JP6257809B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus.

  Conventionally, a refrigeration cycle apparatus such as an air-cooled heat pump chiller that cools and heats water to generate cold water and hot water is known. In a conventional refrigeration cycle apparatus, frost may be generated in an air heat exchanger on the heat source side that functions as an evaporator when hot water is generated under a low outside air temperature. When frost is generated in the air heat exchanger, heat exchange between the outside air and the refrigerant is hindered, and the heating capacity of the refrigeration cycle apparatus is reduced. Therefore, it is known to perform a defrosting operation for melting the frost of the air heat exchanger.

  Patent Document 1 proposes a refrigeration cycle apparatus that performs a defrosting operation. In the refrigeration cycle apparatus of Patent Literature 1, when the defrosting operation condition is satisfied, the refrigerant flow path is reversed, and the air heat exchanger is caused to function as a condenser, thereby melting the frost of the air heat exchanger. Further, in the refrigeration cycle apparatus of Patent Document 1, a bypass circuit having an electromagnetic valve is connected in parallel to a throttle mechanism (expansion valve) provided between the air heat exchanger and the water heat exchanger. . And it is the structure which suppresses the fall of the low pressure pressure by the supply shortage of a refrigerant | coolant by opening a solenoid valve at the time of defrosting operation start, and flowing a refrigerant | coolant to the hydrothermal exchanger side.

JP 2012-7800 A

  Here, in a conventional refrigeration cycle apparatus including a high-pressure receiver for accumulating excess refrigerant, when performing a defrosting operation by inverting the refrigerant flow path, at the start of the defrosting operation, the liquid refrigerant accumulated in the high-pressure receiver Liquid back may occur through the water heat exchanger and into the compressor. In order to suppress such liquid back to the compressor, it is conceivable to install an accumulator on the suction side of the compressor and store the liquid refrigerant in the accumulator. However, the accumulator has a large capacity and requires a large installation space in the machine room, resulting in an increase in size and cost of the apparatus.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration cycle apparatus that suppresses liquid back to the compressor during a defrosting operation.

A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit including a compressor, a flow path switching device, a heat source side heat exchanger, a first expansion device, and a use side heat exchanger, a second expansion device, an on-off valve, and a second restriction. It includes a high pressure receiver is connected between the device and the on-off valve, comprising a liquid back suppression circuit connected in parallel with the first throttle device, and a control unit for controlling the second throttle device and the on-off valve, a control The section closes the second expansion device and the on-off valve when the defrosting operation start condition is satisfied, and then switches the flow path switching device to start the defrosting operation .

  According to the refrigeration cycle apparatus according to the present invention, liquid back to the compressor can be suppressed at the start or end of the defrosting operation.

It is a figure which shows the refrigerant circuit structure of the refrigerating-cycle apparatus in Embodiment 1 of this invention. It is a figure which shows the control structure of the refrigerating-cycle apparatus in Embodiment 1 of this invention. It is a flowchart which shows the flow of the defrost operation in Embodiment 1 of this invention. It is a flowchart which shows the flow at the time of completion | finish of the defrost operation in Embodiment 2 of this invention. It is a figure which shows the refrigerant circuit structure of the refrigerating-cycle apparatus in a prior art example.

Embodiments of a refrigeration cycle apparatus according to the present invention will be described below in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a refrigerant circuit configuration of a refrigeration cycle apparatus 100 according to Embodiment 1 of the present invention. The refrigeration cycle apparatus 100 of the present embodiment is used as an air-cooled heat pump chiller that cools and heats water to generate cold water and hot water. As shown in FIG. 1, the refrigeration cycle apparatus 100 includes a refrigerant circuit including a compressor 11, a flow switching device 12, a heat source side heat exchanger 13, a fan 14, a first expansion device 15, and a use side heat exchanger 17. Prepare. The refrigeration cycle apparatus 100 further includes a liquid back suppression circuit 40 including a second expansion device 18, a high-pressure receiver 16, and an on-off valve 19 that are connected in parallel with the first expansion device 15. Furthermore, the refrigeration cycle apparatus 100 includes a control unit 20 (FIG. 2) that controls the refrigerant circuit and the liquid back suppression circuit 40.

  The compressor 11 is a positive displacement compressor driven by a motor (not shown) controlled by an inverter, for example. The flow path switching device 12 switches the flow direction of the refrigerant, and is composed of, for example, a four-way valve. The flow path switching device 12 switches the flow path of the refrigerant as shown by the solid line in FIG. 1 during the cooling operation, and switches the flow path of the refrigerant as shown by the broken line in FIG. 1 during the heating operation.

  The heat source side heat exchanger 13 is an air heat exchanger that exchanges heat with outdoor air. For example, the heat source side heat exchanger 13 includes a cross-fin type fin-and-tube heat exchanger including a heat transfer tube and a large number of fins. The The heat source side heat exchanger 13 functions as a refrigerant condenser during the cooling operation, and functions as a refrigerant evaporator during the heating operation. The fan 14 is a blower that supplies air to the heat source side heat exchanger 13, and includes, for example, a propeller fan driven by a fan motor (not shown). The fan 14 has a function of sucking outdoor air and discharging the air heat-exchanged with the refrigerant by the heat source side heat exchanger 13 to the outside.

  The first expansion device 15 has a function of decompressing and expanding the refrigerant, and is configured by, for example, an electronic expansion valve. The first expansion device 15 is connected in series between the heat source side heat exchanger 13 and the use side heat exchanger 17. The use-side heat exchanger 17 is a water heat exchanger that exchanges heat with the use-side water, and includes, for example, a plate-type heat exchanger. The use side heat exchanger 17 functions as a refrigerant evaporator during the cooling operation, and functions as a refrigerant condenser during the heating operation.

  The high-pressure receiver 16 has a function of accumulating excess refrigerant, and is connected in series between the second expansion device 18 and the on-off valve 19. The second expansion device 18 has a function of decompressing and expanding the refrigerant, and is configured by, for example, an electronic expansion valve. The second expansion device 18 is connected in series between the heat source side heat exchanger 13 and the high-pressure receiver 16. The on-off valve 19 is composed of, for example, an electromagnetic valve, and is connected in series between the high-pressure receiver 16 and the use side heat exchanger 17. The second expansion device 18, the high-pressure receiver 16 and the on-off valve 19 are connected in series to form a liquid back suppression circuit 40, and are connected in parallel to the first expansion device 15.

  The refrigerant that can be used in the refrigeration cycle apparatus 100 includes a single refrigerant, a pseudo-azeotropic mixed refrigerant, a non-azeotropic mixed refrigerant, and the like. Examples of the pseudo azeotropic refrigerant mixture include R410A and R404A which are HFC refrigerants. This pseudo azeotrope refrigerant has the same characteristic as that of the non-azeotrope refrigerant and has an operating pressure of about 1.6 times that of R22. Non-azeotropic refrigerant mixture includes R407C, which is an HFC (hydrofluorocarbon) refrigerant. Since this non-azeotropic refrigerant mixture is a mixture of refrigerants having different boiling points, it has a characteristic that the composition ratio of the liquid-phase refrigerant and the gas-phase refrigerant is different.

  The refrigeration cycle apparatus 100 is provided with various sensors. Specifically, the heat source side heat exchanger 13 is provided with a heat exchange temperature sensor 31 that detects the temperature of the heat source side heat exchanger 13. The heat exchanger temperature sensor 31 detects the temperature of frost attached to the heat source side heat exchanger 13, and is provided, for example, in a heat transfer tube in the heat source side heat exchanger 13. In addition, an inlet temperature sensor 32 and an outlet temperature sensor 33 that detect the temperature of the refrigerant are respectively provided at the inlet and outlet of the use side heat exchanger 17. Based on the refrigerant temperature detected by the inlet temperature sensor 32 and the outlet temperature sensor 33, the first expansion device 15 and the second expansion device 18 are controlled by the control unit 20. Further, an outside air temperature sensor 34 for detecting the outside air temperature is provided in a portion arranged outside the refrigeration cycle apparatus 100. Although not shown in FIG. 1, the refrigeration cycle apparatus 100 detects a refrigerant suction pressure, a refrigerant discharge temperature sensor, and a refrigerant temperature at the inlet / outlet of the heat source side heat exchanger 13. A sensor or the like may be provided.

  FIG. 2 is a diagram illustrating a control configuration of the refrigeration cycle apparatus 100. The control unit 20 controls each unit of the refrigeration cycle apparatus 100, and includes a microcomputer or a DSP (Digital Signal Processor). The control unit 20 switches the rotation frequency of the compressor 11 and the flow path switching device 12 based on the detection results of various sensors including the heat exchange temperature sensor 31, the inlet temperature sensor 32, the outlet temperature sensor 33, and the outside air temperature sensor 34. The air flow rate of the fan 14, the opening degree of the first throttling device 15 and the second throttling device 18, and the opening and closing of the on-off valve 19 are controlled.

  Next, the operation of the refrigeration cycle apparatus 100 will be described. First, the operation | movement at the time of the cooling operation in the refrigerating-cycle apparatus 100 is demonstrated. During the cooling operation, the flow path of the refrigerant is switched by the flow path switching device 12 as shown by the solid line in FIG. The opening / closing valve 19 is fixed in an opened state, and the opening degree of the first expansion device 15 and the second expansion device 18 is controlled by the control unit 20 based on the degree of superheat. Specifically, the control unit 20 sets the superheat degree (suction superheat degree of the compressor 11) obtained from the temperatures detected by the inlet temperature sensor 32 and the outlet temperature sensor 33 to a target value (for example, 3 ° C to 5 ° C). Thus, the opening degree of the first expansion device 15 and the second expansion device 18 is determined.

  The high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 11 flows into the heat source side heat exchanger 13 through the flow path switching device 12. The high-temperature and high-pressure refrigerant that has flowed into the heat source side heat exchanger 13 dissipates heat to the outdoor air or the like, and is condensed to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the heat source side heat exchanger 13 flows into the first expansion device 15 and is expanded and depressurized to become a low-temperature and low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flowing out from the first expansion device 15 flows into the use side heat exchanger 17. At this time, surplus refrigerant passes through the second expansion device 18 and is stored in the high-pressure receiver 16. The gas-liquid two-phase refrigerant that has flowed into the use-side heat exchanger 17 evaporates by exchanging heat with water and becomes a low-temperature and low-pressure gas refrigerant. The gas refrigerant flowing out from the use side heat exchanger 17 is sucked into the compressor 11 and compressed again.

  Next, the operation during the heating operation will be described. During the heating operation, the flow path of the refrigerant is switched by the flow path switching device 12 as indicated by the broken line in FIG. The opening / closing valve 19 is fixed in an opened state, and the opening degree of the first expansion device 15 and the second expansion device 18 is controlled by the control unit 20 based on the degree of supercooling. Specifically, the control unit 20 sets the degree of supercooling at the outlet of the use side heat exchanger 17 obtained from the temperatures detected by the inlet temperature sensor 32 and the outlet temperature sensor 33 to a target value (for example, 3 ° C. to 5 ° C.). Thus, the opening degree of the first expansion device 15 and the second expansion device 18 is determined.

  The high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 11 flows into the use side heat exchanger 17 through the flow path switching device 12. The high-temperature and high-pressure refrigerant that has flowed into the use-side heat exchanger 17 dissipates heat to water and is condensed to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant that has flowed out of the use-side heat exchanger 17 flows into the first expansion device 15, is expanded and depressurized, and becomes a low-temperature and low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant that has flowed out of the first expansion device 15 flows into the heat source side heat exchanger 13. At this time, surplus refrigerant is stored in the high-pressure receiver 16. The gas-liquid two-phase refrigerant that has flowed into the heat source side heat exchanger 13 evaporates by exchanging heat with outdoor air and becomes a low-temperature and low-pressure gas refrigerant. The gas refrigerant flowing out of the heat source side heat exchanger 13 is sucked into the compressor 11 and compressed again.

  The refrigeration cycle apparatus 100 performs a defrosting operation for melting the frost of the heat source side heat exchanger 13 when frost is generated in the heat source side heat exchanger 13 during the heating operation. Specifically, when determining that the defrosting operation start condition of the heat source side heat exchanger 13 is satisfied during the heating operation, the control unit 20 switches the flow path switching device 12 to cause the heat source side heat exchanger 13 to function as a condenser. Perform cooling operation. At this time, the control unit 20 controls the second expansion device 18 and the on-off valve 19 so that the liquid refrigerant accumulated in the high-pressure receiver 16 flows to the compressor 11 through the use side heat exchanger 17, Suppresses the occurrence of back.

  FIG. 3 is a flowchart showing the flow of the defrosting operation in the present embodiment. As shown in FIG. 3, first, the controller 20 determines whether or not a defrosting operation start condition is satisfied during the heating operation (S1). Here, when the heat exchange temperature detected by the heat exchange temperature sensor 31 provided in the heat source side heat exchanger 13 or the outside air temperature detected by the outside air temperature sensor 34 is lower than a predetermined temperature (for example, 0 ° C.). Further, it is determined that frost is generated in the heat source side heat exchanger 13 and the defrosting operation start condition is satisfied. When the defrosting operation start condition is satisfied (S1: YES), the second expansion device 18 is fully closed (S2), and the on-off valve 19 is also closed (S3). Thereby, the pressure in the high-pressure receiver 16 is maintained at a high pressure, and the liquid refrigerant is stored in the high-pressure receiver 16. In this state, the flow path switching device 12 is switched and the defrosting operation is started (S4).

  When the defrosting operation is started, the flow path switching device 12 switches the flow path of the refrigerant as shown by the solid line in FIG. 1, and the heat source side heat exchanger 13 functions as a condenser as in the cooling operation. Then, the opening degree of the first expansion device 15 is controlled based on the suction superheat degree (S5). Next, it is determined whether or not the suction superheat degree of the compressor 11 is larger than the threshold value B (S6). Here, the suction superheat degree of the compressor 11 is determined by the outlet refrigerant temperature of the usage side heat exchanger 17 detected by the outlet temperature sensor 33 and the inlet side refrigerant temperature of the usage side heat exchanger 17 detected by the inlet temperature sensor 32. It is calculated as the difference. Further, the threshold value B is a value for determining that the suction superheat degree of the compressor 11 is sufficient, and is set to 5 ° C., for example.

  When the suction superheat degree of the compressor 11 is larger than the threshold value B (S6: YES), the second expansion device 18 is opened (S7), and the on-off valve 19 is also opened (S8). Thereafter, the opening degrees of the first expansion device 15 and the second expansion device 18 are controlled based on the suction superheat degree (S9), and the defrosting operation is continued. Then, it is determined whether the defrosting operation end condition is satisfied (S10). If the defrosting operation end condition is not satisfied (S10: NO), the defrosting operation is continued. Here, the temperature detected by the heat exchanger temperature sensor 31 provided in the heat source side heat exchanger 13 or the temperature detected by the outside air temperature sensor 34 by the control unit 20 is higher than a predetermined temperature (for example, 10 ° C.). When it is high, it is determined that the defrosting operation end condition is satisfied, assuming that the frost of the heat source side heat exchanger 13 has melted. On the other hand, when the defrosting operation termination condition is satisfied (S10: YES), the flow path switching device 12 is switched (S11). Thereby, a defrost operation is complete | finished and a heating operation is restarted.

  As described above, in the present embodiment, after the defrosting operation start condition is satisfied (S1: YES), and before the defrosting operation start (S4), the second expansion device 18 and the on-off valve 19 are closed. And the liquid back to the compressor 11 of the liquid refrigerant collected in the high-pressure receiver 16 can be suppressed. When the suction superheat degree of the compressor 11 is equal to or greater than the threshold value (that is, when the liquid back does not occur), the second throttle device 18 and the on-off valve 19 are opened to perform normal control. The defrosting operation can be performed.

  FIG. 5 is a diagram showing a refrigerant circuit configuration of the refrigeration cycle apparatus 200 in the conventional example. As shown in FIG. 5, the conventional refrigeration cycle apparatus 200 includes a compressor 1, a four-way valve 2, an air heat exchanger 3, a fan 4, an expansion valve 5, a high-pressure receiver 6, and a water heat exchanger 7. The expansion valve 5 is connected in series between the air heat exchanger 3 and the water heat exchanger 7, and performs pressure reduction and flow rate control of the refrigerant flowing through the refrigerant circuit. Moreover, the high pressure receiver 6 is installed between the expansion valve 5 and the water heat exchanger 7, and accumulates excess refrigerant. In the case of the conventional refrigeration cycle apparatus 200 shown in FIG. 5, when the defrosting operation is performed by reversing the refrigerant flow path, the liquid refrigerant accumulated in the high-pressure receiver 6 is transferred to the water heat exchanger 7 at the start of the defrosting operation. And flows to the compressor 1 to generate a liquid back. In contrast, in the present embodiment, the liquid back suppression circuit 40 is provided as described above, and the liquid back can be suppressed by controlling the second expansion device 18 and the on-off valve 19 by the control unit 20.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the first embodiment, the second expansion device 18 and the on-off valve 19 are controlled in order to suppress the occurrence of liquid back at the start of the defrosting operation. Here, not only at the start of the defrosting operation but also at the end of the defrosting operation, the liquid refrigerant accumulated in the heat source side heat exchanger 13 may return to the compressor 1 to generate a liquid back. Therefore, the second embodiment is different from the first embodiment in that the second throttle device 18 and the on-off valve 19 are controlled at the end of the defrosting operation to suppress the occurrence of liquid back. The refrigerant circuit configuration and the control configuration of the refrigeration cycle apparatus 100 of the present embodiment are the same as the refrigerant circuit configuration and the control configuration of the first embodiment shown in FIGS. 1 and 2.

  FIG. 4 is a flowchart showing a flow at the end of the defrosting operation in the present embodiment. As shown in FIG. 4, it is determined whether or not the defrosting operation end condition is satisfied (S21). When the defrosting operation end condition is not satisfied (S21: NO), the defrosting operation is performed until it is satisfied. Will continue. On the other hand, when the defrosting operation end condition is satisfied (S21: YES), the on-off valve 19 is closed (S22), and the second expansion device 18 is fully opened (S23). Thereby, the pressure in the high-pressure receiver 16 is set to a high pressure state. And in this state, it waits until predetermined time passes (S24). At this time, the liquid refrigerant of the heat source side heat exchanger 13 is stored in the high-pressure receiver 16 by maintaining the rotational frequency of the compressor 11. And when predetermined time passes (S24: YES), the flow-path switching apparatus 12 is switched, and a defrost operation is complete | finished (S25). Thereafter, the on-off valve 19 is opened (S26), and the heating operation is resumed.

As described above, in the present embodiment, when the condition for ending the defrosting operation is satisfied (S21: YES), the second expansion device 18 is opened and opened / closed before the end of the defrosting operation (S25). By closing the valve 19, the liquid refrigerant stored in the heat source side heat exchanger 13 is stored in the high-pressure receiver 16. Thereby, at the end of the defrosting operation, the liquid refrigerant that has accumulated in the heat source side heat exchanger 13 is suppressed from returning to the compressor 11.

  The above is the description of the embodiment of the present invention. However, the present invention is not limited to the configuration of the above embodiment, and various modifications or combinations are possible within the scope of the technical idea. For example, in the above embodiment, as shown in FIG. 1, the refrigeration cycle apparatus 100 will be described with respect to a case where it includes one compressor 11, a heat source side heat exchanger 13 and a use side heat exchanger 17. There is no particular limitation on the number of units. For example, two or more compressors 11, the heat source side heat exchanger 13, and the use side heat exchanger 17 may be provided. In the above embodiment, the case where the refrigeration cycle apparatus 100 is an air-cooled heat pump chiller that cools and heats water to generate cold water and hot water has been described as an example. The present invention may be applied to an air conditioner used for cooling and heating.

  In the above embodiment, the intake superheat degree control and the supercool degree control are performed based on the refrigerant temperatures detected by the inlet temperature sensor 32 and the outlet temperature sensor 33. However, the present invention is not limited to this. Instead, suction superheat degree control and supercooling degree control may be performed based on other temperature sensors or pressure sensors. In addition to the suction superheat degree control and the supercooling degree control, other controls such as discharge superheat degree control may be performed. Further, the defrosting operation start condition and the defrosting operation end condition are not limited to those described in the above embodiment, and other conditions may be used.

  Further, the control for suppressing the liquid back in the first embodiment and the second embodiment may be performed only at one of them, or at both the start of the defrosting operation and the end of the defrosting operation. May be. Furthermore, by providing the liquid back suppression circuit 40 of the present invention, liquid refrigerant is accumulated in the heat source side heat exchanger 13 such as at the end of the heating (heating) operation at a low outside temperature other than during the defrosting operation. In this state, liquid back that can occur at the next start-up can be suppressed. In this case, similarly to the end of the defrosting operation in the second embodiment, the liquid that has accumulated in the heat source side heat exchanger 13 by opening the second expansion device 18 and the on-off valve 19 before the end of the heating operation. The refrigerant is stored in the high-pressure receiver 16. As a result, the liquid refrigerant that has accumulated in the heat source side heat exchanger 13 at the next start-up is suppressed from returning to the compressor 11.

  1, 11 Compressor, 2 Four-way valve, 3 Air heat exchanger, 4, 14 Fan, 5 Expansion valve, 6, 16 High pressure receiver, 7 Water heat exchanger, 12 Channel switching device, 13 Heat source side heat exchanger, 14 Fan, 15 1st throttle device, 17 User side heat exchanger, 18 Second throttle device, 19 On-off valve, 20 Control unit, 31 Heat exchange temperature sensor, 32 Inlet temperature sensor, 33 Outlet temperature sensor, 34 Outside air temperature sensor , 40 Liquid back suppression circuit, 100, 200 Refrigeration cycle apparatus.

Claims (3)

A refrigerant circuit including a compressor, a flow path switching device, a heat source side heat exchanger, a first expansion device and a use side heat exchanger;
A liquid back suppression circuit including a second throttling device, an on-off valve and a high-pressure receiver connected between the second throttling device and the on-off valve, and connected in parallel to the first throttling device;
A control unit for controlling the second throttle device and the on-off valve ;
When the defrosting operation start condition is satisfied, the control unit closes the second expansion device and the on-off valve, and then switches the flow path switching device to start the defrosting operation . The control unit is configured to open the second expansion device and the on-off valve when an intake superheat degree of the compressor becomes larger than a predetermined value after starting the defrosting operation. refrigeration cycle apparatus according to 1. Wherein, when the defrosting operation end condition is satisfied, opening the second throttle device, closing the on-off valve, then, is to terminate the defrosting operation by switching the flow switching device according Item 3. The refrigeration cycle apparatus according to Item 1 or 2 .

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