GB2574541A

GB2574541A - Refrigeration cycle device and defrost operation method for refrigeration cycle device

Info

Publication number: GB2574541A
Application number: GB1913233.1A
Authority: GB
Inventors: Najima Kohei
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-04-13
Filing date: 2017-04-13
Publication date: 2019-12-11
Anticipated expiration: 2037-04-13
Also published as: JPWO2018189859A1; GB2574541B; JP6723442B2; GB201913233D0; WO2018189859A1

Abstract

The refrigeration cycle device comprises: a compressor; a first heat exchanger; a plurality of throttling devices; a plurality of second heat exchangers; a first temperature detector that detects the ambient temperature around the first heat exchanger; a storage unit that stores the heating capacity of each of the plurality of second heat exchangers; and a control device that executes a heating operation that causes the first heat exchanger to function as an evaporator and at least part of the plurality of second heat exchangers to function as condensers. During a heating operation, the control device selects either a first defrosting operation or a second defrosting operation on the basis of the value detected by the first temperature detector and the total heating capacity of the second heat exchangers functioning as condensers, and if the first defrosting operation has been selected, starts the first defrosting operation when the operation time of the heating operation reaches a first operation time, whereas if the second defrosting operation has been selected, starts the second defrosting operation when the operation time of the heating operation reaches a second operation time, which is shorter than the first operation time.

Description

END SECOND DEFROSTING OPERATION

END FIRST DEFROSTING OPERATION

DESCRIPTION

Title of Invention

REFRIGERATION CYCLE APPARATUS AND DEFROSTING OPERATION METHOD FOR THE SAME

Technical Field [0001]

The present invention relates to a refrigeration cycle apparatus that performs a defrosting operation to remove frost adhering to a heat exchanger, and a defrosting operation method for the refrigeration cycle apparatus.

Background Art [0002]

There are provided existing air-conditioning apparatuses each provided with a refrigeration cycle circuit including a heat-source-side heat exchanger and a use-side heat exchanger. During the heating operation of such an air-conditioning apparatus, refrigerant that circulates in the refrigeration cycle circuit transfers heat to air that is supplied to the use-side heat exchanger that operates as a condenser, and the air is sent to a target space for air-conditioning. It should be noted that there is a case where the heat-source-side heat exchanger that operates as an evaporator during the heating operation is installed outdoors. In such a case, in the case where the temperature of outside air is low, for example, during wintertime, when the heating operation is performed, frost may adhere to the heat-source-side heat exchanger operating as an evaporator. When the frost develops, the refrigeration cycle capacity can be reduced or a failure can occur in the heat-source-side heat exchanger. It is therefore necessary to perform a defrosting operation to melt the frost adhering to the heat-source-side heat exchanger at regular intervals.

[0003]

In a proposed technique applied to an air-conditioning apparatus that performs a defrosting operation, a temperature condition in which frost is expected to adhere to an outdoor heat exchanger to be defrosted is set in advance, and when the temperature of the outdoor heat exchanger becomes lower than or equal to a predetermined temperature during the heating operation, the defrosting operation is started (e.g. see Patent Literature 1).

Citation List

Patent Literature [0004]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-218940 (page 11) Summary of Invention

Technical Problem [0005]

In the related art, a state of frost adhering to the heat exchanger to be defrosted is detected based on an empirical rule from the temperature of the heat exchanger, and the defrosting operation is started. However, there is a possibility that an actual state of frost adhering to the heat exchanger cannot be accurately detected only from the temperature of the heat exchanger to be defrosted. Thus, there is a case where the heating operation is performed with the heating capacity that is low because of a large amount of frost that adheres to the heat exchanger, or the defrosting operation is performed over a long time period. In such a case, inevitably, an integrated heating capacity in a time period in which a set of a heating operation and a defrosting operation are consecutively performed is reduced.

[0006]

The present invention has been made in view of the above problem, and an object of the invention is to provide a refrigeration cycle apparatus that performs a defrosting operation in which a decrease in the integrated heating capacity is reduced, and also provide a defrosting operation method for a refrigeration cycle apparatus in which a decrease in the integrated heating capacity is reduced.

Solution to Problem [0007]

A refrigeration cycle apparatus according to one embodiment of the present invention includes: a compressor; a first heat exchanger; a plurality of expansion devices; a plurality of second heat exchangers; a first temperature detector configured to detect an ambient temperature of the first heat exchanger; a storage unit configured to store data indicating a heating capacity of each of the plurality of second heat exchangers; and a control device configured to cause a heating operation to be performed, in which the first heat exchanger operates as an evaporator and one or more of the plurality of second heat exchangers operates or operate as a condenser or condensers. The control device selects one of a first defrosting operation and a second defrosting operation based on a detection value obtained by detection by the first temperature detector and a total value of the heating capacity or capacities of the one or more of the plurality of second heat exchangers that operates or operate as the condenser or condensers during the heating operation. In the case where the control device selects the first defrosting operation, the control device starts the first defrosting operation when an operating time of the heating operation reaches a first operating time. In the case where the control device selects the second defrosting operation, the control device starts the second defrosting operation when the operating time of the heating operation reaches a second operating time that is shorter than the first operating time.

[0008]

Another embodiment of the present invention relates to a defrosting operation method for a refrigeration cycle apparatus that includes a compressor, a first heat exchanger, a plurality of expansion devices, and a plurality of second heat exchangers, the defrosting operation method includes: detecting an ambient temperature of the first heat exchanger during a heating operation in which the first heat exchanger operates as an evaporator and one or more of the plurality of second heat exchangers operates or operate as a condenser or condensers; selecting one of first defrosting operation and second defrosting operation based on the ambient temperature of the first heat exchanger and a total value of the heating capacity or capacities of the one or more of the plurality of second heat exchangers that operates or operate as the condenser or condensers during the heating operation; and starting the first defrosting operation when an operating time of the heating operation reaches a first operating time in the case where the first defrosting operation is selected, and starting the second defrosting operation when the operating time of the heating operation reaches a second operating time that is shorter than the first operating time in the case where the second defrosting operation is selected.

Advantageous Effects of Invention [0009]

According to the embodiments of the present invention, based on the ambient temperature of the first heat exchanger that operates as a condenser and the total value of the heating capacity or capacities of one or more of the plurality of the second heat exchangers that operates or operate as an evaporator or evaporators, the operating time of the heating operation is varied, and the defrosting operation is started. Thus, the defrosting operation can be started at a timing which more reflects the actual state of frost adhering to the first heat exchanger to be defrosted, as compared with the case where the defrosting operation is started based on an empirical rule from the temperature of the heat exchanger to be defrosted. It is therefore possible to reduce a decrease in the integrated heating capacity in a time period in which a set of heating operation and defrosting operation are consecutively performed.

Brief Description of Drawings [0010] [Fig. 1] Fig. 1 illustrates an example of a circuit configuration of a refrigeration cycle apparatus according to Embodiment 1.

[Fig. 2] Fig. 2 is a functional block diagram of the refrigeration cycle apparatus according to Embodiment 1.

[Fig. 3] Fig. 3 is a flowchart for explaining a heating operation and a defrosting operation in the refrigeration cycle apparatus according to Embodiment 1.

[Fig. 4] Fig. 4 illustrates an example of an integrated heating capacity in a first defrosting operation in Embodiment 1.

[Fig. 5] Fig. 5 illustrates an example of an integrated heating capacity in a second defrosting operation in Embodiment 1.

[Fig. 6] Fig. 6 illustrates an example of a circuit configuration of a refrigeration cycle apparatus according to Embodiment 2.

[Fig. 7] Fig. 7 is a functional block diagram of the refrigeration cycle apparatus according to Embodiment 2.

[Fig. 8] Fig. 8 is a flowchart for explaining a heating operation and a defrosting operation in the refrigeration cycle apparatus according to Embodiment 2. Description of Embodiments [0011]

A refrigeration cycle apparatus according to each of the Embodiments of the present invention is used as an air-conditioning apparatus. The Embodiments will be described with reference to the accompanying drawings. In the figures of the drawings, the relationship in dimension between components may be different from the actual one. Furthermore, in the each of the figures, components which are the same as or equivalent to those in a previous figure are denoted by the same reference signs. The same is true of the entire text of the specification. In addition, the forms of components described in the entire text of the specification are merely examples, and are not limited to those as described in the text.

[0012] Embodiment 1

Fig. 1 illustrates an example of the circuit configuration of a refrigeration cycle apparatus 100 according to Embodiment 1. The refrigeration cycle apparatus 100 is used as an air-conditioning apparatus that heats or cools a target space for airconditioning. In Fig. 1, the flow of refrigerant in a cooling operation is indicated by dashed arrows, and the flow of refrigerant in a heating operation is indicated by solid arrows.

[0013] [Configuration of Refrigeration Cycle Apparatus 100]

The refrigeration cycle apparatus 100 includes a vapor-compression refrigeration cycle circuit obtained by connecting a compressor 1, a first heat exchanger 2, a plurality of expansion devices 3a and 3b, and a plurality of second heat exchangers 4a and 4b with refrigerant pipes. The refrigerant that circulates through the refrigeration cycle circuit is, for example, R410A, R404A, R32, HFO1234yf ora non-azeotropic refrigerant mixture obtained by mixing R32 and HFO1234yf at a given ratio. The refrigeration cycle apparatus 100 includes a first temperature detector 5 that detects an ambient temperature of the first heat exchanger 2. Furthermore, the refrigeration cycle apparatus 100 according to Embodiment 1 includes a refrigerant flow-passage switching device 6, an accumulator 7, a check valve 8, and an outdoor fan 9.

[0014]

Each of the components that form the refrigeration cycle apparatus 100 is provided in a housing of an outdoor unit 30 serving as a heat source unit or in a housing of an indoor unit 40a or 40b serving as a use-side unit. Embodiment 1 will be described by referring to by way of example the case where two indoor units 40a and 40b are connected in parallel with a single outdoor unit 30. However, the number of outdoor units 30 and indoor units 40a and 40b is not limited to the number of units as illustrated in the drawings.

[0015] (Outdoor Unit 30)

The outdoor unit 30 is installed in space separate from the target space for airconditioning, for example, an outdoor space. The outdoor unit 30 houses the compressor 1, the check valve 8, the refrigerant flow-passage switching device 6, the first heat exchanger 2, the accumulator 7, and the outdoor fan 9.

[0016]

The compressor 1 compresses refrigerant that flows in the compressor 1 via the accumulator 7 into high-temperature and high-pressure gas refrigerant, and discharges the high-temperature and high-pressure gas refrigerant. The compressor 1 may be, for example, a rotary compressor, a scroll compressor, a screw compressor or a reciprocating compressor. Also, the compressor 1 may be an inverter compressor whose capacity can be controlled.

[0017]

The check valve 8 is provided at a refrigerant pipe on a discharge side of the compressor 1, and allows the refrigerant to flow only in a single direction. The check valve 8 prevents the refrigerant discharged from the compressor 1 from flowing back toward the compressor 1. It should be noted that the check valve 8 is not an essential component of the refrigeration cycle apparatus 100.

[0018]

The refrigerant flow-passage switching device 6 includes a valve provided at the refrigerant pipe on the discharge side of the compressor 1, and switches, in accordance with opening or closing of the above valve, a flow passage for the refrigerant discharged from the compressor 1 between a flow passage that allows the refrigerant to flow toward the first heat exchanger 2 and a flow passage that allows the refrigerant to flow toward the second heat exchangers 4a and 4b. For example, the refrigerant flow-passage switching device 6 can be formed to include a combination of two-way valves or threeway valves or can be formed to include a four-way valve.

[0019]

The first heat exchanger 2 operates as an evaporator during the heating operation, and operates as a condenser during the cooling operation. The refrigerant that flows through the first heat exchanger 2 exchanges heat with a heat exchange fluid, such as air, which is supplied to the first heat exchanger 2. The first heat exchanger 2 may be, for example, a fin-and-tube heat exchanger or a microchannel heat exchanger. The following description is made by referring to by way of example the case where the first heat exchanger 2 is a fin-and-tube heat exchanger.

[0020]

The first temperature detector 5 detects an ambient temperature of the first heat exchanger 2. The ambient temperature of the first heat exchanger 2 is an air temperature in the space in which the first heat exchanger 2 is installed. In the case where the first heat exchanger 2 is installed outdoors, the first temperature detector 5 detects the temperature of outside air.

[0021]

The accumulator 7 is a surplus-refrigerant reservoir that keeps surplus refrigerant in store and is provided at a refrigerant pipe on a suction side of the compressor 1. Refrigerant can remain as surplus refrigerant in the refrigeration cycle circuit in the case where the flow rate of refrigerant during the heating operation differs from that during the cooling operation, the refrigerant flow rate transiently changes when the number of indoor units being in operation (regarding the indoor units 40a and 40b) varies, or the flow rate of refrigerant varies in accordance with a load condition. The accumulator 7 keeps such surplus refrigerant in store. In the accumulator 7, liquid refrigerant and gas refrigerant are separated from each other, and the gas refrigerant is supplied to the compressor 1. It should be noted that the accumulator 7 is not an essential component of the refrigeration cycle apparatus 100.

[0022]

The outdoor fan 9 is an example of a device that supplies, to the first heat exchanger 2, the heat exchange fluid that is to exchange heat with refrigerant that flows in the first heat exchanger 2. For example, as the outdoor fan 9, a propeller fan having a plurality of blades can be used. The outdoor fan 9 is provided at a location where it can supply air to the first heat exchanger 2.

[0023] (Indoor Units 40a and 40b)

The indoor units 40a and 40b are installed in the target space for air-conditioning. The indoor unit 40a houses the expansion device 3a, the second heat exchanger 4a, and an indoor fan 10a. The indoor unit 40b houses the expansion device 3b, the second heat exchanger 4b, and an indoor fan 10b. It should be noted that since the indoor unit 40a and the components housed in the indoor unit 40a have the same functions and the same basic structures as the indoor unit 40b and the components housed in the indoor unit 40b, only the indoor unit 40a and the components housed therein will be described.

[0024]

The expansion device 3a is provided at a refrigerant pipe that connects the first heat exchanger 2 and the second heat exchanger 4a and narrows the refrigerant flow passage to expand the refrigerant passing through the refrigerant flow passage and reduce the pressure of the refrigerant. For example, as the expansion device 3a, an electric expansion valve including a valve that can adjust the flow rate of the refrigerant can be used. Alternately, for example, a mechanical expansion valve employing a diaphragm as a pressure receiver or a capillary tube can be used as the expansion device 3.

[0025]

The second heat exchanger 4a operates as a condenser during the heating operation, and operates as an evaporator during the cooling operation. The refrigerant flowing through the second heat exchanger 4a and air supplied to the second heat exchanger 4a exchange heat with each other, thereby producing hot air or cool air. For example, a fin-and-tube heat exchanger or a microchannel passage heat exchanger can be used as the second heat exchanger 4a. The following description is made by referring to by way of example the case where the second heat exchanger 4a is a finand-tube heat exchanger including a pipe that allows the refrigerant to flow therethrough and fins attached to the pipe.

[0026]

The indoor fan 10a is a fluid sending device that sends, to the second heat exchanger 4a, air that is to exchange heat with the refrigerant flowing in the second heat exchanger 4a. For example, as the indoor fan 10a, a propeller fan including a plurality of blades can be used. The indoor fan 10a is installed in a location where it can supply air to the second heat exchanger 4a.

[0027]

The plurality of second heat exchangers 4a and 4b each have a predetermined heating capacity (kW) and a predetermined cooling capacity (kW). The heating capacity and the cooling capacity can be defined with various parameters including the sizes of the second heat exchangers 4a and 4b, the amounts of air that is sent from the indoor fans 10a and 10b, and the capacity of the compressor 1; however, the parameters for use in defining the heating capacity and the cooling capacity are not particularly limited. The plurality of second heat exchangers 4a and 4b provided in the refrigeration cycle apparatus 100 may have the same heating capacity and the same cooling capacity, or may have different heating capacities and different cooling capacities. The same is true of the case where the number of second heat exchangers is three or more.

[0028]

Fig. 2 is a functional block diagram of the refrigeration cycle apparatus 100 according to Embodiment 1. A control device 20 controls actuators for the compressor 1, the outdoor fan 9, the indoor fans 10a and 10b, the expansion devices 3a and 3b, and the refrigerant flow-passage switching device 6, etc., which are all provided in the refrigeration cycle apparatus 100. The control device 20 is connected to each of the actuators in such a way as to be allowed to transmit a control signal to each actuator. Furthermore, the control device 20 receives signals from the first temperature detector 5 and a timer 11. The control device 20 controls the actuators based on signals input from the first temperature detector 5 and the timer 11. Each of the indoor units 40a and 40b may be provided with a remote control unit that inputs a set temperature, a command to start an operation, and a command to stop an operation, and a signal from the remote control unit may be input to the control device 20. The control device 20 causes the cooling operation, the heating operation, or the defrosting operation, which will be described later, to be performed based on the set temperature set for each of the indoor units 40a and 40b and information regarding the start and stop of the operation. [0029]

The control device 20 includes a processing circuit 21 and a storage unit 22. The processing circuit 21 includes, for example, dedicated hardware or a central processing unit (CPU) (which is also referred to as a central processing device, a processing device, an arithmetic device, a microprocessor, a microcomputer, or a processor) that executes a program stored in the storage unit.

[0030]

In the case where the processing circuit 21 is the dedicated hardware, the processing circuit 21 corresponds to, for example, a single circuit, a composite circuit, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. The functions that are fulfilled by the processing circuit 21 may be provided as functions of respective hardware, or the functions may be provided as functions of single hardware.

[0031]

In the case where the processing circuit 21 is the CPU, the functions that are fulfilled by the processing circuit 21 are fulfilled by executing software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in an internal memory of the processing circuit 21. The processing circuit 21 reads and executes a program stored in the internal memory to fulfill a function. The internal memory is a nonvolatile or volatile semiconductor memory, such as a program memory, an EPROM, or an EEPROM. [0032]

It should be noted that one or more functions of the control device 20 may be provided as functions of the dedicated hardware, and another one or other functions of the control device 20 may be provided as functions of the software or firmware. Although Fig. 2 illustrates that the control device 20 performs a centralized control of the actuators, it is not indispensable that the control device 20 is physically configured as illustrated in Fig. 2. To be more specific, how the control device 20 is divided into components or the components are combined is not limited to the configuration of the control device 20 as illustrated in Fig. 2. The control device 20 may be functionally or physically divided into components or all the components or an arbitrary number of components are functionally or physically combined, in accordance with, for example, various kinds of loads and usage conditions. Furthermore, the control device 20 can be installed in the outdoor unit 30, but the specific location of the control device 20 is not limited. In the case where the functions of the control device 20 are fulfilled by a plurality of control devices, the plurality of control devices may be arranged such that they are distributed among the outdoor unit 30 and the indoor units 40a and 40b. [0033]

The storage unit 22 stores at least heating capacity information 22a. The heating capacity information 22a is information associating the plurality of second heat exchangers 4a and 4b with a predetermined heating capacity or respective predetermined heating capacities. The storage unit 22 stores various kinds of threshold values for use in a control process by the control device 20, in addition to the heating capacity information 22a. The storage unit 22 is, for example, a nonvolatile semiconductor memory.

[0034] [Operation of Refrigeration Cycle Apparatus 100]

The refrigeration cycle apparatus 100 according to Embodiment 1 performs the cooling operation, the heating operation, and the defrosting operation. The function of the refrigeration cycle circuit in each of the cooling operation, the heating operation, and the defrosting operation will be described along with the flow of the refrigerant. [0035] (Cooling Operation)

The cooling operation is an operation to send cool air to the target space for airconditioning, where the indoor units 40a and 40b are installed. During the cooling operation, the refrigerant flow-passage switching device 6 is set to use a refrigerant flow passage in which the discharge side of the compressor 1 is connected to the first heat exchanger 2. High-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the first heat exchanger 2, which operates as a condenser, via the refrigerant flow-passage switching device 6. The refrigerant having flowed into the first heat exchanger 2 exchanges heat with air sent from the outdoor fan 9, and is thus condensed to change into low-temperature and high-pressure liquid refrigerant, and the low-temperature and high-pressure liquid refrigerant then flows out of the first heat exchanger 2.

[0036]

The low-temperature and high-pressure liquid refrigerant having flowed out of the first heat exchanger 2 flows into both the expansion devices 3a and 3b in a parallel fashion. The low-temperature and high-pressure liquid refrigerant having flowed into the expansion devices 3a and 3b is reduced in pressure by the expansion devices 3a and 3b to change into low-temperature and low-pressure liquid refrigerant or two-phase refrigerant, and the low-temperature and low-pressure liquid refrigerant or two-phase refrigerant then flows out of the expansion devices 3a and 3b. The low-temperature and low-pressure refrigerant having flowed out of the expansion devices 3a and 3b flows into the second heat exchangers 4a and 4b, which operate as evaporators. The refrigerant having flowed into the second heat exchangers 4a and 4b exchanges heat with air sent from the indoor fans 10a and 10b, and is thus evaporated to change into low-temperature and low-pressure gas refrigerant, and the low-temperature and lowpressure gas refrigerant then flows out of the second heat exchangers 4a and 4b. Because of the above heat exchange between the refrigerant and the air in the second heat exchangers 4a and 4b, the refrigerant receives heat from the air, whereby cool air for the target space for air-conditioning is produced.

[0037]

The refrigerant having flowed out of the second heat exchangers 4a and 4b is sucked into the compressor 1 via the refrigerant flow-passage switching device 6 and the accumulator 7. In the cooling operation, such a refrigeration cycle as described above is repeated. It is also possible to switch the state of each of the plurality of indoor units 40a and 40b between performance and stoppage of the cooling operation. For example, in the case where the indoor unit 40a performs the cooling operation and the indoor unit 40b stops the cooling operation, the expansion device 3a of the indoor unit 40a keeps the refrigerant flow passage opened to a predetermined opening degree, whereas the expansion device 3b of the indoor unit 40b closes the refrigerant flow passage to prevent the refrigerant from flowing into the second heat exchanger 4b. Because of such a configuration, only one of the plurality of indoor units 40a and 40b can perform the cooling operation.

[0038] (Heating Operation)

The heating operation is an operation to supply hot or warm air to the target space for air-conditioning, where the indoor units 40a and 40b are installed. During the heating operation, the refrigerant flow-passage switching device 6 is set to use a refrigerant flow passage in which the discharge side of the compressor 1 is connected to the second heat exchangers 4a and 4b. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 flows into the second heat exchangers 4a and 4b, which operates as condensers, in a parallel fashion via the refrigerant flow-passage switching device 6. The refrigerant having flowed into the second heat exchangers 4a and 4b exchanges heat with air sent from the indoor fans 10a and 10b, and is thus condensed to change into low-temperature and high-pressure liquid refrigerant, and the low-temperature and high-pressure liquid refrigerant flows out of the second heat exchangers 4a and 4b. Because of the above heat exchange between the refrigerant and the air in the second heat exchangers 4a and 4b, the refrigerant transfers heat to the air, whereby hot or warm air for the target space for airconditioning is produced.

[0039]

The low-temperature and high-pressure liquid refrigerant having flowed out of the second heat exchangers 4a and 4b flows into the expansion devices 3a and 3b. The low-temperature and high-pressure liquid refrigerant having flowed into the expansion devices 3a and 3b is reduced in pressure by the expansion devices 3a and 3b to change into low-temperature and low-pressure liquid refrigerant or two-phase refrigerant, and the low-temperature and low-pressure liquid refrigerant or two-phase refrigerant flows out of the expansion devices 3a and 3b. The low-temperature and low-pressure refrigerant having flowed out of the expansion devices 3a and 3b flows into the first heat exchanger 2, which operates as an evaporator. The refrigerant having flowed into the first heat exchanger 2 exchanges heat with air sent from the outdoor fan 9, and is then evaporated to change into low-temperature and low-pressure gas refrigerant, and the low-temperature and low-pressure gas refrigerant flows out of the first heat exchanger 2.

[0040]

The refrigerant having flowed out of the first heat exchanger 2 is sucked into the compressor 1 via the refrigerant flow-passage switching device 6 and the accumulator 7. In the heating operation, such a refrigeration cycle as described above is repeated. It is also possible to switch the state of each of the plurality of indoor units 40a and 40b between performance and stoppage of the heating operation. For example, in the case where the indoor unit 40a performs the heating operation and the indoor unit 40b stops the heating operation, the expansion device 3a of the indoor unit 40a keeps the refrigerant flow passage opened to a predetermined opening degree, whereas the expansion device 3b of the indoor unit 40b closes the flow passage to prevent the refrigerant from flowing into the second heat exchanger 4b. Thereby, only one of the plurality of indoor units 40a and 40b can perform the heating operation.

[0041] (Defrosting Operation)

The defrosting operation is an operation to melt frost adhering to the first heat exchanger 2 that operates as an evaporator during the heating operation. The defrosting operation of Embodiment 1 is achieved by causing the refrigerant to flow in the opposite direction to that during the heating operation, that is, by causing the refrigerant to flow in the same direction as that during the cooling operation as described above. However, during the defrosting operation, unlike during the cooling operation, the control device 20 causes the indoor fans 10a and 10b to stop. [0042]

The defrosting operation of Embodiment 1 includes two kinds of defrosting operations, that is, a first defrosting operation and a second defrosting operation. The first defrosting operation and the second defrosting operation are the same as each other in the flow of refrigerant, but different from each other in the requirement (timing) for starting the defrosting operation. Furthermore, in Embodiment 1, the operating time of the first defrosting operation is different from that of the second defrosting operation. That is, the operating time of the second defrosting operation is shorter than that of the first defrosting operation. This will be described below in detail.

[0043] [Operation Control of Heating Operation and Defrosting Operation]

Fig. 3 is a flowchart for explaining the heating operation and the defrosting operation in the refrigeration cycle apparatus 100 according to Embodiment 1. Control by the control device 20 during the heating operation and the defrosting operation will be described with reference to Fig. 3.

[0044]

When the heating operation starts (S1), the control device 20 detects whether or not the ambient temperature of the first heat exchanger 2 falls within the temperature range of TH2 to TH1 based on a detection value obtained by detection by the first temperature detector 5. In this case, TH2 < TH1. The temperature TH1 is, for example, 5 degrees C, and the temperature TH2 is, for example, -3 degrees C. Although the temperatures TH1 and TH2 are not limited to the above values, the upper limit value and the lower limit value of the temperature range are determined as the temperatures TH1 and TH2, respectively, in advance, and are stored in the storage unit 22. It should be noted that when the ambient temperature of the first heat exchanger 2 falls within the temperature range, a larger amount of frost easily forms on the first heat exchanger 2.

[0045]

When the ambient temperature of the first heat exchanger 2 does not fall within the temperature range of TH2 to TH1 (NO in S2), the process proceeds to step S8. When the ambient temperature of the first heat exchanger 2 falls within the temperature range (YES in S2), it is detected whether or not the total heating capacity LQj of the second heat exchanger 4a and/or the second heat exchanger 4b that are/is in the heating operation is larger than or equal to a first value Q that is a predetermined threshold value. As described above, the plurality of indoor units 40a and 40b provided in the refrigeration cycle apparatus 100 according to Embodiment 1 can be individually set regarding performance and stoppage of the heating operation. Therefore, the control device 20 calculates the total heating capacity LQj by adding the heating capacities of the second heat exchanger 4a and/or the second heat exchanger 4b in the indoor unit 40a and/or in the indoor unit 40b that are/is in the heating operation, and compares the total heating capacity LQj with the first value Q, thereby executing the process of step S3. The control device 20 calculates the total heating capacity ZQj based on the heating capacity information 22a stored in the storage unit 22.

[0046]

When the total heating capacity LQj is larger than or equal to the first value Q (YES in S3), the process proceeds to step S4. When the total heating capacity LQj is smaller than the first value Q (NO in S3), the process proceeds to step S8.

[0047]

It should be noted that in step S2 or in step S3, when the answer is “NO”, the process proceeds to step S8. Next, the following processes from step S8 onwards will be described. In step S8, the control device 20 detects whether or not the heating operating time is longer than or equal to a first operating time T11 that is a predetermined threshold value (S8). Although the definition of the heating operating time is not particularly limited, in Embodiment 1, the operating time of the compressor 1 in the heating operation is defined as a heating operating time. The control device 20 uses the timer 11 to measure the operating time of the compressor 1 from the start of the heating operation and compares the measured time with the first operating time T11, thereby executing the process of step S8. The first operating time T11 is, for example, 50 minutes, but is not limited to this value.

[0048]

In step S8, when the heating operating time reaches the first operating time T11, the control device 20 starts the first defrosting operation (S9). When the first defrosting operation is started, the control device 20 controls the refrigerant flow-passage switching device 6, as described above, to connect the flow passage for the refrigerant discharged from the compressor 1 with the first heat exchanger 2. Thereby, hightemperature refrigerant discharged from the compressor 1 is supplied to the first heat exchanger 2, thereby melting the frost adhering to the first heat exchanger 2. [0049]

While the operating time of the first defrosting operation is shorter than a predetermined defrosting time T1 (NO in S10), the control device 20 causes the first defrosting operation to continue. When the operating time of the first defrosting operation becomes longer than or equal to the defrosting time T1 (YES in S10), the control device 20 causes the first defrosting operation (S11) to end. When the first defrosting operation is ended, the control device 20 causes the heating operation to start (S1). In Embodiment 1, the defrosting time T1 of the first defrosting operation can be set longer than a defrosting time T2 of the second defrosting operation, which will be described below. Although the defrosting time T1 is not limited to a specific value, it is, for example, 12 minutes.

[0050]

It should be noted that in step S3, when the answer is “YES”, the process proceeds to step S4. Next, the following processes from step S4 onwards will be described. In step S4, the control device 20 detects whether or not the heating operating time is longer than or equal to a second operating time T12 that is another predetermined threshold value (S4). Although the definition of the heating operating time is not particularly limited, in Embodiment 1, the operating time of the compressor 1 in the heating operation is defined as the heating operating time. The control device 20 uses the timer 11 to measure the operating time of the compressor 1 from the start of the heating operation and compares the measured time with the second operating time T12, thereby executing the process of step S4. The second operating time T12 is shorter than the first operating time T11 indicated in step S8. Although the second operating timeT12 is not limited to a specific value, it is, for example, 40 minutes. [0051]

In step S4, when it is detected that the heating operating time is longer than or equal to the second operating time T12, the control device 20 starts the second defrosting operation (S5). When the second defrosting operation is started, the control device 20 controls the refrigerant flow-passage switching device 6, as described above, to connect the flow passage for the refrigerant discharged from the compressor 1 with the first heat exchanger 2. Thus, high-temperature refrigerant discharged from the compressor 1 is supplied to the first heat exchanger 2, thereby melting the frost adhering to the first heat exchanger 2.

[0052]

While the operating time of the second defrosting operation is shorter than the predetermined defrosting time T2 (NO in S6), the control device 20 causes the second defrosting operation to continue. When the operating time of the second defrosting operation reaches the defrosting time T2 (YES in S6), the control device 20 causes the second defrosting operation to end (S7). When the second defrosting operation is ended, the control device 20 causes the heating operation (S1) to start. The defrosting time T2 of the second defrosting operation may be shorter than the defrosting time T1 of the first defrosting operation. Although the time T2 is not limited to a specific value, it is, for example, 4 minutes.

[0053] [Functions of Heating Operation and Defrosting Operation]

The functions of the heating operation and the defrosting operation of the refrigeration cycle apparatus 100 according to Embodiment 1 will be described with reference to Fig. 4 and 5 and Fig. 3 referred to above. Fig. 4 illustrates an example of an integrated heating capacity in the first defrosting operation in Embodiment 1. Fig. 5 illustrates an example of an integrated heating capacity in the second defrosting operation in Embodiment 1. In Figs. 4 and 5, the vertical axis represents the heating capacity of each of the second heat exchangers 4a and 4b during the heating operation, and the horizontal axis represents time. These figures notionally indicate changes in the heating capacity in the heating operation and the first defrosting operation or second defrosting operation that are repeatedly performed.

[0054]

In Embodiment 1, as indicated in Fig. 3, one of the first defrosting operation and the second defrosting operation is selected based on the ambient temperature of the first heat exchanger 2, which operates as an evaporator during the heating operation and the total heating capacity LQj of the second heat exchanger 4a and/or the second heat exchanger 4b that are/is in the heating operation, and the heating operating time from time at which the heating operation starts to time at which the defrosting operation starts is made to vary between the case where the first defrosting operation is selected and the case where the second defrosting operation is selected. A requirement including a requirement in which the ambient temperature of the first heat exchanger 2 falls within the temperature range in which a larger amount of frost forms as described above with reference to Fig. 3 and a requirement in which the total heating capacity LQj of the second heat exchanger 4a and/or the second heat exchanger 4b that are/is in the heating operation is larger than or equal to the first value Q will be referred to as a first requirement.

[0055]

First of all, the functions of the heating operation and the first defrosting operation that are performed in the case where the above first requirement is not satisfied will be described. In the case where the first requirement is not satisfied during the heating operation, when the heating operating time becomes longer than or equal to the first operating timeT11 that is longer than the second operating timeT12, the heating operation is suspended and the first defrosting operation is started.

[0056]

As illustrated in Fig. 4, when the heating operation starts, the heating capacity increases and reaches its peak. Then, as the operating time elapses, the heating capacity gradually decreases. The heating capacity decreases mainly because of reduction of the heat exchanging efficiency of the first heat exchanger 2 which is caused by frost adhering to the first heat exchanger 2. In the case where the first requirement is not satisfied, that is, in the case where the ambient temperature of the first heat exchanger 2 falls within the temperature range in which a larger amount of frost easily forms as described above or in the case where the heat exchanging load of the first heat exchanger 2 is small because the total heating capacity LQj of the second heat exchanger 4a and/or the second heat exchanger 4b that are/is in the heating operation is relatively small, relatively speaking, frost does not easily adhere to the first heat exchanger 2. Thus, the operating time T11 for the heating operation is set longer than in the case where the second defrosting operation is performed.

[0057]

In the example indicated in Fig. 4, the first defrosting operation is started under a condition in which the heating capacity during the heating operation is 75% (average).

The heating capacity in a time period in which the heating operation and the defrosting operation that follows the heating operation are performed will be referred to as an integrated heating capacity. Since the heating capacity becomes substantially zero during the first defrosting operation, the integrated heating capacity in the time period in which the heating operation and the first defrosting operation following the heating operation are performed is 60% in the example of Fig. 4. In the case where the first defrosting operation is performed, a time period for which each of heating operations is performed is relatively long. Thus, the user hardly feels discomfort which the user would feel in the case where the operation is switched between the heating operation and the defrosting operation after a short time period elapses.

[0058]

Next, the functions of the heating operation and the second defrosting operation that are performed in the case where the above first requirement is satisfied will be described. In the case where the first requirement is satisfied during the heating operation, when the heating operating time reaches the second operating time T12 that is shorter than the first operating time T11, the heating operation is stopped and the second defrosting operation is started.

[0059]

As indicated in Fig. 5, when the heating operation starts, the heating capacity increases and reaches its peak. Then, as the operating time elapses, the heating capacity gradually decreases. The heating capacity decreases mainly because of the reduction of the heat exchanging efficiency of the first heat exchanger 2 that is caused by frost adhering to the first heat exchanger 2. In Embodiment 1, in the case where the first condition is satisfied, that is, in the case where the ambient temperature of the first heat exchanger 2 falls within the temperature range in which a larger amount of frost easily forms as described above and in the case where the heat exchanging load of the first heat exchanger 2 is large because the total heating capacity LQj of the second heat exchanger 4a and/or the second heat exchanger 4b that are/is in the heating operation is relatively large, the heating operation is stopped after performed for a relatively short time period, and the second defrosting operation is started. In such a manner, since the heating operating time is shortened, the defrosting operation can be started before the amount of frost adhering to the first heat exchanger 2 becomes excessively large. Furthermore, since the defrosting operation is started under a condition in which the amount of frost adhering to the first heat exchanger 2 is relatively small, the operating time of the second defrosting operation can be shortened.

[0060]

In the example indicated in Fig. 5, the second defrosting operation is started under a condition in which the heating capacity during the heating operation is 80% (average). Although the heating capacity becomes substantially zero during the second defrosting operation, since the second defrosting operation time may be shortened as described above, an integrated heating capacity of 70% can be obtained through the time period in which the heating operation and the first defrosting operation that follows the heating operation are performed in the example in Fig. 5. Furthermore, because the second defrosting operation time is relatively short, the gradient of the initial rise in the heating capacity in the heating operation that is performed after the second defrosting operation is large, and the heating capacity can thus be increased in a short time period, as compared with the case as indicated in Fig. 4.

[0061]

As described above, the refrigeration cycle apparatus 100 according to Embodiment 1 includes the compressor 1, the first heat exchanger 2, the plurality of expansion devices 3a and 3b, and the plurality of second heat exchangers 4a and 4b. During the heating operation in which the first heat exchanger 2 operates as an evaporator and at least one of the plurality of second heat exchangers 4a and 4b operates as a condenser, the ambient temperature of the first heat exchanger 2 is detected, and one of the first defrosting operation and the second defrosting operation is selected based on the ambient temperature of the first heat exchanger 2, the total value of the heating capacity or capacities of the second heat exchanger 4a and/or the second heat exchanger 4b that operate/operates as condensers I a condenser, and the operating time of the heating operation. In the case where the first defrosting operation is selected, the first defrosting operation is started when the operating time of the heating operation reaches the first operating time. In the case where the second defrosting operation is selected, the second defrosting operation is started when the operating time of the heating operation reaches the second operating time that is shorter than the first operating time. In such a manner, based on the ambient temperature of the first heat exchanger 2 that operates as a condenser and the total value of the heating capacities or capacity of the second heat exchanger 4a and/or the second heat exchanger 4b that operate/operates as evaporators I an evaporator, the operating time of the heating operation is changed and the defrosting operation is started. Therefore, the defrosting operation can be started at a more appropriate timing for the actual state of frost adhering to the first heat exchanger 2 to be defrosted, as compared with the case where the defrosting operation is started based on an empirical rule from the temperature of the heat exchanger to be defrosted. It is therefore possible to reduce a decrease in the integrated heating capacity in the time period in which the heating operation and the defrosting operation following the heating operation are continuously performed. Furthermore, after the second defrosting operation that is performed in a relatively short operating time, it is possible to shorten the time required for starting up the heating operation that follows the second defrosting operation.

[0062]

Furthermore, in the refrigeration cycle apparatus 100 according to Embodiment 1, in the case where the detection value obtained by the first temperature detector 5 that detects the ambient temperature of the first heat exchanger 2 falls within the first temperature range and the total value of the heating capacities is greater than or equal to the first value, the second defrosting operation which is performed for a relatively short time period is selected. Therefore, under a condition in which a larger amount of frost easily adheres to the first heat exchanger 2, it is possible to stop the heating operation earlier, and start the second defrosting operation. It is therefore possible to reduce the decrease in the integrated heating capacity in the time period in which a set of the heating operation and the defrosting operation following the heating operation are consecutively performed.

[0063]

Embodiment 2

In Embodiment 2, a second temperature detector 12 is provided. The second temperature detector 12 detects a surface temperature of the first heat exchanger 2 that operates as an evaporator during the heating operation and operates as a condenser during the defrosting operation. A detection value obtained by detection by the second temperature detector 12 is used in control of the heating operation and the defrosting operation. Embodiment 2 will be described by referring mainly to the differences between Embodiments 1 and 2.

[0064]

Fig. 6 illustrates an example of a circuit configuration of a refrigeration cycle apparatus 100A according to Embodiment 2. The refrigeration cycle apparatus 100 according to Embodiment 2 is provided with the second temperature detector 12 that detects the surface temperature of the first heat exchanger 2. The second temperature detector 12 directly or indirectly detects the surface temperature of the first heat exchanger 2 that reflects the state of frost adhering to the first heat exchanger 2. For example, the second temperature detector 12 can detect the surface temperature of a pipe forming the first heat exchanger 2. Alternatively, the second temperature detector 12 may detect the temperature of refrigerant that flows in the first heat exchanger 2 in order to detect the surface temperature of the first heat exchanger 2 based on the temperature of the refrigerant. Components other than the second temperature detector 12 are the same as those described with respect Embodiment 1.

[0065]

Fig. 7 is a functional block diagram of the refrigeration cycle apparatus 100A according to Embodiment 2. The second temperature detector 12 is connected to the control device 20 in such a manner to be allowed to transmit a signal to the control device 20 and receive a signal from the control device 20. The control device 20 controls the actuators based on the signal input from the second temperature detector 12 in addition to signals input from the first temperature detector 5 and the timer 11. [0066]

Fig. 8 is a flowchart for explaining the heating operation and the defrosting operation in the refrigeration cycle apparatus 100A according to Embodiment 2. In the heating operation and the defrosting operation according to Embodiment 2, a requirement for starting the first defrosting operation and that for ending the first defrosting operation are different from those in Embodiment 1. To be more specific, the flowchart of Fig. 8 is different from that of Fig. 3 relating to Embodiment 1 in what process is executed in step S8A and addition of step S12A in the flowchart of Fig. 8. [0067]

In step S2 and also in step S3, when the answer is “NO”, that is, the first defrosting operation is selected instead of the second defrosting operation, the process proceeds to step S8A. In step S8A, the control device 20 detects whether or not the heating operating time is longer than or equal to the first operating time T11 determined in advance. Furthermore, the control device 20 determines whether or not the surface temperature of the first heat exchanger 2 is lower than or equal to a first temperature TH3 that is a predetermined threshold value, based on a detection value obtained by detection by the second temperature detector 12. The first temperature TH3 is a temperature for determining the amount of frost adhering to the first heat exchanger 2, and a temperature at which a larger amount of frost is assumed to easily adhere to the first heat exchanger 2 is stored as data in the storage unit 22. Preferably, the first temperature TH3 should be lower than the temperature TH2 in step S2, and it is, for example, -10 degrees C, although it is not limited to a specific value.

[0068]

When the heating operating time becomes longer than or equal to the first operating time T11 and the surface temperature of the first heat exchanger 2 becomes lower than or equal to the predetermined first temperature TH3 (YES in S8A), the control device 20 starts the first defrosting operation (S9).

[0069]

During the first defrosting operation, when the surface temperature of the first heat exchanger 2 becomes higher than or equal to a second temperature TH4 that is a predetermined threshold value (YES in S12A), the control device 20 ends the first defrosting operation. The second temperature TH4 is a temperature for determining the amount of frost adhering to the first heat exchanger 2, and a temperature at which defrosting of the first heat exchanger 2 is assumed to be completed is stored as data in the storage unit 22 in advance. The second temperature TH4 is, for example, 10 degrees C, although it is not limited to a specific value. When the surface temperature of the first heat exchanger 2 is below the second temperature TH4 that is a predetermined threshold value (NO in S12A), the process by the control device 20 proceeds to step S10. The processes from step S10 onwards are the same as those described above with reference to Fig. 3.

[0070]

In such a manner, in Embodiment 2, the same configuration as or a similar configuration to that of Embodiment 1 is provided, and it is possible to obtain the same advantages as or similar advantages to those of Embodiment 1. Furthermore, in the case where the first defrosting operation is selected, when the operating time of the heating operation becomes longer than or equal to the first operating time and the surface temperature of the first heat exchanger 2 becomes lower than or equal to the first temperature TH3, the refrigeration cycle apparatus 100A according to Embodiment 2 starts performing the first defrosting operation. Because the first defrosting operation is started based on the surface temperature of the first heat exchanger 2 that reflects the state of frost adhering to the first heat exchanger 2, in addition to the operating time of the heating operation, the timing at which defrosting is needed is detected with a higher accuracy, and the first heat exchanger 2 can be defrosted.

[0071]

In the refrigeration cycle apparatus 100A according to Embodiment 2, when the surface temperature of the first heat exchanger 2 becomes higher than or equal to the second temperature TH4 during the first defrosting operation, the first defrosting operation is ended. Since the timing at which the first defrosting operation is ended is determined based on the state of frost adhering to the first heat exchanger 2, that is, the temperature of the first heat exchanger 2 that reflects the defrosted state, defrosting can be sufficiently performed, that is, defrosting is not insufficient or excessive.

[0072]

In each of step S2 in Figs. 3 and 8 and steps S8Aand S12A in Fig. 8, in the case where it is determined whether a related temperature is above, below or equal to the above threshold, it may be set that when a time period for which the above requirement concerning the relationship between the related temperature and the threshold is satisfied exceeds a predetermined time period, it is determined that the requirement is satisfied, and the process proceeds a subsequent step. Regarding the example of step S8A in Fig. 8, in the case where the control device 20 determines whether or not the surface temperature of the first heat exchanger 2 is lower than or equal to the first temperature TH3, the control device 20 may determine that the surface temperature of the first heat exchanger 2 is lower than or equal to the first temperature when the surface temperature is continuously lower than or equal to the first temperature TH3 for a predetermined time period such as three or more minutes. The same is true of step S12A. It may be set that when the surface temperature of the first heat exchanger 2 is continuously higher than or equal to the second temperature TH4 for a predetermined time such as three or more minutes, the process proceeds to a subsequent step. There is a possibility that detection values output from the first temperature detector 5 and the second temperature detector 12 may vary because of, for example, disturbance. However, by performing the determination based on detection values obtained for a predetermined time period, it is possible to reduce the degree of erroneous determination which would be caused by the above variation of the detections values.

[0073]

Furthermore, in the heating operation as indicated in Figs. 3 and 8, the operating frequency of the compressor 1 may be changed in accordance with the ambient temperature of the first heat exchanger 2 that operates as an evaporator. For example, a table for use in controlling the frequency of the compressor 1 in accordance with the ambient temperature of the first heat exchanger 2 is stored in the storage unit 22 in advance, and when the ambient temperature of the first heat exchanger 2 is low, the operating frequency of the compressor 1 is controlled to be set to a high frequency, as compared with the case where the ambient temperature of the first heat exchanger 2 is high. Thereby, it is possible to reduce a decrease in the heating capacity.

[0074]

The refrigeration cycle apparatus and the defrosting operation method for the refrigeration cycle apparatus, as described with respect to Embodiments 1 and 2, can be applied not only to an air-conditioning apparatus, but to an apparatus using another refrigeration cycle circuit, such as a refrigerator. Also, Embodiments 1 and 2 are described above by referring to by way of example a so-called reverse-cycle defrosting operation in which refrigerant is circulated in an opposite direction to that in the heating operation. However, the specific configuration for the defrosting operation is not limited to this. The processes related to the selection of one of the first defrosting operation and the second defrosting operation and the start and end of the selected defrosting operation as described regarding Embodiments 1 and 2 may also be combined with a defrosting operation that is performed using another specific configuration, such as a defrosting operation that is performed using a heater or heated water. For example, The processes related to the selection of one of the first defrosting operation and the second defrosting operation and the start and end of the selected defrosting operation as described regarding Embodiment 1 and Embodiment 2 can also be applied to a heating-only air-conditioning apparatus which does not include a component corresponding to the refrigerant flow-passage switching device 6 and in which a refrigerant flows in a single direction.

Reference Signs List [0075] compressor 2 first heat exchanger 3a expansion device 3b expansion device 4a second heat exchanger 4b second heat exchanger 5 first temperature detector 6 refrigerant-flow passage switching device 7 accumulator 8 checkvalve 9 outdoor fan 10a indoor fan 10b indoor fan 11 timer 12 second temperature detector 20 control device 21 processing circuit 22 storage unit 22a heating capacity information 30 outdoor unit 40a indoor unit

40b indoor unit 100 refrigeration cycle apparatus 100A refrigeration cycle apparatus

Claims

CLAIMS [Claim 1]

A refrigeration cycle apparatus comprising:

a compressor;

a first heat exchanger;

a plurality of expansion devices;

a plurality of second heat exchangers;

a first temperature detector configured to detect an ambient temperature of the first heat exchanger;

a storage unit configured to store data indicating a heating capacity of each of the plurality of second heat exchangers; and a control device configured to cause a heating operation to be performed, in which the first heat exchanger operates as an evaporator and one or more of the plurality of second heat exchangers operates or operate as a condenser or condensers, wherein the control device is configured to select one of a first defrosting operation and a second defrosting operation based on a detection value obtained by detection by the first temperature detector and a total value of the heating capacity or capacities of the one or more of the plurality of second heat exchangers that operates or operate as the condenser or condensers during the heating operation, and wherein in a case where the control device selects the first defrosting operation, the control device starts the first defrosting operation when an operating time of the heating operation reaches a first operating time, and in a case where the control device selects the second defrosting operation, the control device starts the second defrosting operation when the operating time of the heating operation reaches a second operating time that is shorter than the first operating time.
[Claim 2]

The refrigeration cycle apparatus of claim 1, wherein the control device selects the first defrosting operation in a case where a first requirement is not satisfied, wherein the control device selects the second defrosting operation in a case where the first requirement is satisfied, and wherein the first requirement includes a requirement in which the detection value obtained by the detection by the first temperature detector falls within a first temperature range and the total value of the heating capacity or capacities is greater than or equal to a first value.
[Claim 3]

The refrigeration cycle apparatus of claim 1 or 2, further comprising:

a second temperature detector configured to detect a surface temperature of the first heat exchanger, wherein in a case where the control device selects the first defrosting operation, the control device starts the first defrosting operation when the operating time of the heating operation reaches the first operating time and a detection value obtained by detection by the second temperature detector becomes less than or equal to a first temperature.
[Claim 4]

The refrigeration cycle apparatus of any one of claims 1 to 3, further comprising:

a second temperature detector configured to detect a surface temperature of the first heat exchanger, wherein the control device ends the first defrosting operation and starts the heating operation when a detection value obtained by detection by the second temperature detector becomes greater than or equal to a second temperature during the first defrosting operation.
[Claim 5]

The refrigeration cycle apparatus of any one of claims 1 to 4, wherein an operating time of the second defrosting operation is shorter than an operating time of the first defrosting operation.
[Claim 6]

A defrosting operation method for a refrigeration cycle apparatus including a compressor, a first heat exchanger, a plurality of expansion devices, and a plurality of second heat exchangers, the defrosting operation method comprising:

detecting an ambient temperature of the first heat exchanger during a heating operation in which the first heat exchanger operates as an evaporator and one or more of the plurality of second heat exchangers operates or operate as a condenser or condensers;

selecting one of first defrosting operation and second defrosting operation based on the ambient temperature of the first heat exchanger and a total value of the heating capacity or capacities of the one or more of the plurality of second heat exchangers that operates or operate as the condenser or condensers during the heating operation; and starting the first defrosting operation when an operating time of the heating operation reaches a first operating time in a case where the first defrosting operation is selected, and starting the second defrosting operation when the operating time of the heating operation reaches a second operating time that is shorter than the first operating time in a case where the second defrosting operation is selected.
[Claim 7]

The defrosting operation method of claim 6, wherein the selecting the one of the first defrosting operation and the second defrosting operation includes selecting the first defrosting operation in a case where a first requirement is not satisfied, and selecting the second defrosting operation in a case where the first requirement is satisfied, wherein the first requirement includes a requirement in which the ambient temperature of the first heat exchanger falls within a first temperature range and the total value of the heating capacity or capacities is greater than or equal to a first value. [Claim 8]

The defrosting operation method of claim 6 or 7, further comprising:

starting the first defrosting operation when the operating time of the heating operation reaches the first operating time and a surface temperature of the first heat exchanger becomes lower than or equal to a first temperature in a case where the first defrosting operation is selected.

5 [Claim 9]

The defrosting operation method of any one of claims 6 to 8, further comprising: ending the first defrosting operation when a surface temperature of the first heat exchanger becomes higher than or equal to a second temperature during the first defrosting operation; and

10 starting the heating operation after the first defrosting operation is ended.

[Claim 10]

The defrosting operation method of any one of claims 6 to 9, wherein an operating time of the second defrosting operation is shorter than an operating time of the first defrosting operation.