by the heat source medium. Examples of the heat source medium of the heat source circuit (110) include factory waste heat (for example, waste water), a heat source refrigerant of an air conditioner provided separately, and the like.

    The refrigerant circuit (10) is provided with a supercooling heat exchanger (21) and an injection passage (22). The supercooling heat exchanger (21) is connected between the radiator (13) and the expansion valve (14), and has a high temperature channel (21a) and a low temperature channel (21b). The injection passage (22) has a main passage (23). The main passage (23) branches off from the outlet side passage of the radiator (13) and passes between the low-stage compressor (11) and the high-stage compressor (12) via the supercooling heat exchanger (21). It is connected. That is, the outflow end of the injection passage (22) is connected between the compressors (11, 12). The main passage (23) is provided with a bypass passage (24) that bypasses the supercooling heat exchanger (21). The main passage (23) is provided with a first flow control valve (25) between the inlet side of the supercooling heat exchanger (21) and the bypass passage (24), and the bypass passage (24) A second flow rate adjustment valve (26) is provided.

    The high-temperature channel (21a) of the supercooling heat exchanger (21) has an inflow end connected to the radiator (13) and an outflow end connected to the expansion valve (14). The low-temperature channel (21b) of the supercooling heat exchanger (21) is connected to the main channel (23) of the injection channel (22). In the injection passage (22), a part of the outlet refrigerant of the radiator (13) flows into the main passage (23), and a part of the refrigerant that flows into the main passage (23) flows into the bypass passage (24). . That is, in the injection passage (22), the first branch refrigerant of the outlet refrigerant of the radiator (13) flows into the low-temperature channel (21b) of the supercooling heat exchanger (21), and the outlet refrigerant of the radiator (13) The second branch refrigerant flows into the bypass passage (24). In the supercooling heat exchanger (21), heat is exchanged between the outlet refrigerant of the radiator (13) flowing through the high-temperature channel (21a) and the first branch refrigerant of the outlet refrigerant flowing through the low-temperature channel (21b). While the outlet refrigerant of the channel (21a) is supercooled, the first branch refrigerant of the low temperature channel (21b) evaporates to become superheated gas refrigerant (superheated gas refrigerant). The injection passage (22) includes a first branch refrigerant in the main passage (23) that has become superheated gas refrigerant in the supercooling heat exchanger (21) and a second branch refrigerant (liquid refrigerant) in the bypass passage (24). Are mixed and supplied between the low-stage compressor (11) and the high-stage compressor (12).

    The first flow rate adjustment valve (25) adjusts the flow rate of the first branch refrigerant that is a superheated gas refrigerant, and the second flow rate adjustment valve (26) adjusts the flow rate of the second branch refrigerant that is a liquid refrigerant. Then, the two flow rate adjusting valves (25, 26) are arranged so that the flow rate of the mixed refrigerant of the first branch refrigerant and the second branch refrigerant in the injection passage (22) (that is, the total flow rate of the first branch refrigerant and the second branch refrigerant). ) And a flow rate adjustment mechanism for adjusting the flow ratio of the first branching refrigerant to the second branching refrigerant in the mixed refrigerant (the flow rate ratio of each branching refrigerant in the mixed refrigerant), and the injection adjusting mechanism according to the present invention. Configure.

    Further, the supercooling heat exchanger (21) of the present embodiment has a much higher heat exchange capability than a general supercooling heat exchanger provided in an air conditioner or the like. In general supercooling heat exchangers, the heat exchange capacity is designed so that the refrigerant in the low-temperature channel has a low superheat degree of about 3 ° C at a specified flow rate at the design point, and the refrigerant flow rate in the low-temperature channel is the design flow rate. As soon as it increases, the refrigerant in the low-temperature channel flows out in a wet state without being superheated. On the other hand, in the supercooling heat exchanger (21) of the present embodiment, even if the flow rate of the first branch refrigerant flowing through the low temperature flow path (21b) changes to some extent (even if it increases), the first branch refrigerant is It is designed to flow out with a degree of superheat (as a superheated gas refrigerant). That is, in the supercooling heat exchanger (21) of the present embodiment, the maximum flow rate of the first branch refrigerant allowed to use the first branch refrigerant as the superheated gas refrigerant is set high.

    The refrigerant circuit (10) is provided with various sensors. Specifically, the refrigerant circuit (10) includes a suction pressure sensor (P1) that measures the pressure of the suction refrigerant of the low-stage compressor (11), and the pressure of the discharge refrigerant of the high-stage compressor (12). Pressure of the refrigerant discharged from the low-stage compressor (11) (intake refrigerant of the high-stage compressor (12)) provided between the discharge pressure sensor (P2) to be measured and both compressors (11, 12) And an intermediate pressure sensor (P3) is provided. The measured value of the intermediate pressure sensor (P3) corresponds to the pressure of the first branch refrigerant that has flowed out of the low-temperature flow path (21b) of the supercooling heat exchanger (21) in the injection passage (22). The refrigerant circuit (10) includes a high-stage discharge temperature sensor (T1) that measures the temperature of refrigerant discharged from the high-stage compressor (12), and the temperature of the refrigerant discharged from the low-stage compressor (11). A low-stage discharge temperature sensor (T2) that measures the temperature of the subcooling heat exchanger (21) in the main passage (23), and is provided on the outlet side of the low-temperature passage (21b). An outlet temperature sensor (T3) that measures the temperature of the first branched refrigerant that has flowed out is provided.

    The controller (50) is provided with a map (51), a dryness adjusting unit (52), and an injection adjusting unit (53).

    The map (51) shows the three parameters of the refrigerant pressure of the low-stage compressor (11), the discharge refrigerant pressure and temperature of the low-stage compressor (11), and the outlet refrigerant of the evaporator (15). It is a database showing the correspondence with dryness. The suction refrigerant pressure of the low stage compressor (11) corresponds to the low pressure of the refrigeration cycle, and the discharge refrigerant pressure of the low stage compressor (11) is an intermediate pressure between the low pressure and high pressure of the refrigeration cycle. It corresponds to.

    The dryness adjustment unit (52) is configured to perform a refrigeration cycle so that the refrigerant at the outlet of the evaporator (15) is less than 1 in the refrigerant circuit (10). The injection adjusting unit (53) is configured to adjust the temperature of the refrigerant discharged from the high-stage compressor (12) (discharge temperature) to a target value and the intermediate pressure of the refrigeration cycle to a target value. The opening degree of the flow rate adjusting valve (25) and the second flow rate adjusting valve (26) is adjusted. Details of operations of the dryness adjusting unit (52) and the injection adjusting unit (53) will be described later.

<Operation of heat pump>
When both compressors (11, 12) are driven, the refrigerant compressed by the low-stage compressor (11) is further compressed by the high-stage compressor (12) to become a high-pressure refrigerant. The high-pressure refrigerant (130 ° C.) discharged from the high-stage compressor (12) is heat-exchanged with the heat medium (oil) of the heat medium circuit (100) by the radiator (13) to be condensed and liquid refrigerant (113 ° C. ) Thereby, the heat medium of the heat medium circuit (100) is heated from 110 ° C. to 120 ° C., for example. Part of the high-pressure liquid refrigerant condensed in the radiator (13) flows to the main passage (23) of the injection passage (22), and the rest flows to the high-temperature passage (21a) of the supercooling heat exchanger (21). .

    A part of the liquid refrigerant (first branch refrigerant) flowing into the main passage (23) is depressurized by the first flow control valve (25), and then the low-temperature flow path (21b) of the supercooling heat exchanger (21). To exchange heat with the high-pressure refrigerant in the high-temperature channel (21a). As a result, the high-pressure refrigerant in the high-temperature channel (21a) is supercooled, while the first branch refrigerant (80 ° C) in the low-temperature channel (21b) evaporates to become an intermediate-pressure superheated gas refrigerant (90 ° C). . The high-pressure refrigerant in the high-temperature flow path (21a) is reduced in enthalpy of the refrigerant by being supercooled.

    On the other hand, the remaining liquid refrigerant (second branch refrigerant) flowing in the main passage (23) flows into the bypass passage (24) and passes through the second flow rate adjusting valve (26), and then returns to the main passage (23). It flows and mixes with the 1st branch refrigerant of superheated gas refrigerant. The mixed refrigerant of the first branch refrigerant and the second branch refrigerant (intermediate pressure refrigerant, 87 ° C.) flows between the low-stage compressor (11) and the high-stage compressor (12).

    The high-pressure refrigerant (90 ° C.) supercooled by the supercooling heat exchanger (21) is decompressed by the expansion valve (14) to become a low-pressure refrigerant. The low-pressure refrigerant flows into the evaporator (15), exchanges heat with the heat source medium of the heat source circuit (110), evaporates, and the heat source medium is cooled. Since the enthalpy of the low-pressure refrigerant flowing through the evaporator (15) is reduced by the amount of supercooling as described above, the evaporation capacity (cooling capacity) of the evaporator (15) increases. The refrigerant (40 ° C.) flowing out from the evaporator (15) is sucked into the low stage compressor (11) and compressed again. The refrigerant (82 ° C.) discharged from the low-stage compressor (11) merges with the intermediate-pressure refrigerant (first branch refrigerant and second branch refrigerant) from the injection passage (22), and the combined refrigerant (85 ° C) is sucked into the high stage compressor (12).

    In the heat medium circuit (100), the heat medium (120 ° C.) heated by the radiator (13) flows to the heating heat exchanger (102) to exchange heat with the water in the thermostatic chamber (103), and the water is heated. To warm water (80 ° C.). In addition, the numerical value of the temperature mentioned above is only an example.

<Operation of dryness adjustment unit>
The dryness adjusting unit (52) controls the refrigerant circuit (10) so that the outlet refrigerant of the evaporator (15) becomes less than 1 (so-called wet refrigerant) during the above-described operation. In the present embodiment, the degree of dryness of the outlet refrigerant of the evaporator (15) is adjusted to a target value (for example, 0.8). In the present embodiment, the target value of the dryness may be set to a value less than 1, but is set within a range of 0.7 to 0.9 where the COP of the heat pump (1) is optimal. Is preferred.

    Specifically, the dryness adjusting unit (52) is configured to determine the suction refrigerant pressure (suction pressure) of the low-stage compressor (11), the discharge refrigerant pressure (discharge pressure) and the temperature of the low-stage compressor (11). The dryness of the outlet refrigerant of the evaporator (15) is derived from the three measured values of (discharge temperature) using a map (51) prepared in advance. When the derived dryness is not the target value, the dryness adjusting unit (52) uses the derived dryness and the three measured values to set the dryness of the outlet refrigerant of the evaporator (15) as the target value. Determine the controlled variable or set value.

    Specifically, the opening degree of the expansion valve (14) and the like are controlled. For example, when the opening degree of the expansion valve (14) increases, the suction pressure of the low-stage compressor (11) increases, and the dryness of the outlet refrigerant of the evaporator (15) decreases. When the opening degree of the expansion valve (14) decreases, the suction pressure of the low-stage compressor (11) decreases, and the dryness of the outlet refrigerant of the evaporator (15) increases.

    As described above, when the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the refrigerant drift in the evaporator (15) is suppressed. Since the superheated gas refrigerant has a larger specific volume and a higher flow rate than the wet refrigerant, in an evaporator having a plurality of passes, if superheated gas refrigerant is generated only in some passes, that pass is more than the other passes. Pressure loss increases. Therefore, it becomes difficult for the refrigerant to flow into the path where the superheated gas refrigerant is generated, and a drift occurs in which the refrigerant flows in the other path. However, in this embodiment, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the evaporator (15) has no superheated area of the refrigerant and no superheated gas refrigerant is generated. . Therefore, the refrigerant drift in the evaporator (15) is suppressed.

<Operation of injection adjustment unit>
The injection adjusting unit (53) is configured so that the temperature (discharge temperature) of the refrigerant discharged from the high stage compressor (12) becomes a target value (130 ° C.) during the operation described above, and the low stage compressor ( The opening degree of the first flow rate adjustment valve (25) and the second flow rate adjustment valve (26) is adjusted so that the discharge pressure of 11) (the suction pressure of the high-stage compressor (12)) becomes the target value. The target value of the discharge temperature of the high stage compressor (12) is the high stage compressor required to heat the heat medium of the heat medium circuit (100) to a predetermined temperature (120 ° C) with the radiator (13). The temperature of the discharged refrigerant in (12) is set. The target value of the discharge pressure of the low-stage compressor (11) is determined from the suction pressure of the low-stage compressor (11) and the discharge pressure of the high-stage compressor (12) for each compressor (11, 12). The compression ratio is set to an optimum value. Here, the optimum compression ratio is a value at which the efficiency of the entire refrigeration cycle becomes the best as a combination of the compressor efficiency (operating efficiency) of each compressor (11, 12) with respect to each compression ratio.

    For example, when the discharge pressure of the low-stage compressor (11) is a target value and the discharge temperature of the high-stage compressor (12) is lower than the target value, the first branch refrigerant in the injection passage (22) The flow rate ratio (flow rate) of the first branch refrigerant in the mixed refrigerant increases while maintaining the flow rate of the mixed refrigerant (hereinafter referred to simply as mixed refrigerant) of (superheated gas refrigerant) and the second branched refrigerant (liquid refrigerant). Furthermore, the opening degree of the first flow rate adjusting valve (25) is increased, and the opening degree of the second flow rate adjusting valve (26) is decreased. Then, the state (dryness, superheat degree) of the mixed refrigerant in the injection passage (22) changes. Specifically, the dryness or superheat of the mixed refrigerant increases, or the mixed refrigerant changes from a wet state to an overheated state. That is, the enthalpy of the mixed refrigerant increases. When the enthalpy of the mixed refrigerant in the injection passage (22) increases, the enthalpy of the suction refrigerant of the high stage compressor (12) also increases. As a result, the discharge pressure of the low stage compressor (11) is maintained, The discharge temperature of the high-stage compressor (12) rises to the target value.

    When the discharge pressure of the low stage compressor (11) is the target value and the discharge temperature of the high stage compressor (12) is higher than the target value, the flow rate of the mixed refrigerant in the injection passage (22) Is maintained, while the opening degree of the first flow rate adjustment valve (25) is decreased so that the flow rate ratio (flow rate) of the second branched refrigerant in the mixed refrigerant increases, and the opening degree of the second flow rate adjustment valve (26). Is increased. Then, the state (dryness, superheat degree) of the mixed refrigerant in the injection passage (22) changes. Specifically, the dryness or superheat of the mixed refrigerant is lowered, or the mixed refrigerant is changed from an overheated state to a wet state. That is, the enthalpy of the mixed refrigerant is reduced. When the enthalpy of the mixed refrigerant in the injection passage (22) decreases, the enthalpy of the suction refrigerant of the high-stage compressor (12) also decreases. As a result, the discharge pressure of the low-stage compressor (11) is maintained, The discharge temperature of the high stage compressor (12) is lowered to the target value.

    Further, when the discharge temperature of the high-stage compressor (12) is the target value and the discharge pressure of the low-stage compressor (11) is higher than the target value, the second refrigerant refrigerant in the injection passage (22) The opening degree of both the first flow rate adjustment valve (25) and the second flow rate adjustment valve (26) is decreased so that the flow rate of the mixed refrigerant decreases while maintaining the flow ratio of the first branch refrigerant and the second branch refrigerant. Is done. Then, only the flow rate of the mixed refrigerant decreases while maintaining the enthalpy of the mixed refrigerant. As a result, the discharge pressure of the low-stage compressor (11) decreases to the target value while the discharge temperature of the high-stage compressor (12) is maintained. If the discharge pressure of the low-stage compressor (11) is higher than the target value, the compression ratio of the low-stage compressor (11) becomes higher than the optimum value, and the compression of the high-stage compressor (12) The ratio will be lower than the optimum value.

    Further, when the discharge temperature of the high stage compressor (12) is the target value and the discharge pressure of the low stage compressor (11) is lower than the target value, the second refrigerant in the mixed refrigerant in the injection passage (22). The opening degree of both the first flow rate adjustment valve (25) and the second flow rate adjustment valve (26) is increased so that the flow rate of the mixed refrigerant increases while maintaining the flow rate ratio of the first branch refrigerant and the second branch refrigerant. Is done. Then, only the flow rate of the mixed refrigerant increases while the enthalpy of the mixed refrigerant is maintained. As a result, while the discharge temperature of the high stage compressor (12) is maintained, the discharge pressure of the low stage compressor (11) rises to the target value. If the discharge pressure of the low-stage compressor (11) is lower than the target value, the compression ratio of the low-stage compressor (11) will be lower than the optimum value, and the compression of the high-stage compressor (12) The ratio will be higher than the optimum value.

    Further, when both the discharge temperature of the high-stage compressor (12) and the discharge pressure of the low-stage compressor (11) deviate from the target values, the flow rate of the mixed refrigerant and the first branch refrigerant and the first refrigerant in the mixed refrigerant In order to adjust both the flow ratios of the two-branch refrigerants, the opening degrees of both the first flow rate adjustment valve (25) and the second flow rate adjustment valve (26) are adjusted.

    As described above, the injection adjustment unit (53) increases the flow rate ratio of the first branch refrigerant of the mixed refrigerant in the injection passage (22) when the discharge temperature of the high stage compressor (12) is lower than the target value. If it is higher than the target value, the flow rate ratio of the second branch refrigerant of the mixed refrigerant is increased. In addition, the injection adjustment unit (53) is a refrigerant mixture in the injection passage (22) when the discharge pressure of the low-stage compressor (11) (the suction pressure of the high-stage compressor (12)) is lower than the target value. (The total flow rate of the first branch refrigerant and the second branch refrigerant) is increased, and if higher than the target value, the flow rate of the mixed refrigerant is decreased. As a result, both the discharge temperature of the high-stage compressor (12) and the refrigerant pressure between the compressors (11, 12) (that is, the intermediate pressure of the refrigeration cycle) can be adjusted to the target value.

    In addition, the injection adjusting unit (53) is a low-stage compressor when the degree of superheat of the first branch refrigerant (superheated gas refrigerant) flowing out from the supercooling heat exchanger (21) has decreased (for example, 3 ° C). The adjustment of the discharge temperature of the higher stage compressor (12) is prioritized over the adjustment of the discharge pressure of (11). Specifically, when the degree of superheat of the first branch refrigerant decreases, the injection adjustment unit (53) decreases the flow rate of the first branch refrigerant by reducing the opening of the first flow rate adjustment valve (25). As a result, the degree of superheat of the first branch refrigerant flowing out of the supercooling heat exchanger (21) is secured, and the second flow rate adjustment is performed so that the discharge temperature of the high-stage compressor (12) is maintained at the target value. Adjust the opening of the valve (26). Note that the degree of superheat of the first branch refrigerant is derived from the measured value of the outlet temperature sensor (T3) and the measured value of the intermediate pressure sensor (P3).

    And the operation | movement of the dryness adjustment part (52) mentioned above and the operation | movement of the injection adjustment part (53) are performed alternately every predetermined time (for example, 1 minute).

-Effect of Embodiment 1-
According to the present embodiment, the first branch refrigerant (superheated gas refrigerant) and the second branch refrigerant (liquid refrigerant) are mixed and placed between the low-stage compressor (11) and the high-stage compressor (12). The injection passage (22) to be supplied was provided, and two flow rate adjustment valves (25, 26) for adjusting the total flow rate and flow rate ratio of the first branch refrigerant and the second branch refrigerant were provided. Therefore, both the discharge temperature of the high stage compressor (12) and the intermediate pressure of the refrigeration cycle can be controlled. Since the discharge temperature of the high-stage compressor (12) can be controlled, the required heating capacity can be exhibited in the radiator (13). Further, since the intermediate pressure can be controlled, the compression ratio of each compressor (11, 12) can be set to an optimum value, and thereby the operation efficiency of the compressor (11, 12) can be improved. As a result, it is possible to operate with a high COP (coefficient of performance) while sufficiently satisfying the heating capacity.

    Further, according to the present embodiment, the injection passage (22) is branched from the outlet side passage of the radiator (13) and is connected to the low stage compressor (11) and the high stage via the supercooling heat exchanger (21). A main passage (23) connected between the side compressors (12) and a bypass passage (24) of a supercooling heat exchanger (21) provided in the main passage (23). A first flow rate adjustment valve (25) is provided between the inlet side of the supercooling heat exchanger (21) and the bypass passage (24) in (23), and a second flow rate adjustment valve (26) is provided in the bypass passage (24). It was made to provide. For this reason, the sum of the first branch refrigerant (superheated gas refrigerant) and the second branch refrigerant (liquid refrigerant) easily flowing through the injection passage (22) simply by adjusting the opening of the two flow rate adjustment valves (25, 26). It is possible to reliably adjust the flow rate and the flow rate ratio.

    In addition, since the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the evaporator (15) has no overheated area of refrigerant and no superheated gas refrigerant is generated. The drift of the refrigerant in 15) can be suppressed. As described above, the entire evaporator (15) can be effectively utilized by eliminating the overheating region in the evaporator (15) and suppressing the drift, thereby improving the heat exchange capability of the evaporator (15). be able to. As a result, the COP of the heat pump (1) can be further improved.

    In particular, in this embodiment, since the dryness of the outlet refrigerant of the evaporator (15) is set to 0.7 to 0.9, the heat transfer coefficient with respect to the dryness peaks, so the COP of the heat pump (1) is An optimal value can be obtained.

    Moreover, when the outlet refrigerant of the evaporator (15) has a dryness of less than 1 (wet refrigerant), the discharge temperature of the high-stage compressor (12) is lowered, and it may be difficult to ensure the required discharge temperature. is there. Even in this case, in the present embodiment, the opening amounts of the two flow rate adjustment valves (25, 26) are adjusted, and the first branch refrigerant (superheated gas refrigerant) and the second branch refrigerant (liquid refrigerant) in the injection passage (22) are adjusted. By adjusting the flow rate ratio, the discharge temperature of the high stage compressor (12) can be set to the target value (required temperature). Thereby, sufficient heating capability of the radiator (13) can be ensured.

    In the present embodiment, the target fluid is heated to 100 ° C. or higher in the radiator (13), but the critical temperature as the refrigerant is the heating temperature of the target fluid (the heating temperature of the heating medium of the heating medium circuit (100) is 120 ° C.). Since the refrigerant of R245fa that greatly exceeds is used, it is possible to take a condensing region instead of a supercritical region in the refrigeration cycle. Moreover, since the refrigerant | coolant with a critical temperature exceeding 100 degreeC has a very low density at low pressure, in order to earn a required flow volume in an evaporator (15), it is necessary to make the flow velocity of a refrigerant | coolant high, and thereby an evaporator ( In this embodiment, the outlet refrigerant of the evaporator (15) is made to have a dryness of less than 1 (wet refrigerant), so that the flow rate of the refrigerant in the evaporator (15) is increased. The required flow rate (required capacity) can be secured without increasing the flow rate. As a result, the pressure loss in the evaporator (15) can be reduced while ensuring the condensing region instead of the supercritical region in the refrigeration cycle. As a result, it is possible to improve the COP of the heat pump (1).

    In this embodiment, wet refrigerant is sucked into the low-stage compressor (11), but the refrigeration oil of the low-stage compressor (11) is diluted by the refrigerant, or the compression section is damaged by so-called liquid compression. There is no risk. In particular, in the present embodiment, since the low-stage compressor (11) is a low-pressure dome type compressor, the moist refrigerant flowing into the casing of the low-stage compressor (11) is motorized before flowing into the compressor. The degree of dryness is increased somewhat by heating. Therefore, it is possible to sufficiently prevent damage due to dilution of the refrigerator oil and liquid compression. Moreover, as a refrigerating machine oil of a low stage side compressor (11), the dilution of refrigerating machine oil can be prevented further by using the thing of a PAG type | system | group with low compatibility with the refrigerant | coolant of R245fa. As a result, the reliability of the heat pump (1) can be improved.

    Moreover, in this embodiment, since the high stage side compressor (12) is a low pressure dome type compressor, the heat resistance requested | required of the structural member of a high stage side compressor (12) can be suppressed. In the high-pressure dome type compressor, since the refrigerant compressed in the compression section is further heated by the motor after being discharged into the casing, the temperature in the casing becomes very high. Therefore, in the case of a high-pressure dome type compressor, high heat resistance is required for its constituent members. In a low-pressure dome type compressor, a relatively low temperature refrigerant flows into the casing, while the refrigerant compressed by the compression section flows out of the casing directly without flowing out of the casing. Therefore, in the case of a low-pressure dome type compressor, the temperature in the casing can be kept low, thereby making it possible to suppress the heat resistance required for the constituent members.

<< Embodiment 2 of the Invention >>
A second embodiment of the present invention will be described. As shown in FIG. 2, the heat pump (1) of this embodiment is provided with an intermediate-pressure gas-liquid separator (31) in the first embodiment and the configuration of the injection passage is changed. Here, a different part from the said Embodiment 1 is demonstrated.

    The refrigerant circuit (10) of the present embodiment includes a high-stage expansion valve (16), a gas-liquid separator (in the order from the radiator (13) side, between the radiator (13) and the evaporator (15). 31) and a low stage side expansion valve (17). In the refrigerant circuit (10), the outlet refrigerant of the radiator (13) is depressurized in two stages by the high stage expansion valve (16) and the low stage side expansion valve (17). That is, the refrigerant circuit (10) is configured to perform a two-stage compression / two-stage expansion refrigeration cycle. Accordingly, the intermediate-pressure refrigerant flows into the gas-liquid separator (31) and is separated into the gas refrigerant and the liquid refrigerant.

    The refrigerant circuit (10) is provided with an injection passage (32). In addition, unlike the said Embodiment 1, the supercooling heat exchanger is not provided in the refrigerant circuit (10). The injection passage (32) has a liquid passage (33), a gas passage (34), and a merging passage (35). The inflow end of the liquid passage (33) communicates with the liquid layer of the gas-liquid separator (31), and the inflow end of the gas passage (34) communicates with the gas layer of the gas-liquid separator (31). The confluence passage (35) has an inflow end connected to the outflow end of the liquid passage (33) and the gas passage (34), and an outflow end between the low-stage compressor (11) and the high-stage compressor (12). It is connected to the. In the injection passage (32), the intermediate-pressure liquid refrigerant flowing from the gas-liquid separator (31) into the liquid passage (33) and the intermediate-pressure gas flowing from the gas-liquid separator (31) into the gas passage (34). The refrigerant is mixed in the merge passage (35) and supplied between the low-stage compressor (11) and the high-stage compressor (12). The liquid passage (33) is provided with a first flow rate adjustment valve (36), and the gas passage (34) is provided with a second flow rate adjustment valve (37). The two flow rate adjustment valves (36, 37) are flow rate adjustment mechanisms that adjust the total flow rate of the liquid refrigerant and gas refrigerant (flow rate of the mixed refrigerant) flowing through the injection passage (32).

    The refrigerant circuit (10) is provided with a heating heat exchanger (38) for heating the liquid refrigerant and gas refrigerant flowing through the injection passage (32) by the outlet refrigerant of the radiator (13). The heating heat exchanger (38) has a low temperature channel (38a) and a high temperature channel (38b). The low-temperature flow path (38a) of the heating heat exchanger (38) is connected to the junction path (35) of the injection path (32). The refrigerant circuit (10) is provided with a heating liquid pipe (39). The heating liquid pipe (39) has an inflow end connected between the outlet side of the radiator (13) and the high stage expansion valve (16), and an outflow end connected to the high stage expansion valve (16) It is connected between the separator (31). In the middle of the heating liquid pipe (39), a high-temperature channel (38b) of the heating heat exchanger (38) is connected. The heating liquid pipe (39) is provided with a third flow rate adjustment valve (40) on the outflow end side of the heating heat exchanger (38).

    Part of the outlet refrigerant of the radiator (13) flows into the heating liquid pipe (39). In the heating heat exchanger (38), the mixed refrigerant in the injection passage (32) flowing through the low temperature flow path (38a) exchanges heat with the refrigerant flowing through the high temperature flow path (38b) and is heated. That is, the mixed refrigerant in the injection passage (32) is heated by the heating heat exchanger (38). And the flow volume of the refrigerant | coolant which flows through the high temperature flow path (38b) of a heating heat exchanger (38) is adjusted by adjusting the opening degree of a 3rd flow regulating valve (40), and a heating heat exchanger (38) The heating capacity is adjusted.

    In the present embodiment, the first flow rate adjustment valve (36), the second flow rate adjustment valve (37), and the heating heat exchanger (38) constitute an injection adjustment mechanism according to the present invention.

    The injection adjusting unit (53) of the present embodiment is configured so that the discharge temperature of the high-stage compressor (12) becomes a target value and the discharge pressure of the low-stage compressor (11) becomes a target value. In addition, the opening degree of the three flow rate adjusting valves (36, 37, 40) is adjusted. That is, the injection adjusting unit (53) adjusts the opening degree of the first flow rate adjusting valve (36) and the second flow rate adjusting valve (37), thereby adjusting the flow rate of the mixed refrigerant (liquid refrigerant and gas) in the injection passage (32). Adjusting the heating capacity of the heating heat exchanger (38) by adjusting the opening of the third flow rate adjustment valve (40) and adjusting the state of the mixed refrigerant in the injection passage (32) ( Adjust the degree of dryness and superheat.

    For example, when the discharge pressure of the low-stage compressor (11) is lower than the target value, the two flow rates are set so that the flow rate of the mixed refrigerant (liquid refrigerant and gas refrigerant mixed refrigerant) in the injection passage (32) increases. The opening degree of the regulating valve (36, 37) is adjusted. When the flow rate of the mixed refrigerant increases, the discharge pressure of the low-stage compressor (11) increases and becomes the target value. Further, when the discharge pressure of the low-stage compressor (11) is higher than the target value, the two flow rates are set so that the flow rate of the mixed refrigerant (the mixed refrigerant of the liquid refrigerant and the gas refrigerant) in the injection passage (32) decreases. The opening degree of the regulating valve (36, 37) is adjusted. When the flow rate of the mixed refrigerant decreases, the discharge pressure of the low-stage compressor (11) decreases to the target value. Thus, the refrigerant pressure (that is, the intermediate pressure of the refrigeration cycle) between the two compressors (11, 12) can be adjusted to the target value.

    When the discharge temperature of the high stage compressor (12) is lower than the target value, the opening of the third flow rate adjustment valve (40) is set so that the heating capacity of the heating heat exchanger (38) is increased. Will be increased. As a result, the dryness or superheat (temperature) of the mixed refrigerant supplied between the compressors (11, 12) from the injection passage (32) increases, so that the intake refrigerant of the high-stage compressor (12) As a result, the degree of dryness or superheat increases, and as a result, the discharge temperature of the high-stage compressor (12) rises to the target value. When the discharge temperature of the high stage compressor (12) is higher than the target value, the opening of the third flow rate adjustment valve (40) is set so that the heating capacity of the heating heat exchanger (38) is reduced. Will be reduced. As a result, the dryness or superheat (temperature) of the mixed refrigerant supplied between the compressors (11, 12) from the injection passage (32) decreases, so that the intake refrigerant of the high stage compressor (12) As a result, the degree of dryness or superheat is lowered, and as a result, the discharge temperature of the high stage compressor (12) is lowered to the target value.

    Thus, the injection adjustment part (53) of this embodiment adjusts the discharge temperature of the high stage side compressor (12) by adjusting the heating capability of the heating heat exchanger (38), and the injection passage (32 The refrigerant pressure between the compressors (11, 12) (that is, the intermediate pressure of the refrigeration cycle) is adjusted by adjusting the flow rate of the mixed refrigerant in (2). Thereby, both the discharge temperature of the high-stage compressor (12) and the refrigerant pressure between the compressors (11, 12) can be adjusted to the target value. Other functions and effects are the same as those of the first embodiment.

<< Other Embodiments >>
For example, in each of the above embodiments, it is not always necessary to provide the dryness adjusting unit (52). That is, in each said embodiment, the exit refrigerant | coolant of an evaporator (15) does not need to make it dryness less than one.

    Further, in the injection passage (22) of the first embodiment, although not shown, the inflow end is connected to the outlet side passage of the radiator (13) and the outflow end is the main passage (23) instead of the bypass passage (24). A branch pipe connected to the outlet side of the supercooling heat exchanger (37) may be provided. That is, in the injection passage (22), the first branch refrigerant and the second branch refrigerant may be separately branched from the outlet refrigerant of the radiator (13). In this case, a second flow rate adjustment valve (26) is provided in the branch pipe.

    For example, in the dryness adjusting unit (52) of each of the embodiments, the dryness of the outlet refrigerant of the evaporator (15) is adjusted using the map (51), but the present invention is not limited to this. For example, the enthalpy of the refrigerant sucked in the low-stage compressor (11) using an estimation model consisting of a state equation and an output equation with physical quantities (temperature and pressure) related to the refrigerant sucked in the low-stage compressor (11) as state quantities. (A technique disclosed in Japanese Patent Application Laid-Open No. 2007-278618), and the dryness of the outlet refrigerant of the evaporator (15) may be adjusted based on the detected enthalpy of the suction refrigerant.

    Moreover, in each said embodiment, although the single refrigerant | coolant of R245fa was used as a refrigerant | coolant, you may use the mixed refrigerant | coolant which contains R245fa as a main component. For example, a mixed refrigerant of R245fa and R134a can be used. By mixing R134a, the heat transfer performance of the refrigerant is improved and the density of the refrigerant is increased.

    In each of the above embodiments, a refrigerant having a critical temperature of 120 ° C. or higher, such as pentane (C 5 H 12), may be used instead of the single refrigerant of R245fa.

    In each of the above embodiments, the heat medium of the heat medium circuit (100) is not limited to oil but may be water or a refrigerant. In that case, in the heat medium circuit (100), water or refrigerant in a gas-liquid two-phase state is sucked into the pump (101) and may damage the pump (101). A gas-liquid separator may be provided between the pump (101) and the liquid (single-phase) water or refrigerant may be reliably sucked into the pump (101).

    In the injection passage (22) of the above embodiment, the first branch refrigerant (superheated gas refrigerant) and the second branch refrigerant (liquid refrigerant) are mixed and supplied between the compressors (11, 12). However, you may comprise so that a 1st branch refrigerant | coolant and a 2nd branch refrigerant | coolant may be separately supplied between both compressors (11, 12), without mixing. That is, an injection passage for the first branch refrigerant and an injection passage for the second branch refrigerant may be provided.

    Similarly, the injection passage (32) of the second embodiment is provided with an injection passage for liquid refrigerant and an injection passage for gas refrigerant, so that both compressors ( 11 and 12). In this case, a heating heat exchanger is provided in each injection passage.

    In each of the above embodiments, each compressor (11, 12) may be a so-called high pressure dome type compressor.

    The present invention is useful for a heat pump that performs a two-stage compression refrigeration cycle.

DESCRIPTION OF SYMBOLS 1 Heat pump 10 Refrigerant circuit 11 Low stage side compressor (low stage side compression mechanism)
12 High stage compressor (High stage compression mechanism)
13 Radiator 14 Expansion Valve (Expansion Mechanism)
15 Evaporator 21 Supercooling Heat Exchanger 22 Injection Passage 23 Main Passage 24 Bypass Passage 25 First Flow Control Valve (Flow Control Mechanism)
26 Second flow rate adjustment valve (flow rate adjustment mechanism)
52 Dryness adjuster

Claims (7)

A refrigerant circuit (10) in which a low-stage compression mechanism (11) and a high-stage compression mechanism (12), a radiator (13), and an evaporator (15) are connected in order to perform a two-stage compression refrigeration cycle. ) With a heat pump,
The refrigerant circuit (10)
An injection passage (22, 32) for supplying liquid refrigerant and gas refrigerant flowing downstream from the radiator (13) between the low-stage compression mechanism (11) and the high-stage compression mechanism (12); ,
An injection adjusting mechanism for adjusting a state and a total flow rate of the liquid refrigerant and gas refrigerant supplied between the compression mechanisms (11, 12) from the injection passage (22, 32); Heat pump. In claim 1,
In the refrigerant circuit (10), the outlet liquid refrigerant of the radiator (13) and the first branch refrigerant of the outlet liquid refrigerant exchange heat so that the first branch refrigerant becomes superheated gas refrigerant. With supercooling heat exchanger (21),
The injection passage (22) passes the first branch refrigerant that has become superheated gas refrigerant in the supercooling heat exchanger (21) and the second branch refrigerant that is the outlet liquid refrigerant of the radiator (13) to the low stage. Configured to be supplied between the side compression mechanism (11) and the high stage compression mechanism (12),
The injection adjusting mechanism adjusts a total flow rate of the first branch refrigerant and the second branch refrigerant flowing through the injection passage (22) and adjusts a flow rate ratio between the first branch refrigerant and the second branch refrigerant. A heat pump comprising an adjustment mechanism (25, 26). In claim 2,
The flow rate adjusting mechanism (25, 26) is configured so that the flow rate ratio of the first branch refrigerant increases when the discharge temperature of the high-stage compression mechanism (12) is lower than the target value. When the discharge temperature of the compression mechanism (12) is higher than the target value, the flow rate ratio between the first branch refrigerant and the second branch refrigerant is adjusted so that the flow rate ratio of the second branch refrigerant increases, When the discharge pressure of the low-stage compression mechanism (11) is lower than the target value, the total flow rate of the first branch refrigerant and the second branch refrigerant is increased, and the discharge pressure of the low-stage compression mechanism (11) Is higher than the target value, the total flow rate of the first branch refrigerant and the second branch refrigerant is reduced. In claim 2,
The injection passage (22) branches from the outlet side passage of the radiator (13), and passes through the supercooling heat exchanger (21) to connect the low-stage compression mechanism (11) and the high-stage compression mechanism (12 And a bypass passage (24) of the supercooling heat exchanger (21) provided in the main passage (23),
The flow rate adjustment mechanism includes a first flow rate adjustment valve (1) for the first branch refrigerant provided between the inlet side of the supercooling heat exchanger (21) in the main passage (23) and the bypass passage (24). 25) and a second flow rate regulating valve (26) for the second branch refrigerant provided in the bypass passage (24). In claim 1,
The refrigerant circuit (10) includes an intermediate-pressure gas-liquid separator (31) provided between the radiator (13) and the evaporator (15),
The injection passage (32) supplies the liquid refrigerant and gas refrigerant of the gas-liquid separator (31) between the low-stage compression mechanism (11) and the high-stage compression mechanism (12). Configured,
The injection adjusting mechanism includes a flow rate adjusting mechanism (36, 37) for adjusting a total flow rate of the liquid refrigerant and gas refrigerant flowing through the injection passage (32), and the liquid refrigerant and gas refrigerant flowing through the injection passage (32). And a heating heat exchanger (38) that heats the radiator (13) by the outlet refrigerant of the radiator (13). In claim 5,
The flow rate adjusting mechanism (36, 37) increases the total flow rate of the liquid refrigerant and the gas refrigerant when the discharge pressure of the low stage side compression mechanism (11) is lower than the target value, thereby reducing the low stage side compression. When the discharge pressure of the mechanism (11) is higher than the target value, the total flow rate of the liquid refrigerant and the gas refrigerant is reduced,
The heating heat exchanger (38) is configured to compress the high-stage compression so that the temperatures of the liquid refrigerant and gas refrigerant rise when the discharge temperature of the high-stage compression mechanism (12) is lower than the target value. A heat pump characterized in that when the discharge temperature of the mechanism (12) is higher than the target value, the heating capacity is adjusted so that the temperatures of the liquid refrigerant and the gas refrigerant are lowered. In claim 2 or 5,
A heat pump comprising: a dryness adjusting unit (52) for performing a refrigeration cycle so that an outlet refrigerant of the evaporator (15) in the refrigerant circuit (10) has a dryness of less than 1.

Images