Heat source unit and refrigeration cycle device

Abstract

A heat source unit (10) is provided with a heat source-side heat exchanger (13) and a control unit. The heat source-side heat exchanger (13) has a first heat source heat exchanger (13a) and a second heat source heat exchanger (13b). The second heat source heat exchanger (13b) is disposed below the first heat source heat exchanger (13a). The control unit performs a defrosting operation for removing frost from the heat source-side heat exchanger (13). The control unit is characterized by executing a first defrosting operation when a predetermined first condition is satisfied during the defrosting operation, and executing a second defrosting operation when a predetermined second condition is satisfied. In the first defrosting operation, a first defrosting mode in which frost is removed from the first heat source heat exchanger (13a) and a second defrosting mode in which frost is removed from the second heat source heat exchanger (13b) are switched at least once, and the first defrosting operation is ended in the second defrosting mode. The second defrosting operation removes frost from only one of the first heat source heat exchanger (13a) and the second heat source heat exchanger (13b).

Description

Technical Field

[0001] The present disclosure relates to a heat source unit and a refrigeration cycle device. Background Art

[0002] Patent Document 1 (Japanese Patent Application Laid-Open No. 9-318206) discloses a heat pump air conditioner that heats the room during heating operation by dividing the outdoor heat exchanger into multiple pieces in the vertical direction. Each of the divided outdoor heat exchangers is connected to the indoor heat exchanger in parallel via piping. During defrosting during heating operation, the heat pump air conditioner in Patent Document 1 flows a portion of exhaust gas from the compressor through each of the divided outdoor heat exchangers while switching sequentially from the upper side to the lower side, thereby performing heating and defrosting simultaneously. Summary of the Invention

[0003] However, in the heat pump air conditioner of Patent Document 1, when defrosting during heating operation, heating and defrosting are performed in parallel while switching sequentially from the upper side to the lower side in each outdoor heat exchanger, which may result in low efficiency.

[0004] The heat source unit of the first aspect includes a heat source side heat exchanger and a control unit. The heat source side heat exchanger has a first heat source heat exchanger and a second heat source heat exchanger. The second heat source heat exchanger is arranged below the first heat source heat exchanger. The control unit performs a defrost operation to remove frost from the heat source side heat exchanger. The control unit is characterized in that, when performing the defrost operation, the first defrost operation is performed when a prescribed first condition is satisfied, and the second defrost operation is performed when a prescribed second condition is satisfied. The first defrost operation alternately switches between a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger, and ends with the second defrost mode. The second defrost operation removes frost from only one of the first heat source heat exchanger and the second heat source heat exchanger.

[0005] According to the first aspect, the heat source unit controls whether to execute the first or second defrost operation based on the states of the first and second heat source heat exchangers. Therefore, if the second condition that requires defrosting of either the first or second heat source heat exchanger is met, the second defrost operation can be executed. This reduces unnecessary defrost operations.

[0006] Furthermore, if the first condition is met, the first defrost operation ends with the defrosting of the second heat source heat exchanger, which is located below the first heat source heat exchanger. Therefore, even if water generated by defrosting the first heat source heat exchanger flows to the second heat source heat exchanger below, defrosting the second heat source heat exchanger after the first defrost operation prevents the water from turning into frost (ice). Consequently, efficient defrosting is achieved.

[0007] In this manner, the heat source unit according to the first aspect can suppress a decrease in operating efficiency.

[0008] The heat source unit according to the second aspect is the heat source unit according to the first aspect, wherein the control unit starts the first defrosting operation in the first defrosting mode, switches to the second defrosting mode, and terminates the operation.

[0009] In the heat source unit of the second viewpoint, even if water generated by the defrosting of the first heat source heat exchanger flows to the second heat source heat exchanger below when the first defrost operation starts, the first defrost operation can be ended while suppressing the water from turning into frost by subsequently defrosting the second heat source heat exchanger.

[0010] The heat source unit of the third aspect includes a heat source side heat exchanger and a control unit. The heat source side heat exchanger has a first heat source heat exchanger and a second heat source heat exchanger. The second heat source heat exchanger is arranged below the first heat source heat exchanger. The control unit performs a defrost operation to remove frost from the heat source side heat exchanger. The control unit is characterized in that, when performing the defrost operation, the first defrost operation is performed when a prescribed first condition is satisfied, and the second defrost operation is performed when a prescribed second condition is satisfied. The first defrost operation alternately switches between a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger, and starts from the second defrost mode. The second defrost operation removes frost from only one of the first heat source heat exchanger and the second heat source heat exchanger.

[0011] According to the third aspect, the heat source unit controls whether to execute the first or second defrost operation based on the states of the first and second heat source heat exchangers. Therefore, if the second condition that requires defrosting of either the first or second heat source heat exchanger is met, the second defrost operation can be executed. This reduces unnecessary defrost operations.

[0012] Furthermore, if the first condition is met, during the first defrost operation, defrosting begins with the second heat source heat exchanger, which is located below the first heat source heat exchanger. The second heat source heat exchanger, located below the first heat source heat exchanger, is more susceptible to ice and snow on the ground, and therefore has a higher likelihood of frost. Therefore, by starting defrosting with the second heat source heat exchanger, defrosting the first heat source heat exchanger can be performed after the amount of frost on the second heat source heat exchanger has been reduced. This allows for efficient defrosting.

[0013] In this manner, the heat source unit according to the third aspect can suppress a decrease in operating efficiency.

[0014] The heat source unit of the fourth viewpoint is based on the heat source unit of any one of the first viewpoints to the third viewpoints, and is characterized in that the control unit has the following steps: based on whether the first heat source heat exchanger and the second heat source heat exchanger were used after the last defrost operation, it is judged whether the prescribed first condition or the prescribed second condition is met, and it is decided whether to perform the defrost operation with the first defrost operation or the second defrost operation.

[0015] In the heat source unit of the fourth aspect, whether to perform the first defrost operation or the second defrost operation is determined based on the above. Therefore, when defrosting of one of the first heat source heat exchanger and the second heat source heat exchanger is not necessary, the second defrost operation can be appropriately determined.

[0016] The heat source unit of the fifth viewpoint is based on the heat source unit of any one of the first viewpoint to the third viewpoint, and is characterized in that the control unit has the following steps: based on the state of the refrigerant flowing in at least one of the first heat source heat exchanger and the second heat source heat exchanger, it is judged whether the prescribed first condition or the prescribed second condition is met, and it is decided whether to perform the defrost operation with the first defrost operation or the second defrost operation.

[0017] In the heat source unit of the fifth aspect, whether to perform the first defrost operation or the second defrost operation is determined based on the above content. Therefore, when it is not necessary to perform defrost on one of the first heat source heat exchanger and the second heat source heat exchanger, it can be appropriately determined to perform the second defrost operation.

[0018] A heat source unit according to a sixth aspect is the heat source unit according to any one of the first to fifth aspects, wherein the control unit further executes a third defrost operation. The third defrost operation causes refrigerant to flow in parallel through the first heat source heat exchanger and the second heat source heat exchanger after the first defrost operation or the second defrost operation to remove frost.

[0019] In the heat source unit according to the sixth aspect, frost can be reliably removed from the heat source side heat exchanger by further performing the third defrost operation after performing the first defrost operation or the second defrost operation.

[0020] Furthermore, the third defrost operation is performed after a large amount of frost adhering to the heat source side heat exchanger has been removed by the first or second defrost operation. This shortens the time it takes to perform the third defrost operation. Since the defrost operation can be performed simultaneously with the heating operation during the first or second defrost operation, user discomfort caused by the third defrost operation can be reduced.

[0021] The heat source unit of the seventh aspect includes a heat source side heat exchanger and a control unit. The heat source side heat exchanger has a first heat source heat exchanger and a second heat source heat exchanger. The second heat source heat exchanger is connected in parallel with the first heat source heat exchanger. The control unit performs a defrost operation to remove frost from the heat source side heat exchanger. The control unit is characterized in that, when performing the defrost operation, the first defrost operation is performed when a prescribed first condition is satisfied, and the third defrost operation is performed when a prescribed third condition is satisfied. The first defrost operation alternately switches between a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger. The third defrost operation causes the refrigerant to flow through the first heat source heat exchanger and the second heat source heat exchanger in parallel and removes frost.

[0022] According to the seventh aspect, the heat source unit controls whether to execute the first defrost operation or the third defrost operation based on the states of the first and second heat source heat exchangers. Therefore, when defrosting the first and second heat source heat exchangers is necessary, the third defrost operation can be executed. Consequently, the heat source side heat exchanger can be defrosted efficiently.

[0023] Furthermore, when defrosting is performed without flowing the refrigerant in parallel through the first and second heat source heat exchangers, the heating operation can be continued by performing the first defrosting operation while using one of the heat exchangers as an evaporator.

[0024] In this manner, the heat source unit according to the seventh aspect can suppress a decrease in operating efficiency.

[0025] The heat source unit of the eighth aspect is based on the heat source unit of the seventh aspect, and the control unit has the following steps: based on the external air temperature, it is judged whether the prescribed first condition or the prescribed third condition is satisfied, and whether the defrost operation is performed in the first defrost operation or the third defrost operation.

[0026] In the heat source unit of the eighth aspect, whether to perform the first defrost operation or the third defrost operation is determined based on the outside air temperature. Therefore, if the outside air temperature is low and the efficiency of the first defrost operation, which switches between defrosting the first heat source heat exchanger and the second heat source heat exchanger, decreases, it is possible to determine to perform the third defrost operation.

[0027] A heat source unit according to a ninth aspect is the heat source unit according to any one of the first to eighth aspects, wherein the control unit starts the first defrosting operation in the second defrosting mode, then switches to the first defrosting mode, and then switches to the second defrosting mode and ends.

[0028] In the heat source unit of the ninth aspect, during the first defrost operation, the unit is susceptible to the effects of ice and snow on the ground. Therefore, the defrosting of the second heat source heat exchanger, which has a higher probability of frost formation, is started. Therefore, after the amount of frost has been significantly reduced by defrosting the second heat source heat exchanger, the first heat source heat exchanger can be defrosted. Even if water generated by the defrosting of the first heat source heat exchanger flows to the second heat source heat exchanger below, the second defrost operation can be terminated while the water is prevented from turning into frost by subsequently defrosting the second heat source heat exchanger. Therefore, frost can be efficiently removed from the heat source side heat exchanger.

[0029] A refrigeration cycle apparatus according to a tenth aspect includes the heat source unit according to any one of the first to ninth aspects and a utilization unit. The utilization unit is connected to the heat source unit.

[0030] According to the refrigeration cycle apparatus of the tenth aspect, since the heat source unit according to any one of the first to ninth aspects is included, it is possible to realize a refrigeration cycle apparatus that suppresses a decrease in operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic configuration diagram of a refrigeration cycle apparatus according to the first embodiment of the present disclosure.

[0032] Figure 2 This is a control block diagram of a refrigeration cycle device.

[0033] Figure 3 This is a schematic diagram of the heat exchanger and heat source fan on the heat source side.

[0034] Figure 4 It is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle apparatus during cooling operation.

[0035] Figure 5 It is a diagram showing the operation (flow of refrigerant) of the refrigeration cycle device during heating operation.

[0036] Figure 6This is a diagram showing a control flow during the defrosting operation of the refrigeration cycle apparatus.

[0037] Figure 7 It is a diagram showing the operation (flow of refrigerant) in the first defrosting mode of the refrigeration cycle device.

[0038] Figure 8 It is a diagram showing the operation (flow of refrigerant) in the second defrosting mode of the refrigeration cycle apparatus.

[0039] Figure 9 This is a diagram showing a control flow during the defrosting operation of the refrigeration cycle apparatus according to the second embodiment of the present disclosure.

[0040] Figure 10 This is a diagram showing a control flow during the defrosting operation of the refrigeration cycle apparatus according to the third embodiment of the present disclosure.

[0041] Figure 11 It is a schematic configuration diagram of a refrigeration cycle apparatus according to a modified example of the present disclosure.

[0042] Figure 12 This is a schematic structural diagram of a refrigeration cycle device according to another modified example of the present disclosure.

[0043] Explanation of symbols

[0044] 1. Refrigeration cycle device;

[0045] 4. Heat source control unit (control unit);

[0046] 10 heat source units;

[0047] 13Heat source side heat exchanger

[0048] 13a first heat source heat exchanger;

[0049] 13b second heat source heat exchanger;

[0050] 20 utilization units. DETAILED DESCRIPTION

[0051] <First embodiment>

[0052] (1) Overall structure

[0053] Figure 1 The refrigeration cycle device 1 of one embodiment of the present disclosure is an air conditioning device that uses a vapor compression refrigeration cycle to perform indoor air conditioning in buildings such as residences and buildings. The refrigeration cycle device 1 mainly includes a heat source unit 10, a utilization unit 20, a first communication pipe 31, a second communication pipe 32, a third communication pipe 33, and a control unit 6. The first communication pipe 31, the second communication pipe 32, and the third communication pipe 33 connect the heat source unit 10 and the utilization unit 20. Figure 2 As shown, the control unit 6 includes a heat source control unit 4 and a utilization control unit 5 , and controls components of the heat source unit 10 and the utilization unit 20 .

[0054] The refrigeration cycle device 1 includes a refrigerant circuit 2 and a subcooling circuit 3. The refrigerant circuit 2 is formed by connecting a heat source unit 10, a utilization unit 20, and communication pipes 31, 32, and 33. The subcooling circuit 3 is formed by connecting a subcooling heat exchanger 16 and a third heat source expansion mechanism 15c. The refrigerant circuit 2 and the subcooling circuit 3 are filled with a refrigerant such as R410.

[0055] (2) Detailed structure

[0056] (2-1) Heat source unit

[0057] The heat source unit 10 is installed outdoors (on the roof of a building, near the outer wall of a building, etc.). The heat source unit 10 mainly includes a compressor 11, a first switching mechanism 12a, a second switching valve mechanism 12b, a third switching mechanism 12c, a fourth switching mechanism 12d, a heat source side heat exchanger 13 having a first heat source heat exchanger 13a and a second heat source heat exchanger 13b, a first heat source fan 14a, a second heat source fan 14b, a first heat source expansion valve mechanism 15a, a second heat source expansion mechanism 15b, a third heat source expansion mechanism 15c, a subcooling heat exchanger 16, an accumulator 17, a first stop valve 18a, a second stop valve 18b, and a third stop valve 18c. The compressor 11, the switching mechanisms 12a to 12d, the heat source side heat exchanger 13, the heat source expansion valve mechanisms 15a to 15c, the subcooling heat exchanger 16, the accumulator 17, and the first to third stop valves 18a to 18c are connected by refrigerant piping.

[0058] The compressor 11, the switching mechanism 12a~12d, the heat source side heat exchanger 13, the heat source expansion valve mechanism 15a, 15b, 15c, the first flow path 16a of the subcooling heat exchanger 16, the storage tank 17, the first to third stop valves 18a~18c are connected to the utilization unit 20 via the first connecting pipe 31, the second connecting pipe 32 and the third connecting pipe 33, and constitute a part of the refrigerant circuit 2.

[0059] In addition, the second flow path 16b of the subcooling heat exchanger 16 and the third heat source expansion mechanism 15c constitute a part of the subcooling circuit 3. The subcooling circuit 3 is a circuit for diverting a part of the refrigerant of the refrigerant circuit 2 and delivering it to the suction side of the compressor 11. The subcooling circuit 3 connects the first heat source heat exchanger 13a and the second heat source heat exchanger 13b and the subcooling heat exchanger 16 with the suction side of the compressor 11. Here, the subcooling circuit 3 connects the refrigerant piping between the first heat source expansion mechanism 15a and the second heat source expansion mechanism 15b and the subcooling heat exchanger 16 with the inlet side of the storage tank 17.

[0060] Compressor 11 compresses the low-pressure refrigerant in the refrigeration cycle to a high-pressure state. Here, a closed-type compressor, in which a positive displacement compression element (not shown), such as a rotary or scroll type, is driven by a compressor motor, is used as compressor 11. Furthermore, the speed (frequency) of the compressor motor can be controlled by an inverter, etc., thereby controlling the capacity of compressor 11.

[0061] The switching mechanisms 12a, 12b, 12c, and 12d are valves that switch the flow direction of the refrigerant in the refrigerant circuit. In this embodiment, the switching mechanisms 12a, 12b, 12c, and 12d use four-way reversing valves, and one port is closed.

[0062] The first switching mechanism 12a is a device capable of switching the flow of refrigerant in the refrigerant circuit 2, so as to connect the discharge side of the compressor 11 with the gas side of the first heat source heat exchanger 13a when the first heat source heat exchanger 13a acts as a condenser of the refrigerant, and to connect the suction side of the compressor 11 with the gas side of the first heat source heat exchanger 13a when the first heat source heat exchanger 13a acts as an evaporator of the refrigerant.

[0063] The second switching mechanism 12b is a device capable of switching the flow of refrigerant in the refrigerant circuit 2, so as to connect the discharge side of the compressor 11 with the gas side of the second heat source heat exchanger 13b when the second heat source heat exchanger 13b acts as a condenser of the refrigerant, and to connect the suction side of the compressor 11 with the gas side of the second heat source heat exchanger 13b when the second heat source heat exchanger 13b acts as an evaporator of the refrigerant.

[0064] The third switching mechanism 12c is a device capable of switching the flow of refrigerant in the refrigerant circuit 2, so as to connect the discharge side of the compressor 11 to the second connecting pipe 32 when the refrigerant discharged from the compressor 11 is delivered to the second connecting pipe 32, and to connect the suction side of the compressor 11 to the second connecting pipe 32 when the refrigerant flowing in the second connecting pipe 32 is delivered to the suction side of the compressor 11.

[0065] The fourth switching mechanism 12d is a device capable of switching the flow of refrigerant in the refrigerant circuit 2, so as to connect the discharge side of the compressor 11 to the third connecting pipe 33 when the refrigerant discharged from the compressor 11 is delivered to the third connecting pipe 33, and to connect the suction side of the compressor 11 to the third connecting pipe 33 when the refrigerant flowing in the third connecting pipe 33 is delivered to the suction side of the compressor 11.

[0066] In addition, the switching mechanisms 12a, 12b, 12c, and 12d are not limited to mechanisms composed of four-way reversing valves. For example, they can also be mechanisms that can switch the flow direction of the refrigerant as described above by combining multiple solenoid valves and refrigerant pipes.

[0067] The heat source side heat exchanger 13 exchanges heat between the refrigerant and the outdoor air. The heat source side heat exchanger 13 includes a first heat source heat exchanger 13a and a second heat source heat exchanger 13b. The first heat source heat exchanger 13a and the second heat source heat exchanger 13b exchange heat between the refrigerant and the outdoor air. The first heat source heat exchanger 13a and the second heat source heat exchanger 13b function as a refrigerant condenser or as a refrigerant evaporator.

[0068] The first heat source heat exchanger 13a and the second heat source heat exchanger 13b are connected in parallel. Figure 3 As shown, the second heat source heat exchanger 13b is arranged below the first heat source heat exchanger 13a. Here, the second heat source heat exchanger 13b is arranged vertically below the first heat source heat exchanger 13a, and the bottom surface of the first heat source heat exchanger 13a contacts the top surface of the second heat source heat exchanger 13b.

[0069] The first heat source fan 14a causes air to pass through the first heat source heat exchanger 13a. Specifically, the first heat source fan 14a draws outdoor air into the heat source unit 10, supplies the outdoor air primarily to the first heat source heat exchanger 13a, and then exhausts the air outside the heat source unit 10. Thus, the first heat source heat exchanger 13a acts as a cooling source or a heating source for the outdoor air, condensing or evaporating the refrigerant.

[0070] The second heat source fan 14b causes air to pass through the second heat source heat exchanger 13b. Specifically, the second heat source fan 14b draws outdoor air into the heat source unit 10, supplies the outdoor air primarily to the second heat source heat exchanger 13b, and then exhausts the air outside the heat source unit 10. Therefore, the second heat source heat exchanger 13b acts as a cooling source or a heating source for the outdoor air, causing the refrigerant to condense or evaporate.

[0071] The first heat source fan 14a and the second heat source fan 14b of the present embodiment are driven by motors controlled by inverters, and are configured to be able to change the air blowing volumes.

[0072] The opening degrees of the first, second, and third heat source expansion mechanisms 15a, 15b, and 15c are variable. By adjusting the opening degrees of the first, second, and third heat source expansion mechanisms 15a, 15b, and 15c, the degree of pressure reduction can be adjusted.

[0073] Specifically, the first heat source expansion mechanism 15a is an electric expansion valve with adjustable opening, and adjusts the flow rate of the refrigerant flowing through the first heat source heat exchanger 13a. The first heat source expansion mechanism 15a is provided corresponding to the liquid side of the first heat source heat exchanger 13a.

[0074] The second heat source expansion mechanism 15b is an electric expansion valve with adjustable opening, and adjusts the flow rate of the refrigerant flowing through the second heat source heat exchanger 13b, etc. The second heat source expansion mechanism 15b is provided corresponding to the liquid side of the second heat source heat exchanger 13b.

[0075] The third heat source expansion mechanism 15c is an electrically operated expansion valve with adjustable opening, and performs functions such as adjusting the flow rate of the refrigerant flowing through the second flow path 16b of the subcooling heat exchanger 16. The third heat source expansion mechanism 15c is disposed between the refrigerant piping and the accumulator 17. The refrigerant piping is located between the first and second heat source expansion mechanisms 15a, 15b, and the subcooling heat exchanger 16.

[0076] The subcooling heat exchanger 16 is arranged between the first heat source heat exchanger 13a and the second heat source heat exchanger 13b and the first stop valve 18a. The subcooling heat exchanger 16 has a first flow path 16a and a second flow path 16b. The first flow path 16a is connected to the utilization unit 20. Here, the first flow path 16a constitutes a part of the refrigerant piping that connects the first heat source expansion mechanism 15a, the second heat source expansion mechanism 15b and the first stop valve 18a. The second flow path 16b is for the refrigerant that exchanges heat with the refrigerant in the first flow path 16a to flow through. Here, the second flow path 16b constitutes a part of the subcooling circuit 3. The subcooling heat exchanger 16 is a heat exchanger that cools the refrigerant flowing in the first flow path 16a by the refrigerant flowing in the second flow path 16b.

[0077] The accumulator 17 is provided on the suction side of the compressor 11. The accumulator 17 temporarily stores the refrigerant to be sucked into the compressor 11. In other words, the accumulator 17 stores excess refrigerant.

[0078] The first stop valve 18a is provided at the connection between the heat source unit 10 and the first communication pipe 31. The second stop valve 18b is provided at the connection between the heat source unit 10 and the second communication pipe 32. The third stop valve 18c is provided at the connection between the heat source unit 10 and the third communication pipe 33. The first stop valve 18a, the second stop valve 18b, and the third stop valve 18c are valves that are manually opened and closed.

[0079] In addition, various sensors are provided in the heat source unit 10. Specifically, Figure 2As shown, the heat source unit 10 is provided with an outdoor temperature sensor 41 for detecting the outside air temperature, a suction pressure sensor 42 for detecting the suction pressure of the compressor 11 , a discharge pressure sensor 43 for detecting the discharge pressure of the compressor 11 , and the like.

[0080] (2-2) Connecting pipes

[0081] The connecting pipes 31, 32, and 33 are refrigerant pipes installed on-site when the refrigeration cycle apparatus 1 is installed in a building or other installation location. The first connecting pipe 31 connects the first stop valve 18a to the utilization unit 20. The first connecting pipe 31 is a pipe for liquid refrigerant to pass through. The second connecting pipe 32 connects the utilization unit 20 to the second stop valve 18b. The second connecting pipe 32 is a pipe for gaseous refrigerant to pass through. The third connecting pipe 33 connects the utilization unit 20 to the third stop valve 18c. The third connecting pipe 33 is a pipe for gaseous refrigerant to pass through.

[0082] (2-3) Utilization Unit

[0083] The usage unit 20 is installed indoors (inside a building) and is connected to the heat source unit 10 via the first communication pipe 31 , the second communication pipe 32 , and the third communication pipe 33 as described above, and constitutes a part of the refrigerant circuit 2 .

[0084] The utilization unit 20 mainly includes a first utilization expansion mechanism 21a, a second utilization expansion valve mechanism 21b, a first utilization heat exchanger 22a, a second utilization heat exchanger 22b, a first utilization fan 23a, and a second utilization fan 23b. The utilization expansion mechanisms 21 and 21b are connected to the utilization heat exchangers 22a and 22b via refrigerant piping.

[0085] The first utilization expansion mechanism 21a is connected in series with the first utilization heat exchanger 22a. The second utilization expansion mechanism 21b is directly connected with the second utilization heat exchanger 22b. The first utilization heat exchanger 22a and the second utilization heat exchanger 22b are connected in parallel with each other.

[0086] The opening degrees of the first expansion mechanism 21a and the second expansion mechanism 21b can be changed. By adjusting the opening degrees of the first expansion mechanism 21a and the second expansion mechanism 21b, the degree of pressure reduction can be adjusted.

[0087] Specifically, the first utilization expansion mechanism 21a is an electric expansion valve with adjustable opening, and adjusts the flow rate of the refrigerant flowing through the first utilization heat exchanger 22a, etc. The first utilization expansion mechanism 21a is provided corresponding to the liquid side of the first utilization heat exchanger 22a.

[0088] The second utilization expansion mechanism 21b is an electric expansion valve with adjustable opening, and adjusts the flow rate of the refrigerant flowing through the second utilization heat exchanger 22b, etc. The second utilization expansion mechanism 21b is provided corresponding to the liquid side of the second utilization heat exchanger 22b.

[0089] The first heat exchanger 22a and the second heat exchanger 22b perform heat exchange between the refrigerant and the indoor air. The first heat exchanger 22a and the second heat exchanger 22b are heat exchangers that function as condensers of the refrigerant or as evaporators of the refrigerant.

[0090] The first utilization fan 23a primarily passes air through the first utilization heat exchanger 22a. Specifically, the first utilization fan 23a draws indoor air into the utilization unit 20, supplies the indoor air primarily to the first utilization heat exchanger 22a, and then exhausts the indoor air outside the utilization unit 20. Thus, the first utilization heat exchanger 22a serves as a cooling or heating source for the indoor air, condensing or evaporating the refrigerant. The first utilization fan 23a is located on one side of the first utilization heat exchanger 22a.

[0091] The second utilization fan 23b primarily passes air through the second utilization heat exchanger 22b. Specifically, the second utilization fan 23b draws indoor air into the utilization unit 20, supplies the indoor air primarily to the second utilization heat exchanger 22b, and then exhausts the indoor air outside the utilization unit 20. Therefore, the second utilization heat exchanger 22b serves as a cooling or heating source for the indoor air, condensing or evaporating the refrigerant. The second utilization fan 23b is located on one side of the second utilization heat exchanger 22b.

[0092] In addition, various sensors are provided in the utilization unit 20. Specifically, Figure 2 As shown, the usage unit 20 is provided with an indoor temperature sensor 44 and the like for detecting the temperature of the indoor air sucked into the usage unit 20 .

[0093] (2-4) Control Unit

[0094] (2-4-1) Overview

[0095] like Figure 1 As shown, the refrigeration cycle apparatus 1 includes a heat source control unit 4 and a utilization control unit 5 connected via a transmission line and a communication line, and a control unit 6 is provided to control the operation of the components. The heat source control unit 4 is provided in the heat source unit 10. The utilization control unit 5 is provided in the utilization unit 20. The heat source control unit 4 and the utilization control unit 5 can be connected by wire or wirelessly via a transmission line and a communication line.

[0096] The heat source control unit 4 and the utilization control unit 5, which constitute the control unit 6 of the refrigeration cycle device 1, are implemented by a computer. The controller 6 includes a control operation device and a storage device. The control operation device can use a processor such as a CPU or a GPU. The control operation device reads a program stored in the storage device and performs predetermined image processing or operation processing in accordance with the program. In addition, the control operation device can write operation results to the storage device according to the program and can read information stored in the storage device according to the program.

[0097] like Figure 2 As shown, the heat source control unit 4 is configured to receive detection signals from an outdoor temperature sensor 41, a suction pressure sensor 42, a discharge pressure sensor 43, and the like. Furthermore, the heat source control unit 4 controls the operation of components of the heat source unit 10, such as the compressor 11, the first switching mechanism 12a, the second switching mechanism 12b, the third switching mechanism 12c, the fourth switching mechanism 12d, the first heat source fan 14a, the second heat source fan 14b, the first heat source expansion valve mechanism 15a, the second heat source expansion mechanism 15b, and the third heat source expansion mechanism 15c.

[0098] The utilization control unit 5 is configured to receive detection signals from the indoor temperature sensor 44 and the like. Furthermore, the utilization control unit 5 controls the operation of the first utilization expansion mechanism 21a, the second utilization expansion mechanism 21b, the first utilization fan 23a, the second utilization fan 23b, and the like, which are components of the utilization unit 20.

[0099] As described above, the refrigeration cycle apparatus 1 includes a control unit 6 that performs operational control of the component devices. Furthermore, the control unit 6 is configured to control the component devices, such as the compressor 11, the first switching mechanism 12a, the second switching mechanism 12b, the third switching mechanism 12c, the fourth switching mechanism 12d, the first heat source fan 14a, the second heat source fan 14b, the first heat source expansion valve mechanism 15a, the second heat source expansion mechanism 15b, the third heat source expansion mechanism 15c, the first utilization expansion mechanism 21a, the second utilization expansion mechanism 21b, the first utilization fan 23a, and the second utilization fan 23b, based on detection signals from the outdoor temperature sensor 41, the suction pressure sensor 42, the discharge pressure sensor 43, and the indoor temperature sensor 44, thereby performing air conditioning operations such as cooling operation, heating operation, and defrosting operation, as well as various other controls.

[0100] (2-4-2) Control during defrosting operation

[0101] Hereinafter, control during the defrosting operation performed by the heat source control unit 4 of the control unit 6 of the refrigeration cycle apparatus 1 will be described.

[0102] The defrosting operation removes frost from the heat source side heat exchanger 13. The defrosting operation in the present embodiment is an operation for removing frost from at least a portion of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b.

[0103] During the defrosting operation, the heat source control unit 4 performs a first defrosting operation when a predetermined first condition is satisfied, performs a second defrosting operation when a predetermined second condition is satisfied, and performs a third defrosting operation when a predetermined third condition is satisfied.

[0104] The first defrost operation alternates between a first defrost mode for removing frost from the first heat source heat exchanger 13 a and a second defrost mode for removing frost from the second heat source heat exchanger 13 b , and ends with the second defrost mode.

[0105] In the first defrost mode, the refrigerant is condensed in the first heat source heat exchanger 13a and evaporated in the second heat source heat exchanger 13b. In other words, in the first defrost mode, the first heat source heat exchanger 13a is used as a condenser for defrosting, and the second heat source heat exchanger 13b is used as an evaporator for heating operation.

[0106] In the second defrost mode, the refrigerant is condensed in the second heat source heat exchanger 13b and evaporated in the first heat source heat exchanger 13a. In other words, in the second defrost mode, the second heat source heat exchanger 13b is used as a condenser for defrosting, and the first heat source heat exchanger 13a is used as an evaporator for heating operation.

[0107] Furthermore, the heat source control unit 4 performs at least one of the first and second defrost modes as a first defrost operation. In this embodiment, the heat source control unit 4 starts with the first defrost mode, then switches to the second defrost mode and ends. In this case, the defrost operation only includes one first defrost mode and one second defrost mode.

[0108] The second defrost operation removes frost from only one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b. In other words, during the second defrost operation, the refrigerant condenses in one of the first heat source heat exchanger 13a or the second heat source heat exchanger 13b, and evaporates in the other. In other words, during the second defrost operation, one of the first heat source heat exchanger 13a or the second heat source heat exchanger 13b functions as a condenser for defrosting, and the other functions as an evaporator for heating.

[0109] The third defrost operation causes the refrigerant to flow in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b to remove frost. The third defrost operation preferably utilizes a flow splitting structure in which the refrigerant reaches the first heat source heat exchanger 13a and the second heat source heat exchanger 13b simultaneously. Alternatively, the refrigerant may reach the first heat source heat exchanger 13a and the second heat source heat exchanger 13b at different times, without compromising the effects of the present disclosure.

[0110] The third defrost operation is performed after the first or second defrost operation. During the third defrost operation, the refrigerant is condensed in both the first heat source heat exchanger 13a and the second heat source heat exchanger 13b. Therefore, the refrigerant flow during the third defrost operation is the same as that during the cooling operation, and the heating operation is not performed.

[0111] The prescribed first condition is different from the prescribed second condition. The prescribed second condition is a relative condition of the prescribed first condition. In the present embodiment, the heat source control unit 4 has the following steps: based on whether the first heat source heat exchanger 13a and the second heat source heat exchanger 13b were used after the last defrost operation, it is judged whether the prescribed first condition or the prescribed second condition is met, and it is decided whether the defrost operation is performed with the first defrost operation or the second defrost operation. Specifically, the first condition is that the first heat source heat exchanger 13a and the second heat source heat exchanger 13b were used after the last defrost operation. The second condition is that the first heat source heat exchanger 13a and the second heat source heat exchanger 13b were not used after the last defrost operation. The last defrost operation was the previous defrost operation that was immediately adjacent to the current heating operation.

[0112] If both the first heat source heat exchanger 13a and the second heat source heat exchanger 13b have been used since the previous defrost operation, the heat source control unit 4 determines that the first condition is satisfied and executes the first defrost operation. If only one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b has been used, the heat source control unit 4 determines that the second condition is satisfied and executes the second defrost operation to defrost the previously used heat exchanger. For example, if the operating capacity is low and only the second heat source heat exchanger 13b has been used since the previous defrost operation, the heat source control unit 4 determines that the second condition is satisfied and executes the second defrost operation to defrost only the second heat source heat exchanger 13b.

[0113] The prescribed third condition is different from the prescribed first and second conditions. The third condition is that there is residual melted frost after the first or second defrost operation. In this case, after performing the first or second defrost operation, if the heat source control unit 4 determines that there is residual melted frost in the heat source-side heat exchanger 13, it returns to heating operation and determines that the next defrost operation will be the third defrost operation. Alternatively, after performing the first or second defrost operation, if the heat source control unit 4 determines that there is residual melted frost in the heat source-side heat exchanger 13, it immediately determines to perform the third defrost operation. This condition is the prescribed third condition of this embodiment.

[0114] Alternatively, the third condition may be that the first defrost operation or the second defrost operation has been performed. In this case, the heat source control unit 4 determines to perform the third defrost operation after performing the first defrost operation or the second defrost operation without determining whether there is any melted frost residue in the heat source side heat exchanger 13.

[0115] (3) Action

[0116] Reference Figures 1 to 8 The operation of the refrigeration cycle device 1 will be described. The refrigeration cycle device 1 performs cooling operation, heating operation, and defrosting operation. The operation of the refrigeration cycle device 1 including the above-mentioned operations is performed by the control unit 6.

[0117] (3-1) Refrigeration Operation

[0118] Below, refer to Figure 4 Next, the operation during cooling operation of the refrigeration cycle apparatus 1 will be described. Here, the case where all of the plurality of utilization heat exchangers of the utilization unit 20 cool the indoor air will be described.

[0119] The control unit 6 which receives the cooling operation instruction controls the operation of the compressor 11, the first switching mechanism 12a, the second switching valve mechanism 12b, the third switching mechanism 12c, the fourth switching mechanism 12d, the first heat source fan 14a, the second heat source fan 14b, the first heat source expansion valve mechanism 15a, the second heat source expansion mechanism 15b, the third heat source expansion mechanism 15c, the first utilization expansion valve mechanism 21a, the second utilization expansion valve mechanism 21b, the first utilization fan 23a, the second utilization fan 23b, etc. Figure 4 Cooling operation shown.

[0120] The first switching mechanism 12a, the second switching mechanism 12b, the third switching mechanism 12c and the fourth switching mechanism 12d are switched to a state in which the first heat source heat exchanger 13a and the second heat source heat exchanger 13b act as condensers of the refrigerant, and the first utilization heat exchanger 22a and the second utilization heat exchanger 22b act as evaporators of the refrigerant.

[0121] like Figure 4 As shown, in this state of the refrigerant circuit 2, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 11, compressed to the high pressure within the refrigeration cycle, and then discharged. The high-pressure refrigerant discharged from the compressor 11 is branched and delivered to the first heat source heat exchanger 13a via the first switching mechanism 12a, and then to the second heat source heat exchanger 13b via the second switching mechanism 12b. The refrigerant delivered to the first heat source heat exchanger 13a condenses by exchanging heat with outdoor air supplied by the first heat source fan 14a in the first heat source heat exchanger 13a. This refrigerant is delivered to the first flow path 16a of the subcooling heat exchanger 16 via the first heat source expansion mechanism 15a. Furthermore, the refrigerant delivered to the second heat source heat exchanger 13b condenses by exchanging heat with outdoor air supplied by the second heat source fan 14b in the second heat source heat exchanger 13b. This refrigerant is delivered to the first flow path 16a of the subcooling heat exchanger 16 via the second heat source expansion mechanism 15b. The refrigerants that have merged and are further cooled in the subcooling heat exchanger 16 pass through the first stop valve 18 a and flow out of the heat source unit 10 .

[0122] The refrigerant flowing out of the heat source unit 10 is transported to the utilization unit 20 through the first connecting pipe 31. The refrigerant transported to the utilization unit 20 is branched and reduced in pressure to the low pressure within the refrigeration cycle by the first and second expansion mechanisms 21a and 21b. The refrigerant transported to the first and second heat exchangers 22a and 22b is heated and evaporated by heat exchange with indoor air supplied from the room by the first and second fans 23a and 23b in the first and second heat exchangers 22a and 22b, which function as evaporators. This refrigerant then flows out of the utilization unit 20. Meanwhile, the indoor air cooled by the first and second heat exchangers 22a and 22b is transported back into the room, thereby cooling the room.

[0123] The refrigerant flowing out of the utilization unit 20 and passing through the first utilization heat exchanger 22a is transported to the heat source unit 10 via the second connecting pipe 32. The refrigerant transported to the heat source unit 10 passes through the second shutoff valve 18b and the third switching mechanism 12c, and is then transported to the accumulator 17. The refrigerant flowing out of the utilization unit 20 and passing through the second utilization heat exchanger 22b is transported to the heat source unit 10 via the third connecting pipe 33. The refrigerant transported to the heat source unit 10 passes through the third shutoff valve 18c and the fourth switching mechanism 12d, and is then transported to the accumulator 17. The refrigerant that has been combined in the accumulator 17 is then drawn into the compressor 11.

[0124] During the cooling operation described above, the control unit 6 uses the refrigerant flowing in the second flow path 16b of the refrigerant circuit 2 to cool the refrigerant flowing in the first flow path 16a of the refrigerant circuit 2 through the subcooling heat exchanger 16 and the subcooling circuit 3, and then delivers the refrigerant to the first connecting pipe 31. Specifically, a portion of the refrigerant that has passed through the first heat source expansion mechanism 15a and the second heat source expansion mechanism 15b and converged is branched, passed through the subcooling circuit 3, and delivered to the compressor 11. At this time, the flow rate of the refrigerant flowing in the second flow path 16b is adjusted by controlling the opening degree of the third heat source expansion mechanism 15c.

[0125] During refrigeration operation, the operating frequency of the compressor 11 is controlled so that the low pressure value of the refrigeration cycle (the detection value of the suction pressure sensor 42) becomes a constant value, and the opening of the first expansion mechanism 21a and the second expansion mechanism 21b is adjusted so that the superheat of the refrigerant at the outlet of the first heat exchanger 22a and the second heat exchanger 22b becomes a specified target value.

[0126] In the cooling operation, one of the utilization heat exchangers in the utilization unit 20 and one of the heat source heat exchangers in the heat source unit 10 may not be used depending on the load.

[0127] (3-2) Heating operation

[0128] Below, refer to Figure 5 Next, the operation during the heating operation of the refrigeration cycle apparatus 1 will be described. Here, the case where all of the plurality of utilization heat exchangers of the utilization unit 20 heat the indoor air will be described.

[0129] The control unit 6 which receives the instruction of the heating operation controls the operation of the compressor 11, the first switching mechanism 12a, the second switching valve mechanism 12b, the third switching mechanism 12c, the fourth switching mechanism 12d, the first heat source fan 14a, the second heat source fan 14b, the first heat source expansion valve mechanism 15a, the second heat source expansion mechanism 15b, the third heat source expansion mechanism 15c, the first utilization expansion valve mechanism 21a, the second utilization expansion valve mechanism 21b, the first utilization fan 23a, the second utilization fan 23b, etc. Figure 5 Heating operation shown.

[0130] The first switching mechanism 12a, the second switching mechanism 12b, the third switching mechanism 12c and the fourth switching mechanism 12d are switched to change the state in which the first heat source heat exchanger 13a and the second heat source heat exchanger 13b act as evaporators of the refrigerant, and the first utilization heat exchanger 22a and the second utilization heat exchanger 22b act as condensers of the refrigerant.

[0131] like Figure 5 As shown, in this state of the refrigerant circuit 2, low-pressure refrigerant in the refrigeration cycle is drawn into the compressor 11, compressed to high pressure in the refrigeration cycle, and then discharged. The high-pressure refrigerant discharged from the compressor 11 branches, flows out of the heat source unit 10 through the third switching mechanism 12c and the second stop valve 18b, and then flows out of the heat source unit 10 through the fourth switching mechanism 12d and the third stop valve 18c.

[0132] The refrigerant flowing out of the heat source unit 10 through the second stop valve 18b is transported via the second connecting pipe 32 to the first utilization heat exchanger 22a of the utilization unit 20. The refrigerant flowing out of the heat source unit 10 through the third stop valve 18c is transported via the third connecting pipe 33 to the second utilization heat exchanger 22b of the utilization unit 20. The high-pressure refrigerant transported to the first and second utilization heat exchangers 22a and 22b is cooled and condensed by heat exchange with indoor air supplied from the room by the first and second utilization fans 23a and 23b in the first and second utilization heat exchangers 22a and 22b, which function as refrigerant condensers. This refrigerant is decompressed by the first and second utilization expansion mechanisms 21a and 21b before flowing out of the utilization unit 20. Meanwhile, the indoor air heated in the first and second utilization heat exchangers 22a and 22b is transported indoors, thereby heating the room.

[0133] The refrigerant that has converged and flowed out of the utilization unit 20 is delivered to the heat source unit 10 through the first communication pipe 31. The refrigerant delivered to the heat source unit 10 passes through the first shutoff valve 18a and is delivered to the first flow path 16a of the subcooling heat exchanger 16. The refrigerant cooled in the subcooling heat exchanger 16 branches and is delivered to the first heat source expansion valve mechanism 15a and the second heat source expansion mechanism 15b.

[0134] The refrigerant supplied to the first heat source expansion mechanism 15a is decompressed to the low pressure in the refrigeration cycle by the first heat source expansion mechanism 15a and then supplied to the first heat source heat exchanger 13a. The refrigerant supplied to the first heat source heat exchanger 13a is heated by heat exchange with the outdoor air supplied by the first heat source fan 14a, thereby evaporating. This refrigerant is supplied to the accumulator 17 through the first switching mechanism 12a. The refrigerant supplied to the second heat source expansion mechanism 15b is decompressed to the low pressure in the refrigeration cycle by the second heat source expansion mechanism 15b and then supplied to the second heat source heat exchanger 13b. The refrigerant supplied to the second heat source heat exchanger 13b is heated by heat exchange with the outdoor air supplied by the second heat source fan 14b, thereby evaporating. This refrigerant is supplied to the accumulator 17 through the second switching mechanism 12b. The refrigerant that has merged in the accumulator 17 is sucked into the compressor 11.

[0135] During the heating operation described above, the controller 6 uses the refrigerant flowing in the second flow path 16b of the refrigerant circuit 2 to cool the refrigerant flowing in the first flow path 16a of the refrigerant circuit 2 through the subcooling heat exchanger 16 and the subcooling circuit 3, and then delivers the refrigerant to the first heat source expansion mechanism 15a and the second heat source expansion mechanism 15b. Specifically, a portion of the refrigerant that has passed through the first flow path 16a of the subcooling heat exchanger 16 is branched, passed through the subcooling circuit 3, and delivered to the compressor 11. At this time, the flow rate of the refrigerant flowing in the second flow path 16b is adjusted by controlling the opening degree of the third heat source expansion mechanism 15c.

[0136] During heating operation, the operating frequency of the compressor 11 is controlled so that the high pressure value of the refrigeration cycle (the detection value of the discharge pressure sensor 43) becomes a constant value, and the opening degree of the first expansion mechanism 21a and the second expansion mechanism 21b is adjusted so that the subcooling degree of the refrigerant at the outlet of the first heat exchanger 22a and the second heat exchanger 22b becomes a specified target value.

[0137] In addition, in the heating operation described above, depending on the load, one of the utilization heat exchangers in the utilization unit 20 and one of the heat source heat exchangers in the heat source unit 10 may not be used.

[0138] (3-3) Defrost operation

[0139] In the refrigeration cycle device 1, during heating operation, a defrost operation is performed to remove frost from the heat source side heat exchanger 13 when predetermined defrost conditions are met. The defrost operations include a first defrost operation, a second defrost operation, and a third defrost operation. The following describes the operation of the defrost operation in this embodiment.

[0140] like Figure 6 As shown, the heat source control unit 4 of the control unit 6 determines whether a predetermined defrost condition related to frost formation is satisfied during the heating operation (step S1) (step S2). The predetermined defrost condition is not particularly limited, and can be determined by, for example, at least one of the following conditions: the outside air temperature measured by the outdoor temperature sensor 41 is below a predetermined value; a predetermined time has passed since the defrost operation was last completed; the temperature of at least one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b is below a predetermined value; and the evaporation pressure or evaporation temperature of the refrigerant in the refrigerant circuit 2 is below a predetermined value.

[0141] In step S2, if the heat source control unit 4 determines that the defrosting conditions are not met, the heating operation is continued (step S1). On the other hand, in step S2, if the heat source control unit 4 determines that the defrosting conditions are met, the defrosting operation is performed (step S3).

[0142] When performing the defrost operation, the heat source control unit 4 determines whether the first condition or the second condition is satisfied, and decides whether to perform the defrost operation in the first defrost operation or the second defrost operation (step S4). In step S4, the heat source control unit 4 determines whether the first heat source heat exchanger 13a and the second heat source heat exchanger 13b have been used since the previous defrost operation.

[0143] In step S4, if it is determined that the first heat source heat exchanger 13a and the second heat source heat exchanger 13b have been used since the previous defrost operation, a decision is made to execute the first defrost operation (step S5). On the other hand, in step S3, if it is determined that the first heat source heat exchanger 13a and the second heat source heat exchanger 13b have not been used since the previous defrost operation, a decision is made to execute the second defrost operation (step S6).

[0144] In the first defrosting operation determined in step S5, a first defrosting mode for removing frost from the first heat source heat exchanger 13a and a second defrosting mode for removing frost from the second heat source heat exchanger 13b are switched. Figure 7 The first defrost mode shown in FIG. 1 starts (step S7), and then switches to Figure 8 The first defrosting operation in which the second defrosting mode is shown and the first defrosting operation is completed (step S8) will be described.

[0145] In step S7, first, a switching operation for implementing the first defrosting mode is performed. Specifically, the heat source control unit 4 switches the first switching mechanism 12a to condense the refrigerant in the first heat source heat exchanger 13a and evaporate the refrigerant in the second heat source heat exchanger 13b. Figure 7 As shown in FIG. 1 , the heat source control unit 4 switches the first switching mechanism 12a to the same state as the cooling operation. Here, the rotation speed of the compressor 11 is reduced.

[0146] Then, the heat source control unit 4 starts the first defrosting mode. Here, the heat source control unit 4 controls the first heat source fan 14a and the second heat source fan 14b so that the rotation speed of the first heat source fan 14a is different from the rotation speed of the second heat source fan 14b. In addition, the rotation speed of the compressor 11 is increased.

[0147] In the first defrost mode, if Figure 7 As shown, in the refrigerant circuit 2 , low-pressure gas refrigerant in the refrigeration cycle is compressed to high pressure in the refrigeration cycle by the compressor 11 and then branches to the first switching mechanism 12 a , the third switching mechanism 12 c , and the fourth switching mechanism 12 d .

[0148] The refrigerant flowing into the third switching mechanism 12c flows through the third switching mechanism 12c, the second stop valve 18b, the second connecting pipe 32, the first utilization heat exchanger 22a, the first utilization expansion mechanism 21a, the first connecting pipe 31, the first stop valve 18a, and the subcooling heat exchanger 16, similarly to the operation in the heating operation, and then flows into the second heat source expansion mechanism 15b. The refrigerant flowing into the fourth switching mechanism 12d flows through the fourth switching mechanism 12d, the third stop valve 18c, the third connecting pipe 33, the second utilization heat exchanger 22b, the second utilization expansion mechanism 21b, the first connecting pipe 31, the first stop valve 18a, and the subcooling heat exchanger 16, similarly to the operation in the heating operation, and then flows into the second heat source expansion mechanism 15b.

[0149] Alternatively, a portion of the refrigerant that has passed through the first flow path 16 a of the subcooling heat exchanger 16 may be branched to the subcooling circuit 3 .

[0150] Meanwhile, the refrigerant flowing toward the first switching mechanism 12a passes through the first switching mechanism 12a and flows into the first heat source heat exchanger 13a. The high-pressure refrigerant flowing into the first heat source heat exchanger 13a supplies heat to the first heat source heat exchanger 13a. This melts the frost adhering to the first heat source heat exchanger 13a, defrosting the first heat source heat exchanger 13a.

[0151] The high-pressure refrigerant flowing out of the first heat source heat exchanger 13a merges with the refrigerant flowing out of the first utilization heat exchanger 22a and the second utilization heat exchanger 22b, which serve as condensers for heating operation, before the second heat source expansion mechanism 15b. The merged refrigerant passes through the second heat source expansion mechanism 15b, becoming a low-pressure gas-liquid two-phase refrigerant and flowing into the second heat source heat exchanger 13b. The low-pressure refrigerant flowing into the second heat source heat exchanger 13b exchanges heat with the outdoor air delivered by the second heat source fan 14b, becoming a low-pressure gas refrigerant, and then flows out of the second heat source heat exchanger 13b. The low-pressure gas refrigerant flowing out of the second heat source heat exchanger 13b passes through the accumulator 17 and is again drawn into the compressor 11.

[0152] When the heat source control unit 4 determines that the completion condition for the first defrost operation is satisfied, it shifts to the second defrost mode (step S8). The completion condition for the first defrost mode is not particularly limited, and may be, for example, at least one of the following conditions: a predetermined time has passed since the start of the first defrost mode; the temperature of the first heat source heat exchanger 13a is above a predetermined value; or the condensing pressure or condensing temperature of the refrigerant is above a predetermined value.

[0153] In step S8, first, a switching operation for implementing the second defrosting mode is performed. Specifically, the heat source control unit 4 switches the second switching mechanism 12b to evaporate the refrigerant in the first heat source heat exchanger 13a and condense the refrigerant in the second heat source heat exchanger 13b. Figure 8 As shown in FIG. 1 , the heat source control unit 4 switches the second switching mechanism 12 b to the same state as the cooling operation. Here, the rotation speed of the compressor 11 is reduced.

[0154] Then, the heat source control unit 4 starts the second defrosting mode. Here, the heat source control unit 4 controls the first heat source fan 14a and the second heat source fan 14b so that the rotation speed of the first heat source fan 14a is different from the rotation speed of the second heat source fan 14b. In addition, the rotation speed of the compressor 11 is increased.

[0155] Specifically, if Figure 8 As shown, in the refrigerant circuit 2 , low-pressure gas refrigerant in the refrigeration cycle is compressed to high pressure in the refrigeration cycle by the compressor 11 and branches to the second switching mechanism 12 b , the third switching mechanism 12 c , and the fourth switching mechanism 12 d .

[0156] The refrigerant flowing into the third switching mechanism 12c flows through the second stop valve 18b, the second connecting pipe 32, the first utilization heat exchanger 22a, the first utilization expansion mechanism 21a, the first connecting pipe 31, the first stop valve 18a, and the subcooling heat exchanger 16, similarly to the operation in the heating operation, and then flows into the second heat source expansion mechanism 15b. The refrigerant flowing into the fourth switching mechanism 12d flows through the third stop valve 18c, the third connecting pipe 33, the second utilization heat exchanger 22b, the second utilization expansion mechanism 21b, the first connecting pipe 31, the first stop valve 18a, and the subcooling heat exchanger 16, similarly to the operation in the heating operation, and then flows into the first heat source expansion mechanism 15a.

[0157] Alternatively, a portion of the refrigerant that has passed through the first flow path 16 a of the subcooling heat exchanger 16 may be branched to the subcooling circuit 3 .

[0158] Meanwhile, the refrigerant flowing toward the second switching mechanism 12b passes through the second switching mechanism 12b and flows into the second heat source heat exchanger 13b. The high-pressure refrigerant flowing into the second heat source heat exchanger 13b supplies heat to the second heat source heat exchanger 13b. This melts the frost adhering to the second heat source heat exchanger 13b, defrosting the second heat source heat exchanger 13b.

[0159] The high-pressure refrigerant flowing out of the second heat source heat exchanger 13b merges with the refrigerant flowing out of the first utilization heat exchanger 22a and the second utilization heat exchanger 22b, which serve as condensers for heating operation, before the first heat source expansion mechanism 15a. The merged refrigerant passes through the second heat source expansion mechanism 15a, becoming a low-pressure gas-liquid two-phase refrigerant and then flowing into the first heat source heat exchanger 13a. The low-pressure refrigerant flowing into the first heat source heat exchanger 13a exchanges heat with the outdoor air delivered by the first heat source fan 14a, becoming a low-pressure gas refrigerant and flowing out of the first heat source heat exchanger 13a. The low-pressure gas refrigerant flowing out of the first heat source heat exchanger 13a passes through the accumulator 17 and is again drawn into the compressor 11.

[0160] When the heat source control unit 4 determines that the completion conditions for the second defrost mode have been met, it terminates the first defrost operation and proceeds to step S9. The completion conditions for the second defrost mode are not particularly limited and may be the same as those for the first defrost mode. In this embodiment, the second heat source heat exchanger 13b is located below the first heat source heat exchanger 13a. Therefore, the completion conditions for the second defrost mode differ from those for the first defrost mode, taking into account that water generated by the defrost operation of the first heat source heat exchanger 13a during the first defrost mode flows to the second heat source heat exchanger 13b below. Here, the completion conditions include, for example, that the time elapsed from the start of the second defrost mode is longer than the time elapsed from the start of the first defrost mode. Another completion condition includes, for example, that the specified temperature value of the second heat source heat exchanger 13b is higher than the specified temperature value of the first heat source heat exchanger 13a. Another completion condition includes, for example, that the specified condensing pressure or condensing temperature of the refrigerant in the second defrost mode is higher than the specified condensing pressure or condensing temperature of the refrigerant in the first defrost mode.

[0161] Furthermore, in the second defrost operation determined in step S6, frost is removed from only one of the first heat source heat exchanger 13a or the second heat source heat exchanger 13b. Therefore, first, the heat source control unit 4 determines whether the first heat source heat exchanger 13a has been used since the previous defrost operation (step S10). In step S10, if it is determined that the first heat source heat exchanger 13a has been used, only the first heat source heat exchanger 13a has been used since the previous defrost operation, and therefore, the defrost operation of the first heat source heat exchanger 13a is performed (step S11). This step S11 is the same as step S7 for implementing the first defrost method. On the other hand, in step S10, if it is determined that the first heat source heat exchanger 13a has not been used, only the second heat source heat exchanger 13b has been used since the previous defrost operation, and therefore, the defrost operation of the second heat source heat exchanger 13b is performed (step S12). This step S12 is the same as step S8 for implementing the second defrost method.

[0162] When step S11 or step S12 is completed, the second defrosting operation is ended and the process proceeds to step S9.

[0163] In step S9, the heat source control unit 4 determines whether a predetermined third condition is satisfied. In this embodiment, the heat source control unit 4 determines whether any remaining frost is present in the heat source-side heat exchanger 13. The presence of remaining frost can be determined, for example, by determining whether a maximum time to meet the defrost completion condition has been requested. If, in step S9, it is determined that no remaining frost is present, the system switches to heating operation (step S2).

[0164] On the other hand, in step S9, if it is determined that there is frost melt residue, the third defrost operation is executed (step S13). In step S13, the refrigerant is made to flow in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b to remove the frost. Figure 4 The cooling operation is the same as shown. The execution time of the third defrosting operation in this embodiment is shorter than the execution time of the first defrosting operation and the second defrosting operation. When step S13 is completed, the third defrosting operation ends and the heating operation is switched (step S1).

[0165] When the operation is transferred from step S9 to step S1 and when the operation is transferred from step S13 to step S1, the heat source control unit 4 switches to evaporate the refrigerant in the first heat source heat exchanger 13a and the second heat source heat exchanger 13b to enter the heating operation. Figure 5 As shown in FIG. 1 , the heat source control unit 4 switches the second switching mechanism 12 b to the same state as the heating operation and reduces the rotation speed of the compressor 11 .

[0166] (4) Characteristics

[0167] (4-1)

[0168] The heat source unit 10 of this embodiment includes a heat source side heat exchanger 13 and a control unit (heat source control unit 4). The heat source side heat exchanger 13 has a first heat source heat exchanger 13a and a second heat source heat exchanger 13b. The second heat source heat exchanger 13b is arranged below the first heat source heat exchanger 13a. The heat source control unit 4 performs a defrost operation to remove frost from the heat source side heat exchanger 13. The heat source control unit 4 is characterized in that, when performing the defrost operation, the first defrost operation is performed when a prescribed first condition is satisfied, and the second defrost operation is performed when a prescribed second condition is satisfied. The first defrost operation alternately (i.e., more than once) switches between a first defrost mode for removing frost from the first heat source heat exchanger 13a and a second defrost mode for removing frost from the second heat source heat exchanger 13b, and ends with the second defrost mode. The second defrost operation removes frost from only one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b.

[0169] In the heat source unit 10 of this embodiment, the heat source control unit 4 determines whether to perform the first or second defrost operation based on the states of the first and second heat source heat exchangers 13a, 13b. Therefore, if the second condition is met, which eliminates the need for defrosting either the first or second heat source heat exchanger 13a, 13b, the second defrost operation can be performed. Consequently, unnecessary defrost operations can be reduced.

[0170] Furthermore, if the first condition is met, the first defrost operation ends with the defrosting of the second heat source heat exchanger 13b, which is located below the first heat source heat exchanger 13a. Therefore, even if water generated by the defrosting of the first heat source heat exchanger 13a flows to the second heat source heat exchanger 13b below, defrosting the second heat source heat exchanger 13b after the first defrost operation prevents the water from turning into frost. Consequently, efficient defrosting is achieved.

[0171] In this manner, the heat source unit 10 of the present embodiment can suppress a decrease in operating efficiency.

[0172] Furthermore, the first defrosting operation can cope with an outdoor environment with a low outside air temperature and can reliably perform defrosting by switching two or more times between the first defrosting mode for removing frost from the first heat source heat exchanger 13a and the second defrosting mode for removing frost from the second heat source heat exchanger 13b.

[0173] (4-2)

[0174] In the heat source unit 10 of the present embodiment, it is preferable that the heat source control section 4 starts the first defrosting operation in the first defrosting mode, and then switches to the second defrosting mode and ends the operation.

[0175] Here, even if the water generated by the defrosting of the first heat source heat exchanger 13a flows to the second heat source heat exchanger 13b below when the first defrost operation starts, the first defrost operation can be ended while suppressing the water from turning into frost by subsequently defrosting the second heat source heat exchanger 13b.

[0176] (4-3)

[0177] In the heat source unit 10 of this embodiment, it is preferred that the heat source control unit 4 has the following steps: based on whether the first heat source heat exchanger 13a and the second heat source heat exchanger 13b were used after the last defrost operation, it is judged whether the prescribed first condition or the prescribed second condition is met, and it is decided whether to perform the defrost operation with the first defrost operation or the second defrost operation.

[0178] Here, based on the above, it is decided whether to perform the first defrost operation or the second defrost operation. Therefore, when it is not necessary to defrost one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, it can be appropriately decided to perform the second defrost operation.

[0179] (4-4)

[0180] In the heat source unit 10 of this embodiment, the heat source control unit 4 is preferably characterized by further executing a third defrost operation. The third defrost operation removes frost by flowing the refrigerant in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b after the first defrost operation or the second defrost operation.

[0181] Here, by further performing the third defrost operation after performing the first defrost operation or the second defrost operation, frost can be reliably removed from the heat source side heat exchanger 13 .

[0182] Furthermore, the third defrost operation is performed after a large amount of frost adhering to the heat source side heat exchanger 13 has been largely removed by the first or second defrost operation, thereby shortening the time required for the third defrost operation. Since the defrost operation can be performed simultaneously with the heating operation during the first or second defrost operation, user discomfort caused by the third defrost operation can be reduced.

[0183] (4-5)

[0184] The refrigeration cycle apparatus 1 of this embodiment includes the above-mentioned heat source unit 10 and a utilization unit 20. The utilization unit 20 is connected to the heat source unit 10.

[0185] Here, since the heat source unit 10 is included, it is possible to realize the refrigeration cycle apparatus 1 in which a decrease in operation efficiency is suppressed.

[0186] <Second embodiment>

[0187] (1) Overall structure

[0188] The heat source unit 10 and the refrigeration cycle apparatus 1 of the second embodiment are basically the same as those of the first embodiment, but the second embodiment differs in that the first defrosting operation starts from the second defrosting mode.

[0189] (2) Detailed structure

[0190] The defrost control performed by the heat source control unit 4 in the second embodiment will be described. The heat source control unit 4 begins the first defrost operation in the second defrost mode and performs both the first defrost mode and the second defrost mode at least once as the first defrost operation. In this embodiment, the heat source control unit 4 begins in the second defrost mode, then switches to the first defrost mode, then switches back to the second defrost mode and ends. Therefore, the first defrost operation consists of only two runs in the second defrost mode and one run in the first defrost mode.

[0191] (3) Action

[0192] The defrosting operation of the second embodiment is basically the same as that of the first embodiment, but differs in the defrosting operation. The differences will be described below.

[0193] Specifically, if Figure 9 As shown, when the heat source control unit 4 determines to execute the first defrost operation (step S5), it starts with the second defrost mode (step S14). Step S14 is the same as step S8. However, the completion conditions of the second defrost mode in step S14 can be more relaxed than those in step S8. Here, the completion conditions of the second defrost mode in step S14 are the same as those of the first defrost mode in step S7.

[0194] (4) Characteristics

[0195] (4-1)

[0196] The heat source unit 10 of this embodiment includes a heat source side heat exchanger 13 and a control unit (heat source control unit 4). The heat source side heat exchanger 13 has a first heat source heat exchanger 13a and a second heat source heat exchanger 13b. The second heat source heat exchanger 13b is arranged below the first heat source heat exchanger 13a. The heat source control unit 4 performs a defrost operation to remove frost from the heat source side heat exchanger 13. The heat source control unit 4 is characterized in that, when performing the defrost operation, the first defrost operation is performed when a prescribed first condition is satisfied, and the second defrost operation is performed when a prescribed second condition is satisfied. The first defrost operation alternately switches between a first defrost mode for removing frost from the first heat source heat exchanger 13a and a second defrost mode for removing frost from the second heat source heat exchanger 13b, and starts from the second defrost mode. The second defrost operation removes frost from only one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b.

[0197] In the heat source unit 10 of this embodiment, the heat source control unit 4 determines whether to perform the first or second defrost operation based on the states of the first and second heat source heat exchangers 13a, 13b. Therefore, if the second condition is met, which eliminates the need for defrosting either the first or second heat source heat exchanger 13a, 13b, the second defrost operation can be performed. Consequently, unnecessary defrost operations can be reduced.

[0198] Furthermore, if the first condition is met, during the first defrost operation, defrosting begins with the second heat source heat exchanger 13b, located below the first heat source heat exchanger 13a. The second heat source heat exchanger 13b, located below the first heat source heat exchanger 13a, is susceptible to ice and snow on the ground, and therefore has a higher likelihood of frost. Therefore, by starting defrosting with the second heat source heat exchanger 13b, the amount of frost on the second heat source heat exchanger 13b can be reduced before defrosting the first heat source heat exchanger 13a. This allows for efficient defrosting.

[0199] In this manner, the heat source unit 10 of the present embodiment can suppress a decrease in operating efficiency.

[0200] (4-2)

[0201] In the heat source unit 10 of this embodiment, it is preferable that the heat source control section 4 starts the first defrosting operation from the second defrosting mode, then switches to the first defrosting mode, and then switches to the second defrosting mode and ends.

[0202] In the heat source unit 10 of this embodiment, the first defrost operation is easily affected by ice or snow on the ground. Therefore, defrosting begins with the second heat source heat exchanger 13b, which has a higher likelihood of frost formation. Therefore, after the amount of frost has been significantly reduced by defrosting the second heat source heat exchanger 13b, defrosting the first heat source heat exchanger 13a can be performed. Even if water generated by defrosting the first heat source heat exchanger 13a flows to the second heat source heat exchanger 13b below, the subsequent defrosting of the second heat source heat exchanger 13b allows the second defrost operation to be terminated while preventing the water from turning into frost. Consequently, frost can be efficiently removed from the heat source side heat exchanger 13.

[0203] <Modifications of the First and Second Embodiments>

[0204] (5-1) Modification 1

[0205] In the above-mentioned first and second embodiments, in step S4 of deciding whether to perform the defrost operation in the first defrost operation or the second defrost operation, whether the prescribed first condition or the prescribed second condition is satisfied is judged based on whether the first heat source heat exchanger 13a and the second heat source heat exchanger 13b were used after the previous defrost operation is described as an example, but it is not limited to this.

[0206] In this variation, in step S4, the heat source control unit 4 determines whether a predetermined first condition or a predetermined second condition is satisfied based on the state of the refrigerant flowing through at least one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, and determines whether to perform the defrost operation using the first defrost operation or the second defrost operation. Here, the first defrost operation is performed when the difference between the outlet temperature of the first heat source heat exchanger 13a and the outlet temperature of the second heat source heat exchanger 13b is below a predetermined value, and the second defrost operation is performed when the difference exceeds the predetermined value.

[0207] The heat source unit 10 of the modified example of the first embodiment and the second embodiment is characterized in that the heat source control unit 4 has the following steps: based on the state of the refrigerant flowing in at least one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, it is judged whether the prescribed first condition or the prescribed second condition is satisfied, and it is decided whether to perform the defrost operation with the first defrost operation or the second defrost operation.

[0208] Here, based on the above, it is decided whether to perform the first defrost operation or the second defrost operation. Therefore, when it is not necessary to defrost one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, it can be appropriately decided to perform the second defrost operation.

[0209] (5-2) Modification 2

[0210] In the first and second embodiments described above, the third defrosting operation is performed when the predetermined third condition is satisfied. However, the third defrosting operation may be omitted.

[0211] <Third embodiment>

[0212] (1) Overall structure

[0213] The heat source unit 10 and the refrigeration cycle apparatus 1 of the third embodiment are basically the same as those of the first embodiment, but differ in that the heat source control unit 4 of the third embodiment determines whether to execute the defrosting operation in the first defrosting operation or the third defrosting operation.

[0214] (2) Detailed structure

[0215] The defrost control performed by the heat source control unit 4 of the third embodiment will be described. When performing the defrost operation, the heat source control unit 4 executes either the first defrost operation or the third defrost operation. The first defrost operation is the same as that of the first embodiment. In the third defrost operation of this embodiment, when a predetermined third condition is satisfied, the refrigerant is caused to flow in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b to remove frost.

[0216] Specifically, the third defrost operation of this embodiment is different in that it is performed before the first or second defrost operation. In addition, the heat source control unit 4 may also perform the third defrost operation after the first or second defrost operation, as in the first embodiment.

[0217] Furthermore, the third condition for determining whether to execute the third defrost operation before the first or second defrost operation differs from the third condition for determining whether to execute the third defrost operation after the first or second defrost operation. The third condition for determining whether to execute the third defrost operation before the first or second defrost operation is that the outside air temperature is below a threshold. The threshold is the temperature at which a large amount of frost forms on the heat source-side heat exchanger 13, for example, 0°C.

[0218] (3) Action

[0219] The defrosting operation of the third embodiment is basically the same as that of the first embodiment, but differs in the defrosting operation. The differences will be described below.

[0220] Specifically, if Figure 10 As shown, when the heat source control unit 4 determines to execute the defrost operation (step S3), it determines whether the predetermined first condition or the predetermined third condition is satisfied based on the outside air temperature, and determines whether to execute the defrost operation in the first defrost operation or the third defrost operation (step S21). In step S21, the heat source control unit 4 obtains the outside air temperature from the outdoor temperature sensor 41 and determines whether the obtained outside air temperature is below a threshold value.

[0221] If the outside air temperature is equal to or lower than the threshold value in step S21, it is determined to execute the third defrosting operation (step S13). Step S13 is the same as that of the first embodiment.

[0222] On the other hand, if the outside air temperature exceeds the threshold in step S21, a determination is made as to whether the first or second condition is satisfied in order to determine whether the first or second defrost operation is to be executed (step S4). In step S4, similarly to the first embodiment, the heat source control unit 4 determines whether the first heat source heat exchanger 13a and the second heat source heat exchanger 13b have been used since the previous defrost operation.

[0223] (4) Characteristics

[0224] (4-1)

[0225] The heat source unit 10 of this embodiment includes a heat source side heat exchanger 13 and a control unit (heat source control unit 4). The heat source side heat exchanger 13 has a first heat source heat exchanger 13a and a second heat source heat exchanger 13b. The second heat source heat exchanger 13b is connected in parallel with the first heat source heat exchanger 13a. The heat source control unit 4 performs a defrost operation to remove frost from the heat source side heat exchanger 13. The heat source control unit 4 is characterized in that, when performing the defrost operation, when a prescribed first condition is satisfied, a first defrost operation is performed, and when a prescribed third condition is satisfied, a third defrost operation is performed. The first defrost operation alternately switches between a first defrost mode for removing frost from the first heat source heat exchanger 13a and a second defrost mode for removing frost from the second heat source heat exchanger 13b. The third defrost operation causes the refrigerant to flow in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, and removes frost.

[0226] In the heat source unit 10 of this embodiment, the heat source control unit 4 determines whether to perform the defrost operation using the first defrost operation or the third defrost operation based on the states of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b. Therefore, when defrosting of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b is necessary, the third defrost operation can be performed. Consequently, the heat source side heat exchanger 13 can be defrosted efficiently.

[0227] Furthermore, when defrosting does not require flowing the refrigerant in parallel through the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, the heating operation can be continued by performing the first defrosting operation while using one as an evaporator.

[0228] In this manner, the heat source unit 10 of the present embodiment can suppress a decrease in operating efficiency.

[0229] (4-2)

[0230] In the heat source unit 10 of this embodiment, the heat source control section 4 preferably includes the steps of determining whether a prescribed first condition or a prescribed third condition is satisfied based on the outside air temperature, and determining whether to perform the defrosting operation in the first defrosting operation or the third defrosting operation.

[0231] Here, whether to perform the first defrost operation or the third defrost operation is determined based on the outside air temperature. Therefore, if the outside air temperature is low and the efficiency of the first defrost operation, which switches to defrosting one of the first heat source heat exchanger 13a and the second heat source heat exchanger 13b, decreases, the third defrost operation can be determined.

[0232] <Modification of the Third Embodiment>

[0233] (5-1) Modification 1

[0234] In the third embodiment, the first defrost operation of the first embodiment is performed, but the present invention is not limited thereto. The first defrost operation of the third embodiment may also start from the second defrost mode as in the second embodiment, and the number of first and second defrost modes is not limited.

[0235] (5-2) Modification 2

[0236] In the third embodiment described above, Figure 3 As shown, the second heat source heat exchanger 13b is arranged below the first heat source heat exchanger 13a. However, the first heat source heat exchanger 13a and the second heat source heat exchanger 13b do not need to be arranged in the vertical direction as long as they are connected in parallel.

[0237] (5-3) Modification 3

[0238] In the third embodiment described above, the second defrosting operation is executed when the predetermined second condition is satisfied. However, the second defrosting operation may be omitted.

[0239] <Modifications of the First to Third Embodiments>

[0240] (5-1) Modification 1

[0241] In the first to third embodiments described above, the first defrost mode is described as follows: in the first defrost mode, the first heat source heat exchanger 13a is used as a condenser, and the second heat source heat exchanger 13b is used as an evaporator for heating operation; in the second defrost mode, the second heat source heat exchanger 13b is used as a condenser, and the first heat source heat exchanger 13a is used as an evaporator for heating operation. However, this is not limiting. In the first defrost mode, frost can also be removed from the first heat source heat exchanger 13a without using the second heat source heat exchanger 13b. Furthermore, in the second defrost mode, frost can also be removed from the second heat source heat exchanger 13b without using the first heat source heat exchanger 13a.

[0242] (5-2) Modification 2

[0243] In the above embodiment, the heat source side heat exchanger 13 including two heat source heat exchangers 13a and 13b is described as an example, but the present invention is not limited thereto. The heat source side heat exchanger of the present disclosure may include three or more heat source heat exchangers as long as it includes a plurality of heat source heat exchangers.

[0244] (5-3) Modification 3

[0245] In the first to third embodiments described above, the capacity of the first heat source heat exchanger 13 a and the capacity of the second heat source heat exchanger 13 b are the same, but they may be different.

[0246] (5-4) Modification 4

[0247] In the first to third embodiments, the first heat source fan 14a for supplying air through the first heat source heat exchanger 13a and the second heat source fan 14b for supplying air through the second heat source heat exchanger 13b are provided separately. However, the number of heat source fans is not limited and they may be shared.

[0248] In addition, in the first to third embodiments, the first utilization fan 23a for supplying air through the first utilization heat exchanger 22a and the second utilization fan 23b for supplying air through the second utilization heat exchanger 22b are provided separately, but the number of utilization fans is not limited. Figure 11 As shown, a utilization fan 23a is provided for supplying air through the first utilization heat exchanger 22a and the second utilization heat exchanger 22b.

[0249] (5-5) Modification 5

[0250] In the above embodiment, the refrigerant passes through the subcooling circuit 3 during the heating operation and the defrosting operation, but it is also possible not to pass through the subcooling circuit 3. In addition, the subcooling circuit 3 can be omitted from the refrigeration cycle device of the present disclosure.

[0251] (5-6) Modification 6

[0252] In the first to third embodiments, the refrigeration cycle device 1 including one utilization unit 20 having two utilization heat exchangers 22a and 22b is described as an example, but the present invention is not limited thereto. The utilization unit constituting the refrigeration cycle device of the present disclosure may also be as follows. Figure 12 As shown, the refrigeration cycle device may include one utilization unit or multiple utilization units. In this case, the refrigeration cycle device can also be used as a refrigeration cycle device that can enable multiple utilization units to independently perform cooling operation or heating operation.

[0253] (5-7) Modification 7

[0254] In the first to third embodiments, the refrigeration cycle device 1 that performs cooling, heating, and defrosting operations is described as an example, but the present invention is not limited thereto. The refrigeration cycle device of the present disclosure may also perform a dehumidification operation, or may omit the cooling operation.

[0255] (5-8) Modification 8

[0256] In the first to third embodiments, an air conditioner is described as an example of the refrigeration cycle device 1, but the present invention is not limited thereto. The refrigeration cycle device of the present disclosure may also be a water heater, a floor heating device, a refrigeration device, or the like.

[0257] While the embodiments of the present disclosure have been described above, it should be understood that various modifications in form and detail can be made without departing from the spirit and scope of the present disclosure as described in the claims.

[0258] Prior art literature

[0259] Patent Literature

[0260] Patent Document 1: Japanese Patent Application Laid-Open No. 9-318206.

Claims

1. A heat source unit (10), characterized in that: include: a heat source side heat exchanger (13), the heat source side heat exchanger comprising a first heat source heat exchanger (13a) and a second heat source heat exchanger (13b) arranged below the first heat source heat exchanger; and a control unit (4) that performs a defrosting operation to remove frost from the heat source side heat exchanger, When the control unit performs the defrosting operation, When a predetermined first condition is satisfied, a first defrost operation is performed, wherein the first defrost operation is switched at least once between a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger, and the operation is terminated with the second defrost mode. When a predetermined second condition is satisfied, a second defrosting operation is executed in which frost is removed from only one of the first heat source heat exchanger and the second heat source heat exchanger.

2. The heat source unit according to claim 1, wherein The control unit starts the first defrosting operation in the first defrosting mode, switches to the second defrosting mode, and ends the operation.

3. A heat source unit (10), characterized in that: include: a heat source side heat exchanger (13), the heat source side heat exchanger comprising a first heat source heat exchanger (13a) and a second heat source heat exchanger (13b) arranged below the first heat source heat exchanger; and a control unit (4) that performs a defrosting operation to remove frost from the heat source side heat exchanger, When the control unit performs the defrosting operation, When a predetermined first condition is satisfied, a first defrost operation is performed, wherein in the first defrost operation, a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger are switched at least once, and the second defrost mode is started. When a predetermined second condition is satisfied, a second defrosting operation is executed in which frost is removed from only one of the first heat source heat exchanger and the second heat source heat exchanger.

4. The heat source unit according to any one of claims 1 to 3, characterized in that The control unit has the following steps: based on whether the first heat source heat exchanger and the second heat source heat exchanger were used after the last defrost operation, it is judged whether the prescribed first condition or the prescribed second condition is met, and it is decided whether to perform the defrost operation with the first defrost operation or the second defrost operation.

5. The heat source unit according to any one of claims 1 to 3, characterized in that The control unit has the following steps: based on the state of the refrigerant flowing in at least one of the first heat source heat exchanger and the second heat source heat exchanger, it is judged whether the prescribed first condition or the prescribed second condition is satisfied, and whether the defrost operation is performed in the first defrost operation or the second defrost operation.

6. The heat source unit according to any one of claims 1 to 3, characterized in that The control unit further performs a third defrost operation after the first defrost operation or the second defrost operation, in which the refrigerant is caused to flow in parallel through the first heat source heat exchanger and the second heat source heat exchanger to remove frost.

7. A heat source unit, characterized in that: include: a heat source side heat exchanger (13), the heat source side heat exchanger having a first heat source heat exchanger (13a) and a second heat source heat exchanger (13b) connected in parallel with the first heat source heat exchanger; and a control unit (4) that performs a defrosting operation to remove frost from the heat source side heat exchanger, When the control unit performs the defrosting operation, When a predetermined first condition is satisfied, a first defrost operation is executed, wherein a first defrost mode for removing frost from the first heat source heat exchanger and a second defrost mode for removing frost from the second heat source heat exchanger are switched at least once in the first defrost operation. When a predetermined third condition is satisfied, a third defrosting operation is executed in which refrigerant is caused to flow in parallel through the first heat source heat exchanger and the second heat source heat exchanger to remove frost.

8. The heat source unit according to claim 7, characterized in that The control unit includes a step of determining whether the predetermined first condition or the predetermined third condition is satisfied based on the outside air temperature, and determining whether to execute the defrosting operation in the first defrosting operation or the third defrosting operation.

9. The heat source unit according to any one of claims 1 to 3, 7 and 8, characterized in that: The control unit starts the first defrosting operation from the second defrosting mode, switches to the first defrosting mode, and then switches to the second defrosting mode and ends.

10. A refrigeration cycle device (10), characterized in that: include: The heat source unit according to any one of claims 1 to 3, 7, and 8; as well as A utilization unit (20) connected to the heat source unit.

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