Refrigeration cycle device

Abstract

This refrigeration cycle device comprises: a main circuit in which a compressor, a four-way valve, a first heat source-side heat exchanger, a first on-off valve, a second heat source-side heat exchanger, a first expansion valve, and a load-side heat exchanger are connected in this order by refrigerant piping; a first bypass circuit that connects a first connection point on the discharge side of the compressor in the main circuit and a second connection point between the first heat source-side heat exchanger and the first on-off valve in the main circuit, and to which a second on-off valve is connected; and a second bypass circuit that has a second expansion valve connected thereto and connects a third connection point between the first heat source-side heat exchanger and the first expansion valve in the main circuit and a fourth connection point between the first on-off valve and the second heat source-side heat exchanger in the main circuit. The first heat source-side heat exchanger and the second heat source-side heat exchanger are housed in a housing of a heat source-side unit such that the first heat source-side heat exchanger is disposed further outward than the second heat source-side heat exchanger. Simultaneous heating and defrosting operation is performed in which one portion of refrigerant that is compressed by the compressor and discharged flows into the load-side heat exchanger via the four-way valve and circulates through the main circuit, another portion of the refrigerant compressed by the compressor and discharged flows through the first bypass circuit and the first heat source-side heat exchanger and merges with the one portion of the refrigerant in the second bypass circuit, and the result returns to the compressor via the second heat source-side heat exchanger.

Description

Refrigeration Cycle Equipment

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

[0002] In a refrigeration cycle apparatus using an air heat exchanger as an outdoor unit, when the outdoor air temperature drops, the temperatures of the fins and refrigerant drop, causing water in the air to freeze and 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. For example, Patent Document 1 discloses a defrosting operation in which a four-way valve is switched to perform cooling operation using the air heat exchanger as a condenser, thereby flowing high-pressure refrigerant through the air heat exchanger and melting the frost on the air heat exchanger.

[0003] Patent No. 6377259

[0004] As in Patent Document 1, defrosting operation during cooling operation requires switching the four-way valve from heating operation, which lengthens the overall time required for defrosting operation. In defrosting operation, if there are multiple heat exchangers on the heat source side, all but the heat exchangers located on the outside are not exposed to low-temperature outside air, and it is possible that frost will not form. However, since defrosting operation is performed simultaneously on all heat exchangers regardless of their locations, there is a possibility that defrosting operation will be ineffective. Furthermore, in defrosting operation during cooling operation, for example, the water heat exchanger on the user side removes heat from the water to warm the air heat exchanger, which temporarily reduces the water temperature on the user side.

[0005] An object of the present disclosure is to provide a refrigeration cycle device that can suppress a decrease in water temperature while defrosting a heat exchanger that is prone to frost formation.

[0006] The refrigeration cycle device according to the present disclosure includes a main circuit in which a compressor, a four-way valve, a first heat source side heat exchanger, a first on-off valve, a second heat source side heat exchanger, a first expansion valve, and a load side heat exchanger are connected in this order by refrigerant piping, a first connection point on the discharge side of the compressor in the main circuit, and a second connection point between the first heat source side heat exchanger and the first on-off valve in the main circuit, and a first bypass circuit to which a second on-off valve is connected, and a third connection point between the first heat source side heat exchanger and the first expansion valve in the main circuit, and a fourth connection point between the first on-off valve and the second heat source side heat exchanger in the main circuit, and a second expansion valve is connected. and a second bypass circuit, wherein the first heat source side heat exchanger and the second heat source side heat exchanger are housed in a housing of a heat source side unit such that the first heat source side heat exchanger is positioned outside the second heat source side heat exchanger, and a portion of the refrigerant compressed by the compressor and discharged flows into the load side heat exchanger via the four-way valve and circulates through the main circuit, and the other portion of the refrigerant compressed by the compressor and discharged flows through the first bypass circuit and the first heat source side heat exchanger, joins with the portion of the refrigerant in the second bypass circuit, passes through the second heat source side heat exchanger, and returns to the compressor, thereby performing simultaneous heating and defrosting operation.

[0007] According to the refrigeration cycle device of the present disclosure, during simultaneous heating and defrosting operation, the first heat source side heat exchanger, which is particularly prone to frost formation, can be made to function as a condenser to defrost, while the user side heat exchanger can be made to function as a condenser to suppress a drop in water temperature.

[0008] Fig. 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 simultaneous heating and defrosting operation. Fig. 6 is a flow chart illustrating processing by a control device of the refrigeration cycle device according to embodiment 1.

[0009] 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.

[0010] 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, a first bypass circuit BP1, and a second bypass circuit BP2, 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.

[0011] 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.

[0012] 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 user side unit 102 is, for example, a heat exchanger that cools or heats indoor air using cold water or hot water. The user side unit 102 may also be, for example, a radiator that heats by circulating hot water.

[0013] <Configuration of Refrigerant Circuit> In the refrigeration cycle apparatus 100, each component is connected by a refrigerant pipe 100A to form a refrigerant circuit. 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, a first on-off valve 42, a second on-off valve 43, and a second expansion valve 44. The user side heat exchanger 12 is an example of a load side heat exchanger.

[0014] 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 on-off valve 42, the second on-off valve 43, and the second expansion valve 44 are housed in the heat source side unit 101. The user side heat exchanger 12, together with the first expansion valve 41, is housed in the user side unit 102.

[0015] 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 heat source-side unit 101 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.

[0016] <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.

[0017] <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.

[0018] <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 a refrigerant and water. 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. The use-side heat exchanger 12 is, for example, a plate heat exchanger made of multiple stacked thin copper plates.

[0019] <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.

[0020] <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.

[0021] <First On-Off Valve 42 and Second On-Off Valve 43> The first on-off valve 42 and the second on-off valve 43 may be configured to be openable and closable, and may be, for example, a solenoid valve.

[0022] <Main Circuit M> The main circuit M is composed of a compressor 10, a four-way valve 11, a first heat source side heat exchanger 20, a first on-off valve 42, a second heat source side heat exchanger 21, a first expansion valve 41, and a 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 first on-off valve 42, 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 100A. 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 first on-off valve 42 is disposed between the first heat source side heat exchanger 20 and the second heat source side heat exchanger 21.

[0023] <First Bypass Circuit BP1> The first bypass circuit BP1 is configured by connecting a first connection point 1 and a second connection point 2 of the main circuit M by a refrigerant pipe 100A. The first connection point 1 is located on the discharge side of the compressor 10, and the second connection point 2 is located between the first heat source side heat exchanger 20 and the first on-off valve 42. A second on-off valve 43 is connected to the first bypass circuit BP1.

[0024] <Second Bypass Circuit BP2> The second bypass circuit BP2 is configured by connecting a third connection point 3 and a fourth connection point 4 of the main circuit M by a refrigerant pipe 100A. The third connection point 3 is located between the first heat source side heat exchanger 20 and the first expansion valve 41, and the fourth connection point 4 is located between the first on-off valve 42 and the second heat source side heat exchanger 21. A second expansion valve 44 is connected to the second bypass circuit BP2.

[0025] <Control device 50> 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.

[0026] 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 operations of the first on-off valve 42 and the second on-off valve 43. 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.

[0027] 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.

[0028] <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 the circuit so that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M.

[0029] The control device 50 controls each so that the first on-off valve 42 is open, the second on-off valve 43 is closed, the first expansion valve 41 is open, and the second expansion valve 44 is closed. The control device 50 switches the four-way valve 11 so that the second heat source side heat exchanger 21 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 cooling operation will be referred to as OFF.

[0030] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the second heat source-side heat exchanger 21, passes through the first on-off valve 42, and further exchanges heat with air in the first heat source-side heat exchanger 20, condenses, and flows out of the first heat source-side heat exchanger 20. The refrigerant flowing out of the first heat source-side heat exchanger 20 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 as a secondary 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, cooling the water and generating chilled water. During cooling 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.

[0031] <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 the circuit so that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M, similar to during cooling.

[0032] The control device 50 controls the first on-off valve 42 to be open, the second on-off valve 43 to be closed, the first expansion valve 41 to be open, and the second expansion valve 44 to be closed, as in cooling mode. The control device 50 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 mode will be referred to as ON.

[0033] The high-temperature, high-pressure refrigerant discharged from the compressor 10 flows into the user-side heat exchanger 12, where it exchanges heat with water, condenses, and flows out of the user-side heat exchanger 12. In the user-side heat exchanger 12, the refrigerant releases heat to the water, heating the water and generating hot water.

[0034] The refrigerant flowing out of the user-side heat exchanger 12 is decompressed in the first expansion valve 41, flows into the first heat-source-side heat exchanger 20, passes through the first on-off valve 42, and flows into the second heat-source-side heat exchanger 21. 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 second heat-source-side heat exchanger 21, 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.

[0035] <Simultaneous heating and defrosting operation> Fig. 5 is a circuit configuration diagram of the refrigeration cycle apparatus 100 according to Embodiment 1 during simultaneous heating and defrosting operation. As shown in Fig. 5, in simultaneous heating and defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures the circuit so that high-temperature, high-pressure refrigerant discharged from the compressor 10 passes through the first bypass circuit BP1 and the second bypass circuit BP2. The simultaneous heating and defrosting operation is an operating mode in which defrosting is performed in the first heat source side heat exchanger 20 while heating operation in the use side heat exchanger 12 is continued.

[0036] The control device 50 keeps the first on-off valve 42 closed, the second on-off valve 43 open, and the first expansion valve 41 open, and adjusts the opening degree of the second expansion valve 44. The control device 50 keeps the orientation of the four-way valve 11 in the heating operation state, in which the utilization side heat exchanger 12 is connected to the high pressure side of the compressor 10, i.e., in the ON state.

[0037] During simultaneous heating and defrosting operation, the high-temperature, high-pressure refrigerant discharged from the compressor 10 is branched at the first connection point 1 before reaching the four-way valve 11, with one portion flowing through the main circuit M and the other portion flowing into the first bypass circuit BP1. As in heating operation, the portion of the refrigerant flowing through the main circuit M reaches the user-side heat exchanger 12, exchanges heat there, flows out of the user-side heat exchanger 12, passes through the opened first expansion valve 41, and reaches the third connection point 3. The portion of the refrigerant dissipates heat to water in the user-side heat exchanger 12, thereby heating the water and contributing to the production of hot water.

[0038] The other portion of the refrigerant that has flowed into the first bypass circuit BP1 passes through the second on-off valve 43 and reaches the second connection point 2. The other portion of the refrigerant flows into the first heat source side heat exchanger 20 via the second connection point 2, undergoes heat exchange in the first heat source side heat exchanger 20, and then flows out. The other portion of the refrigerant dissipates heat in the first heat source side heat exchanger 20, 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 other portion of the refrigerant reaches the third connection point 3 and merges with the portion of the refrigerant that has passed through the first expansion valve 41 of the main circuit M.

[0039] The refrigerant that joins at the third connection point 3 is decompressed by the second expansion valve 44 of the second bypass circuit BP2, becomes low-pressure refrigerant, passes through the fourth connection point 4, and returns to the main circuit M. The refrigerant that has returned to the main circuit M evaporates by exchanging heat with air in the second heat source side heat exchanger 21, becomes low-temperature, low-pressure refrigerant, passes through the low-pressure side of the four-way valve 11, and returns to 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 receives air before it flows into the second heat source-side heat exchanger 21. Therefore, 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. During simultaneous heating and defrosting operation, the user-side heat exchanger 12 and the first heat source-side heat exchanger 20 function as condensers, and the second heat source-side heat exchanger 21 functions as an evaporator. Heat is extracted from the outdoor air using the second heat source-side heat exchanger 21, which is not frosted, and allocated to defrosting. Therefore, by performing simultaneous heating and defrosting operation, it is possible to defrost the first heat source-side heat exchanger 20 while continuing heating operation using the user-side heat exchanger 12, and a decrease in water temperature during defrosting operation is suppressed.

[0041] Furthermore, because the simultaneous heating and defrosting operation can be performed without changing the orientation of the four-way valve 11 during heating operation, the time required for switching the four-way valve 11, which does not contribute to defrosting, can be reduced, thereby shortening the overall time required for defrosting. Furthermore, by performing the defrosting operation only on the first heat source side heat exchanger 20, which is particularly susceptible to frost formation, it is possible to suppress frost formation throughout the heat source side unit 101.

[0042] Increasing the flow rate of the other refrigerant in the first bypass circuit BP1 increases the defrosting capacity in the first heat source side heat exchanger 20, thereby shortening the time required to complete defrosting. Furthermore, if the flow rate of the other refrigerant flowing into the first bypass circuit BP1 is small compared to the flow rate of the portion of the refrigerant circulating in the main circuit M, it is possible to suppress a decrease in the water temperature in the user side heat exchanger 12. Furthermore, during simultaneous heating and defrosting operation, the fan 30 may be operated at a low speed.

[0043] The control device 50 may, for example, control the aperture of the second expansion valve 44 so that the degree of superheat of the refrigerant drawn into the compressor 10 is a target value that prevents liquid refrigerant from returning to the compressor 10. The control device 50 may, for example, control the aperture of the second expansion valve 44 to a value determined in advance through testing. When the aperture of the second expansion valve 44 is reduced, the evaporation temperature of the refrigerant decreases and the dryness of the refrigerant flowing into the second heat source side heat exchanger 21 increases. By bringing the refrigerant flowing into the second heat source side heat exchanger 21 closer to a heated state, the amount of frost formation in the second heat source side heat exchanger 21 can be reduced.

[0044] <Defrosting operation> Fig. 6 is a circuit configuration diagram during defrosting operation of the refrigeration cycle apparatus 100 according to Embodiment 1. As shown in Fig. 6, during defrosting operation of the refrigeration cycle apparatus 100, the control device 50 configures the circuit so that high-temperature, high-pressure refrigerant discharged from the compressor 10 circulates through the main circuit M.

[0045] The control device 50 controls each so that the first on-off valve 42 is open, the second on-off valve 43 is closed, the first expansion valve 41 is open, and the second expansion valve 44 is closed. The control device 50 switches the four-way valve 11 to the OFF state so that the second heat source side heat exchanger 21 is connected to the high pressure side of the compressor 10. In other words, the circuit configuration during defrosting operation is the same as the circuit configuration during cooling operation, and reverse defrosting operation is performed.

[0046] The high-temperature, high-pressure refrigerant discharged from the compressor 10 exchanges heat with air in the second heat source-side heat exchanger 21, passes through the first on-off valve 42, and further exchanges heat with air in the first heat source-side heat exchanger 20, where it condenses and flows out of the first heat source-side heat exchanger 20. The high-temperature refrigerant that has flowed into the second heat source-side heat exchanger 21 and the first heat source-side heat exchanger 20 melts the frost that has adhered to the second heat source-side heat exchanger 21 and the first heat source-side heat exchanger 20.

[0047] The refrigerant flowing out of the first heat source-side heat exchanger 20 is decompressed in the first expansion valve 41 to become two-phase refrigerant, passes through the user-side heat exchanger 12, and returns to the compressor 10 via the four-way valve 11. The defrosting operation can melt frost that has adhered to the second heat source-side heat exchanger 21. Furthermore, by performing the defrosting operation, it is possible to defrost the first heat source-side heat exchanger 20 even when the second heat source-side heat exchanger 21 cannot extract enough heat to melt the frost that has adhered to the first heat source-side heat exchanger 20. Note that during the defrosting operation, the fan 30 is slowed down or stopped, thereby suppressing heat exchange in the heat source-side unit 101 and making it possible to suppress cooling of water due to heat exchange in the user-side heat exchanger 12.

[0048] <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 simultaneous heating and defrosting operation or reverse defrosting operation, and performs one of them.

[0049] When a defrosting operation is performed in the heat source unit 101, the control device 50 determines in step S1 whether the required defrosting capacity can be achieved by collecting heat from the air when the process is started. The required defrosting capacity and the amount of collected heat from the air are calculated.

[0050] If the control device 50 determines in step S1 that the operation is feasible (YES in step S1), the control device 50 proceeds to step S2. In step S2, the control device 50 closes the first on-off valve 42, opens the second on-off valve 43, and maintains the four-way valve 11 in the ON state during heating operation, i.e., the state in which the high-pressure side of the compressor 10 is connected to the utilization-side heat exchanger 12.

[0051] Next, the control device 50 proceeds to step S4, performs simultaneous heating and cooling 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.

[0052] If the control device 50 determines in step S1 that the required defrosting capacity cannot be achieved by extracting heat from the air (NO in step S1), the control device 50 proceeds to step S3. In step S3, 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 second heat source-side heat exchanger 21.

[0053] Next, the control device 50 proceeds to step S5, performs a defrosting operation using the circuit configuration during cooling operation, that is, a reverse defrosting operation, and ends the process after a predetermined time has elapsed, for example.

[0054] 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.

[0055] 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.

[0056] The refrigeration cycle apparatus 100 according to the first embodiment described above performs simultaneous heating and defrosting operation in which high-temperature and high-pressure refrigerant branches, condenses in the user-side heat exchanger 12 and the first heat-source-side heat exchanger 20, merges, evaporates in the second heat-source-side heat exchanger 21, and is drawn into the compressor 10. The high-temperature and high-pressure refrigerant discharged from the compressor 10 flows preferentially into the first heat-source-side heat exchanger 20, which is located outside the housing 101a of the heat-source-side unit 101 and is particularly susceptible to frosting. This allows for efficient defrosting. Furthermore, even during defrosting of the first heat-source-side heat exchanger 20, the user-side heat exchanger 12 continues to function as a condenser, thereby suppressing a decrease in the water temperature in the user-side unit 102. Furthermore, because switching the refrigerant flow direction using the four-way valve 11 is not required, the time spent on defrosting per life cycle is shortened, thereby suppressing impairment of user comfort.

[0057] Furthermore, for example, if the refrigeration cycle apparatus 100 is used as a water heater and is operated with a target water temperature of 45°C, a defrosting operation performed by switching the four-way valve 11, i.e., a reverse defrosting operation, may result in the water temperature dropping below the target water temperature. Therefore, the target water temperature may be increased in advance, for example, to 60°C or 70°C, but this increases the discharge pressure from the compressor 10. If the discharge pressure increases and deviates from the operating range permitted by the compressor 10, the components may be damaged. If the discharge pressure exceeds the designed pressure, the refrigeration cycle apparatus 100 may not be able to be configured. The ability to perform simultaneous heating and defrosting operations reduces the time the defrosting operation is performed per life cycle and reduces the possibility of being affected by an increase in discharge pressure.

[0058] Furthermore, during simultaneous heating and defrosting operation, the control device 50 controls the first on-off valve 42, the second on-off valve 43, and the second expansion valve 44, thereby forming a refrigerant circuit that passes through the first bypass circuit BP1 and the second bypass circuit BP2. This allows high-temperature, high-pressure refrigerant to flow into the first heat source-side heat exchanger 20 for defrosting, while allowing high-temperature, high-pressure refrigerant to flow into the user-side heat exchanger 12 to suppress a decrease in water temperature.

[0059] In addition, simultaneous cooling and defrosting operation is performed by the control device 50 when the amount of heat extracted is greater than the required defrosting capacity, thereby preventing the amount of heat supplied to the first heat source side heat exchanger 20 from being insufficient, making defrosting impossible.

[0060] Furthermore, the control device 50 switches the four-way valve 11 to perform a defrosting operation in which the refrigerant discharged from the compressor 10 flows into the second heat source side heat exchanger 21. This makes it possible to defrost the second heat source side heat exchanger 21 when frost forms on the second heat source side heat exchanger 21. Furthermore, even when the amount of heat collected by the second heat source side heat exchanger 21 is not enough to defrost the first heat source side heat exchanger 20, the defrosting operation makes it possible to defrost the first heat source side heat exchanger 20.

[0061] Furthermore, the control device 50 performs a defrosting operation when the amount of heat collected is equal to or less than the required defrosting capacity. Therefore, even if the required defrosting capacity is equal to or less than the amount of heat collected by the second heat source side heat exchanger 21 and the amount of heat collected by the second heat source side heat exchanger 21 that can be used for defrosting is considered to be insufficient, performing a defrosting operation makes it possible to defrost the first heat source side heat exchanger 20.

[0062] 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, 20 First heat source side heat exchanger, 21 Second heat source side heat exchanger, 30 Fan, 41 First expansion valve, 42 First opening / closing valve, 43 Second opening / closing valve, 44 Second expansion valve, 50 Control device, 100 Refrigeration cycle device, 100A Refrigerant piping, 101 Heat source side unit, 101a Housing, 102 Use side unit.

Claims

1. The main circuit consists of a compressor, a four-way valve, a second heat source side heat exchanger, a first on-off valve, a first heat source side heat exchanger, a first expansion valve, and a load side heat exchanger, all connected in this order via refrigerant piping. A first connection point on the discharge side of the compressor in the main circuit and a second connection point between the first heat source side heat exchanger and the first on-off valve in the main circuit are connected, and the first bypass circuit to which the second on-off valve is connected, A third connection point between the first heat source side heat exchanger and the first expansion valve in the main circuit and a fourth connection point between the first on-off valve and the second heat source side heat exchanger in the main circuit are connected, and a second bypass circuit to which the second expansion valve is connected is also connected. Equipped with, The first heat source side heat exchanger and the second heat source side heat exchanger are, The first heat source side heat exchanger is housed within the casing of the heat source side unit such that it is positioned outside the second heat source side heat exchanger. A portion of the refrigerant compressed and discharged by the compressor flows into the load-side heat exchanger via the four-way valve and circulates through the main circuit. The remaining portion of the refrigerant, compressed and discharged by the compressor, flows through the first bypass circuit and the first heat source side heat exchanger, merges with the portion of the refrigerant in the second bypass circuit, and returns to the compressor via the second heat source side heat exchanger, thereby performing simultaneous heating and defrosting operation. Refrigeration cycle device.

2. The system further comprises a control device for controlling the first on-off valve, the second on-off valve, and the second expansion valve. The control device is In simultaneous heating and defrosting operation, The first on-off valve is closed, the second on-off valve is opened, and the second expansion valve is controlled to open. The refrigeration cycle apparatus according to claim 1.

3. The control device is The required defrosting capacity and the amount of heat extracted by the second heat source side heat exchanger are calculated, If the amount of heat extracted is greater than the required defrosting capacity, simultaneous heating and defrosting operation will be performed. The refrigeration cycle apparatus according to claim 2.

4. The control device is By switching the four-way valve to allow the refrigerant discharged from the compressor to flow into the second heat source side heat exchanger, a defrosting operation is performed to defrost the second heat source side heat exchanger. The refrigeration cycle apparatus according to claim 2 or 3.

5. The control device is The required defrosting capacity and the amount of heat extracted by the second heat source side heat exchanger are calculated, The defrosting operation is performed when the amount of heat collected is less than or equal to the required defrosting capacity. The refrigeration cycle apparatus according to claim 4.