JP2008164226A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce noise in operation by inhibiting the flowing noise of a refrigerant. <P>SOLUTION: This refrigerating device 1 utilizing a supercritical refrigerant and operated in an area where high-pressure is a critical pressure or more, comprises a compressor 21, gas coolers 23, 31, expansion mechanisms V2, V5, evaporators 31, 23, discharge pressure detecting means P1, T2, T3 and a control portion 5. The compressor compresses the supercritical refrigerant. The gas coolers cool the supercritical refrigerant compressed by the compressor. The expansion mechanisms reduce the pressure of the supercritical refrigerant. The evaporators evaporate the supercritical refrigerant of which the pressure is reduced by the expansion mechanisms. The discharge pressure detecting means can detect a discharge pressure of the compressor. The control portion adjusts an opening of the expansion mechanism to make the discharge pressure to be higher than the supercritical pressure, in starting and when the discharge pressure is less than the critical pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus using a refrigerant that operates in a supercritical region.

There is a refrigeration apparatus using a supercritical refrigerant (for example, CO2 refrigerant) that operates in a supercritical region as a refrigerant (see Patent Document 1).
JP 2000-234814 A

  However, when the high pressure of the refrigerant is not fully raised at startup, or when the refrigerant is not above the critical temperature at low outside air temperature, the refrigerant flows into the expansion mechanism in a gas-liquid two-phase state. There is. In this case, a flow noise is likely to be generated near the inlet of the expansion mechanism, leading to noise during operation.

  The subject of this invention is reducing generation | occurrence | production of the noise at the time of driving | operation by suppressing generation | occurrence | production of the flow sound of a refrigerant | coolant.

A refrigeration apparatus according to a first aspect of the present invention is a refrigeration apparatus that uses a supercritical refrigerant and operates in a region where the high pressure is higher than the critical pressure, and includes a compressor, a gas cooler, an expansion mechanism, an evaporator, and a control unit. With. The compressor compresses the supercritical refrigerant. The gas cooler cools the supercritical refrigerant compressed by the compressor. The expansion mechanism depressurizes the supercritical refrigerant. The evaporator evaporates the supercritical refrigerant decompressed by the expansion mechanism. The control unit adjusts the opening of the expansion mechanism when the supercritical refrigerant near the inlet of the expansion mechanism is in a gas-liquid two-phase state at the time of start-up, and the supercritical refrigerant near the inlet of the expansion mechanism is super Control to be in a critical state or liquid phase state.

  A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect of the present invention, further comprising discharge pressure detecting means. The discharge pressure detecting means can detect the discharge pressure of the compressor. The control unit determines that the supercritical refrigerant is in a gas-liquid two-phase state when the discharge pressure is less than the critical pressure, and determines that the supercritical refrigerant is in the supercritical state or liquid state when the discharge pressure is equal to or higher than the critical pressure. Determined to be in phase state.

  A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the second aspect of the present invention, wherein the control unit adjusts the opening of the expansion mechanism when starting up and when the discharge pressure is less than the critical pressure, The discharge pressure is controlled so as to be higher than the critical pressure.

A refrigeration apparatus according to a fourth aspect of the present invention is the refrigeration apparatus according to the second or third aspect of the present invention , wherein when the discharge pressure is less than the critical pressure, the control unit fully opens or slightly opens the expansion mechanism. The first control is performed.

  In the present invention, when the discharge pressure is less than the critical pressure, the control unit causes the opening of the expansion mechanism to be fully closed or set to a minute opening. Therefore, the high pressure in the refrigeration cycle can easily become higher than the critical pressure, and the generation of flow noise in the vicinity of the inlet of the expansion mechanism can be suppressed.

A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to the fourth aspect of the present invention, wherein the control unit controls the opening degree of the expansion mechanism after the first control and when the discharge pressure is not less than the critical pressure. The second control to be enlarged is performed.

  When the pressure of the supercritical refrigerant exceeds the critical pressure, the refrigerant becomes a supercritical state or a liquid phase state and is not a gas-liquid two-phase state, thus reducing the generation of flow noise near the inlet of the expansion mechanism without further increasing the pressure. can do.

  In the present invention, the control unit performs the second control for opening the expansion mechanism when the discharge pressure is equal to or higher than the critical pressure after the first control for easily increasing the high pressure. For this reason, it can control to an optimal pressure, without raising discharge pressure wastefully, and can reduce energy consumption.

A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to any one of the second to fifth aspects, wherein the discharge pressure detecting means is a pressure sensor provided on the discharge side of the compressor.

  In the present invention, the discharge pressure is detected by a pressure sensor, and it is determined whether or not the refrigerant is in a supercritical state. Therefore, the high pressure in the refrigeration cycle can be directly detected from the discharge pressure, and the time for the first control can be minimized to shift to the second control. It is possible to control to an optimum pressure without increasing the high pressure pressure unnecessarily, and energy loss can be reduced.

A refrigeration apparatus according to a seventh aspect is the refrigeration apparatus according to any one of the second to sixth aspects, wherein the control unit calculates an inlet pressure of the expansion mechanism from the discharge pressure and the operating capacity of the compressor. In addition, when the inlet pressure is less than the critical pressure, the control unit adjusts the opening of the expansion mechanism to control the discharge pressure to be equal to or higher than the critical pressure.

  In the present invention, the inlet pressure of the expansion mechanism is calculated from the discharge pressure and the compressor capacity. The discharge pressure and the inlet pressure of the expansion mechanism have different values due to the pressure loss of the refrigerant piping. Therefore, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism that causes noise can be more reliably controlled from the gas-liquid two-phase state to the supercritical state or the liquid phase state.

A refrigeration apparatus according to an eighth invention is the refrigeration apparatus according to any one of the second to fifth inventions, wherein the pressure detection means detects the temperature of the supercritical refrigerant between the outlet of the gas cooler and the inlet of the expansion mechanism. This is a detectable temperature sensor. When the inlet temperature is lower than the critical temperature, the control unit determines that the inlet pressure may be lower than the critical pressure, and adjusts the opening of the expansion mechanism so that the inlet temperature becomes equal to or higher than the critical temperature. To control.

In the present invention, the temperature of the refrigerant from the outlet of the gas cooler to the inlet of the expansion mechanism is detected by the temperature sensor to determine whether or not the refrigerant is in a supercritical state. For this reason, it can be determined that the state of the refrigerant in the vicinity of the inlet of the expansion mechanism is not a gas-liquid two-phase state, and it is possible to reduce the burst sound of bubbles that cause flow noise. Further, since a temperature sensor that is less expensive than the pressure sensor can be used as a substitute for the pressure sensor in the sixth aspect of the invention, the production cost can be reduced.

A refrigeration apparatus according to a ninth invention is the refrigeration apparatus according to any one of the second to eighth inventions, further comprising a blower. The blower promotes cooling of the gas cooler. The control unit controls the air volume of the blower to be zero or small at the time of start-up and when the discharge pressure is less than the critical pressure.

  In the present invention, at the time of start-up and when the discharge pressure is less than the critical pressure, the air volume of the blower that blows air to the gas cooler and promotes cooling is reduced to 0 or reduced. Therefore, the cooling effect in the gas cooler can be reduced, and the temperature and pressure of the refrigerant in the gas cooler can be increased. For this reason, the state of the refrigerant at the outlet of the gas cooler can be changed to a supercritical state or a liquid phase state, and the flow noise in the vicinity of the inlet of the expansion mechanism can be reduced.

A refrigeration apparatus according to a tenth aspect of the present invention is the refrigeration apparatus according to any of the second to ninth aspects of the present invention, wherein the control unit adjusts the opening of the expansion mechanism during steady operation so that the discharge pressure is a critical pressure. Control to be above.

  In the present invention, control is performed so that the discharge pressure becomes equal to or higher than the critical pressure not only during startup but also during steady operation. Therefore, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism can always be set to the supercritical state or the liquid phase, and the flow noise at the inlet of the expansion mechanism can be reduced.

A refrigeration apparatus according to an eleventh aspect of the present invention is the refrigeration apparatus according to any of the second to ninth aspects of the present invention, wherein the control unit adjusts the opening of the expansion mechanism during steady operation and at a low outside air temperature. The discharge pressure is controlled to be higher than the critical pressure.

  During steady operation, when the outside air temperature is low, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism may become a gas-liquid two-phase state. In the present invention, even when the outside air temperature is low, the opening degree of the expansion mechanism is adjusted so that the high pressure is equal to or higher than the critical pressure. Therefore, even at a low outside temperature, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism can be set to a supercritical state or a liquid phase state.

A refrigeration apparatus according to a twelfth aspect of the present invention is the refrigeration apparatus according to the eleventh aspect of the present invention, wherein the outside air temperature is 20 ° C. or lower at a low outside air temperature.

  In the present invention, the discharge pressure is controlled to be equal to or higher than the critical pressure under the condition that the supercritical refrigerant whose outside air temperature is 20 ° C. or less is likely to be in a gas-liquid two-phase state. Therefore, even when the outside air temperature is 20 degrees or less, the state of the supercritical refrigerant in the vicinity of the inlet of the expansion mechanism can be changed from the gas-liquid two-phase state to the supercritical state or the liquid phase state.

A refrigeration apparatus according to a thirteenth aspect of the present invention is a refrigeration apparatus that uses a supercritical refrigerant and operates in a region where the high pressure is higher than the critical pressure, and includes a compressor, a gas cooler, an expansion mechanism, an evaporator, and temperature detection. Means and a control unit. The compressor compresses the supercritical refrigerant. The gas cooler cools the supercritical refrigerant compressed by the compressor. The expansion mechanism depressurizes the supercritical refrigerant. The evaporator evaporates the supercritical refrigerant decompressed by the expansion mechanism. The temperature detection means can detect the inlet temperature of the expansion mechanism. The controller controls the opening temperature of the expansion mechanism so that the inlet temperature becomes equal to or higher than the critical temperature at the time of startup and when the inlet temperature is lower than the critical temperature.

  In the present invention, when it is determined that the inlet temperature of the expansion mechanism is lower than the critical temperature, the control unit adjusts the opening degree of the expansion mechanism and controls the inlet temperature of the expansion mechanism to be equal to or higher than the critical temperature. Therefore, by setting the inlet temperature of the expansion mechanism of the supercritical refrigerant in the refrigeration cycle to a critical temperature or higher, the state of the supercritical refrigerant at the inlet of the expansion mechanism can be changed to a supercritical state that is not a gas-liquid two-phase state. For this reason, generation | occurrence | production of the flow sound in the inlet_port | entrance vicinity of an expansion mechanism can be suppressed.

A refrigeration apparatus according to a fourteenth aspect of the invention is the refrigeration apparatus according to any one of the first to thirteenth aspects of the invention, wherein the supercritical refrigerant is a CO2 refrigerant.

  In the present invention, a CO2 refrigerant is used as the refrigerant. The CO2 refrigerant does not destroy the ozone layer because the ozone destruction coefficient is zero. In addition, the CO2 refrigerant has a global warming potential of 1 and is much lower than a fluorocarbon refrigerant of several hundred to 10,000. Therefore, the deterioration of the global environment can be suppressed by using the CO2 refrigerant having a small environmental load.

In the refrigeration apparatus according to the third aspect of the invention, the supercritical refrigerant state can be changed from the gas-liquid two-phase state to the supercritical state or the liquid phase state by setting the high pressure of the supercritical refrigerant in the refrigeration cycle to a critical pressure or higher. Therefore, it is possible to suppress the generation of a flow sound due to the bursting of bubbles.

In the refrigeration apparatus according to the fourth aspect of the invention, the high pressure in the refrigeration cycle can easily be higher than the critical pressure, and the generation of flow noise due to bubble bursting can be suppressed.

In the refrigeration apparatus according to the fifth aspect of the invention, it is possible to control the pressure optimally without unnecessarily increasing the discharge pressure, and to reduce energy consumption.

In the refrigeration apparatus according to the sixth aspect of the present invention, the high pressure in the refrigeration cycle can be directly detected from the discharge pressure, and the second control can be shifted to the required minimum time. It is possible to control to an optimum pressure without increasing the high pressure pressure unnecessarily, and energy loss can be reduced.

In the refrigeration apparatus according to the seventh aspect of the invention, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism that causes noise can be controlled more reliably from the gas-liquid two-phase state to the supercritical state or the liquid phase state.

In the refrigeration apparatus according to the eighth aspect of the invention, it can be determined that the state of the refrigerant in the vicinity of the inlet of the expansion mechanism is not a gas-liquid two-phase state, and it is possible to reduce the burst sound of bubbles that cause flow noise. Further, since a temperature sensor that is less expensive than the pressure sensor can be used as a substitute for the pressure sensor in the sixth aspect of the invention, the production cost can be reduced.

In the refrigeration apparatus according to the ninth aspect , the cooling effect in the gas cooler can be reduced, and the temperature and pressure of the refrigerant in the gas cooler can be increased. For this reason, the state of the refrigerant at the outlet of the gas cooler can be changed to a supercritical state or a liquid phase state, and the flow noise in the vicinity of the inlet of the expansion mechanism can be reduced.

In the refrigeration apparatus according to the tenth aspect of the invention, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism can always be set to the supercritical state or the liquid phase, and the flow noise at the inlet of the expansion mechanism can be reduced.

In the refrigeration apparatus according to the eleventh aspect of the invention, the state of the refrigerant in the vicinity of the inlet of the expansion mechanism can be changed to a supercritical state or a liquid phase state even at a low outside air temperature.

In the refrigeration apparatus according to the twelfth aspect of the invention, even when the outside air temperature is 20 degrees or less, the supercritical refrigerant state can be changed from the gas-liquid two-phase state to the supercritical state or the liquid phase state.

In the refrigeration apparatus according to the thirteenth invention, the supercritical refrigerant state at the inlet of the expansion mechanism is not a gas-liquid two-phase state by setting the inlet temperature of the expansion mechanism of the supercritical refrigerant in the refrigeration cycle to a critical temperature or higher. Can be in a state. For this reason, generation | occurrence | production of the flow sound by burst of a bubble etc. can be suppressed.

In the refrigeration apparatus according to the fourteenth aspect, the deterioration of the global environment can be suppressed by using a CO2 refrigerant with a small environmental load.

  Hereinafter, an embodiment of an air-conditioning apparatus according to the present invention will be described based on the drawings.

<Configuration of air conditioner>
FIG. 1 is a schematic configuration diagram of an air-conditioning apparatus 1 according to an embodiment of the present invention. The air conditioning apparatus 1 is an apparatus used for air conditioning in a room such as a building. In the present invention, a CO2 refrigerant that is a supercritical refrigerant is used as the refrigerant. The air conditioner 1 mainly includes an outdoor unit 2 as one heat source unit, an indoor unit 3 as a utilization unit connected thereto, and a refrigerant communication pipe 4 that connects the outdoor unit 2 and the indoor unit 3. I have. The refrigerant communication pipe 4 includes a liquid refrigerant communication pipe 41 and a gas refrigerant communication pipe 42. That is, the refrigerant circuit 10 of the air conditioner 1 of the present embodiment is configured by connecting the outdoor unit 2, the indoor unit 3, and the refrigerant communication pipe 4.

(1) Outdoor unit The outdoor unit 2 is installed outside a building or the like, and is connected to the indoor unit 3 via the refrigerant communication pipe 4 to constitute the refrigerant circuit 10.

  Next, the configuration of the outdoor unit 2 will be described. The outdoor unit 2 mainly has an outdoor refrigerant circuit 20 that constitutes a part of the refrigerant circuit 10. The outdoor refrigerant circuit 20 mainly includes a compressor 21, a four-way switching valve V1, an outdoor heat exchanger 23 as a heat source side heat exchanger, an outdoor expansion valve V2 as an expansion mechanism, and a liquid side closing valve. V3 and the gas side closing valve V4 are provided.

  The compressor 21 is a compressor whose operating capacity can be varied. In the present embodiment, the compressor 21 is a positive displacement compressor driven by a motor 22 whose rotational speed is controlled by an inverter. In the present embodiment, the number of the compressors 21 is only one. However, the present invention is not limited to this, and two or more compressors may be connected in parallel according to the number of indoor units connected.

  The four-way switching valve V1 is a valve provided to cause the outdoor heat exchanger 23 to function as a gas cooler and an evaporator. The four-way switching valve V1 is connected to the outdoor heat exchanger 23, the suction side of the compressor 21, the discharge side of the compressor 21, and the gas refrigerant communication pipe 42. When the outdoor heat exchanger 23 functions as a gas cooler, the discharge side of the compressor 21 and the outdoor heat exchanger 23 are connected, and the suction side of the compressor 21 and the gas refrigerant communication pipe 42 are connected. (The state of the solid line in FIG. 1). Conversely, when the outdoor heat exchanger 23 functions as an evaporator, the outdoor heat exchanger 23 and the suction side of the compressor 21 are connected, and the discharge side of the compressor 21 and the gas refrigerant communication pipe 42 are connected. Connect (state of broken line in FIG. 1).

  The outdoor heat exchanger 23 is a heat exchanger that can function as a gas cooler or an evaporator, and in this embodiment, a cross-fin fin-and-tube heat exchange that exchanges heat with a refrigerant using air as a heat source. It is a vessel. One of the outdoor heat exchangers 23 is connected to the four-way switching valve V1, and the other is connected to the outdoor expansion valve V2.

  The outdoor expansion valve V2 is an electric expansion valve connected between the outdoor heat exchanger 23 and the liquid side closing valve V3 in order to adjust the pressure and flow rate of the refrigerant flowing in the outdoor refrigerant circuit 20. .

  The outdoor unit 2 has an outdoor fan 24 as a blower fan for sucking outdoor air into the unit and exchanging heat with the refrigerant in the outdoor heat exchanger 23 and then discharging it to the outside. The outdoor fan 24 is a fan capable of changing the air volume of air supplied to the outdoor heat exchanger 23. In the present embodiment, the outdoor fan 24 is a propeller fan or the like driven by a motor 25 including a DC fan motor.

  The outdoor unit 2 is provided with various sensors. Specifically, the outdoor unit 2 is provided with a discharge pressure sensor P1 that detects the discharge pressure Pd of the compressor 21. An outdoor air temperature sensor T <b> 1 that detects the temperature of the outdoor air that flows into the outdoor unit 2 (that is, the outdoor air temperature) is provided on the outdoor air inlet side of the outdoor unit 2. In the present embodiment, the outside air temperature sensor T1 is a thermistor.

  In addition, the outdoor unit 2 includes an outdoor control unit 27 that controls the operation of each unit constituting the outdoor unit 2. The outdoor control unit 27 includes an inverter circuit that controls a microcomputer, a memory, a motor 22, and the like provided for controlling the outdoor unit 2. Control signals and the like can be exchanged with the unit 34 via the transmission line 51. That is, the control part 5 which performs operation control of the whole air conditioning apparatus 1 is comprised by the outdoor side control part 27, the indoor side control part 34, and the transmission line 51 which connects between each control part 27 and 34. FIG.

  The control unit 5 is connected so as to receive the detection signals of the various sensors P1, T1, and controls the various devices 21, 24, 32 and the valves V1, V2, V5 based on these detection signals. Connected so that it can. Here, FIG. 2 is a control block diagram of the air conditioner 1.

(2) Indoor unit The indoor unit 3 is installed in a ceiling of a room such as a building or suspended, or installed on a wall surface of the room by a wall or the like. The indoor unit 3 is connected to the outdoor unit 2 via the refrigerant communication pipe 4 and constitutes a part of the refrigerant circuit 10.

  Next, the configuration of the indoor unit 3 will be described. The indoor unit 3 mainly has an indoor refrigerant circuit 30 that constitutes a part of the refrigerant circuit 10. The indoor side refrigerant circuit 30 mainly has an indoor heat exchanger 31 as a use side heat exchanger and an indoor expansion valve V5 as an expansion mechanism.

  The indoor heat exchanger 31 is a cross fin type fin-and-tube heat exchanger composed of heat transfer tubes and a large number of fins, and functions as a refrigerant evaporator during cooling operation to cool indoor air. It is a heat exchanger that functions as a refrigerant gas cooler during heating operation and heats indoor air.

  Similarly to the outdoor expansion valve V2, the indoor expansion valve V5 is an electric expansion valve connected to the liquid side of the indoor heat exchanger 31 in order to adjust the pressure and flow rate of the refrigerant flowing in the indoor refrigerant circuit 30. It is.

  The indoor unit 3 has an indoor fan 32 as a blower fan that sucks indoor air into the unit and exchanges heat with the refrigerant in the indoor heat exchanger 31 and then supplies the air as indoor air. . The indoor fan 32 is a fan capable of changing the air volume supplied to the indoor heat exchanger 31. In this embodiment, the indoor fan 32 is a centrifugal fan or a multiblade fan driven by a motor 33 including a DC fan motor. It is.

  In addition, the indoor unit 3 includes an indoor control unit 34 that controls the operation of each unit constituting the indoor unit 3. And the indoor side control part 34 has the microcomputer, memory, etc. which were provided in order to control the indoor unit 3, and is with the remote control (not shown) for operating the indoor unit 3 separately. It is possible to exchange control signals and the like between them, and exchange control signals and the like with the outdoor unit 2 via the transmission line 51.

(3) Refrigerant communication pipe The refrigerant communication pipe 4 is a refrigerant pipe that is constructed on site when the air conditioner 1 is installed at a location such as a building, and the installation location, the outdoor unit 2, the indoor unit 3, Those having various lengths and pipe diameters are used depending on the installation conditions such as the combination of the above.

<Operation of air conditioner>
Next, operation | movement of the air conditioning apparatus 1 of this embodiment is demonstrated.

  As an operation mode of the air conditioner 1 of the present embodiment, there are an activation mode that is performed until the refrigeration cycle is stabilized at the time of activation and a normal mode after the refrigeration cycle is stabilized. The normal mode includes a cooling operation for cooling the indoor unit 3 and a heating operation for heating the indoor unit 3 according to the cooling / heating load of the indoor unit 3.

  Hereinafter, the operation | movement in each operation mode of the air conditioning apparatus 1 is demonstrated.

(1) Start Mode FIG. 3 is a flowchart showing the flow of control in the start mode. The activation mode starts when the air conditioner 1 is operated (the compressor 21 is activated) regardless of the cooling operation or the heating operation. Hereinafter, the activation mode will be described with reference to FIG.

  First, in step S1, it is confirmed whether or not the discharge pressure Pd detected by the discharge pressure sensor P1 is less than the critical pressure Pk of the CO 2 refrigerant. If the discharge pressure Pd is less than the critical pressure Pk, the process proceeds to step S2, and if it is equal to or higher than the critical pressure Pk, the process proceeds to step S3. In step S2, throttle control is performed to reduce the throttle opening θ1 of the outdoor expansion valve V2 in the cooling operation, and throttle control is performed to reduce the throttle opening θ2 of the indoor expansion valve V5 in the heating operation. In the “throttle control” here, the throttle opening degree θ1 is set to an opening degree α that does not cause a flow noise when the CO2 refrigerant in the gas-liquid two-phase state passes through the outdoor expansion valve V2 or the indoor expansion valve V5. , Θ2 are controlled (see FIG. 5 described later). If the discharge pressure Pd is less than the critical pressure Pk, the CO2 refrigerant is likely to be in a gas-liquid two-phase state rather than a supercritical state. When the CO2 refrigerant is in a gas-liquid two-phase state, flow noise is likely to occur near the outdoor expansion valve V2 or the indoor expansion valve V5. Therefore, by setting the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening degree θ2 of the indoor expansion valve V5 to the opening degree α, the high pressure of the CO2 refrigerant in the refrigeration cycle is made faster than the critical pressure Pk. ing. When step S2 ends, the process returns to step S1. In step S3, the process proceeds to the normal mode.

(2) Normal Mode FIG. 4 is a flowchart showing the flow of control in the normal mode. The normal mode is performed after the above-described start mode ends.

  First, in step S11, it is confirmed whether or not the discharge pressure Pd detected by the discharge pressure sensor P1 is less than the critical pressure Pk of the CO2 refrigerant. If the discharge pressure Pd is less than the critical pressure Pk, the process proceeds to step S12. If the discharge pressure Pd is equal to or higher than the critical pressure Pk, the process proceeds to step S15. In step S12, throttle control is performed to reduce the throttle opening θ1 of the outdoor expansion valve V2 in the cooling operation, and throttle control is performed to reduce the throttle opening θ2 of the indoor expansion valve V5 in the heating operation. When step S12 ends, the process proceeds to step S13. In step S13, it is confirmed whether or not the outdoor fan 24 is being driven in the case of the cooling operation, and whether or not the indoor fan 32 is being driven in the case of the heating operation. If the outdoor fan 24 or the indoor fan 32 is being driven, the process proceeds to step S14. If the outdoor fan 24 or the indoor fan 32 is not being driven, the process returns to step S11. In step S14, the outdoor fan 24 or the indoor fan 32 is stopped. When step S14 ends, the process returns to step S11. In step S11, when the outside air temperature exceeds 20 ° C., in step S15, it is confirmed whether or not the outdoor expansion valve V2 or the indoor expansion valve V5 is under throttle control. If the outdoor expansion valve V2 or the indoor expansion valve V5 is under throttle control, the process proceeds to step S16, and if the outdoor expansion valve V2 or the indoor expansion valve V5 is under normal control, the process returns to step S11. In step S16, normal control of the outdoor expansion valve V2 or the indoor expansion valve V5 is performed. The “normal control” referred to here is control performed in a cooling operation or a heating operation described later. When step S16 ends, the process proceeds to step S17. In step S17, it is confirmed whether or not the outdoor fan 24 or the indoor fan 32 is stopped. If the outdoor fan 24 or the indoor fan 32 is stopped, the process proceeds to step S18. If the outdoor fan 24 or the indoor fan is being driven, the process returns to step S11. In step S18, the outdoor fan 24 or the indoor fan 32 is activated, and normal control is performed in the outdoor fan 24 or the indoor fan 32. When step S18 ends, the process returns to step S11.

(3) Throttle control and normal control As in the flowchart of the normal mode described above, the control unit 5 switches between the case where the outdoor expansion valve V2 or the indoor expansion valve V5 is subjected to the throttle control and the case where the normal control is performed. FIG. 5 is a time flow chart showing the timing of switching from aperture control to normal control and from normal control to aperture control. In FIG. 5, the horizontal axis indicates time t, and the vertical axis indicates the discharge pressure Pd and the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening degree θ2 of the indoor expansion valve V5. If the starting time is t1, and the discharge pressure Pd at that time is the initial discharge pressure P0, the throttle control is performed from time t1, and the throttle opening θ1 of the outdoor expansion valve V2 or the throttle opening θ2 of the indoor expansion valve V5. Is set to the opening degree α. When the discharge pressure Pd changes from the initial discharge pressure P0 to the critical pressure Pk at time t2, the control shifts from throttle control to normal control, and the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening degree θ2 of the indoor expansion valve V5 is the opening degree. set to β. Further, for example, when the discharge pressure Pd becomes equal to or lower than the critical pressure Pk (time t3) under the condition that the outside air temperature is 20 ° C. or less, the control shifts again from the normal control to the throttle control. At this time, the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening degree θ2 of the indoor expansion valve V5 is set to the opening degree α.

  Next, cooling operation and heating operation in normal control will be described.

(4) Cooling Operation First, the cooling operation will be described with reference to FIG. During the cooling operation, in the outdoor refrigerant circuit 20 of the outdoor unit 2, the four-way switching valve V1 is switched to the state shown by the solid line in FIG. 1, so that the outdoor heat exchanger 23 functions as a gas cooler and The heat exchanger 31 functions as an evaporator.

  When the compressor 21, the outdoor fan 24, and the indoor fan 32 are activated in the state of the refrigerant circuit 10, the low-pressure Pl gas refrigerant is sucked into the compressor 21 and compressed to become high-pressure Ph gas refrigerant. The gas refrigerant compressed to the high pressure Ph flows into the outdoor heat exchanger 23. At this time, the outdoor heat exchanger 23 functions as a gas cooler and releases heat to the outdoor air supplied by the outdoor fan 24 to cool the refrigerant. Then, the pressure is reduced from the high pressure Ph to the low pressure Pl by the outdoor expansion valve V2. The refrigerant decompressed to the low pressure Pl becomes a gas-liquid two-phase refrigerant, and is sent to the indoor unit 3 via the liquid side shut-off valve V3 and the liquid refrigerant communication pipe 41.

  The low-pressure Pl gas-liquid two-phase refrigerant sent to the indoor unit 3 is controlled in flow rate by the indoor expansion valve V5 and is evaporated by exchanging heat with indoor air in the indoor heat exchanger 31. Thus, it becomes a low-pressure Pl gas refrigerant. The low-pressure Pl gas refrigerant is sent to the outdoor unit 2 via the gas refrigerant communication pipe 42 and is again sucked into the compressor 21 through the gas-side shut-off valve V4.

(5) Heating operation During the heating operation, in the outdoor refrigerant circuit 20 of the outdoor unit 2, the four-way switching valve V1 is switched to the state shown by the broken line in FIG. The indoor heat exchanger 31 functions as a gas cooler.

  When the compressor 21, the outdoor fan 24, and the indoor fan 32 are started in the state of the refrigerant circuit 10, the low-pressure Pl gas refrigerant is sucked into the compressor 21 and compressed into a high-pressure Ph gas refrigerant. It is sent to the gas refrigerant communication pipe 42 via the switching valve V1 and the gas side closing valve V4.

  The high-pressure Ph gas refrigerant sent to the gas refrigerant communication pipe 42 is sent to the indoor unit 3. The high-pressure Ph gas refrigerant sent to the indoor unit 3 is sent to the indoor heat exchanger 31. In the indoor heat exchanger 31, the refrigerant is cooled by exchanging heat with room air to become high-pressure Ph liquid refrigerant, and then when the refrigerant passes through the indoor expansion valve V5, the throttle opening degree of the indoor expansion valve V5. The pressure is reduced to a low pressure Pl in accordance with θ2, and a gas-liquid two-phase state is obtained.

  The refrigerant in the gas-liquid two-phase state is sent to the outdoor unit 2 via the liquid refrigerant communication pipe 41. This refrigerant flows into the outdoor heat exchanger 23 via the liquid side closing valve V3 and the outdoor expansion valve V2.

  The refrigerant exchanges heat with the outside air in the outdoor heat exchanger 23 and evaporates to become a low-pressure Pl gas refrigerant. At this time, the outdoor expansion valve V2 is fully opened. The low-pressure Pl gas refrigerant is again sucked into the compressor 21 via the four-way switching valve V1.

<Supercritical refrigeration cycle>
Next, the refrigeration cycle in the air conditioner 1 will be described. FIG. 6 shows a refrigeration cycle under supercritical conditions by a ph diagram (Mollier diagram). A, B, C, and D in FIG. 6 represent the state of the refrigerant corresponding to each point in FIG. 1 in the cooling operation. In addition, parentheses A, F, E, and D in FIG. 6 represent refrigerant states corresponding to the respective points in FIG. 1 in the case of heating operation.

  In the refrigerant circuit 10, the refrigerant is compressed by the compressor 21 and becomes high temperature and high pressure Ph (A → B). At this time, CO2 which is a refrigerant changes from gas to a supercritical state. The “supercritical state” referred to here is a state of a substance at a temperature and pressure above the critical point K and is a state having both gas diffusibility and liquid solubility. The supercritical state is the state of the refrigerant in the region on the right side of the critical temperature isotherm Tk in FIG. 6 and the critical pressure Pk or higher. Note that when the refrigerant (substance) is in a supercritical state, there is no distinction between the gas phase and the liquid phase. The “gas phase” referred to here is the state of the refrigerant on the right side of the saturated vapor line Sv and in the region below the critical pressure Pk. Further, the “liquid phase” is a state of the refrigerant in a region on the left side of the saturated liquid line S1 and on the left side of the critical temperature isotherm Tk. Then, the refrigerant that has been compressed by the compressor 21 and is in a supercritical state of high temperature and high pressure Ph is radiated by the outdoor heat exchanger 23 that functions as a gas cooler to become a refrigerant of low temperature and high pressure Ph (B → C ). At this time, since the refrigerant is in a supercritical state, the refrigerant operates in the outdoor heat exchanger 23 with a sensible heat change (temperature change). The refrigerant radiated in the outdoor heat exchanger 23 expands when the outdoor expansion valve V2 is opened, and the pressure is reduced from the high pressure Ph to the low pressure Pl (C → D). The refrigerant decompressed by the outdoor expansion valve V2 absorbs heat in the indoor heat exchanger 31 functioning as an evaporator, evaporates, and returns to the compressor 21 (D → A).

<Features>
(1)
In the present embodiment, when the control unit 5 determines that the discharge pressure Pd in the refrigeration cycle is less than the critical pressure Pk, the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening of the indoor expansion valve V5 in the start mode. The degree θ2 is adjusted to the opening degree α which is a minute opening degree, and the discharge pressure Pd is controlled so as to become more than the critical pressure Pk. The same control is performed in the normal mode.

  Accordingly, the state of the CO2 refrigerant can be changed from the gas-liquid two-phase state to the supercritical state or the liquid phase state, and the generation of flow noise in the vicinity of the inlets of the outdoor expansion valve V2 and the indoor expansion valve V5 can be suppressed.

(2)
In the present embodiment, after the throttle control, the control unit 5 performs normal control of the outdoor expansion valve V2 or the indoor expansion valve V5 when the discharge pressure Pd is equal to or higher than the critical pressure Pk. When the pressure of the CO2 refrigerant becomes equal to or higher than the critical pressure Pk, the CO2 refrigerant enters a supercritical state and there is no distinction between the gas phase and the liquid phase. For this reason, it can control to an optimal pressure, without raising the discharge pressure Pd wastefully, and can reduce the loss of energy.

(3)
In the present embodiment, the discharge pressure Pd is detected by the discharge pressure sensor P1, and it is determined whether or not the state of the CO 2 refrigerant on the high pressure side is a supercritical state or a liquid phase state. Accordingly, the high pressure Ph in the refrigeration cycle can be directly detected from the discharge pressure Pd, and the control can be shifted to the normal control with the required time (t2-t1) for the throttle control. For this reason, it can control to an optimal pressure, without raising discharge pressure Pd wastefully, and can reduce energy consumption.

(4)
In this embodiment, at the time of starting, the outdoor fan 24 or the indoor fan 32 that blows air to the outdoor heat exchanger 23 or the indoor heat exchanger 31 that functions as a gas cooler and promotes cooling is stopped. Therefore, the cooling effect in the outdoor heat exchanger 23 or the indoor heat exchanger 31 can be minimized, and the temperature and pressure of the CO 2 refrigerant in the outdoor heat exchanger 23 or the indoor heat exchanger 31 can be increased. . For this reason, the state of the refrigerant at the outlet of the outdoor heat exchanger 23 or the indoor heat exchanger 31 functioning as a gas cooler can be changed to a supercritical state or a liquid phase state, and the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5. The flow noise in the vicinity can be reduced.

(5)
In the present embodiment, even at a low outside air temperature at which the outside air temperature is 20 degrees or less, the throttle opening degree θ1 of the outdoor expansion valve V2 or the throttle opening degree θ2 of the indoor expansion valve V5 is adjusted so that the discharge pressure Pd is Control is performed so that the critical pressure Pk is reached. Therefore, the refrigerant can be brought into a supercritical state or a liquid phase state even at a low outside air temperature where the outside air temperature is 20 degrees or less.

(6)
In the present embodiment, a CO2 refrigerant is used as the refrigerant. The CO2 refrigerant does not destroy the ozone layer because the ozone destruction coefficient is zero. In addition, the CO2 refrigerant has a global warming potential of 1 and is much lower than a fluorocarbon refrigerant of several hundred to 10,000. Therefore, the deterioration of the global environment can be suppressed by using the CO2 refrigerant having a small environmental load.

<Modification>
(1)
In this embodiment, the discharge pressure sensor P1 detects the discharge pressure Pd of the compressor 21, and determines whether or not to perform throttling control based on whether or not the discharge pressure Pd is less than the critical pressure Pk of the CO2 refrigerant. However, it is not limited to this. Even if the inlet pressure near the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5 is calculated from the discharge pressure Pd and the compressor capacity of the compressor 21, it is determined whether or not the throttle control is performed based on the inlet pressure. good.

  The discharge pressure Pd and the inlet pressure of the outdoor expansion valve V2 or the indoor expansion valve V5 have different values due to the pressure loss of the refrigerant piping from the discharge side of the compressor 21 to the expansion valves V2 and V5. Here, it is determined whether or not the throttle control is performed based on the calculated inlet pressure, and the refrigerant in the gas-liquid two-phase state at the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5 that causes noise. Can be more reliably controlled to a supercritical state or a liquid phase state.

(2)
In this embodiment, the discharge pressure sensor P1 detects the discharge pressure Pd of the compressor 21, and determines whether or not to perform throttling control based on whether or not the discharge pressure Pd is less than the critical pressure Pk of the CO2 refrigerant. However, it is not limited to this. For example, as shown in FIG. 7, the first liquid pipe temperature sensor T2 is provided in the first liquid refrigerant pipe 28 between the outdoor heat exchanger 23 and the outdoor expansion valve V2, and the indoor heat exchanger 31 and the indoor expansion valve V5 are provided. A second liquid pipe temperature sensor T3 is provided in the second liquid refrigerant pipe 35 between and the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5 to detect the inlet temperature, and the inlet temperature is the critical temperature of the CO2 refrigerant. Whether or not the aperture control is performed may be determined based on whether or not the temperature is less than 31 ° C.

  Therefore, by detecting the inlet temperature near the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5, it can be determined whether or not the CO2 refrigerant is in a supercritical state. For this reason, it can be determined that the state of the refrigerant in the vicinity of the inlet of the outdoor expansion valve V2 or the indoor expansion valve V5 is not a gas-liquid two-phase state, and it is possible to reduce the burst sound of bubbles that cause flow noise. Further, since a temperature sensor that is cheaper than the pressure sensor can be used as a substitute for the pressure sensor, the production cost can be reduced.

(3)
In this embodiment, although the air conditioning apparatus 1 was mentioned as what uses the freezing apparatus, it is not restricted to this, You may have a heat pump water heater, a refrigerator, etc.

  The refrigeration apparatus according to the present invention has an effect of suppressing generation of noise, and is useful as a refrigeration apparatus using a refrigerant that operates in a supercritical region.

The refrigerant circuit figure of the air conditioning apparatus which concerns on one Embodiment of this invention. The control block diagram of an air conditioning apparatus. The flowchart of starting mode. The flowchart of a normal mode. The time flow figure showing the timing of switching between aperture control and normal control. Ph diagram (Mollier diagram) of the supercritical refrigeration cycle. The refrigerant circuit figure of the air harmony device concerning a modification (2).

Explanation of symbols

1,1a Air conditioning equipment (refrigeration equipment)
5 Control unit 21 Compressor 23 Outdoor heat exchanger (gas cooler, evaporator)
24 Outdoor fan (blower)
31 Indoor heat exchanger (gas cooler, evaporator)
32 Indoor fan (blower)
P1 Discharge pressure sensor (pressure sensor)
T2 First liquid pipe temperature sensor (temperature sensor)
T3 Second liquid pipe temperature sensor (temperature sensor)
V2 outdoor expansion valve (expansion mechanism)
V5 indoor expansion valve (expansion mechanism)

Claims (12)

A refrigeration system that uses a supercritical refrigerant and operates in a region where the high pressure exceeds the critical pressure,
A compressor (21) for compressing the supercritical refrigerant;
A gas cooler (23, 31) for cooling the supercritical refrigerant compressed by the compressor;
An expansion mechanism (V2, V5) for depressurizing the supercritical refrigerant;
Evaporators (31, 23) for evaporating the supercritical refrigerant decompressed by the expansion mechanism;
Discharge pressure detection means (P1, T2, T3) capable of detecting the discharge pressure of the compressor;
A control unit (5) that controls an opening of the expansion mechanism to control the discharge pressure to be equal to or higher than the critical pressure at the time of start-up and when the discharge pressure is lower than the critical pressure;
A refrigeration apparatus (1). The control unit performs a first control to make the opening degree of the expansion mechanism fully closed or a minute opening degree when the discharge pressure is less than the critical pressure.
The refrigeration apparatus (1) according to claim 1. The controller performs second control to increase the opening of the expansion mechanism after the first control and when the discharge pressure is equal to or higher than the critical pressure.
The refrigeration apparatus (1) according to claim 2. The discharge pressure detecting means is a pressure sensor (P1) provided on the discharge side of the compressor.
The refrigeration apparatus (1) according to any one of claims 1 to 3. The controller calculates the inlet pressure of the expansion mechanism from the discharge pressure and the operating capacity of the compressor, and adjusts the opening of the expansion mechanism when the inlet pressure is less than the critical pressure. Controlling the discharge pressure to be equal to or higher than the critical pressure;
The refrigeration apparatus according to any one of claims 1 to 4. The pressure detection means is a temperature sensor (T2, T3) capable of detecting the temperature of the supercritical refrigerant between the outlet of the gas cooler and the inlet of the expansion mechanism,
The controller determines that the inlet pressure may be lower than the critical pressure when the inlet temperature is lower than the critical temperature, and adjusts the opening of the expansion mechanism to adjust the inlet The refrigerating apparatus (1a) according to any one of claims 1 to 3, wherein the temperature is controlled so as to be equal to or higher than the critical temperature. A blower (24, 32) for promoting cooling of the gas cooler,
In addition,
The control unit controls to reduce or reduce the air volume of the blower when starting and when the discharge pressure is less than the critical pressure.
The refrigeration apparatus (1) according to any one of claims 1 to 6. The control unit adjusts the opening of the expansion mechanism during steady operation to control the discharge pressure to be equal to or higher than the critical pressure.
The refrigeration apparatus (1) according to any one of claims 1 to 7. The control unit adjusts the opening degree of the expansion mechanism to control the discharge pressure to be equal to or higher than the critical pressure even at a low outside air temperature during steady operation.
The refrigeration apparatus (1) according to any one of claims 1 to 7. The low outside air temperature is a case where the outside air temperature is 20 ° C. or less.
The refrigeration apparatus (1) according to claim 9. A refrigeration system that uses a supercritical refrigerant and operates in a region where the high pressure exceeds the critical pressure,
A compressor (21) for compressing the supercritical refrigerant;
A gas cooler (23, 31) for cooling the supercritical refrigerant compressed by the compressor;
An expansion mechanism (V2, V5) for depressurizing the supercritical refrigerant;
Evaporators (31, 23) for evaporating the supercritical refrigerant decompressed by the expansion mechanism;
Temperature detecting means (T2, T3) capable of detecting the inlet temperature of the expansion mechanism;
A control unit (5) for controlling the opening temperature of the expansion mechanism to control the inlet temperature to be equal to or higher than the critical temperature when starting and when the inlet temperature is lower than the critical temperature;
A refrigeration apparatus (1). The supercritical refrigerant is a CO2 refrigerant.
The refrigeration apparatus (1) according to any one of claims 1 to 11.

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