JP2016048132A - Steam compression type refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam compression type refrigeration cycle employing an injection system, capable of reducing power consumption of a compressor.SOLUTION: A steam compression type refrigeration cycle can switch between an injection operation and a non-injection operation, and opens a second valve 15A in starting the injection operation. Consequently, damage of a second compressor 9B due to a liquid compressor is suppressed, and a steam compression type refrigeration cycle 1 employing an injection system capable of reducing consumption power of a first compressor 9A and the second compressor 9B can be obtained.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vapor compression refrigeration cycle that moves heat on a low temperature side to a high temperature side.

  In a general vapor compression refrigeration cycle, since the gas-phase refrigerant is cooled and liquefied (condensed) by a high-pressure heat exchanger such as a condenser, the liquid-phase refrigerant tends to stay in the condenser. If a large amount of liquid-phase refrigerant accumulates in the condenser, the amount of circulating refrigerant decreases, so that sufficient refrigeration capacity may not be obtained. Therefore, for example, in the invention described in Patent Document 1, the preparatory operation is executed when the vapor compression refrigeration cycle (compressor) is started.

JP 2007-78242 A

  By the way, if the intermediate pressure refrigerant is injected during the compression stroke, the power consumption of the compressor can be reduced. For this reason, it is particularly effective to use the injection operation when the pressure of the high-pressure refrigerant is high, such as when using cold heat with a high outside air temperature.

  However, when the outside air temperature is low, such as in winter, the pressure of the high-pressure side refrigerant is low, so the injection operation may not be effective. That is, when the pressure of the high-pressure side refrigerant is reduced, the consumption power required by injecting the intermediate pressure refrigerant is larger due to the reduction in power consumption expected by injecting the intermediate pressure refrigerant in the middle of the compression stroke. A case occurs.

  The present invention has been made in view of the above points, and an object thereof is to provide an injection-type vapor compression refrigeration cycle that can further reduce power consumption of a compressor.

  In order to achieve the above object, the present invention provides a high-pressure heat exchanger (3) for cooling a high-temperature side refrigerant and a low-temperature side refrigerant in a vapor compression refrigeration cycle that moves low-temperature side heat to a high temperature side. The pressure is reduced by the low pressure heat exchanger (7) to be heated and evaporated, the first pressure reducer (5A) for reducing and expanding the high pressure refrigerant flowing out from the high pressure heat exchanger (3), and the first pressure reducer (5A). The gas-liquid separator (11) that separates the intermediate pressure refrigerant into the gas-phase refrigerant and the liquid-phase refrigerant, and the low-pressure heat exchanger by decompressing and expanding the liquid-phase refrigerant separated by the gas-liquid separator (11) The second pressure reducer (5B) supplied to (7) and the low-pressure heat exchanger (7) side suck in and compress the gas-phase refrigerant and discharge the compressed refrigerant to the high-pressure heat exchanger (3) side. The gas-phase refrigerant is sucked and compressed from the first compressor (9A) and the gas-liquid separator (11) and compressed. A second compressor (9B) for discharging the refrigerant to the discharge side of the first compressor (9A), and an injection control unit (21) for controlling the operation of the second compressor (9B), When switching from the non-injection operation to the injection operation, the injection control unit (21) capable of switching between the injection operation for operating the compressor (9B) and the non-injection operation for stopping the second compressor (9B), It is provided with the supply suppression system (15A, 21) which suppresses that the liquid phase refrigerant which exists in a 2nd compressor (9B) is supplied to the high pressure heat exchanger (3) side.

  Thereby, in the present invention, since it is possible to switch between the injection operation and the non-injection operation, an injection-type vapor compression refrigeration cycle capable of further reducing the power consumption of the compressor can be obtained.

  That is, when the consumption power required by injecting the intermediate pressure refrigerant becomes larger due to the reduction in power consumption expected by injecting the intermediate pressure refrigerant in the middle of the compression stroke, the injection operation is not performed. By switching to injection operation, power consumption can be reduced.

  By the way, in the non-injection operation according to the present invention, since the second compressor (9B) is stopped, the gas phase refrigerant remaining when the second compressor (9B) is stopped is condensed and liquefied. There is a possibility that.

  If the liquid refrigerant remains in the second compressor (9B), when the second compressor (9B) is started, that is, when the non-injection operation is shifted to the injection operation, the second compressor In (9B), overcompression occurs due to liquid compression, and the second compressor (9B) may be damaged.

  On the other hand, in the present invention, when shifting from the non-injection operation to the injection operation, the liquid refrigerant present in the second compressor (9B) is supplied to the high-pressure heat exchanger (3) side. Since it suppresses, it can suppress that overcompression generate | occur | produces in a 2nd compressor (9B). Therefore, damage to the second compressor (9B) can be suppressed.

That is, in the present invention, it is possible to switch between the injection operation and the non-injection operation to further reduce the power consumption of the compressor, and it is possible to suppress damage to the second compressor (9B).
The present invention may be configured as follows.

  When the supply suppression system (15A, 21) shifts from the non-injection operation to the injection operation, the refrigerant circuit from the gas-liquid separator (11) to the low-pressure heat exchanger (7) and the second compressor (9B) A communication circuit (15) that communicates with the discharge side may be provided. The “refrigerant circuit” according to this example includes the inflow side of the gas-liquid separator (11) and the outflow side of the low-pressure heat exchanger (7).

  Thereby, the liquid phase refrigerant in the second compressor (9B) is supplied to the intermediate pressure side or the low pressure side without being supplied to the high pressure heat exchanger (3) side. Therefore, it is possible to suppress the occurrence of overcompression in the second compressor (9B).

  The supply suppression system (15A, 21) may be configured to directly or indirectly heat the liquid refrigerant in the second compressor (9B) with a high-pressure refrigerant. Thereby, the liquid phase refrigerant in the second compressor (9B) can be vaporized. Therefore, it can suppress that the liquid phase refrigerant | coolant which exists in a 2nd compressor (9B) is supplied to the high pressure heat exchanger (3) side.

  The supply suppression system (15A, 21) is configured to supply the high-pressure refrigerant discharged from the first compressor (9A) to the suction side of the second compressor (9B), or generated in the first compressor (9A). The heat may be directly or indirectly supplied to the second compressor (9B). Thereby, the liquid phase refrigerant in the second compressor (9B) can be vaporized.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

1 is a schematic diagram of a vapor compression refrigeration cycle according to a first embodiment of the present invention. 1 is a block diagram of a control system of a vapor compression refrigeration cycle according to a first embodiment of the present invention. It is a schematic diagram of the vapor compression refrigeration cycle which concerns on 2nd Embodiment of this invention. It is a block diagram of a control system of a vapor compression refrigeration cycle according to a second embodiment of the present invention. It is a schematic diagram of the vapor compression refrigeration cycle which concerns on 3rd Embodiment of this invention. It is a schematic diagram of the vapor compression refrigeration cycle which concerns on 3rd Embodiment of this invention. It is a schematic diagram of the vapor compression refrigeration cycle which concerns on 4th Embodiment of this invention. It is a block diagram of the control system of the vapor compression refrigeration cycle which concerns on 5th Embodiment of this invention.

  The “embodiment of the invention” described below shows an example of the embodiment. In other words, the invention specific items described in the claims are not limited to the specific means and structures shown in the following embodiments.

  In the present embodiment, the present invention is applied to a vapor compression refrigeration cycle for an air conditioner that cools a server room. In the server room, electrical devices such as an ICT device and an emergency power supply (battery) are installed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that at least one member or part described with at least a reference numeral is provided, except for cases where “plural”, “two or more” and the like are omitted.

(First embodiment)
1. Configuration of Vapor Compression Refrigeration Cycle As shown in FIG. 1, a vapor compression refrigeration cycle 1 according to this embodiment includes a high pressure heat exchanger 3, a first pressure reducer 5A, a second pressure reducer 5B, and a low pressure heat exchanger 7. The first compressor 9A, the second compressor 9B, and the gas-liquid separator 11 are provided.

  The high-pressure heat exchanger 3 cools a high-pressure refrigerant (hereinafter also referred to as a discharge refrigerant) discharged from at least one of the first compressor 9A and the second compressor 9B. That is, the high-pressure heat exchanger 3 cools the discharged refrigerant by exchanging heat between the outdoor air and the discharged refrigerant.

In this embodiment, the pressure of the discharged refrigerant is smaller than the critical pressure of the refrigerant. For this reason, the discharged refrigerant in the gas phase is cooled and condensed (liquefied) by the high-pressure heat exchanger 3.
The first decompressor 5A decompresses and expands the high-pressure refrigerant that has flowed out of the high-pressure heat exchanger 3. The refrigerant decompressed by the first decompressor 5 </ b> A (hereinafter referred to as “intermediate pressure refrigerant”) is separated into a gas-phase refrigerant and a gas-phase refrigerant by the gas-liquid separator 11.

  The gas-liquid separator 11 separates the refrigerant using the density difference between the gas-phase refrigerant and the liquid-phase refrigerant. For this reason, liquid-phase refrigerant accumulates on the lower side of the gas-liquid separator 11, and gas-phase refrigerant accumulates on the upper side of the gas-liquid separator 11.

  Incidentally, the degree of supercooling of the refrigerant flowing out from the high-pressure heat exchanger 3 is usually small except when a supercooler or the like is provided. For this reason, the refrigerant decompressed by the first decompressor 5A is in a gas-liquid two-phase state.

  The second decompressor 5B decompresses and expands the liquid-phase refrigerant separated by the gas-liquid separator 11 and supplies it to the low-pressure heat exchanger 7. The low pressure heat exchanger 7 evaporates the low pressure liquid phase refrigerant decompressed by the second decompressor 5B. That is, in the low-pressure heat exchanger 7, the refrigerant decompressed by the second decompressor 5B is heated by the air supplied to the room, thereby mainly evaporating (vaporizing) the liquid-phase refrigerant and cooling the air. To do.

  The first compressor 9A sucks and compresses the refrigerant flowing out from the low pressure heat exchanger 7 side, and discharges the compressed refrigerant to the high pressure heat exchanger 3 side. The second compressor 9B sucks and compresses the gas-phase refrigerant from the gas-liquid separator 11, and discharges the compressed refrigerant to the discharge side of the first compressor 9A.

  The first accumulator 17A separates and extracts the gas-phase refrigerant from the refrigerant flowing out from the low-pressure heat exchanger 7, and supplies the gas-phase refrigerant to the suction side of the first compressor 9A. The second accumulator 17B separates and extracts the gas-phase refrigerant from the refrigerant supplied from the gas-liquid separator 11 to the second compressor 9B, and supplies the gas-phase refrigerant to the suction side of the second compressor 9B.

  The first valve 19 prevents the discharge side of the first compressor 9A and the discharge side of the second compressor 9B from communicating during a non-injection operation described later. The first valve 19 according to the present embodiment is configured by a check valve that restricts the high-pressure refrigerant discharged from the first compressor 9A from flowing back to the second compressor 9B.

  The communication circuit 15 makes the refrigerant circuit from the gas-liquid separator 11 to the low pressure heat exchanger 7 communicate with the second compressor 9B. The communication circuit 15 according to the present embodiment is provided on the lower side of the gas-liquid separator 11, that is, “between the liquid phase side of the gas-liquid separator 11 and the second decompressor 5B” and “the discharge of the second compressor 9B. "Side".

  The communication circuit 15 is provided with a second valve 15A. The second valve 15 </ b> A adjusts the communication state of the communication circuit 15. The first blower 3 </ b> A blows cooling air (outdoor air) to the high-pressure heat exchanger 3. The second blower 7 </ b> A blows room air to the low-pressure heat exchanger 7.

2. 2. Control of Vapor Compression Refrigeration Cycle 2.1 Control System Configuration The operations of the first compressor 9A, the second compressor 9B, the first decompressor 5A, the second decompressor 5B, the second valve 15A, etc. are shown in FIG. As shown, it is controlled by the control device 21. The control device 21 is configured by a microcomputer having a CPU, a ROM, a RAM, and the like.

  A program (software) for executing control of the first compressor 9A and the like is stored in advance in a nonvolatile storage unit such as a ROM. When the control of the first compressor 9A and the like is executed, the program is read and executed by the CPU.

  The control device 21 receives detection signals from the first discharge pressure sensor S1, the second discharge pressure sensor S2, the intermediate pressure sensor S3, the low pressure temperature sensor S4, the evaporation temperature sensor S5, the outside air temperature sensor S6, and the indoor temperature sensor S7. Have been entered.

  The first discharge pressure sensor S1 detects the pressure of refrigerant discharged from the first compressor 9A (hereinafter referred to as first discharge pressure Pd1). The second discharge pressure sensor S2 detects the pressure of the refrigerant discharged from the second compressor 9B (hereinafter referred to as the second discharge pressure Pd2). The control device 21 according to the present embodiment regards the refrigerant pressure detected by the first discharge pressure sensor S1 as the refrigerant pressure in the high-pressure heat exchanger 3.

  The intermediate pressure sensor S3 detects the suction side refrigerant pressure of the second compressor 9B, that is, the pressure of the intermediate pressure refrigerant. The low-pressure temperature sensor S <b> 4 detects the refrigerant temperature on the refrigerant outlet side of the low-pressure heat exchanger 7. The evaporation temperature sensor S5 detects the temperature of the low-pressure heat exchanger 7, that is, the refrigerant evaporation temperature in the low-pressure heat exchanger 7.

  The outside air temperature sensor S6 detects the temperature of the cooling air supplied to the high-pressure heat exchanger 3, that is, the outside air. The room temperature sensor S7 detects the temperature of the air in the server room. The room temperature sensor S7 according to the present embodiment detects the temperature of the room air sucked into the low pressure heat exchanger 7 side.

  The low-pressure temperature sensor S4 and the evaporation temperature sensor S5 are sensors for detecting the degree of refrigerant superheat on the refrigerant outlet side of the low-pressure heat exchanger 7, that is, the cooling load (heat load) in the low-pressure heat exchanger 7. Therefore, instead of the evaporation temperature sensor S5, the evaporation pressure in the low-pressure heat exchanger 7 may be detected.

2.2 Control of First Compressor The control device 21 controls the rotation speed of the first compressor 9 </ b> A so that a necessary refrigeration capacity (cooling capacity) is generated in the low-pressure heat exchanger 7. Specifically, the control device 21 operates the first compressor 9A so that the room temperature (the temperature detected by the room temperature sensor S7) falls within a preset temperature range (for example, 10 ° C. to 30 ° C.). Control.

  When the room temperature is lowered, the control device 21 increases the refrigerating capacity generated in the low-pressure heat exchanger 7 by increasing the rotation speed of the first compressor 9A. At this time, the control device 21 increases the amount of air blown by the second blower 7A until at least the surface temperature of the low-pressure heat exchanger 7 becomes higher than the dew point.

  That is, when the rotation speed of the first compressor 9A increases, the evaporation temperature may decrease and the surface temperature of the low-pressure heat exchanger 7 may become the dew point or lower. When the surface temperature falls below the dew point, much of the refrigeration capacity generated in the low-pressure heat exchanger 7 is consumed to condense the vapor in the air. For this reason, the power consumption required for lowering the room temperature increases.

  Therefore, in the present embodiment, when the rotation speed of the first compressor 9A is increased, the air flow rate of the second blower 7A, that is, the heat load of the low-pressure heat exchanger 7 is increased to increase the sensible heat ratio (SHF). Becomes a preset value (for example, 0.95) or more.

  When the cooling capacity is reduced, the control device 21 reduces the number of revolutions of the first compressor 9A to reduce the refrigeration capacity generated in the low-pressure heat exchanger 7 and changes the second according to the reduced refrigeration capacity. The air volume of the blower 7A is reduced.

2.3 Control of the second compressor The control device 21 controls the injection operation for operating the second compressor 9B and the second compressor 9B based on the size of the heat load in the low-pressure heat exchanger 7 and the outside air temperature. Switching control is performed for non-injection operation to be stopped.

  That is, when the heat load is large and the outside air temperature is high as in summer, the control device 21 executes the injection operation. Conversely, when the heat load is small and the outside air temperature is low, such as in winter, the control device 21 performs a non-injection operation.

  Specifically, in the present embodiment, when the outside air temperature is equal to or higher than a predetermined temperature (hereinafter referred to as a first outside temperature), and when the room temperature is determined in advance (hereinafter referred to as a first room temperature). The injection operation is executed in any of the above cases.

  In the present embodiment, when the outside air temperature is lower than a predetermined temperature (hereinafter referred to as a second outside air temperature), and when the room temperature is lower than a predetermined temperature (hereinafter referred to as a second room temperature). In any case, the non-injection operation is executed.

  The first outside air temperature and the second outside air temperature may be either the same temperature or different temperatures. The first indoor temperature and the second indoor temperature may be either the same temperature or different temperatures.

  At the time of execution of the injection operation, the control device 21 controls the rotation speed of the second compressor 9B so that the gas-phase refrigerant amount contained in the intermediate-pressure refrigerant and the suction refrigerant amount of the second compressor 9B are the same. To do. Thereby, the gaseous-phase refrigerant | coolant contained in the refrigerant | coolant which flows in into the low voltage | pressure heat exchanger 7 is reduced, and the refrigerating capacity which generate | occur | produces in the low voltage | pressure heat exchanger 7 is enlarged.

2.2 Control of the first pressure reducer The first pressure reducer 5A is constituted by a variable throttle device. The variable throttle device has an electric actuator (not shown) that changes and adjusts the throttle opening. The control device 21 controls the operation of the actuator to change the throttle opening of the first decompressor 5A.

  That is, the control device 21 controls the throttle opening of the first pressure reducer 5A using detection signals from the first discharge pressure sensor S1 and the intermediate pressure sensor S3. At this time, the control device 21 controls the throttle opening so that the wetness (ratio of the liquid phase refrigerant) of the refrigerant flowing out from the first pressure reducer 5A is increased.

2.3 Control of Second Pressure Reducer The second pressure reducer 5B is configured by a variable throttle device (not shown). The variable throttle device has an electric actuator (not shown) that changes and adjusts the throttle opening. The control device 21 controls the operation of the actuator to change the throttle opening of the second decompressor 5B. Specifically, the control device 21 restricts the second decompressor 5B so that the refrigerant superheat degree on the refrigerant outlet side of the low-pressure heat exchanger 7 is a value not less than 0 and a predetermined value set in advance. Control the opening.

2.4 Control of Second Valve The control device 21 closes the second valve 15A during the non-injection operation, and controls the second valve 15A in the transition control mode when the non-injection operation is shifted to the injection operation.

  In the transition control mode, the second valve 15A is opened simultaneously with the start of the second compressor 9B or when a preset time has elapsed after the start of the second compressor 9B. The opening degree of the second valve 15A is a certain opening degree at which a preset pressure loss occurs.

  When the transition control mode ends, the second valve 15A is closed. The timing at which the transition control mode ends is when a predetermined time (hereinafter referred to as an end time) has elapsed since the start of the second compressor 9B.

  The end time is determined based on the time required to discharge the liquid refrigerant present in the second compressor 9B when the second compressor 9B is started. The end time according to the present embodiment is a fixed time set in advance and is stored in advance in a nonvolatile storage unit such as a ROM.

3. Features of Vapor Compression Refrigeration Cycle According to this Embodiment In this embodiment, since it is possible to switch between injection operation and non-injection operation, the power consumption of the first compressor 9A and the second compressor 9B is further reduced. A possible injection-type vapor compression refrigeration cycle 1 can be obtained.

  That is, when the consumption power required by injecting the intermediate pressure refrigerant becomes larger due to the reduction in power consumption expected by injecting the intermediate pressure refrigerant in the middle of the compression stroke, the injection operation is not performed. By switching to injection operation, power consumption can be reduced.

  By the way, the gas-phase refrigerant is condensed and liquefied at the time of non-injection operation, and when the injection operation is started, overcompression occurs due to liquid compression in the second compressor 9B, and the second compressor 9B is damaged. there is a possibility.

  On the other hand, in the present invention, since the second valve 15A is opened in the transition control mode, the liquid-phase refrigerant in the second compressor 9B is not supplied to the high-pressure heat exchanger 3 side, and the intermediate-pressure side or low-pressure side is supplied. Supplied to the side. Therefore, it is possible to suppress the occurrence of overcompression in the second compressor 9B.

  That is, the second valve 15A is a supply suppression system that suppresses the liquid-phase refrigerant present in the second compressor 9B from being supplied to the high-pressure heat exchanger 3 side when shifting from the non-injection operation to the injection operation. Function as. Therefore, damage to the second compressor 9B can be suppressed.

  As described above, in the present embodiment, it is possible to switch between the injection operation and the non-injection operation to further reduce the power consumption of the compressor, and to suppress damage to the second compressor 9B.

(Second Embodiment)
The communication circuit 15 according to the present embodiment is connected to at least one of the suction side of the second compressor 9B and the drain port provided in the second compressor 9B. The drain port is a discharge port for discharging the liquid phase refrigerant in the second compressor 9B.

  The pump 15B is provided in the communication circuit 15, and circulates liquid phase refrigerant or the like from the second compressor 9B side to the gas-liquid separator 11 side. As shown in FIG. 4, the control device 21 controls the second valve 15A and the pump 15B in conjunction with each other.

  That is, the control device 21 executes the transition control mode when starting the second compressor 9B. In the transition control mode according to the present embodiment, the second valve 15A is opened and the pump 15B is also activated at the same time. Thereby, the liquid phase refrigerant in the second compressor 9B is supplied to the intermediate pressure side or the low pressure side without being supplied to the high pressure heat exchanger 3 side.

When the transition control mode ends, the control device 21 closes the second valve 15A and stops the pump 15B.
(Third embodiment)
In the present embodiment and the fourth embodiment, the liquid phase refrigerant generated in the second compressor 9B is directly supplied by directly or indirectly supplying the heat generated in the first compressor 9A to the second compressor 9B. The liquid phase refrigerant is suppressed from being supplied to the high-pressure heat exchanger 3 side.

  That is, in this embodiment, as shown in FIGS. 5 and 6, a heat pipe 25 that transmits heat generated in the first compressor 9 </ b> A to the second compressor 9 </ b> B is provided. The heat pipe 25 is desirably made of a metal having high thermal conductivity such as copper or aluminum.

  The heat pipe 25 according to FIG. 5 is a method of directly connecting the first compressor 9A and the second compressor 9B. The heat pipe 25 according to FIG. 5 is a system in which the first compressor 9A and the second compressor 9B are indirectly connected via the discharge side refrigerant pipe of the first compressor 9A.

5 and 6, the heat generated in the first compressor 9A is always transmitted to the second compressor 9B, but the present embodiment is not limited to this.
For example, the heat pipe 25 may be movable so that the heat generated in the first compressor 9A can be switched to the second compressor 9B between the case where the heat is transmitted and the case where the heat is not transmitted, and the heat is transmitted only in the transition control mode. Good.

  Moreover, you may provide the air blower which sends the heat which generate | occur | produced in 9 A of 1st compressors to the 2nd compressor 9B. That is, only in the transition control mode, the second compressor 9B may be heated by supplying the air heated by the first compressor 9A to the second compressor 9B.

(Fourth embodiment)
In the present embodiment, as shown in FIG. 7, the housing of the second compressor 9B is heated by the high-temperature discharged refrigerant discharged from the first compressor 9A. The heating circuit 27 guides the high-temperature refrigerant discharged from the first compressor 9A to the housing of the second compressor 9B, and causes heat exchange between the high-temperature refrigerant and the liquid-phase refrigerant in the second compressor 9B.

  The switching valve 27 </ b> A is a valve that switches between a case where the high-temperature refrigerant is circulated through the heating circuit 27 and a case where the high-temperature refrigerant is not circulated through the heating circuit 27, and the operation thereof is controlled by the control device 21.

  The control device 21 causes the high-temperature refrigerant to flow through the heating circuit 27 in the transition control mode. Then, after the transition control mode is completed, the control device 21 causes the high-temperature refrigerant to flow to the high-pressure heat exchanger 3 side without causing the heating circuit 27 to flow.

  In addition, in this embodiment and 3rd Embodiment, although the liquid phase refrigerant | coolant in the 2nd compressor 9B was heated, this embodiment etc. are not limited to this. For example, the refrigerant pipe extending from the discharge port of the second compressor 9B to the high pressure heat exchanger 3 may be heated by the high pressure refrigerant or the heat generated by the first compressor 9A.

(Fifth embodiment)
The control device 21 according to the present embodiment controls the operation of the first compressor 9A so that the temperature of the blown air supplied from the low-pressure heat exchanger 7 into the room falls within a preset temperature range. For this reason, as shown in FIG. 8, the output signal from the blowing temperature sensor S8 that detects the temperature of the blown air is input to the control device 21.

  In the present embodiment, the amount of air blown by the second blower 7A is controlled based on the difference between the room temperature (the detected temperature of the room temperature sensor S7) and the blown air temperature (the detected temperature of the blown temperature sensor S8). .

  FIG. 8 shows the application of the present invention to the first embodiment, but the control method of the first compressor 9A and the second blower 7A according to the present embodiment is related to the second to fourth embodiments. It can also be applied to a vapor compression refrigeration cycle.

(Other embodiments)
In the above-described embodiment, the first compressor 9A and the second compressor 9B are arranged in parallel to the refrigerant flow, but the present invention is not limited to this, and the first compressor 9A. And the second compressor 9B may be arranged in series with respect to the refrigerant flow.

  In addition, when the first compressor 9A and the second compressor 9B are arranged in series with respect to the refrigerant flow, the refrigerant discharged from the first compressor 9A during the non-injection operation is used as the second compressor 9B. It is necessary to provide a bypass route that bypasses and leads to the high-pressure heat exchanger 3.

  In the above-described embodiment, the first compressor 9A and the second compressor 9B are independent compressors, but the present invention is not limited to this, and a single compressor provided with an injection port or the like. You may comprise. The format of the compressor is not questioned. That is, any method such as a reciprocating method, a rotary method, a vane method, a scroll method, or the like may be used.

  In the above-described embodiment, the second accumulator 17B is provided, but the present invention is not limited to this. For example, when the pressure loss in the refrigerant passage from the gas-liquid separator 11 to the second compressor 9B is small or when the cooling is small in the refrigerant passage, the gas phase refrigerant may be condensed (liquefied) in the refrigerant passage. If not, the second accumulator 17B may be eliminated.

  In the above-described embodiment, the first accumulator 17A is provided, but the present invention is not limited to this. For example, when the second pressure reducer 5B can ensure the refrigerant superheat degree at the outlet of the low pressure heat exchanger 7 to 0 or more, that is, when the second pressure reducer 5B can follow a transient change, One accumulator 17A may be abolished.

  The end time according to the above-described embodiment is a fixed time set in advance, but the present invention is not limited to this. For example, when the transition control mode is started, the second compressor 9B and the outside air temperature are Etc., the end time may be determined each time. This is because the amount of liquid-phase refrigerant that is condensed increases as the second compressor 9B and the outside air temperature decrease.

  In the above-described embodiment, the refrigerating capacity generated in the high-pressure heat exchanger 3 is controlled by controlling the rotation speed of the first compressor 9A, but the present invention is not limited to this. That is, for example, the throttle opening degree of the second decompressor 5B and the rotation speed of the first compressor 9A are adjusted to control the refrigerating capacity. The rotation speed of the second blower 7A is controlled to control the air blown into the room. The temperature may be controlled.

  The present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims. Therefore, at least two of the vapor compressor refrigeration cycles shown in the first to fourth embodiments may be combined.

DESCRIPTION OF SYMBOLS 1 ... Vapor compression refrigeration cycle 3 ... High pressure heat exchanger 5A ... 1st decompressor 5B ... 2nd decompressor 7 ... Low pressure heat exchanger 9A ... 1st compressor 9B ... 2nd compressor 11 ... Gas-liquid separator 19 ... the first valve,
15 ... Communication circuit, 15A ... Second valve

Claims (6)

In the vapor compression refrigeration cycle that moves the heat on the low temperature side to the high temperature side,
A high-pressure heat exchanger that cools the high-temperature refrigerant;
A low-pressure heat exchanger that heats and evaporates the refrigerant on the low temperature side;
A first decompressor for decompressing and expanding the high-pressure refrigerant flowing out of the high-pressure heat exchanger;
A gas-liquid separator that separates the intermediate-pressure refrigerant decompressed by the first decompressor into a gas-phase refrigerant and a liquid-phase refrigerant;
A second decompressor that decompresses and expands the liquid-phase refrigerant separated by the gas-liquid separator and supplies the refrigerant to the low-pressure heat exchanger;
A first compressor that sucks and compresses the refrigerant flowing out from the low-pressure heat exchanger side and discharges the compressed refrigerant to the high-pressure heat exchanger side;
A second compressor that sucks and compresses the gas-phase refrigerant from the gas-liquid separator and discharges the compressed refrigerant to the discharge side of the first compressor;
An injection control unit for controlling the operation of the second compressor, the injection control unit capable of switching control between an injection operation for operating the second compressor and a non-injection operation for stopping the second compressor;
A supply suppression system that suppresses the liquid refrigerant present in the second compressor from being supplied to the high-pressure heat exchanger when the non-injection operation is shifted to the injection operation. Vapor compression refrigeration cycle. The supply suppression system includes:
A communication circuit that communicates the refrigerant circuit from the gas-liquid separator to the low-pressure heat exchanger and the second compressor when the non-injection operation shifts to the injection operation. The vapor compression refrigeration cycle according to claim 1, wherein   The vapor compression refrigeration cycle according to claim 2, wherein the communication circuit communicates the discharge side of the second compressor and the lower side of the gas-liquid separator. The supply suppression system includes:
The vapor compression refrigeration cycle according to claim 1, wherein the high-pressure refrigerant heats the liquid-phase refrigerant generated in the second compressor directly or indirectly. The supply suppression system includes:
The vapor compression refrigeration cycle according to claim 4, wherein the second compressor is heated by the high-pressure refrigerant discharged from the first compressor. The supply suppression system includes:
The vapor compression refrigeration cycle according to claim 1, wherein heat generated in the first compressor is directly or indirectly supplied to the second compressor.