GB2541607A

GB2541607A - Refrigeration cycle device

Info

Publication number: GB2541607A
Application number: GB1620966.0A
Authority: GB
Inventors: Okano Hiroyuki
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2014-05-19
Filing date: 2014-05-19
Publication date: 2017-02-22
Anticipated expiration: 2034-05-19
Also published as: GB2541607B; JPWO2015177852A1; GB201620966D0; JP6042037B2; WO2015177852A1

Abstract

A refrigeration cycle device equipped with: a heat storage unit that is provided between multiple heat-source-side units and load-side units, and that performs a heat exchange with a refrigerant flowing between the multiple heat-source-side units and load-side units; a heat storage switching device that switches between a flow path that introduces refrigerant from the multiple heat-source-side units to the heat storage unit and a flow path that introduces refrigerant from the load-side units to the heat storage unit; a heat-source-side unit selection unit that, when the heat storage switching device switches to the flow path for introducing refrigerant from the load-side units to the heat storage unit, selects a heat-source-side unit into which the refrigerant flowing from the heat storage unit is introduced; and a control device that performs a control so as to turn off a first on-off valve and turn on a second on-off valve in the heat-source-side unit selected by the heat-source-side selection unit.

Description

DESCRIPTION

Title of Invention REFRIGERATION CYCLE APPARATUS Technical Field [0001]

The present invention relates to a refrigeration cycle apparatus including a plurality of heat source unit.

Background Art [0002]

Hitherto, there has been known a refrigeration cycle apparatus including a heat storage tank, and there has been proposed an air-conditioning apparatus capable of heating the inside of a room in a defrosting operation through use of heat stored in the heat storage tank (see, for example, Patent Literature 1), In Patent Literature 1, there is disclosed an air-conditioning apparatus in which, in a heating and heat storage operation mode, a use-side heat exchanger and a heat exchanger for heat storage function as a condenser, a heat source-side heat exchanger functions as an evaporator, and, in the defrosting operation, the heat source-side heat exchanger functions as a condenser and the heat exchanger for heat storage functions as an evaporator. In other words, in Patent Literature 1, through utilization of, in the defrosting operation, heat stored in the heat storage tank in the heating and heat storage operation mode, the heating operation continues even in the defrosting operation.

Citation List Patent Literature [0003]

Patent Literature 1: Japanese Patent No. 4457755 Summary of Invention

Technical Problem [0004]

In Patent Literature 1, one heat storage tank is connected to one heat source unit. When this configuration is applied to a refrigeration cycle apparatus including a plurality of heat source-side units, as many heat storage tanks as the number of the heat source-side units are necessary. As a result, the footprint and the costs increase.

[0005]

The present invention has been made to solve the problem described above, and an object of the present invention is to provide an air-conditioning apparatus that is space-saving, and at the same time, is capable of defrosting a plurality of heat source-side units through use of a heat storage unit.

Solution to Problem [0006]

According to one embodiment of the present invention, there is provided a refrigeration cycle apparatus, including a plurality of heat source-side units, each including a compressor, a flow switching device, and a heat source-side heat exchanger connected in the stated order, and the plurality of heat source-side units each further including, a first on/off vaive arranged on a refrigerant flow path extending from the load-side unit to the heat source-side heat exchanger, a bypass pipe configured to connect a discharge side of the compressor and the heat source-side heat exchanger to each other, and a second on/off valve arranged on the bypass pipe, the second on/off valve being configured to control an inflow of refrigerant from the compressor to the heat source-side heat exchanger, a load-side unit connected to the plurality of heat source-side unit, the load-side unit including a load-side heat exchanger, a refrigerant circuit including a load-side unit having a load-side heat exchanger, the plurality of heat source-side units being connected the refrigerant circuit, the refrigerant circuit being configured to circulate refrigerant between the plurality of heat source-side units and the load-side unit, a heat storage unit arranged between the plurality of heat source-side units and the load-side unit, the heat storage unit being configured to exchange heat with the refrigerant flowing between the plurality of heat source-side units and the load-side unit; a heat storage switching device configured to switch between a flow of refrigerant flowing from the plurality of heat source-side units into the heat storage unit and a flow of refrigerant flowing from the load-side unit into the heat storage unit; a heat source-side unit selection unit configured to select one of the plurality of heat source-side units that, when the heat storage switching device switches to the flow of refrigerant flowing from the load-side unit into the heat storage unit, allows the refrigerant flowing out of the heat storage unit to flow therein; and a controller configured to exert control such that, in the one of the plurality of heat source-side units selected by the heat source-side unit selection unit, the first on/off valve is in a closed state and the second on/off valve is in an open state.

Advantageous Effects of Invention [0007]

With the air-conditioning apparatus according to one embodiment of the present invention, through control of the heat source-side unit selected by the heat source-side unit selection unit such that the first on/off valve thereof is in a closed state and the second on/off valve thereof is in an open state, the plurality of heat source-side units can be defrosted through use of heat storage units fewer than the number of the heat source-side units. Thus, space is saved, and at the same time, the heat source-side units can be defrosted through use of the heat storage unit.

Brief Description of Drawings [0008] [Fig. 1] Fig. 1 is a refrigerant circuit diagram for illustrating an exemplary refrigeration cycle apparatus according to an embodiment of the present invention.

[Fig. 2] Fig. 2 is a refrigerant circuit diagram for illustrating a refrigerant flow in a heating only operation mode of the refrigeration cycle apparatus illustrated in Fig. 1.

[Fig. 3] Fig. 3 is a refrigerant circuit diagram for illustrating a refrigerant flow in a defrosting operation mode of the refrigeration cycle apparatus illustrated in Fig. 1.

[Fig. 4] Fig, 4 is a flow chart for illustrating exemplary operation of a heat source-side unit selection unit 24 in a defrosting operation illustrated in Fig. 3.

[Fig. 5] Fig. 5 is a graph for showing exemplary control of an operation frequency of a compressor in the refrigeration cycle apparatus illustrated in Fig. 1.

Description of Embodiments [0009]

Embodiment 1

An embodiment of the present invention is described below with reference to the drawings. Fig. 1 is a refrigerant circuit diagram for illustrating an exemplary refrigeration cycle apparatus according to the embodiment of the present invention. A refrigeration cycle apparatus 1 is described with reference to Fig. 1. In the drawings referred to below including Fig. 1, there is a case in which components are not drawn to scale.

[0010]

The refrigeration cycle apparatus 1 is installed in, for example, a building or a condominium to perform a cooling and heating mixed operation through use of a refrigeration cycle (heat pump cycle) for circulating refrigerant. The refrigeration cycle apparatus 1 includes a plurality of heat source-side units 10A and 10B, a heat storage unit 20, a refrigerant control unit 30, and a plurality of load-side units 40A and 40B. The plurality of heat source-side units 10A and 10B, the heat storage unit 20, the refrigerant control unit 30, and the plurality of load-side units 40A and 40B are connected in the stated order.

[0011]

The plurality of heat source-side units 10A and 10B are connected to the heat storage unit 20 via low-pressure pipes 2A and 2B and high-pressure pipes 3A and 3B, respectively. Specifically, the low-pressure pipes 2A and 2B are connected to a low-pressure junction pipe 2C, and the low-pressure junction pipe 2C is connected to the heat storage unit 20 via a low-pressure pipe 2D, The low-pressure junction pipe 2C branches refrigerant flowing from the heat storage unit 20 via the low-pressure pipe 2D into the low-pressure pipes 2A and 2B to cause the refrigerant to flow into the heat source-side units 10Aand 10B, respectively.

[0012]

The high-pressure pipes 3A and 3B are connected to a high-pressure junction pipe 3C: and the high-pressure junction pipe 3C is connected to the heat storage unit 20 via a high-pressure pipe 3D. The high-pressure junction pipe 3C joins refrigerant flowing through the high-pressure pipes 3A and 3B, and causes the joined refrigerant to flow into the heat storage unit 20 via the high-pressure pipe 3D. Further, the plurality of heat source-side units 10A and 10B are independently connected to the heat storage unit 20 via pipes 5A and 5B, respectively, such that the refrigerant flows from the heat storage unit 20 into the plurality of heat source-side units 10A and 10B via the pipes 5A and 5B, respectively. In this way, the plurality of heat source-side units 10A and 10B and the heat storage unit 20 are connected through use of the four pipes of the low-pressure pipe 2D, the high-pressure pipe 3D, and the pipes 5A and 5B.

[0013]

Further, the heat storage unit 20 and the refrigerant control unit 30 are connected via two pipes of a low-pressure pipe 2E and the high-pressure pipe 3D. The refrigerant control unit 30 and the plurality of load-side units 40A and 40B are connected via liquid pipes 6A and 6B and gas pipes 7A and 7B, respectively. In this way, the plurality of heat source-side units 10A and 10B, the heat storage unit 20, the refrigerant control unit 30, and the plurality of load-side units 40A and 40B form a refrigeration cycle.

[0014]

The refrigeration cycle can use various kinds of known refrigerants, for example, a natural refrigerant, e.g., carbon dioxide, a hydrocarbon, or helium, an alternative refrigerant that does not contain chlorine, e.g., HFC410A, HFC407C, or HFC404A, or a fluorocarbon refrigerant, e.g., R22 or R134a that is used in existing products.

[0015] [Heat Source-side Units 10A and 10B]

The plurality of heat source-side units 10A and 10B have the function of supplying cooling energy or heating energy to the load-side units 40A and 40B. An exemplary case in which the plurality of heat source-side units 10A and 10B have the same configuration is described below, but the plurality of heat source-side units 10A and 10B may have different configurations.

[0016]

Each of the heat source-side units 10A and 10B includes a compressor 11, a first flow switching device 12, a heat source-side heat exchanger 13, and an accumulator 14, and those components form a refrigerant circuit in which those components are connected in series. The compressor 11 sucks low-temperature and low-pressure gas refrigerant, compresses the refrigerant into high-temperature and high-pressure gas refrigerant, and circulates the refrigerant in the system, thereby performing air-conditioning operation. As the compressor 11, a known compressor can be used, for example, a capacity-controllable inverter type compressor, a constant speed compressor, or a compressor that is a combination of the inverter type compressor and the constant speed compressor. Further, it is only necessary that the compressor 11 can compress sucked refrigerant into a high pressure state, and the type thereof is not specifically limited. For example, the compressor 11 can be formed through use of various types, e.g., a reciprocating one, a rotary one, a scroll one, or a screw one.

[0017]

The first flow switching device 12 is formed of, for example, a four-way valve, and is formed on a discharge side of the compressor 11 to switch the refrigerant flow between in the cooling operation and in the heating operation. In the heating operation, the first flow switching device 12 connects the heat source-side heat exchanger 13 and the accumulator 14, and connects the discharge side of the compressor 11 and a check valve 15c. Then, the refrigerant discharged from the compressor 11 flows to the heat storage unit 20 side. On the other hand, in the cooling operation, the first flow switching device 12 connects the accumulator 14 and a check valve 15a, and connects the discharge side of the compressor 11 and the heat source-side heat exchanger 13. Then, the refrigerant discharged from the compressor 11 flows to the heat source-side heat exchanger 13 side. An exemplary case in which a four-way valve is used as the first flow switching device 12 is described, but the present invention is not limited thereto, and, for example, a plurality of two-way valves may be combined.

[0018]

The heat source-side heat exchanger 13 exchanges heat between, for example, a heat medium, e.g., ambient air or water and the refrigerant, and, in the heating operation, evaporates and gasifies the refrigerant as an evaporator, and, in the cooling operation, condenses and liquefies the refrigerant as a condenser (radiator). The heat source-side heat exchanger 13 is formed of, for example, an aircooled heat exchanger, e g., a fin tube type heat exchanger, and is provided with a fan 13A configured to control a heat exchange amount of the heat source-side heat exchanger 13. Through control of the number of revolutions made by the fan 13A, a condensing capacity or an evaporating capacity is controlled. An exemplary case in which the heat source-side heat exchanger 13 is an air-cooled heat exchanger is described, but the heat source-side heat exchanger 13 may be a water-cooled heat exchanger. In this case, the condensing capacity or the evaporating capacity is controlled by the number of revolutions of a water circulation pump.

[0019]

The accumulator 14 is arranged on a suction side of the compressor 11, and has the function of storing redundant refrigerant and the function of separating liquid refrigerant and gas refrigerant. The compressor 11 sucks and compresses gas refrigerant in the refrigerant stored in the accumulator 14.

[0020]

Further, the heat source-side unit 10A includes four check valves 15a to 15d configured to direct a refrigerant flow into the heat storage unit 20 in a fixed direction in any case of a heating flow and a cooiing flow that are switched by the first flow switching device 12. The check valve 15a is located between the first flow switching device 12 and the low-pressure pipe 2A to allow flowing of the refrigerant from the low-pressure pipe 2A toward the first flow switching device 12. The check valve 15b is located between the low-pressure pipe 2A and the heat source-side heat exchanger 13 to allow flowing of the refrigerant from the low-pressure pipe 2A toward the heat source-side heat exchanger 13. The check valve 15c is located between the first flow switching device 12 and the high-pressure pipe 3A to allow flowing of the refrigerant from the first flow switching device 12 toward the high-pressure pipe 3D. The check valve 15d is located between the heat source-side heat exchanger 13 and the high-pressure pipe 3A to allow flowing of the refrigerant from the heat source-side heat exchanger 13 toward the high-pressure pipes 3A or 3B.

[0021]

The heat source-side unit 10A further includes four check valves 16a to 16d configured to direct a refrigerant flow into the heat source-side heat exchanger 13 in a fixed direction in any case of a heating flow and a cooiing flow that are switched by the first flow switching device 12, The check valve 16a is located between the first flow switching device 12 and the heat source-side heat exchanger 13 to allow flowing of refrigerant from the first flow switching device 12 toward the heat source-side heat exchanger 13. The check valve 16b is located between the high-pressure pipe 3A and the heat source-side heat exchanger 13 to allow flowing of the refrigerant from the high-pressure pipe 3A toward the heat source-side heat exchanger 13. The check valve 16c is located between the heat source-side heat exchanger 13 and the accumulator 14 to allow flowing of the refrigerant from the heat source-side heat exchanger 13 toward the accumulator 14. The check valve 16d is located between the heat source-side heat exchanger 13 and the high-pressure pipe 3A to allow flowing of the refrigerant from the heat source-side heat exchanger 13 toward the high-pressure pipe 3A.

[0022]

Further, each of the heat source-side units 10A and 10B includes a first on/off valve 17, a bypass pipe 18, and a second on/off valve 19 arranged on a refrigerant inflow side of the heat source-side heat exchanger 13. The first on/off valve 17 is arranged on a refrigerant flow path extending from the load-side unit 40A or 40B to the heat source-side heat exchanger 13, and controls a flow rate of the refrigerant flowing to the heat source-side heat exchanger 13 via the first flow switching device 12 through an opening and closing operation thereof.

[0023]

The bypass pipe 18 connects the discharge side of the compressor 11 and the heat source-side heat exchanger 13. The second on/off valve 19 is arranged on the bypass pipe 18 to control an inflow of the refrigerant from the compressor 11 to the heat source-side heat exchanger 13. In a defrosting operation, control is exerted such that the first on/off valve 17 is in a closed state and the second on/off valve 19 is in an open state. Then, the gas refrigerant discharged from the compressor 11 can flow in the heat source-side heat exchanger 13 to defrost the heat source-side heat exchanger 13 (hot gas defrost).

[0024] [Heat Storage Unit 20]

The heat storage unit 20 is placed between the heat source-side units 10A and 10B and the refrigerant control unit 30, and stores heat supplied from the heat source-side units 10A and 10B to be a utilized-heat source in the defrosting operation. The heat storage unit 20 includes a heat storage flow switching device 21, a heat storage unit 22, a refrigerant branch unit 23, and a heat source-side unit selection unit 24.

The heat storage flow switching device 21 is formed of, for example, a four-way valve, and is configured to switch between a flow of refrigerant flowing from the plurality of heat source-side units 10A and 10B into the heat storage unit 22 and a flow of refrigerant flowing from the load-side units 40A and 40B into the heat storage unit 22. Specifically, in the heating operation, the heat storage flow switching device 21 causes part of the refrigerant flowing through the high-pressure pipe 3D to flow to a heat storage heat exchanger 22B side. On the other hand, in the defrosting operation, the heat storage flow switching device 21 switches such that the refrigerant flowing out of the heat storage heat exchanger 22B to flow to the heat source-side units 10A and 10B side via the heat source-side unit selection unit 24.

[0025]

The heat storage unit 22 is arranged between the plurality of heat source-side units 10A and 10B and the ioad-side units 40A and 40B and exchanges heat with the refrigerant flowing between the plurality of heat source-side units 10A and 10B and the load-side units 40A and 40B. Specifically, the heat storage unit 22 has a configuration in which the heat storage heat exchanger 22B is housed in a heat storage tank 22A having a medium, e.g., heat storage water stored therein. One end of the heat storage heat exchanger 22B is connected to the heat storage flow switching device 21, while an other end thereof is connected to the refrigerant branch unit 23.

[0026]

The refrigerant branch unit 23 joins or branches the refrigerant flowing in from the low-pressure pipe 2E into the low-pressure pipe 2D and the heat storage heat exchanger 22B in accordance with an operation mode. The refrigerant branch unit 23 includes a check valve 23a and an expansion device 23b that are arranged between the heat storage flow switching device 21 and the low-pressure pipe 2E so as to be connected in parallel with each other. The check valve 23a is mounted so as to allow flowing of the refrigerant from the low-pressure pipe 2E toward the heat storage heat exchanger 22B. The expansion device 23b is configured to decompress the refrigerant flowing out of the heat storage heat exchanger 22B.

[0027]

In a heating operation mode, the refrigerant branch unit 23 joins the refrigerant flowing in from the refrigerant control unit 30 via the low-pressure pipe 2E and the check valve 23a and the refrigerant flowing out of the heat storage heat exchanger 22B and decompressed by the expansion device 23b, and the refrigerant flows to the low-pressure pipe 2D side. On the other hand, in a defrosting operation mode, the refrigerant branch unit 23 branches the refrigerant flowing in from the refrigerant control unit 30 via the low-pressure pipe 2E and the check valve 23a into the low-pressure pipe 2D and the heat storage heat exchanger 22B.

[0028]

The heat source-side unit selection unit 24 supplies the refrigerant flowing out of the heat storage heat exchanger 22B in the defrosting operation to the heat source-side unit 10A or the heat source-side unit 10B in which the defrosting operation is performed. The heat source-side unit selection unit 24 includes a first heat storage-side on/off valve 24A connected to the heat source-side unit 10A via a pipe 5A, and a second heat storage-side on/off valve 24B connected to the heat source-side unit 10B via a pipe 5B. When the first heat storage-side on/off valve 24A is in the open state and the second heat storage-side on/off valve 24B is in the closed state, the refrigerant flows from the heat storage heat exchanger 22B to the heat source-side unit 10A. On the other hand, when the first heat storage-side on/off valve 24A is in the dosed state and the second heat storage-side on/off valve 24B is in the open state, the refrigerant flows from the heat storage heat exchanger 22B to the heat source-side unit 10B.

[0029]

In Fig. 1, the heat storage unit 20 is a unit separate from the heat source-side units 10A and 10B, but may be built in any one of the heat source-side units 10A and 10B. Further, an exemplary case in which the heat source-side unit selection unit 24 is arranged in the heat storage unit 20 is described, but the heat source-side unit selection unit 24 may be arranged in each of the heat source-side units 10A and 10B, or may be arranged between the heat source-side units 10A and 10B and the heat storage unit 20.

[0030] [Refrigerant Control Unit 30]

The refrigerant control unit 30 is placed between the load-side units 40A and 40B and the heat storage unit 20, and diverges the refrigerant to the load-side units 40A and 40B, and switches the refrigerant flow depending on the operation status of the load-side units 40A and 40B. The refrigerant control unit 30 includes a gas-liquid separator 31, a second fiow switching device 32, a first inter-refrigerant heat exchanger 33, a second inter-refrigerant heat exchanger 34, a first expansion device 35, and a second expansion device 36.

[0031]

The gas-liquid separator 31 is arranged to the high-pressure pipe 3D, and has the function of separating the two-phase refrigerant flowing through the high-pressure pipe 3D into gas refrigerant and liquid refrigerant. The gas refrigerant after separation by the gas-liquid separator 31 is supplied to the second flow switching device 32 via a first connecting pipe 37, and the liquid refrigerant is supplied to the first inter-refrigerant heat exchanger 33. Insofar as the gas-liquid separator 31 separates the two-phase refrigerant into a gas phase and a liquid phase, the type and the shape thereof are not limited, and, for example, a gravity separation type or a centrifugal separation type separator can be adopted. Further, the separation efficiency of the gas-liquid separator 31 is not limited, and may be selected depending on a liquid return amount allowable in the system, the amount of the circulated refrigerant, a target performance value, a target cost, and other conditions.

[0032]

The second flow switching device 32 controls supply of the refrigerant to the load-side units 40A and 40B in accordance with the operation mode, and is connected to the liquid pipes 6A and 6B and the gas pipes 7A and 7B. The second flow switching device 32 includes first on/off valves 32a and 32b and second on/off valves 32c and 32d. One ends of the first on/off valves 32a and 32b are connected to the gas-liquid separator 31, while other ends thereof are connected to the gas pipes 7A and 7B of the load-side units 40A and 40B, respectively. One ends of the second on/off valves 32c and 32d are connected to the low-pressure pipe 2E, while other ends thereof are connected to one end side of the refrigerant flow of the load-side units 40A and 40B.

[0033]

Opening and closing of the first on/off valves 32a and 32b and the second on/off valves 32c and 32d are independently controlled in accordance with the operation mode of the load-side units 40A and 40B. When the load-side units 40A and 40B are in the heating operation, the first on/off valves 32a and 32b are in the open state and the second on/off valves 32c and 32d are in the closed state. Then, the refrigerant flows from the gas-liquid separator 31 side to the load-side units 40A and 40B via the first on/off valves 32a and 32b. On the other hand, when the load-side units 40A and 40B are in the cooling operation, the first on/off valves 32a and 32b side is in the closed state and the second on/off valves 32c and 32d are in the open state. Then, the refrigerant flows from the load-side units 40A and 40B side to the low-pressure pipe 2E side via the second on/off valves 32c and 32d. An exemplary case in which the first on/off valves 32a and 32b and the second on/off valves 32c and 32d are formed of solenoid valves is described, but, for example, three-way valves may be used. As described above, through switching of the refrigerant flow in the second flow switching device 32, the cooling operation or the heating operation can be independently controlled in each of the load-side units 40A and 40B.

[0034]

The first inter-refrigerant heat exchanger 33 is arranged between the gas-liquid separator 31 and the first expansion device 35, and exchanges heat between the refrigerant flowing out of the gas-liquid separator 31 and the refrigerant flowing out of the second inter-refrigerant heat exchanger 34. The second inter-refrigerant heat exchanger 34 exchanges heat between the refrigerant flowing out of the first expansion device 35 and the refrigerant flowing out of the second expansion device 36.

[0035]

The first expansion device 35 is arranged between the gas-liquid separator 31 and the liquid pipes 6A and 6B (between the first inter-refrigerant heat exchanger 33 and the second inter-refrigerant heat exchanger 34), and has the function of a pressure reducing valve and an expansion valve and decompresses and expands the refrigerant. If is preferred that the first expansion device 35 be formed of an expansion device having a variably controllable opening degree, for example, a highly-precise flow rate control device through use of an electronic expansion valve, or inexpensive refrigerant flow rate control means, e.g., a capillary tube.

[0036]

The second expansion device 36 is arranged on an upstream side of the second inter-refrigerant heat exchanger 34 on the secondary side in a second connecting pipe 38, and has the function of a pressure reducing valve and an expansion valve and decompresses and expands the refrigerant. It is preferred that the second expansion device 36 be, similarly to the first expansion device 35, formed of an expansion device having a variably controllable opening degree, for example, a highly-precise flow rate control device through use of an electronic expansion valve, or inexpensive refrigerant flow rate control means, e.g., a capillary tube.

[0037]

As described above, through arrangement of the first inter-refrigerant heat exchanger 33 and the second inter-refrigerant heat exchanger 34, heat can be exchanged between the refrigerant flowing from the gas-liquid separator 31 and the refrigerant flowing to the second connecting pipe 38 to put the refrigerant in an appropriate subcooled state. Further, a bypass amount is controlled through the opening degree of the second expansion device 36 such that appropriate subcooling is provided at an outlet of the second inter-refrigerant heat exchanger 34 on the primary side.

[0038] [Load-side Units 40A and 40B]

The load-side units 40A and 40B are in charge of a cooling load or a heating load with the supply of cooling energy or heating energy from the heat source-side units 10A and 10B. Each of the load-side units 40A and 40B includes an indoor expansion device 41 and a load-side heat exchanger 42, and the indoor expansion device 41 and the load-side heat exchanger 42 are connected in series. The indoor expansion device 41 has the function of a pressure reducing valve and an expansion valve and decompresses and expands the refrigerant. St is preferred that the indoor expansion device 41 be formed of an expansion device having a variably controllable opening degree, for example, a highly-precise flow rate control device through use of an electronic expansion valve, or inexpensive refrigerant flow rate control means, e.g., a capillary tube.

[0039]

The load-side heat exchanger 42 exchanges heat between a heat medium, e.g., ambient air or water and the refrigerant, and, in the heating operation, condenses and liquefies the refrigerant as a condenser (radiator), and, in the cooling operation, evaporates and gasifies the refrigerant as an evaporator. A fan (not shown) configured to supply air to the load-side heat exchanger 42 is arranged. Further, the load-side heat exchanger 42 may exchange heat between the refrigerant and a heat medium, e.g., water, which is different from the refrigerant.

[0040] in the refrigeration cycle apparatus 1 having the configuration described above, a controller 50 configured to control the operation of the refrigeration cycle apparatus 1 is arranged in, for example, the heat source-side unit 10A. The controller 50 controls the operation of components of the refrigeration cycle apparatus 1 in accordance with information sensed by various kinds of sensors and input by a user. For example, the load-side units 40A and 40B have a temperature sensor 43 configured to sense the temperature of the refrigerant flowing between the indoor expansion device 41 and the load-side heat exchanger 42, and a temperature sensor 44 configured to sense the temperature of a refrigerant pipe between the load-side heat exchanger 42 and the second flow switching device 32. The controller 50 controls the operation of the refrigeration cycle apparatus 1 based on temperature information sensed by the temperature sensors 43 and 44.

[0041]

An exemplary case in which the controller 50 is mounted on the heat source-side units 10A and 10B is described, but the controller 50 may be arranged in the refrigerant control unit 30 or the load-side units 40A and 40B, or may be arranged outside as a separate element. Further, the controller 50 may be separated into a plurality of controllers depending on the functions thereof, and the separated controilers may be arranged in the heat source-side units 10A and 10B, the refrigerant control unit 30, and the load-side units 40A and 40B, respectively. In this case, it is preferred that the respective controllers be wirelessly or wiredly connected to be communicable, [0042]

The refrigeration cycle apparatus 1 is operable in four operation modes through switching of the refrigerant flow by the first flow switching device 12 and the second flow switching device 32. Specifically, the refrigeration cycle apparatus 1 can select a cooling only operation mode in which all of the load-side units 40A and 40B perform the cooling operation, a heating only operation mode in which all of the load-side units 40A and 40B perform the heating operation, a cooling main operation mode in which the cooling operation and the heating operation can be selected for the load-side units 40A and 40B, respectively, or vice versa and the cooling load is heavier, or a heating main operation mode in which the cooling operation and the heating operation can be selected for the load-side units 40A and 40B, respectively, or vice versa and the heating load is heavier. Further, in the heating only operation mode and in the heating main operation mode, heat is stored in the heat storage tank in the heat storage unit 20 (heat-storing heating operation mode).

[0043]

In particular, in the heating only operation mode and in the heating main operation mode, there is a case in which the heat source-side heat exchanger 13 is frosted. Specifically, the heat source-side heat exchanger 13 acts as an evaporator, and thus, for example, under a condition in which outside air wet-bulb temperature is lower than 6 degrees C, the heat source-side heat exchanger 13 is frosted as the operating time elapses. When frosted, the heat source-side heat exchanger 13 has increased ventilation resistance and the heat exchange amount is reduced, and thus, defrosting is necessary. Therefore, the refrigeration cycle apparatus 1 further has the defrosting operation mode in which, while the heating operation is continued through use of the heat storage unit 20, the plurality of heat source-side units 10A and 10B are defrosted one by one. The heating only operation mode and the defrosting operation mode are described in detail below.

[0044] [Heating only Operation Mode (Heat-storing Heating Operation Mode)]

Fig. 2 is a refrigerant circuit diagram for illustrating a refrigerant flow in the heating only operation mode of the refrigeration cycle apparatus illustrated in Fig. 1. An operation in the heating only operation mode of the refrigeration cycle apparatus 1 is described with reference to Fig. 2. At this time, the controller 50 switches the flow to a refrigerant flow for the heating only operation. Specifically, in the heat source-side units 10A and 10B, the first flow switching device 12 is switched such that the refrigerant discharged from the compressor 11 flows to the heat storage unit 20 side. Further, control is exerted such that the first on/off valve 17 is in the open state and the second on/off valve 19 is in the closed state. Further, in the heat storage unit 20, the heat storage flow switching device 21 is switched such that the refrigerant flowing in from the heat source-side units 10A and 10B flows to the heat storage heat exchanger 22B. Further, in the second flow switching device 32 of the refrigerant control unit 30, control is exerted such that the first on/off valves 32a and 32b are in the open state and the second on/off valves 32c and 32d are in the closed state.

[0045]

First, the low-temperature and low-pressure refrigerant is compressed in the compressor 11 into high-temperature and high-pressure gas refrigerant and is discharged. The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows through the first flow switching device 12 and the check valve 15c to the high-pressure pipes 3A and 3B. The high-temperature and high-pressure gas refrigerant flowing out of each of the heat source-side units 10A and 10B is joined with each other by the high-pressure junction pipe 3C, and after that, flows to the heat storage unit 20 side.

[0046]

In the heat storage unit 20, part of the high-temperature and high-pressure gas refrigerant flows to the refrigerant control unit 30, and part thereof flows into the heat storage heat exchanger 22B via the heat storage flow switching device 21. The heat storage heat exchanger 22B exchanges heat between the high-temperature and high-pressure refrigerant fiowing into the heat storage heat exchanger 22B and the medium housed in the heat storage tank 22A, and the refrigerant becomes low-temperature and high-pressure refrigerant. At this time, heat is stored in the heat storage tank 22A, After that, the refrigerant flowing out of the heat storage heat exchanger 22B is decompressed by the expansion device 23b and is joined with the refrigerant returning from the refrigerant control unit 30.

[0047]

Meanwhile, the high-temperature and high-pressure gas refrigerant flowing into the refrigerant control unit 30 side flows into the load-side units 40A and 40B via the gas-liquid separator 31 and the first on/off valves 32a and 32b, respectively. The gas refrigerant flowing into each of the load-side units 40A and 40B flows into the corresponding load-side heat exchanger 42 that functions as a condenser, and exchanges heat with ambient air to be condensed and liquefied. At this time, heat transfer from the refrigerant to the surroundings heats an air-conditioned space, e.g., an interior After that, the liquid refrigerant fiowing out of the load-side heat exchanger 42 is decompressed by the indoor expansion device 41 and flows out of each of the load-side units 40A and 40B, [0048]

The liquid refrigerant decompressed by the indoor expansion device 41 flows through the liquid pipes 6A and 6B to flow into the refrigerant control unit 30. The liquid refrigerant flowing into the refrigerant control unit 30 reaches the low-pressure pipe 2E via the second expansion device 36, the second inter-refrigerant heat exchanger 34, the first inter-refrigerant heat exchanger 33, and the second connecting pipe 38. The refrigerant flowing through the low-pressure pipe 2E returns to the heat storage unit 20 to be joined with the refrigerant flowing out of the heat storage heat exchanger 22B, and flows to the low-pressure pipe 2D side. The refrigerant flowing through the low-pressure pipe 2D is branched into the low-pressure pipes 2A and 2B at the low-pressure junction pipe 2C to flow into the heat source-side units 10A and 10B, respectively.

[0049]

The refrigerant flowing into the heat source-side units 10A and 10B reaches the heat source-side heat exchanger 13 via the check valves 15b and 16b and the first on/off valve 17. In the heat source-side heat exchanger 13, the refrigerant exchanges heat with the ambient air, and the refrigerant is evaporated and gasified. After that, the refrigerant flowing out of the heat source-side heat exchanger 13 flows into the accumulator 14 via the first flow switching device 12. The refrigerant in the accumulator 14 is sucked by the compressor 11. In this way, the refrigeration is circulated in the system, thereby forming the refrigeration cycle.

[0050] [Defrosting Operation Mode]

Fig. 3 is a refrigerant circuit diagram for illustrating a refrigerant flow in the defrosting operation mode of the refrigeration cycle apparatus illustrated in Fig. 1.

An operation of the refrigeration cycle apparatus 1 in the defrosting operation mode is described with reference to Fig. 3. Referring to Fig. 3, a case is described in which the heat source-side unit 10A side is defrosted and the heat source-side unit 10B side continues the normal heating operation mode. In this case, the controller 50 switches the flow to a refrigerant flow for the defrosting operation described above. Specifically, in the heat source-side unit 10A, control is exerted such that the second on/off valve 19 is in the open state and the first on/off valve 17 is in the closed state. On the heat source-side unit 10B side, similarly to the case of the heating only operation mode described above, control is exerted such that the first on/off valve 17 is in the open state and the second on/off valve 19 is in the closed state. Further, in the heat storage unit 20, the heat storage flow switching device 21 is switched such that the refrigerant flowing in from the low-pressure pipe 2E flows to the heat storage heat exchanger 22B. In the second flow switching device 32 of the refrigerant control unit 30, similarly to the case of the heating only operation mode described above, control is exerted such that the first on/off valves 32a and 32b are in the open state and the second on/off valves 32c and 32d are in the closed state.

[0051]

First, in the heat source-side unit 10A, the low-temperature and low-pressure refrigerant is compressed by the compressor 11 into high-temperature and high-pressure gas refrigerant and is discharged. Part of the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows to the second on/off valve 19 side, and part thereof flows to the high-pressure pipe 3A via the first flow switching device 12 and the check valve 15c. The refrigerant flowing to the second on/off valve 19 flows, after being expanded to have a low pressure, into the heat source-side heat exchanger 13. At this time, the refrigerant exchanges heat with frost in the heat source-side heat exchanger 13, and defrosting is thus performed (hot gas defrost). The refrigerant passing through the heat source-side heat exchanger 13 passes through the check valve 16c and a joining portion A, and flows into the accumulator 14 via the first flow switching device 12.

[0052]

Meanwhile, in the heat source-side unit 10B, similarly to the case of the heating operation mode described above, the low-temperature and low-pressure refrigerant is compressed by the compressor 11 into high-temperature and high-pressure gas refrigerant. The high-temperature and high-pressure gas refrigerant flows into the high-pressure junction pipe 3C via the check valve 15c and the high-pressure pipe 3B. In the high-pressure junction pipe 3C, the high-temperature and high-pressure gas refrigerants flowing out of the heat source-side units 10A and 10B, respectively, are joined with each other to flow into the refrigerant control unit 30 via the high-pressure pipe 3D.

[0053]

The high-temperature and high-pressure gas refrigerant flowing into the refrigerant control unit 30 side flows into the load-side units 40A and 40B via the gas-liquid separator 31 and the first on/off vaives 32a and 32b, respectively. The gas refrigerant flowing into each of the load-side units 40A and 40B flows into the corresponding load-side heat exchanger 42 that functions as a condenser, and exchanges heat with ambient air to be condensed and liquefied. At this time, heat transfer from the refrigerant to the surroundings heats an air-conditioned space, e.g., an interior. After that, the liquid refrigerant flowing out of the load-side heat exchanger 42 is decompressed by the indoor expansion device 41 and flows out of each of the load-side units 40A and 40B.

[0054]

The liquid refrigerant decompressed by the indoor expansion device 41 flows through the liquid pipes 6A and 6B to flow into the refrigerant control unit 30. The liquid refrigerant flowing into the refrigerant control unit 30 reaches the low-pressure pipe 2E via the second expansion device 36, the second inter-refrigerant heat exchanger 34, the first inter-refrigerant heat exchanger 33, and the second connecting pipe 38. The refrigerant flowing through the low-pressure pipe 2E returns to the heat storage unit 20. In the refrigerant branch unit 23, part of the refrigerant flowing into the heat storage unit 20 flows to the heat storage heat exchanger 22B and part thereof flows to the low-pressure pipe 2D. The refrigerant flowing to the heat storage heat exchanger 22B exchanges heat with the medium in the heat storage tank 22A, which has reached a saturation temperature of the refrigerant or higher in the heating operation mode, to be evaporated and gasified. The evaporated and gasified refrigerant reaches the heat source-side unit selection unit 24 via the heat storage flow switching device 21. Then, the refrigerant flows into the heat source-side unit 10A in which the defrosting is performed via the heat source-side unit selection unit 24 and the pipe 5A.

[0055]

In the heat source-side unit 10A, the refrigerant flowing from the pipe 5A into the heat source-side unit 10A is joined with the refrigerant flowing out of the heat source-side heat exchanger 13 that is defrosted, and flows into the accumulator 14. Then, the compressor 11 sucks the refrigerant in the accumulator 14.

[0056]

Meanwhile, the refrigerant flowing to the low-pressure pipe 2D flows into the heat source-side unit 10B via the low-pressure junction pipe 2C and the low-pressure pipe 2B. In the low-pressure junction pipe 2G, the first on/off valve 17 of the heat source-side unit 10A is closed, and thus, the refrigerant does not flow through the refrigerant flow path leading to the low-pressure pipe 2A and the check valves 15b and 16b on the heat source-side unit 10A side. The refrigerant flowing into the heat source-side unit 10B reaches the heat source-side heat exchanger 13 via the check valves 15b and 16b and the first on/off valve 17. In the heat source-side heat exchanger 13, the refrigerant exchanges heat with ambient air, and the refrigerant is evaporated and gasified. After that, the refrigerant flowing out of the heat source-side heat exchanger 13 flows into the accumulator 14 via the first flow switching device 12.

[0057]

As described above, when the heat source-side heat exchanger 13 of the heat source-side unit 10A is defrosted, the load-side heat exchanger 42 does not function as an evaporator. Therefore, the refrigerant circulating through the heat storage heat exchanger 22B is caused to flow into the heat source-side unit 10A such that the heat storage heat exchanger 22B functions as an evaporator. The refrigerant flowing out of the heat source-side heat exchanger 13 is in a wet state (depending on the operation status, saturated liquid), and the refrigerant exchanging heat in the heat storage heat exchanger 22B is refrigerant with a degree of superheat. Those refrigerants join at the joining portion A and flow into the accumulator 14. The refrigerant in the accumulator 14 is sucked by the compressor 11 and the refrigerant is circulated in the system, thereby forming the refrigeration cycle on the heat source-side unit 10A side. Meanwhile, in the heat source-side unit 10B, the heating operation continues, and the refrigeration cycle in which the load-side heat exchanger 42 is a condenser is formed.

[0058]

In other words, in the defrosting operation, in the refrigeration cycle apparatus 1 including the plurality of heat source-side units 10A and 10B, on the one heat source-side unit 10A side, while hot gas defrost is performed, the refrigeration cycle in which the heat source-side heat exchanger 13 is a condenser and the heat storage heat exchanger 22B is an evaporator is formed. At the same time, on the other heat source-side unit 10B side, the refrigeration cycle in which the load-side heat exchanger 42 is a condenser and the heat source-side heat exchanger 13 is an evaporator is formed, and the heating operation continues.

[0059]

In particular, during the defrosting, heat is used in the defrosting operation, and thus, there is a case in which heat is not sufficient for the load-side heat exchanger 42. When the maximum frequency in the heating operation is determined to be equal to or lower than an operable frequency of the compressor 11 due to restriction, e.g., operation efficiency, reduction in heating capacity can be suppressed through increase of the frequency of the compressor 11 so as to suppress reduction in capacity exclusively for the defrost mode. Fig. 5 is a graph for showing exemplary control of an operation frequency of the compressor in the refrigeration cycle apparatus illustrated in Fig. 1. As shown in Fig. 5, for example, when the maximum frequency in the heating operation is Fmaxl, reduction in heating capacity can be suppressed through setting of the maximum frequency at and after a time t1 at which the defrosting operation mode starts to be Fmax2 (>Fmax1).

[0060]

Operations of the respective components in the defrosting operation described above are controlled by the controller 50. The controller 50 exerts control such that, in the defrosting operation, hot gas defrost of the heat source-side units is performed one by one. Fig. 4 is a flow chart for illustrating exemplary operation of the heat source-side unit selection unit 24 in the defrosting operation illustrated in Fig. 3. Exemplary operation in the defrosting operation is described with reference to Fig. 4. First, when the refrigeration cycle apparatus 1 operates in the heating operation mode (see Fig. 2), the controller 50 determines whether or not the defrosting operation mode is to be performed (Step ST1). Whether or not the defrosting operation is to be performed can be determined through use of a known technology, for example, by making a determination depending on the temperature of the heat source-side heat exchanger 13 in each of the heat source-side units 10A and 10B. When it is determined that the defrosting operation is necessary, which of the heat source-side units 10A and 10B requires defrosting is determined (Step ST2).

[0061]

When it is determined that the heat source-side unit 10A requires defrosting, the first on/off valve 17 on the heat source-side unit 10A side is in the closed state and the second on/off valve 19 on that side is in the open state. Further, in the heat storage unit 20, the heat storage fiow switching device 21 is switched, and the first heat storage-side on/off vaive 24A side of the heat source-side unit selection unit 24 is in the open state (Step STS). In this state, defrosting on the heat source-side unit 10A side is performed, while the heating operation continues on the heat source-side unit 10B side (see Fig. 3). When it is determined that defrosting of the heat source-side unit 10A is completed (Step ST4), the first on/off valve 17 on the heat source-side unit 10A side is in the open state and the second on/off valve 19 on that side is in the closed state. Further, in the heat storage unit 20, the heat storage flow switching device 21 is switched, and the first heat storage-side on/off valve 24A side of the heat source-side unit selection unit 24 is in the closed state (Step STS). Then, the heating operation mode is restarted (Step ST6). The controller 50 may determine that the defrosting is completed when a predetermined period of time elapses from the defrosting operation, or, a known technology can be used, e.g,, making a determination depending on the temperature of the heat source-side heat exchanger 13 in each of the heat source-side units 10A and 10B, for example.

[0062]

On the other hand, when it is determined that the heat source-side unit 10B requires defrosting, the first on/off valve 17 on the heat source-side unit 10B side is in the closed state and the second on/off valve 19 on that side is in the open state. Further, in the heat storage unit 20, the heat storage flow switching device 21 is switched, and the first heat storage-side on/off valve 24A side of the heat source-side unit selection unit 24 is in the open state (Step ST7). In this state, defrosting on the heat source-side unit 10B side is performed, while the heating operation continues on the heat source-side unit 10A side (see Fig. 3). When it is determined that defrosting of the heat source-side unit 10A is completed (Step STS), the first on/off valve 17 on the heat source-side unit 10A side is in the open state and the second on/off valve 19 on that side is in the closed state. Further, in the heat storage unit 20, the heat storage flow switching device 21 is switched, and the first heat storage-side on/off valve 24A side of the heat source-side unit selection unit 24 is in the closed state (Step ST9). Then, the heating operation mode is restarted (Step ST10).

[0063]

According to the embodiment described above, in the refrigeration cycle apparatus 1 including the plurality of heat source-side units 10A and 10B, in the defrosting operation, in the one heat source-side unit 10A, while hot gas defrost is performed, the refrigeration cycle in which the heat storage heat exchanger 22B is an evaporator is formed, and in the other heat source-side unit 10B, the refrigeration cycle in which the load-side heat exchanger 42 is an evaporator is formed. Thus, while upsizing of the heat source-side units 10A and 10B is suppressed, the defrosting operation can be performed while continuing the heating operation.

When, as in the related art, the heat storage tank is arranged in each heat source unit, as many heat storage tanks as the number of the heat source unit are necessary. As a result, the unit cost and increases the footprint increase. On the other hand, in the refrigeration cycle apparatus 1 illustrated in Fig. 1, the plurality of heat source-side units 10A and 10B are connected to the one heat storage unit 20 and the defrosting operation is performed. Thus, cost reduction and space saving can be achieved.

[0064]

Further, in the defrosting operation mode, the heat source-side units are defrosted one by one through connection of, for example, the one heat source-side unit 10A of the heat source-side units 10A and 10B to the heat storage unit 20 and continuation of the heating operation in the other heat source-side unit 10B. Thus, while upsizing of the heat source-side units 10A and 10B is suppressed, both the defrosting operation and the heating operation can be performed. Specifically, in the heating and heat storage operation mode, while the heating operation is performed, heat sufficient for maintaining the heating capacity in the defrosting through use of stored heat is required to be stored in the heat storage tank, and the heat source-side units 10A and 10B output horsepower more than horsepower appropriate for the air-conditioning capacity of the load-side units 40A and 40B. Therefore, if the plurality of heat source-side units 10A and 10B are simultaneously defrosted at a time, a large heat source unit and a large heat storage tank are necessary. As a result, the footprint increases, or the installation weight increases. Through connection of the one heat source-side unit 10A to the heat storage unit 20 and continuation of the heating operation in the other heat source-side unit 10B, upsizing of the heat source-side units 10A and 10B and of the heat storage tank 22A can be suppressed.

[0065]

Further, when the refrigerant branch unit 23 is further arranged between the load-side units 40A and 40B and the heat storage unit 22, which is configured to branch the refrigerant flowing out of the load-side units 40A and 40B into the heat storage unit 22 side and the heat source-side units 10A and 10B side, while the heat source-side unit 10A is defrosted, the heating operation can be continued in the heat source-side unit 10B.

[0066]

Embodiments of the present invention are not limited to the embodiment described above. For example, in the embodiment described above, an exemplary case in which the refrigeration cycle apparatus 1 includes the two heat source-side units 10A and 10B, the one refrigerant control unit 30, and the two load-side units 40A and 40B is described, but the numbers of the units are not limited thereto. Three or more heat source-side units and three or more load-side units may be included. Further, in the embodiment described above, an exemplary case in which the refrigeration cycle apparatus 1 is applied to an air-conditioning apparatus is described, but the refrigeration cycle apparatus 1 can be applied to other systems through use of a refrigeration cycle, e.g., a refrigeration system.

[0067]

Further, in the embodiment described above, an exemplary case in which the one heat storage unit 22 is arranged is described, but a plurality of heat storage units may be arranged. In this case, the number of the heat storage units 22 is smaller than the number of the pluraiity of heat source-side units 10A and 10B. This enables defrosting of the predetermined heat source-side unit 10A while continuing the heating operation with the space being saved.

Reference Signs List [0068] 1 refrigeration cycle apparatus 2A, 2B, 2D, 2E low-pressure pipe 2C low-pressure junction pipe 3A, 3B, 3D high-pressure pipe 3C high-pressure junction pipe 5A, 5B pipe 6A, 6B liquid pipe 7A, 7B gas pipe 10A, 10B heat source-side unit 11 compressor 12 flow switching device 13 heat source-side heat exchanger 13A fan 14 accumulator 15a-15d check valve 16a-16d check valve 17 first on/off valve 18 bypass pipe 19 second on/off valve 20 heat storage unit 21 heat storage flow switching device 22 heat storage unit 22A heat storage tank 22B heat storage heat exchanger 23 refrigerant branch unit 23a check valve 23b expansion device 24 heat source-side unit selection unit 24A first heat storage-side on/off valve 24B second heat storage-side on/off valve 30 refrigerant control unit 31 gas-liquid separator 32 second flow switching device 32a, 32b first on/off valve 32c, 32d second on/off valve 33 first inter-refrigerant heat exchanger 34 first inter-refrigerant heat exchanger 35 first expansion device 36 second expansion device 37 first connecting pipe 38 second connecting pipe 40A, 40B load-side unit 41 expansion device 42 load-side heat exchanger 43, 44 temperature sensor 50 controller A joining portion

Claims

CLAIMS [Claim 1] A refrigeration cycle apparatus, comprising: a plurality of heat source-side units each including a compressor, a flow switching device, and a heat source-side heat exchanger connected in a stated order, and the plurality of heat source-side units each further including a first on-off valve arranged on a refrigerant flow path through which refrigerant flows from the load-side unit to the heat source-side heat exchanger, a bypass pipe configured to connect a discharge side of the compressor and the heat source-side heat exchanger to each other, and a second on-off valve arranged on the bypass pipe, and configured to control an inflow of refrigerant from the compressor to the heat source-side heat exchanger; a load-side unit having a load-side heat exchanger, and connected to the plurality of heat source-side units to form a refrigerant circuit, the refrigerant circuit being configured to circulate refrigerant between the plurality of heat source-side units and the load-side unit; a heat storage unit arranged between the plurality of heat source-side units and the load-side unit, and configured to exchange heat with the refrigerant flowing between the plurality of heat source-side units and the load-side unit; a heat storage switching device configured to switch between a flow of refrigerant flowing from the plurality of heat source-side units into the heat storage unit and a flow of refrigerant flowing from the load-side unit into the heat storage unit; a heat source-side unit selection unit configured to select one of the plurality of heat source-side units that, when the heat storage switching device switches to the flow of refrigerant flowing from the load-side unit into the heat storage unit, allows the refrigerant flowing out of the heat storage unit to flow therein; and a controller configured to exert control such that, in the one of the plurality of heat source-side units selected by the heat source-side unit selection unit, the first on-off valve is in a closed state and the second on-off valve is in an open state. [Claim 2] The refrigeration cycle apparatus of claim 1, further comprising a refrigerant branch unit arranged between the load-side unit and the heat storage unit, and configured to branch the refrigerant flowing out of the load-side unit into the heat storage unit side and the heat source-side unit side. [Claim 3] The refrigeration cycle apparatus of claim 2, wherein the controlier is configured to exert control such that a heating operation mode and a defrosting operation mode are performed, and, in the defrosting operation mode, exert control such that the heat source-side unit selection unit selects one of the plurality of heat source-side units to be defrosted and the first on-off valve thereof is in a closed state and the second on-off valve thereof is in an open state, and such that an other of the plurality of heat source-side units performs heating operation. [Claim 4] The refrigeration cycle apparatus of claim 3, wherein the controller is configured to select one of the plurality of heat source-side units to be defrosted one by one. [Claim 5] The refrigeration cycle apparatus of any one of claims 1 to 4, wherein a number of the heat storage units arranged is smaller than a number of the plurality of heat source-side units. [Claim 6] The refrigeration cycle apparatus of claim 5, wherein the number of the heat storage units provided is one. [Claim 7] The air-conditioning apparatus of any one of claims 1 to 6, wherein the heat storage unit is a unit separated from of the plurality of heat source-side units. [Claim 8] The air-conditioning apparatus of any one of claims 1 to 6, wherein the heat storage unit is built in any one of the plurality of heat source-side units.