Refrigeration cycle device

Abstract

This refrigeration cycle device comprises: a main circuit comprising a compressor, a four-way valve, a first heat source-side heat exchanger, a first expansion valve, a second heat source-side heat exchanger, a second expansion valve, and a load-side heat exchanger; and a bypass circuit connecting an intake side of the compressor and a connection point between the second heat source-side heat exchanger and the second expansion valve. During a heating operation, a heating circuit is formed in which a refrigerant that has been compressed by and discharged from the compressor flows through the four-way valve to the load-side heat exchanger, the first expansion valve, the second heat source-side heat exchanger, and the first heat source-side heat exchanger, in that order, and then returns to the compressor via the four-way valve. During a cooling operation, a cooling circuit is formed in which the refrigerant that has been compressed by and discharged from the compressor flows through the four-way valve to the first heat source-side heat exchanger, the second heat source-side heat exchanger, the first expansion valve, and the load-side heat exchanger, in that order, and then returns to the compressor via the four-way valve. During a first defrosting operation, a first defrosting circuit is formed in which the refrigerant that has been compressed by and discharged from the compressor flows through the four-way valve to the first heat source-side heat exchanger, the second expansion valve, and the second heat source-side heat exchanger, in that order, and then returns to the compressor from the bypass circuit.

Description

Refrigeration Cycle Equipment

[0001] The present disclosure relates to a refrigeration cycle device, and more particularly to defrosting of a refrigeration cycle device.

[0002] In a refrigeration cycle device using an air heat exchanger as its outdoor unit, if the temperature of the fins drops below 0°C during heating operation, moisture in the air may freeze, causing frost to form on the fins. The frost on the fins blocks the fan's air passage and increases pressure loss, making it impossible to achieve the desired heating capacity. Therefore, when the desired heating capacity can no longer be achieved due to frost, the refrigerant circuit is switched using a four-way valve to perform cooling operation, supplying high-temperature, high-pressure refrigerant to the air heat exchanger and performing a defrosting operation to melt the frost on the air heat exchanger.

[0003] In addition, in order to suppress the drop in water temperature during defrosting operation, a smart defrost technology is known in which the rate of drop in water temperature on the load side is estimated before starting defrosting operation, the capacity of other refrigeration cycle devices is increased, and the water temperature is raised above the target water temperature in advance.

[0004] Patent No. 6377259

[0005] Since defrosting operation is configured to extract heat from the hot water on the load side and allocate it to defrosting, the water temperature on the load side will drop, especially in housings and systems consisting of multiple refrigeration cycles.Even when smart defrost is adopted, the compressor discharge pressure will increase during operation when the target water temperature is raised, so if the target water temperature cannot be raised sufficiently before defrosting begins, the drop in water temperature cannot be prevented.

[0006] An object of the present disclosure is to provide a refrigeration cycle device in which a decrease in water temperature during defrosting operation is suppressed.

[0007] A refrigeration cycle device according to the present disclosure includes a main circuit including a compressor, a four-way valve, a first heat source side heat exchanger, a first expansion valve, a second heat source side heat exchanger, a second expansion valve, and a load side heat exchanger, and a bypass circuit connecting the suction side of the compressor and a connection point between the second heat source side heat exchanger and the second expansion valve, and during heating operation, a heating circuit is configured in which refrigerant compressed by the compressor and discharged flows through the four-way valve, the load side heat exchanger, the first expansion valve, the second heat source side heat exchanger, and the first heat source side heat exchanger in this order, and returns to the compressor again via the four-way valve. During cooling operation, the refrigerant compressed by the compressor and discharged flows through the four-way valve, the first heat source side heat exchanger, the second heat source side heat exchanger, the first expansion valve, and the load side heat exchanger in this order, and then returns to the compressor via the four-way valve, thereby forming a cooling circuit; during first defrosting operation, the refrigerant compressed by the compressor and discharged flows through the four-way valve, the first heat source side heat exchanger, the second expansion valve, and the second heat source side heat exchanger in this order, and then returns to the compressor via the bypass circuit, thereby forming a first defrosting circuit.

[0008] According to the refrigeration cycle device of the present disclosure, defrosting is performed in the first heat source side heat exchanger, heat is extracted from the air in the second heat source side heat exchanger, and a first defrosting operation is performed in which no refrigerant flows through the user side heat exchanger, thereby suppressing a drop in water temperature during the defrosting operation.

[0009] 1 is a circuit configuration diagram of a refrigeration cycle device according to embodiment 1. FIG. 2 is a schematic configuration diagram of a heat source side unit of the refrigeration cycle device according to embodiment 1. FIG. 3 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 1 during cooling operation. FIG. 4 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 1 during heating operation. FIG. 5 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 1 during a first defrosting operation. FIG. 6 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 1 during a second defrosting operation. FIG. 7 is a flowchart explaining processing by a control device of the refrigeration cycle device according to embodiment 1. FIG. 8 is a circuit configuration diagram of a refrigeration cycle system using the refrigeration cycle device according to embodiment 1. FIG. 9 is a graph showing a water temperature change in the refrigeration cycle system using the refrigeration cycle device according to embodiment 1. FIG. 10 is a circuit configuration diagram of a refrigeration cycle system using a refrigeration cycle device according to a comparative example. FIG. 11 is a graph showing a water temperature change in the refrigeration cycle system using a refrigeration cycle device according to a comparative example. FIG. 11 is a circuit configuration diagram of a refrigeration cycle device according to a modified example of embodiment 1. FIG. 2 is a circuit configuration diagram of a refrigeration cycle device according to embodiment 2. FIG. 3 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 2 during heating operation. FIG. 4 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 2 during a first defrosting operation. FIG. 5 is a circuit configuration diagram of the refrigeration cycle device according to embodiment 2 during a second defrosting operation. 10 is a flowchart illustrating processing by a control device of a refrigeration cycle device according to a second embodiment.

[0010] Embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the following embodiments and can be modified in various ways without departing from the spirit and scope of the present disclosure. Furthermore, the present disclosure includes all possible combinations of the configurations shown in the following embodiments. In particular, the combinations of components are not limited to those in each embodiment; components described in one embodiment can be applied to another embodiment. The configurations shown in the drawings are merely examples of the configurations of the present disclosure, and the present disclosure is not limited to the configurations shown in the drawings. In the following description, directional terms (e.g., "up," "down," "right," "left," "front," "rear," etc.) are used as appropriate to facilitate understanding, but these are for explanatory purposes and do not limit the present disclosure. In each drawing, components designated with the same reference numerals are identical or equivalent, and this applies throughout the entire specification. The relative dimensional relationships or shapes of the components in each drawing may differ from those in the actual product.

[0011] Embodiment 1. <Configuration of Refrigeration Cycle Apparatus 100> Fig. 1 is a circuit configuration diagram of a refrigeration cycle apparatus 100 according to Embodiment 1. Fig. 2 is a schematic configuration diagram of a heat source side unit 101 of the refrigeration cycle apparatus 100 according to Embodiment 1. As shown in Figs. 1 and 2, the refrigeration cycle apparatus 100 has a main circuit M and a bypass circuit BP, and is, for example, a top-flow type modular chiller system. During heating operation, the refrigeration cycle apparatus 100 supplies hot water to the user side by removing heat from a medium serving as a heat source, and during cooling operation, supplies cold water to the user side by releasing heat to the medium serving as a heat source. The heat source medium is, for example, air.

[0012] The refrigeration cycle apparatus 100 includes a heat source side unit 101, which is a heat pump type heat source machine, and a user side unit 102. The refrigeration cycle apparatus 100 may have a configuration in which a plurality of heat source side units 101 are installed.

[0013] The first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 are arranged within the housing 101a of the heat source side unit 101, with the first heat source side heat exchanger 20 on the outside and the second heat source side heat exchanger 21 on the inside. The second heat source side heat exchanger 21 may be composed of multiple heat exchangers. A fan 30 is attached to the housing 101a of the heat source side unit 101. The fan 30 is provided, for example, on the upper part of the housing 101a. The fan 30 may be a bidirectional fan that is capable of changing the air blowing direction.

[0014] The user-side unit 102 is, for example, a heat exchanger that cools or heats indoor air by using cold water or hot water flowing through the water circuit W. The user-side unit 102 may also be, for example, a radiator that heats the room by using hot water flowing through the water circuit W.

[0015] <Configuration of Refrigerant Circuit> In the refrigeration cycle apparatus 100, a refrigerant circuit is configured by connecting each component via refrigerant piping 103. The refrigerant circuit includes, as components, a compressor 10, a four-way valve 11, a first heat source side heat exchanger 20, a second heat source side heat exchanger 21, a first expansion valve 41, a user side heat exchanger 12, an on-off valve 42, and a second expansion valve 44. The user side heat exchanger 12 is an example of a load side heat exchanger.

[0016] Of the components of the refrigerant circuit, for example, the compressor 10, the four-way valve 11, the first heat source side heat exchanger 20, the second heat source side heat exchanger 21, the first expansion valve 41, the on-off valve 42, and the second expansion valve 44 are housed in the heat source side unit 101. The user side heat exchanger 12 is housed in the user side unit 102.

[0017] The user-side unit 102 may be provided with a pump and a cushion tank (not shown). The pump may be built into the user-side unit 102 or may be arranged externally. The cushion tank reduces the temperature change range by mixing the water supplied from the user-side unit 102 with the water in the tank, and is used when the water temperature fluctuates greatly. The cushion tank has the effect of suppressing a drop in water temperature, and is also expected to have the effect of making the cushion tank more compact.

[0018] <Compressor 10> The compressor 10 draws in low-temperature, low-pressure refrigerant, compresses it, and discharges it as high-temperature, high-pressure refrigerant. The compressor 10 may be one whose capacity, i.e., the amount of refrigerant delivered per unit time, can be changed by, for example, arbitrarily changing the drive frequency using an inverter circuit (not shown) or the like.

[0019] <First Heat Source Side Heat Exchanger 20 and Second Heat Source Side Heat Exchanger 21> The first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 are air heat exchangers that exchange heat between a refrigerant and air. When functioning as a condenser, the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 condense and liquefy the refrigerant and heat the air, and when functioning as an evaporator, they evaporate and vaporize the refrigerant and cool the air. The first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 are, for example, fin-and-tube heat exchangers. The first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 may be, for example, a vertical flat tube (VFT) heat exchanger.

[0020] <Use-side heat exchanger 12> The use-side heat exchanger 12 is a water heat exchanger that cools or heats water by exchanging heat between the refrigerant flowing through the refrigerant circuit and the water flowing through the water circuit W. The use-side heat exchanger 12 is, for example, a plate heat exchanger in which multiple thin copper plates are stacked. When functioning as a condenser, the use-side heat exchanger 12 condenses and liquefies the refrigerant and heats the water, and when functioning as an evaporator, it evaporates and vaporizes the refrigerant and cools the water.

[0021] <Four-way valve 11> The four-way valve 11 has a function of switching the flow direction of the refrigerant discharged from the compressor 10. For example, in the case of cooling operation, the four-way valve 11 causes the high-temperature, high-pressure refrigerant discharged from the compressor 10 to flow into the second heat source-side heat exchanger 21, and in the case of heating operation, causes the high-temperature, high-pressure refrigerant discharged from the compressor 10 to flow into the user-side heat exchanger 12.

[0022] <First Expansion Valve 41 and Second Expansion Valve 44> The first expansion valve 41 and the second expansion valve 44 adjust the pressure of the refrigerant by changing their opening degrees. The first expansion valve 41 and the second expansion valve 44 are, for example, electronic expansion valves whose opening degrees can be changed. The first expansion valve 41 and the second expansion valve 44 may also be temperature-sensing expansion valves whose opening degrees change based on the temperature of the refrigerant. The opening degrees of the first expansion valve 41 and the second expansion valve 44 are adjusted by the control device 50. By adjusting the opening degrees of the first expansion valve 41 and the second expansion valve 44, the pressure of the refrigerant is adjusted, and, for example, refrigerant in a liquid state is prevented from entering the compressor 10.

[0023] <On-Off Valve 42> The on-off valve 42 may be any valve capable of being opened and closed, and may be, for example, a solenoid valve.

[0024] <Main Circuit M> The main circuit M is made up of the compressor 10, the four-way valve 11, the first heat source side heat exchanger 20, the second expansion valve 44, the second heat source side heat exchanger 21, the first expansion valve 41, and the user side heat exchanger 12. In the main circuit M, the compressor 10, the four-way valve 11, the first heat source side heat exchanger 20, the second expansion valve 44, the second heat source side heat exchanger 21, the first expansion valve 41, and the user side heat exchanger 12 are connected in this order by refrigerant piping 103. In other words, the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 are connected in series, and the second expansion valve 44 is disposed between the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21.

[0025] <Bypass circuit BP> The bypass circuit BP is configured by connecting a first connection point 1 and a second connection point 2 of the main circuit M by a refrigerant pipe 103. The first connection point 1 is located on the suction side of the compressor 10, and the second connection point 2 is located between the second heat source side heat exchanger 21 and the first expansion valve 41. An on-off valve 42 is connected to the bypass circuit BP.

[0026] <Control Device> The refrigeration cycle apparatus 100 has a control device 50. The control device 50 controls the operation of the refrigeration cycle apparatus 100 by controlling each component of the refrigeration cycle apparatus 100. For example, sensors (not shown) provided in the refrigeration cycle apparatus 100 are connected to the control device 50. The control device 50 controls each component based on values ​​of the various sensors.

[0027] The control device 50 controls the amount of refrigerant discharged from the compressor 10 per unit time by, for example, controlling the drive frequency of the compressor 10. The control device 50 controls, for example, switching the flow direction of the four-way valve 11 between NO and OFF. The control device 50 controls, for example, the opening and closing operation of the on-off valve 42. The control device 50 controls, for example, changing the opening degrees of the first expansion valve 41 and the second expansion valve 44. The control device 50 controls, for example, the compressor 10, the first expansion valve 41, and the second expansion valve 44 so that the temperature of the refrigerant discharged from the compressor 10 reaches a target value. The control device 50 controls, for example, the compressor 10, the first expansion valve 41, and the second expansion valve 44 so that the degree of subcooling and the degree of superheating of the refrigerant flowing out of the first heat source side heat exchanger 20, the second heat source side heat exchanger 21, or the user side heat exchanger 12 reach target values, respectively.

[0028] The control device 50 is configured by, for example, a CPU (Central Processing Unit, also called a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)). The control device 50 has a memory configured by, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), etc. The control device 50 realizes processing by a program stored in the memory.

[0029] <Cooling operation> Fig. 3 is a circuit configuration diagram during cooling operation of the refrigeration cycle apparatus 100 according to Embodiment 1. As shown in Fig. 3, during cooling operation of the refrigeration cycle apparatus 100, the control device 50 configures a refrigerant circuit in which high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M.

[0030] The control device 50 performs control to close the on-off valve 42, open the second expansion valve 44, and adjust the opening degree of the first expansion valve 41. The control device 50 switches the four-way valve 11 so that the first heat source side heat exchanger 20 is connected to the high pressure side of the compressor 10. In the following description, for convenience, the state of the four-way valve 11 during cooling operation will be referred to as the OFF state.

[0031] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the first heat source-side heat exchanger 20, passes through the second expansion valve 44, and further exchanges heat with air in the second heat source-side heat exchanger 21, condensing and flowing out of the second heat source-side heat exchanger 21. The refrigerant flowing out of the second heat source-side heat exchanger 21 is decompressed in the first expansion valve 41 to become a two-phase refrigerant, flows into the user-side heat exchanger 12, exchanges heat with water in the water circuit W as a secondary-side medium, evaporates, and flows out as a low-temperature, low-pressure refrigerant. The refrigerant flowing out of the user-side heat exchanger 12 passes through the four-way valve 11 and returns to the compressor 10. In the user-side heat exchanger 12, the refrigerant absorbs heat from the water in the water circuit W, thereby cooling the water and generating chilled water. During cooling operation, the fan 30 operates, for example, in the forward direction to promote heat exchange in the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21.

[0032] <Heating operation> Fig. 4 is a circuit configuration diagram during heating operation of the refrigeration cycle apparatus 100 according to Embodiment 1. As shown in Fig. 4, during heating operation of the refrigeration cycle apparatus 100, the control device 50 configures a heating circuit such that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M.

[0033] As in cooling, the control device 50 closes the on-off valve 42, opens the second expansion valve 44, and adjusts the opening degree of the first expansion valve 41. The control device 50 also switches the four-way valve 11 so that the user-side heat exchanger 12 is connected to the high-pressure side of the compressor 10. In the following description, for convenience, the orientation of the four-way valve 11 during heating operation will be referred to as ON.

[0034] The high-temperature, high-pressure refrigerant discharged from the compressor 10 flows into the user-side heat exchanger 12, where it exchanges heat with the water in the water circuit W, condenses, and flows out of the user-side heat exchanger 12. In the user-side heat exchanger 12, the refrigerant dissipates heat to the water in the water circuit W, heating the water and generating hot water.

[0035] The refrigerant flowing out of the user-side heat exchanger 12 is decompressed in the first expansion valve 41, flows into the second heat-source-side heat exchanger 21, passes through the second expansion valve 44, and flows into the first heat-source-side heat exchanger 20. As the refrigerant passes through the first heat-source-side heat exchanger 20 and the second heat-source-side heat exchanger 21, it exchanges heat with the air and evaporates, becoming a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant flows out of the first heat-source-side heat exchanger 20, passes through the four-way valve 11, and returns to the compressor 10. Even during heating operation, the fan 30 operates to promote heat exchange in the first heat-source-side heat exchanger 20 and the second heat-source-side heat exchanger 21.

[0036] <First defrosting operation> Fig. 5 is a circuit configuration diagram of the refrigeration cycle apparatus 100 according to Embodiment 1 during the first defrosting operation. As shown in Fig. 5, in the first defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures a first defrosting circuit such that high-temperature, high-pressure refrigerant discharged from the compressor 10 passes through a bypass circuit BP. The first defrosting operation is an operating mode in which the first heat source-side heat exchanger 20 functions as a condenser and the second heat source-side heat exchanger 21 functions as an evaporator to perform dehumidification. The first defrosting operation is selected when frost has formed on the first heat source-side heat exchanger 20 and the heat required to melt the frost on the first heat source-side heat exchanger 20, i.e., the required defrosting capacity, can be provided by the heat collected by the second heat source-side heat exchanger 21.

[0037] The control device 50 opens the on-off valve 42, closes the first expansion valve 41, and adjusts the opening degree of the second expansion valve 44. The control device 50 switches the orientation of the four-way valve 11 to a state during cooling operation in which the first heat source side heat exchanger 20 is connected to the high pressure side of the compressor 10, i.e., to the OFF state.

[0038] During the first defrosting operation, high-temperature, high-pressure refrigerant discharged from the compressor 10 flows through the four-way valve 11 into the first heat source side heat exchanger 20, and dissipates heat in the first heat source side heat exchanger 20. This melts frost that has adhered to the first heat source side heat exchanger 20. The refrigerant that has dissipated heat in the first heat source side heat exchanger 20 flows out of the first heat source side heat exchanger 20 and reaches the second expansion valve 44, where it is converted into low-pressure refrigerant and flows into the second heat source side heat exchanger 21.

[0039] The refrigerant evaporates in the second heat source-side heat exchanger 21 and collects heat from the air surrounding the second heat source-side heat exchanger 21. The refrigerant evaporates and becomes a gas at a low temperature and pressure, passes through the second connection point 2, the on-off valve 42, and reaches the first connection point 1. The refrigerant flows from the first connection point 1 to merge with the main circuit M on the suction side of the compressor 10 and flows back into the compressor 10.

[0040] The first heat source-side heat exchanger 20 is disposed in the first row on the upstream side of the airflow in the housing 101a and is the heat exchanger into which outside air first enters, receiving air before it flows into the second heat source-side heat exchanger 21. For this reason, frost is more likely to form in the first heat source-side heat exchanger 20 than in the second heat source-side heat exchanger 21. In the first defrosting operation, the second heat source-side heat exchanger 21, which is less likely to form frost, is made to function as an evaporator, and heat is extracted from the air in the second heat source-side heat exchanger 21 and allocated to defrosting the first heat source-side heat exchanger 20. In the first defrosting operation, heat is not extracted from the water in the use-side heat exchanger 12, and therefore cooling of the water flowing through the use-side unit 102 during defrosting is suppressed.

[0041] In the first defrosting operation, a circuit in which the refrigerant circulates is formed between the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21, and the refrigerant does not flow through the use side heat exchanger 12. If the water flowing through the water circuit W of the use side heat exchanger 12 is cooled and freezes, the use side heat exchanger 12 may burst and be damaged. By configuring the use side heat exchanger 12 so that no refrigerant flows through it, the water flowing through the water circuit W of the use side heat exchanger 12 is not cooled, so there is no risk of the water freezing, and damage to the use side heat exchanger 12 due to frozen water can be suppressed.

[0042] <Second defrosting operation> Fig. 6 is a circuit configuration diagram of the refrigeration cycle apparatus 100 according to Embodiment 1 during the second defrosting operation. As shown in Fig. 6, during the second defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures a second defrosting circuit such that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M. The second defrosting operation is selected when the heat required to melt the frost on the first heat source side heat exchanger 20, i.e., the required defrosting capacity, cannot be provided by the heat collected by the second heat source side heat exchanger 21.

[0043] The control device 50 controls each so that the on-off valve 42 is closed, the opening degree of the first expansion valve 41 is adjusted, and the second expansion valve 44 is opened. The control device 50 switches the four-way valve 11 to the OFF state so that the first heat source side heat exchanger 20 is connected to the high pressure side of the compressor 10. In other words, the circuit configuration during the second defrosting operation is the same as the circuit configuration during the cooling operation shown in Fig. 3, and a reverse defrosting operation is performed.

[0044] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the first heat source-side heat exchanger 20, passes through the second expansion valve 44, and further exchanges heat with air in the second heat source-side heat exchanger 21, where it condenses and flows out of the second heat source-side heat exchanger 21. The high-temperature refrigerant that has flowed into the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21 melts the frost that has adhered to the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21.

[0045] The refrigerant flowing out of the second heat source-side heat exchanger 21 is decompressed in the first expansion valve 41 to become a two-phase refrigerant, passes through the user-side heat exchanger 12, and returns to the compressor 10 via the four-way valve 11. By performing the second defrosting operation, even when the second heat source-side heat exchanger 21 cannot extract enough heat to melt the frost adhering to the first heat source-side heat exchanger 20, it is possible to defrost the first heat source-side heat exchanger 20 and melt the frost adhering to the second heat source-side heat exchanger 21. Note that in the second defrosting operation, the fan 30 is operated at a low speed or stopped, thereby suppressing heat exchange in the heat source-side unit 101 and suppressing cooling of the water in the water circuit W due to heat exchange in the user-side heat exchanger 12.

[0046] In this way, when it is difficult to complete defrosting with the amount of heat extracted from the outdoor air, a second defrosting circuit having the same circuit configuration as the cooling circuit can be configured, and a second defrosting operation, which is a reverse defrosting operation, can be performed. This ensures that defrosting in the heat source unit 101 is eliminated.

[0047] Here, when a method called smart defrost is employed in reverse defrosting that extracts heat from the water circuit W, the discharge pressure of the compressor 10 is likely to increase. Smart defrost is a method in which, for example, in a water heater, if the target temperature during normal operation is set to, for example, 45°C, the target temperature is raised in advance to, for example, 60°C or 70°C during defrosting operation in consideration of a drop in water temperature. If the discharge pressure of the compressor 10 increases, it may deviate from the operating range allowed by the compressor 10, potentially damaging the components that make up the refrigeration cycle apparatus 100. Furthermore, if the pressure exceeds the design pressure, the refrigeration cycle apparatus 100 cannot be constructed.

[0048] In contrast, the refrigeration cycle apparatus 100 according to the first embodiment can selectively perform a first defrosting operation that extracts heat from the air and a second defrosting operation that extracts heat from the water circuit W. This reduces the time per life cycle during which the second defrosting operation that extracts heat from the water circuit W is performed, and even if a smart defrost defrosting method is adopted, an increase in the discharge pressure of the compressor 10 and the resulting inconveniences can be suppressed.

[0049] <Flowchart> Fig. 7 is a flowchart illustrating processing by the control device 50 of the refrigeration cycle apparatus 100 according to Embodiment 1. As shown in Fig. 7, when frost has formed on the heat source side unit 101, the control device 50 determines whether to perform the first defrosting operation or the second defrosting operation, and performs one of the operations.

[0050] When a defrosting operation is performed in the heat source unit 101, the control device 50 estimates the required defrosting capacity and the amount of heat collected by the air in step S1 after processing is started. The control device 50 calculates and estimates the required defrosting capacity and the amount of heat collected by the air.

[0051] Next, in step S2, the control device 50 determines whether the required defrosting capacity can be achieved by extracting heat from the air.

[0052] If the control device 50 determines in step S2 that the required defrosting capacity can be achieved by extracting heat from the air (YES in step S2), the control device 50 proceeds to step S3. In step S3, the control device 50 closes the first expansion valve 41, opens the on-off valve 42, and switches the four-way valve 11 to the OFF state during heating operation, i.e., the state in which the high-pressure side of the compressor 10 is connected to the first heat source-side heat exchanger 20.

[0053] Next, the control device 50 proceeds to step S5, performs the first defrosting operation, and terminates the process after a predetermined time has elapsed, for example. As a result, the first heat source side heat exchanger 20 is defrosted preferentially over the second heat source side heat exchanger 21.

[0054] If the control device 50 determines in step S2 that the required defrosting capacity cannot be achieved by extracting heat from the air (NO in step S2), the control device 50 proceeds to step S4. In step S4, the control device 50 switches the four-way valve 11 to the OFF state during cooling operation, that is, the state in which the high-pressure side of the compressor 10 is connected to the first heat source-side heat exchanger 20.

[0055] Next, the control device 50 proceeds to step S6, performs a second defrosting operation using the circuit configuration for cooling operation, i.e., a reverse defrosting operation, and terminates the process after a predetermined time has elapsed, for example. This allows defrosting operations to be performed in both the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21.

[0056] Here, the required defrosting capacity can be calculated by incorporating the relationship between the capacity decrease during defrosting and the amount of frost as an equation into the control device 50 in advance, using, for example, machine learning. The capacity decrease during defrosting refers to a decrease in the density of the refrigerant drawn into the compressor 10. Therefore, if the pressure of the refrigerant decreases due to frost when the first heat source side heat exchanger 20 is functioning as an evaporator, the amount of frost can be calculated from the rate of pressure decrease. Note that the calculation of the amount of frost based on the rate of pressure decrease is based on experiments or empirical rules.

[0057] If the pressure of the refrigerant downstream of the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 can be detected, the amount of frost formed in the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21 can be calculated from the rate of pressure drop. If the amount of frost formed can be calculated, the capacity decrease during defrosting can be calculated, and the required defrosting capacity can be calculated. Furthermore, the defrosting capacity by air heat extraction, which is heat extraction from the air, can be calculated based on, for example, the outside air temperature, the water temperature, and the frequency of the compressor 10 during defrosting operation.

[0058] <Refrigeration Cycle System> Fig. 8 is a circuit configuration diagram of a refrigeration cycle system using the refrigeration cycle apparatus 100 according to the first embodiment. As shown in Fig. 8, the refrigeration cycle system includes a first refrigeration cycle apparatus 100A and a second refrigeration cycle apparatus 100B. The first refrigeration cycle apparatus 100A and the second refrigeration cycle apparatus 100B each include a second expansion valve 44 between the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21, and a bypass circuit BP connected to an on-off valve 42. The first refrigeration cycle apparatus 100A and the second refrigeration cycle apparatus 100B are configured such that their respective utilization side heat exchangers 12 are connected to the same water circuit W. Fig. 8 illustrates an example in which the first refrigeration cycle apparatus 100A, which is located upstream, is performing a heating operation, and the second refrigeration cycle apparatus 100B, which is located downstream, is performing a first defrosting operation.

[0059] 9 is a graph showing the change in water temperature in the refrigeration cycle system using the refrigeration cycle apparatus 100 according to embodiment 1, with the horizontal axis representing the position from the inlet to the outlet in the water circuit W and the vertical axis representing the water temperature. In Fig. 9, the dotted line represents the change in water temperature when it is assumed that the second refrigeration cycle apparatus 100B on the downstream side is operating in heating mode.

[0060] 9 , the water temperature increases toward the downstream side in the water circuit W, i.e., in the first refrigeration cycle apparatus 100A. In the upstream first refrigeration cycle apparatus 100A, high-temperature refrigerant flows into the user-side heat exchanger 12 during heating operation, heating the water circuit W and producing hot water. Furthermore, a constant water temperature is maintained downstream, i.e., in the second refrigeration cycle apparatus 100B. In the downstream second refrigeration cycle apparatus 100B, refrigerant is not flowing through the user-side heat exchanger 12 during the first defrosting operation, and therefore the water circuit W is neither heated nor cooled, resulting in no temperature change.

[0061] <Comparative Example> Fig. 10 is a circuit configuration diagram of a refrigeration cycle system using a refrigeration cycle apparatus 100 according to a comparative example. As shown in Fig. 10, the refrigeration cycle system includes a first refrigeration cycle apparatus 100A and a second refrigeration cycle apparatus 100B.

[0062] The first refrigeration cycle apparatus 100A and the second refrigeration cycle apparatus 100B according to the comparative example each include a first heat source side heat exchanger 20 and are connected to the same water circuit W. The first refrigeration cycle apparatus 100A, which is located upstream, performs heating operation, and the second refrigeration cycle apparatus 100B, which is located downstream, performs reverse defrosting operation.

[0063] Fig. 11 is a graph showing the change in water temperature in a refrigeration cycle system using the refrigeration cycle apparatus 100 according to the comparative example, with the horizontal axis representing the position from the inlet to the outlet in the water circuit W and the vertical axis representing the water temperature. In Fig. 11, the dotted line represents the change in water temperature assuming that the downstream second refrigeration cycle apparatus 100B is in heating operation. As shown in Fig. 11, in the upstream side of the water circuit W, i.e., in the first refrigeration cycle apparatus 100A, the water temperature increases downstream.

[0064] In the upstream first refrigeration cycle apparatus 100A, high-temperature refrigerant flows into the utilization-side heat exchanger 12 during heating operation, heating the water in the water circuit W and producing hot water. Meanwhile, downstream, i.e., in the second refrigeration cycle apparatus 100B, the water temperature decreases downstream. In the downstream second refrigeration cycle apparatus 100B, a reverse defrosting operation is performed by configuring a cooling circuit, and the refrigerant flowing through the utilization-side heat exchanger 12 absorbs heat from the water in the water circuit W and cools the water in the water circuit W.

[0065] In the comparative example, the water flowing out of the refrigeration cycle system is heated by the heating operation, but is cooled again by the reverse dehumidification performed by the cooling circuit, causing the temperature to drop.

[0066] In contrast, in the refrigeration cycle system using the refrigeration cycle apparatus 100 according to embodiment 1, the first defrosting operation or the second defrosting operation is selected and performed according to the required defrosting capacity, so that frost can be melted without causing a decrease in temperature in the water circuit W. Furthermore, because the first defrosting operation or the second defrosting operation is selected and performed according to the required defrosting capacity, the water flowing through the water circuit W of the use-side heat exchanger 12 is cooled, and the possibility of the water freezing can be reduced.

[0067] <Modification> Fig. 12 is a circuit configuration diagram of a refrigeration cycle apparatus 100 according to a modification of Embodiment 1. In Fig. 12, the solid lines around the four-way valve 11 indicate the circuit configuration during cooling operation, and the dashed lines around the four-way valve 11 indicate the circuit configuration during heating operation. As shown in Fig. 12, the refrigeration cycle apparatus 100 may include a second on-off valve 43. The second on-off valve 43 is connected to a bypass circuit BP that connects the third connection point 3 and the fourth connection point 4. The third connection point 3 is located on the discharge side of the compressor 10, and the fourth connection point 4 is located between the second connection point 2 and the second heat source side heat exchanger 21.

[0068] In cooling operation, the control device 50 closes the on-off valve 42 and the second on-off valve 43 and fully opens the second expansion valve 44. The refrigerant discharged from the compressor 10 passes through the high-pressure side of the four-way valve 11 and passes in series through the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21, where it is condensed, reduced in pressure by the first expansion valve 41, evaporated in the user side heat exchanger 12, and then drawn into the compressor 10.

[0069] In the heating operation, the control device 50 closes the on-off valve 42 and the second on-off valve 43 and fully opens the expansion valve D. The refrigerant discharged from the compressor 10 passes through the high-pressure side of the four-way valve 11, condenses in the user-side heat exchanger 12, evaporates through the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21, and is drawn into the compressor 10.

[0070] In the third defrosting operation, the control device 50 maintains the four-way valve 11 in the orientation it has during heating operation, closes the first expansion valve 41 and the on-off valve 42, and opens the second on-off valve 43. The refrigerant discharged from the compressor 10 passes through the second on-off valve 43 and condenses in the second heat source-side heat exchanger 21. The condensed refrigerant is decompressed by the second expansion valve 44, evaporates in the first heat source-side heat exchanger 20, and is drawn into the compressor 10. At this time, the fan 30 of the heat source-side unit 101 operates at a low airflow rate. In the third defrosting operation, the four-way valve 11 is not switched, thereby shortening the overall defrosting time. Furthermore, because high-temperature refrigerant flows into the second heat source-side heat exchanger 21 out of the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21, this operation is particularly effective when defrosting the second heat source-side heat exchanger 21.

[0071] The first defrosting operation can be performed by the control device 50 switching the four-way valve 11 to the direction for cooling operation and closing the first expansion valve 41 and the second on-off valve 43. The refrigerant discharged from the compressor 10 passes through the high-pressure side of the four-way valve 11 and condenses in the first heat source-side heat exchanger 20. The condensed refrigerant is decompressed by the second expansion valve 44, evaporates in the second heat source-side heat exchanger 21, and is drawn into the compressor 10 through the on-off valve 42. The fan 30 of the heat source-side unit 101 is operated at a low airflow rate.

[0072] Furthermore, the second defrosting operation can be performed by the control device 50 switching the four-way valve 11 to the orientation for cooling operation, closing both the on-off valve 42 and the second on-off valve 43, and fully opening the second expansion valve 44. The refrigerant discharged from the compressor 10 passes through the high-pressure side of the four-way valve 11 and condenses in the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21. The condensed refrigerant is decompressed by the first expansion valve 41, evaporates in the user side heat exchanger 12, and is drawn into the compressor 10.

[0073] According to the refrigeration cycle apparatus 100 of the first embodiment described above, during the first defrosting operation, the bypass circuit BP forms a refrigerant circuit in which frost is melted in the first heat source-side heat exchanger 20 and heat is collected in the second heat source-side heat exchanger 21. Therefore, the refrigerant circuit is formed with the first heat source-side heat exchanger 20 functioning as a condenser and the second heat source-side heat exchanger 21 functioning as an evaporator. Because refrigerant does not flow through the use-side heat exchanger 12, heat exchange is not performed, and a decrease in water temperature during the defrosting operation is suppressed. Furthermore, because heat exchange is not performed in the use-side heat exchanger 12, the possibility of freezing due to a decrease in water temperature or damage to the use-side heat exchanger 12 due to freezing can be reduced. Furthermore, the first defrosting operation can be performed by adding one on-off valve 42 and one second expansion valve 44, thereby achieving a simple, low-cost configuration that can suppress a decrease in water temperature.

[0074] Furthermore, when a defrosting capacity higher than that required during the first defrosting operation is required, the second defrosting operation is performed by the cooling circuit. In this way, whether the first defrosting operation or the second defrosting operation is performed is determined depending on the required defrosting capacity, so that the decrease in water temperature during the defrosting operation can be reduced and freezing of the user-side heat exchanger 12 can be suppressed.

[0075] Furthermore, the control device 50 performs either the first defrosting operation or the second defrosting operation by controlling the on-off valve 42 depending on whether defrosting of the first heat source side heat exchanger 20 is possible with the heat collection amount by the second heat source side heat exchanger 21. As a result, the first defrosting operation can be performed if defrosting is possible with the heat collection amount of the second heat source side heat exchanger 21, thereby reducing the time required for the second defrosting operation per life cycle and preventing water from being cooled and freezing.

[0076] In addition, the control device 50 configures the air conditioning circuit and performs the second defrosting operation only when the amount of heat collected by the second heat source side heat exchanger 21 is insufficient, thereby minimizing the drop in water temperature during the defrosting operation.

[0077] Embodiment 2. Fig. 13 is a circuit configuration diagram of a refrigeration cycle apparatus 100 according to embodiment 2, showing the circuit configuration during cooling operation. Embodiment 2 differs from embodiment 1 in that it includes a six-way valve 13. In embodiment 2, parts common to embodiment 1 are assigned the same reference numerals and description thereof will be omitted, and the description will focus on the differences from embodiment 1.

[0078] 13 , the refrigeration cycle apparatus 100 includes a six-way valve 13 connected to a main circuit M and a bypass circuit BP. Specifically, five of the six ports of the six-way valve 13 are connected to the first heat source-side heat exchanger 20, the second heat source-side heat exchanger 21, the first expansion valve 41, the user-side heat exchanger 12, and the bypass circuit BP, respectively. One port of the six-way valve 13 is closed and connected to a closed circuit through which refrigerant does not flow. The bypass circuit BP is connected to the six-way valve 13 at a second connection point 2.

[0079] During cooling operation, the control device 50 controls to adjust the opening degree of the first expansion valve 41. The control device 50 switches the four-way valve 11 so that the first heat source side heat exchanger 20 is connected to the high-pressure side of the compressor 10. In the following, for convenience, the state of the four-way valve 11 during cooling operation will be referred to as the OFF state. The control device 50 switches the six-way valve 13 so that the first expansion valve 41 is connected to the user side heat exchanger 12, the first heat source side heat exchanger 20 is connected to the second heat source side heat exchanger 21, and the bypass circuit BP is connected to the closed circuit. In the following, the state in which the bypass circuit BP is connected to the closed circuit will be referred to as the OFF state.

[0080] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the first heat source-side heat exchanger 20 and flows into the second heat source-side heat exchanger 21 via the six-way valve 13. In the second heat source-side heat exchanger 21, the refrigerant further exchanges heat with air, condenses, and flows out of the second heat source-side heat exchanger 21. The refrigerant flowing out of the second heat source-side heat exchanger 21 is decompressed in the first expansion valve 41 to become a two-phase refrigerant, flows into the user-side heat exchanger 12 via the six-way valve 13, exchanges heat with water in the water circuit W, which serves as a secondary-side medium, and evaporates, flowing out as a low-temperature, low-pressure refrigerant. The refrigerant flowing out of the user-side heat exchanger 12 passes through the four-way valve 11 and returns to the compressor 10. In the user-side heat exchanger 12, the refrigerant absorbs heat from the water in the water circuit W, cooling the water and producing chilled water.

[0081] <Heating operation> Fig. 14 is a circuit configuration diagram during heating operation of the refrigeration cycle apparatus 100 according to embodiment 2. As shown in Fig. 14, during heating operation of the refrigeration cycle apparatus 100, the control device 50 configures a heating circuit such that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M.

[0082] The control device 50 switches the four-way valve 11 so that the utilization-side heat exchanger 12 is connected to the high-pressure side of the compressor 10. In the following description, for convenience, the state of the four-way valve 11 during heating operation will be referred to as the ON state. The control device 50 switches the six-way valve 13 so that the utilization-side heat exchanger 12 is connected to the first expansion valve 41, the first heat source-side heat exchanger 20 is connected to the second heat source-side heat exchanger 21, and the bypass circuit BP is connected to the closed circuit.

[0083] The high-temperature, high-pressure refrigerant discharged from the compressor 10 flows into the user-side heat exchanger 12, where it exchanges heat with the water in the water circuit W, condenses, and flows out of the user-side heat exchanger 12. In the user-side heat exchanger 12, the refrigerant dissipates heat to the water in the water circuit W, heating the water and generating hot water.

[0084] The refrigerant flowing out of the user-side heat exchanger 12 passes through the six-way valve 13 and reaches the first expansion valve 41, where it is decompressed before flowing into the second heat source-side heat exchanger 21 and then through the six-way valve 13 into the first heat source-side heat exchanger 20. As the refrigerant passes through the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21, it exchanges heat with air and evaporates, becoming a low-temperature, low-pressure refrigerant. The low-temperature, low-pressure refrigerant flows out of the first heat source-side heat exchanger 20, passes through the four-way valve 11, and returns to the compressor 10.

[0085] <First defrosting operation> Fig. 15 is a circuit configuration diagram during the first defrosting operation of the refrigeration cycle apparatus 100 according to Embodiment 2. As shown in Fig. 15, during the first defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures a first defrosting circuit such that the high-temperature, high-pressure refrigerant discharged from the compressor 10 flows into the first heat source side heat exchanger 20.

[0086] The control device 50 switches the four-way valve 11 so that the first heat source side heat exchanger 20 is connected to the high-pressure side of the compressor 10. The control device 50 switches the six-way valve 13 so that the first heat source side heat exchanger 20 is connected to the first expansion valve 41, the second heat source side heat exchanger 21 is connected to the low-pressure side of the compressor 10, and the circuit connected to the user side heat exchanger 12 is connected to the closed circuit. In the following description, the state in which the circuit connected to the user side heat exchanger 12 is connected to the closed circuit will be referred to as the ON state.

[0087] During the first defrosting operation, the high-temperature, high-pressure refrigerant discharged from the compressor 10 flows through the four-way valve 11 into the first heat source side heat exchanger 20, and dissipates heat in the first heat source side heat exchanger 20, thereby melting the frost that has adhered to the first heat source side heat exchanger 20. After flowing out of the first heat source side heat exchanger 20, the refrigerant is decompressed by the first expansion valve 41 to become low-pressure refrigerant, and flows into the second heat source side heat exchanger 21 via the six-way valve 13.

[0088] The refrigerant evaporates in the second heat source-side heat exchanger 21, extracts heat from the air surrounding the second heat source-side heat exchanger 21, and is vaporized into a low-temperature, low-pressure state, which flows into the bypass circuit BP via the six-way valve 13. The refrigerant flows from the bypass circuit BP to the first connection point 1, merges with the main circuit M on the suction side of the compressor 10, and flows back into the compressor 10.

[0089] <Second defrosting operation> Fig. 16 is a circuit configuration diagram during the second defrosting operation of the refrigeration cycle apparatus 100 according to Embodiment 2. As shown in Fig. 16, during the second defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures a second defrosting circuit such that the high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M. In other words, during the second defrosting operation, a second defrosting circuit having the same circuit configuration as the cooling circuit shown in Fig. 13 is formed.

[0090] The control device 50 switches the four-way valve 11 so that the first heat source side heat exchanger 20 is connected to the high-pressure side of the compressor 10. The control device 50 switches the six-way valve 13 so that the first heat source side heat exchanger 20 is connected to the first expansion valve 41, the second heat source side heat exchanger 21 is connected to the constant-pressure side of the compressor 10, and the circuit connecting to the user side heat exchanger 12 is closed.

[0091] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the first heat source-side heat exchanger 20, flows into the second heat source-side heat exchanger 21 via the six-way valve 13, and further exchanges heat with air in the second heat source-side heat exchanger 21, condensing, and then flows out of the second heat source-side heat exchanger 21. The high-temperature refrigerant that has flowed into the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21 melts the frost that has adhered to the first heat source-side heat exchanger 20 and the second heat source-side heat exchanger 21.

[0092] The refrigerant flows out of the second heat source-side heat exchanger 21, passes through the six-way valve 13, and reaches the first expansion valve 41. The refrigerant is reduced in pressure in the first expansion valve 41 to become a two-phase refrigerant, passes through the six-way valve 13, and reaches the user-side heat exchanger 12, where it absorbs heat from water, evaporates, and flows out. The refrigerant flowing out of the user-side heat exchanger 12 returns to the compressor 10 via the four-way valve 11. By performing the second defrosting operation, even when the second heat source-side heat exchanger 21 cannot extract enough heat to melt the frost adhering to the first heat source-side heat exchanger 20, it is possible to defrost the first heat source-side heat exchanger 20 and melt the frost adhering to the second heat source-side heat exchanger 21.

[0093] In this way, by using the six-way valve 13, it is possible to switch the refrigerant circuit so that it can perform the first defrosting operation and the second defrosting operation in addition to the heating operation and the cooling operation, as in Embodiment 1. Furthermore, by using the six-way valve 13, it is possible to share the first expansion valve 41 and the second expansion valve 44, and the six-way valve 13 can function as the on-off valve 42, thereby eliminating the on-off valve 42. Therefore, the number of connection terminals in the refrigeration cycle apparatus 100 is reduced, and the refrigeration cycle apparatus 100 capable of performing the first defrosting operation and the second defrosting operation can be realized at low cost.

[0094] <Flowchart> Fig. 17 is a flowchart illustrating processing by the control device 50 of the refrigeration cycle apparatus 100 according to Embodiment 2. As shown in Fig. 17 , when frost has formed on the heat source side unit 101, the control device 50 determines whether to perform the first defrosting operation or the second defrosting operation, as in Embodiment 1, and performs one of the operations.

[0095] When a defrosting operation is performed in the heat source side unit 101, the control device 50 starts the process and, in step S10, estimates the required defrosting capacity and the maximum heat quantity of the air, as in embodiment 1. The required defrosting capacity and the amount of heat collected from the air are calculated and estimated by computation.

[0096] Next, in step S11, the control device 50 determines whether the required defrosting capacity can be achieved by extracting heat from the air, and if it is determined that the required defrosting capacity can be achieved (YES in step S11), the control device 50 proceeds to step S12. In step S12, the control device 50 turns the six-way valve 13 ON and the four-way valve 11 OFF. That is, the four-way valve 11 switches the high-pressure side of the compressor 10 to a state connected to the first heat source-side heat exchanger 20, and the six-way valve 13 connects the first heat source-side heat exchanger 20 to the first expansion valve 41, and the second heat source-side heat exchanger 21 to the bypass circuit BP.

[0097] Next, the control device 50 proceeds to step S14, performs the first defrosting operation, and terminates the process after a predetermined time has elapsed, for example. As a result, the first heat source side heat exchanger 20 is defrosted preferentially over the second heat source side heat exchanger 21.

[0098] If the control device 50 determines in step S11 that the required defrosting capacity cannot be achieved by extracting heat from the air (NO in step S11), the control device 50 proceeds to step S13. In step S13, the control device 50 switches the four-way valve 11 to the OFF state during cooling operation, that is, the state in which the high-pressure side of the compressor 10 is connected to the first heat source-side heat exchanger 20.

[0099] Next, the control device 50 proceeds to step S15, performs the second defrosting operation using the circuit configuration during cooling operation, that is, the reverse defrosting operation, and ends the process after a predetermined time has elapsed, for example.

[0100] In this way, even when the six-way valve 13 is used, the first defrosting operation and the second defrosting operation can be selectively performed, thereby suppressing the drop in water temperature during the defrosting operation and suppressing the increase in the discharge pressure of the compressor 10.

[0101] The refrigeration cycle apparatus 100 according to the first embodiment described above includes the six-way valve 13, and does not include the on-off valve 42 and the second expansion valve 44. This reduces the number of connection terminals in the refrigeration cycle apparatus 100, and makes it possible to realize the refrigeration cycle apparatus 100 capable of performing the first defrosting operation and the second defrosting operation at low cost.

[0102] 1 First connection point, 2 Second connection point, 3 Third connection point, 4 Fourth connection point, 10 Compressor, 11 Four-way valve, 12 Use side heat exchanger, 13 Six-way valve, 20 First heat source side heat exchanger, 21 Second heat source side heat exchanger, 30 Fan, 41 First expansion valve, 42 On-off valve, 43 Second on-off valve, 44 Second expansion valve, 50 Control device, 100 Refrigeration cycle device, 100A First refrigeration cycle device, 100B Second refrigeration cycle device, 101 Heat source side unit, 101a Housing, 102 Use side unit, 103 Refrigerant piping.

Claims

1. A heating circuit is provided, comprising: a main circuit having a compressor, a four-way valve, a first heat source side heat exchanger, a first expansion valve, a second heat source side heat exchanger, a second expansion valve, and a load side heat exchanger; and a bypass circuit connecting the suction side of the compressor and a connection point between the second heat source side heat exchanger and the second expansion valve, wherein during heating operation, the refrigerant compressed by the compressor and discharged flows through the four-way valve, the load side heat exchanger, the first expansion valve, the second heat source side heat exchanger, and the first heat source side heat exchanger in this order, and returns to the compressor again via the four-way valve; and during cooling operation, a cooling circuit is configured in which the refrigerant compressed by the compressor and discharged flows through the four-way valve, the first heat source side heat exchanger, the second heat source side heat exchanger, the first expansion valve, and the load side heat exchanger in this order, and returns to the compressor again via the four-way valve; and during a first defrosting operation, a first defrosting circuit is configured in which the refrigerant compressed by the compressor and discharged flows through the four-way valve, the first heat source side heat exchanger, the second expansion valve, and the second heat source side heat exchanger in this order, and returns to the compressor again via the bypass circuit.

2. The refrigeration cycle device according to claim 1, wherein a second defrosting operation is performed that requires a higher defrosting capacity than that required during the first defrosting operation, and the cooling circuit is configured during the second defrosting operation.

3. A refrigeration cycle apparatus according to claim 1 or 2, further comprising: an on-off valve provided in the bypass circuit; and a control device that controls the on-off valve, wherein the control device calculates a required defrosting capacity and an amount of heat collected by the second heat source side heat exchanger, and controls the on-off valve based on a comparison between the required defrosting capacity and the amount of heat collected.

4. The refrigeration cycle device according to claim 3, wherein the control device controls the on-off valve to open when the required defrosting capacity is smaller than the amount of heat collected by the second heat source side heat exchanger, and controls the on-off valve to close when the required defrosting capacity is equal to or greater than the amount of heat collected by the second heat source side heat exchanger, thereby configuring the cooling circuit.

5. A refrigeration cycle device according to claim 3 or 4, further comprising a six-way valve instead of the first expansion valve and the second expansion valve, the six-way valve being connected to the main circuit and the bypass circuit.

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