REFRIGERATION CYCLE APPARATUS

Abstract

A refrigeration cycle apparatus includes a compressor, an expansion valve, a flow switching device, a heat source side heat exchanger including a first heat source side heat exchanger and a second heat source side heat exchanger connected in parallel, an opening-and-closing valve provided on downstream of the second heat source side heat exchanger through which refrigerant flows during a defrosting operation, and a controller that, when the defrosting operation is performed, controls the flow switching device so that the refrigerant discharged from the compressor flows into the heat source side heat exchanger. The controller switches the opening-and-closing valve from an open state to a closed state when the defrosting operation is started, determines a point in time when defrosting targets to be defrosted are switched, and switches the opening-and-closing valve from the closed state to the open state in accordance with the point in time determined.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. National Stage Application of International Application No. PCT/JP2019/044375 filed on Nov. 12, 2019, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus that conditions air in an air-conditioned space.

BACKGROUND

In an existing air-conditioning apparatus, there is a heat exchanger including a plurality of flat pipes that are vertically arrayed and each have a refrigerant passage, and a plurality of fins that partition a space between adjacent flat pipes into a plurality of air flow passages through which air flows (for example, see Patent Literature 1).

A heat exchanger disclosed in Patent Literature 1 includes a main heat exchange section, and a sub heat exchange section provided at a position different from a position of the main heat exchange section in a vertical direction and connected in series with the main heat exchange section. In the main heat exchange section, many flat pipes are provided in comparison with the sub heat exchange section located downstream of the main heat exchange section. Furthermore, a lowermost flat pipe in the heat exchanger is provided in a main heat exchanger located upstream of the sub heat exchange section. This configuration reduces the time taken to melt frost that has adhered to a lowermost heat exchange section during a defrosting operation.

PATENT LITERATURE

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2019-11941

In an air conditioner disclosed in Patent Literature 1, in the defrosting operation, refrigerant discharged from a compressor passes through the main heat exchange section and then flows into the sub heat exchange section. That is, even after defrosting of the main heat exchange section is finished, the refrigerant discharged from the compressor flows through the main heat exchange section before flowing into the sub heat exchange section. For this reason, before the heat of the refrigerant reaches the sub heat exchange section, heat exchange between the refrigerant and air is performed in the main heat exchange section in which defrosting is unnecessary, and the heat is uselessly released. Consequently, defrosting is unable to be efficiently performed.

SUMMARY

The present disclosure has been made to overcome such an issue and provides a refrigeration cycle apparatus capable of efficiently performing defrosting.

A refrigeration cycle apparatus according to an embodiment of the present disclosure includes a compressor configured to compress and discharge refrigerant; an expansion valve configured to reduce pressure of the refrigerant to cause the refrigerant to expand; a load side heat exchanger connected to the expansion valve; a flow switching device connected to the compressor and the load-side heat exchanger; a heat source side heat exchanger including a first heat source side heat exchanger and a second heat source side heat exchanger connected in parallel between the flow switching device and the expansion valve; an opening-and-closing valve provided on downstream of the second heat source side heat exchanger through which the refrigerant flows during a defrosting operation; and a controller configured to, when the defrosting operation is performed, control the flow switching device so that the refrigerant discharged from the compressor flows into the heat source side heat exchanger. The controller includes a first defrosting unit configured to switch the opening-and-closing valve from an open state to a closed state when the defrosting operation is started, a determination unit configured to determine a point in time when defrosting targets to be defrosted are switched, and a second defrosting unit configured to switch the opening-and-closing valve from the closed state to the open state in accordance with the point in time determined by the determination unit.

In the embodiment of the present disclosure, the first defrosting unit closes the opening-and-closing valve when defrosting is started, and thus the refrigerant discharged from the compressor flows intensively to the first heat source side heat exchanger of two heat source side heat exchangers. Subsequently, when the second defrosting unit opens the opening-and-closing valve, most of the heat of the refrigerant is consumed to defrost the second heat source side heat exchanger. Thus, the heat of the refrigerant is kept from being uselessly consumed in comparison with a case where two heat source side heat exchangers connected in series are simultaneously defrosted. Consequently, the two heat source side heat exchangers can be efficiently defrosted.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus according to Embodiment 1.

FIG. 2 is a functional block diagram illustrating an example configuration of a controller illustrated in FIG. 1.

FIG. 3 is a hardware configuration diagram illustrating an example configuration of the controller illustrated in FIG. 2.

FIG. 4 is a hardware configuration diagram illustrating another example configuration of the controller illustrated in FIG. 2.

FIG. 5 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus illustrated in FIG. 1.

FIG. 6 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus in Modification 1.

FIG. 7 is a functional block diagram illustrating an example configuration of the controller in Modification 1.

FIG. 8 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus in Modification 2.

FIG. 9 is a functional block diagram illustrating an example configuration of the controller in Modification 2.

FIG. 10 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus illustrated in FIG. 8.

FIG. 11 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus in Modification 3.

FIG. 12 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus according to Embodiment 2.

FIG. 13 is a side view illustrating an example configuration of a first heat source side heat exchanger illustrated in FIG. 12.

FIG. 14 is a side view illustrating an example configuration of a second heat source side heat exchanger illustrated in FIG. 12.

FIG. 15 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus in a comparative example.

FIG. 16 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus in the comparative example illustrated in FIG. 15.

FIG. 17 includes graphs illustrating an example of the relationship between a refrigerant flow rate and a position of a heat source side heat exchanger during a defrosting operation.

FIG. 18 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus according to Embodiment 3.

FIG. 19 is an external perspective view illustrating an example configuration of a heat source side unit illustrated in FIG. 18.

FIG. 20 is an external perspective view of the heat source side unit illustrated in FIG. 18 as seen from a direction different from that in FIG. 19.

FIG. 21 is a schematic view illustrating the layout of heat source side heat exchangers in the heat source side unit illustrated in FIG. 20 as seen from above.

FIG. 22 is a side view illustrating an example configuration of a first division heat exchanger illustrated in FIG. 19.

FIG. 23 is a side view illustrating an example configuration of the second heat source side heat exchanger illustrated in FIG. 20.

FIG. 24 is a refrigerant circuit diagram illustrating an example configuration of a refrigeration cycle apparatus in Modification 4.

DETAILED DESCRIPTION

Embodiment 1

A configuration of a refrigeration cycle apparatus in Embodiment 1 will be described. FIG. 1 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus according to Embodiment 1. As illustrated in FIG. 1, a refrigeration cycle apparatus 1 includes a heat source side unit 10, load side units 20a and 20b, and a controller 30 that controls refrigerant devices included in the heat source side unit 10 and the load side units 20a and 20b. Although FIG. 1 illustrates the case where the refrigeration cycle apparatus 1 includes two load side units that are the load side units 20a and 20b, the number of load side units may be one or may be three or more.

The heat source side unit 10 includes a compressor 2 that compresses and discharges refrigerant, a heat source side heat exchanger 15 that causes the refrigerant to exchange heat with outside air, a flow switching device 5, an accumulator 6, and an opening-and-closing valve 7. The heat source side heat exchanger 15 includes a first heat source side heat exchanger 3 and a second heat source side heat exchanger 4. The load side unit 20a includes a load side heat exchanger 21a that causes the refrigerant to exchange heat with air in a room where the load side unit 20a is installed, and an expansion valve 22a that reduces the pressure of the refrigerant to cause the refrigerant to expand. The load side unit 20b includes a load side heat exchanger 21b that causes the refrigerant to exchange heat with air in a room where the load side unit 20b is installed, and an expansion valve 22b that reduces the pressure of the refrigerant to cause the refrigerant to expand.

The first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 are connected in parallel between the flow switching device 5 and the expansion valves 22a and 22b. Of two refrigerant inlet/outlet ports of the first heat source side heat exchanger 3, one refrigerant inlet/outlet port is connected to a first gas pipe 43a, and the other refrigerant inlet/outlet port is connected to a first liquid pipe 44a. Of two refrigerant inlet/outlet ports of the second heat source side heat exchanger 4, one refrigerant inlet/outlet port is connected to a second gas pipe 43b, and the other refrigerant inlet/outlet port is connected to a second liquid pipe 44b. The first gas pipe 43a and the second gas pipe 43b are joined to a gas pipe 41 and communicate with the flow switching device 5. The first liquid pipe 44a and the second liquid pipe 44b are joined to a liquid pipe 47 and communicate with the expansion valves 22a and 22b. The opening-and-closing valve 7 is provided in the second liquid pipe 44b.

The flow switching device 5 is connected to the load side heat exchangers 21a and 21b via a refrigerant pipe 42 and is connected to the accumulator 6 via a refrigerant pipe 48. Furthermore, the flow switching device 5 is connected to the compressor 2 and the accumulator 6 via a refrigerant pipe 49. The accumulator 6 is connected to a refrigerant inlet of the compressor 2. The compressor 2, the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4, the expansion valve 22a, and the load side heat exchanger 21a are connected with pipes, such as the refrigerant pipe 42, to form a refrigerant circuit 60a. Furthermore, the compressor 2, the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4, the expansion valve 22b, and the load side heat exchanger 21b are connected with pipes, such as the refrigerant pipe 42, to form a refrigerant circuit 60b.

In the second heat source side heat exchanger 4, a heat exchanger temperature sensor 11 is provided that detects a temperature Te of refrigerant. In the second liquid pipe 44b, a refrigerant temperature sensor 12 is provided that detects a temperature Tn2 of refrigerant that flows through the second liquid pipe 44b. In the load side unit 20a, a room temperature sensor 23a is provided that detects a temperature of air in the room where the load side unit 20a is installed. In the load side unit 20b, a room temperature sensor 23b is provided that detects a temperature of air in the room where the load side unit 20b is installed. The heat exchanger temperature sensor 11, the refrigerant temperature sensor 12, and the room temperature sensors 23a and 23b are, for example, thermistors. The heat exchanger temperature sensor 11 may be provided on a first heat source side heat exchanger 3 side in place of the second heat source side heat exchanger 4.

The compressor 2 is a compressor whose displacement is variable, for example, an inverter compressor. The accumulator 6 is a container that keeps liquid refrigerant from being sucked into the compressor 2. The expansion valves 22a and 22b are, for example, electronic expansion valves. The flow switching device 5 switches, to the gas pipe 41 or the refrigerant pipe 42, a direction in which the refrigerant discharged from the compressor 2 flows. The flow switching device 5 is, for example, a four-way valve. The opening-and-closing valve 7 is, for example, a shutoff valve whose state can be switched, of a closed state and an open state, from one state to the other state. The opening-and-closing valve 7 may be an electronic expansion valve that adjusts a flow rate of refrigerant that circulates. The first heat source side heat exchanger 3 and the second heat source side heat exchanger 4, and the load side heat exchangers 21a and 21b are, for example, fin-and-tube heat exchangers.

The controller 30 is connected to, via a signal line not illustrated in the figure, devices that are the compressor 2, the flow switching device 5, the expansion valves 22a and 22b, and the opening-and-closing valve 7. Furthermore, the controller 30 is connected to, via a signal line not illustrated in the figure, sensors that are the room temperature sensors 23a and 23b, the heat exchanger temperature sensor 11, and the refrigerant temperature sensor 12. Communication connections of the controller 30 to the devices that are the compressor 2, the flow switching device 5, the expansion valve 22a, the expansion valve 22b, and the opening-and-closing valve 7 may be established not only by wire but also wirelessly. Regarding the sensors as well, communication connections of the controller 30 to the sensors that are the room temperature sensor 23a, the room temperature sensor 23b, the heat exchanger temperature sensor 11, and the refrigerant temperature sensor 12 may be established not only by wire but also wirelessly.

Before a configuration of the controller 30 illustrated in FIG. 1 will be described, the flow of refrigerant in each of operation modes of the refrigeration cycle apparatus 1 will be simply described. Here, the case of the refrigerant circuit 60a will be described. Furthermore, assume that the opening-and-closing valve 7 is in an open state.

[Cooling Operation]

First, the flow of refrigerant in the case where the refrigeration cycle apparatus 1 performs a cooling operation will be described with reference to FIG. 1. In the case where the refrigeration cycle apparatus 1 performs the cooling operation, the controller 30 switches between flow passages of the flow switching device 5 so that refrigerant discharged from the compressor 2 flows into the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. When low-temperature, low-pressure refrigerant is compressed by the compressor 2, high-temperature, high-pressure gaseous refrigerant is discharged from the compressor 2. The gaseous refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. The refrigerant having flowed into the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 is condensed into low-temperature, high-pressure liquid refrigerant by exchanging heat with air in these heat exchangers connected in parallel and flows out of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4.

The liquid refrigerant having flowed out of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 is caused to turn into low-temperature, low-pressure liquid refrigerant by the expansion valve 22a. The liquid refrigerant flows into the load side heat exchanger 21a. The refrigerant having flowed into the load side heat exchanger 21a evaporates into low-temperature, low-pressure gaseous refrigerant by exchanging heat with air in the load side heat exchanger 21a and flows out of the load side heat exchanger 21a. In the load side heat exchanger 21a, when the refrigerant receives heat from air in the room, the air in the room is cooled. The refrigerant having flowed out of the load side heat exchanger 21a is sucked into the compressor 2 via the flow switching device 5. During the cooling operation, a cycle is repeated in which the refrigerant discharged from the compressor 2 flows through the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4, the expansion valve 22a, and the load side heat exchanger 21a in sequence and then is sucked into the compressor 2.

[Heating Operation]

Next, the flow of refrigerant in the case where the refrigeration cycle apparatus 1 performs a heating operation will be described with reference to FIG. 1. In the case where the refrigeration cycle apparatus 1 performs the heating operation, the controller 30 switches between the flow passages of the flow switching device 5 so that refrigerant discharged from the compressor 2 flows into the load side heat exchanger 21a. When low-temperature, low-pressure refrigerant is compressed by the compressor 2, high-temperature, high-pressure gaseous refrigerant is discharged from the compressor 2. The high-temperature, high-pressure gaseous refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the load side heat exchanger 21a. The refrigerant having flowed into the load side heat exchanger 21a is condensed into high-temperature, high-pressure liquid refrigerant by exchanging heat with air in the load side heat exchanger 21a and flows out of the load side heat exchanger 21a. In the load side heat exchanger 21a, when the refrigerant transfers heat to air in the room, the air in the room is heated.

The high-temperature, high-pressure liquid refrigerant having flowed out of the load side heat exchanger 21a is caused to turn into low-temperature, low-pressure liquid refrigerant by the expansion valve 22a. The liquid refrigerant flows into the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. In the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4, the refrigerant evaporates into low-temperature, low-pressure gaseous refrigerant by exchanging heat with air and flows out of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. The refrigerant having flowed out of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 is sucked into the compressor 2 via the flow switching device 5. While the refrigeration cycle apparatus 1 is performing the heating operation, a cycle is repeated in which the refrigerant discharged from the compressor 2 flows through the load side heat exchanger 21a, the expansion valve 22a, and the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 in sequence and then is sucked into the compressor 2.

[Defrosting Operation]

The flow of refrigerant in the case where the refrigeration cycle apparatus 1 performs a defrosting operation will be described with reference to FIG. 1. In the case where the refrigeration cycle apparatus 1 switches an operation mode from the heating operation to the defrosting operation, the controller 30 switches between the flow passages of the flow switching device 5 so that refrigerant discharged from the compressor 2 flows into the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. Furthermore, the controller 30 performs control to put the expansion valve 22a in a fully open state. In the case of the defrosting operation, a direction in which refrigerant in the refrigerant circuit 60a flows is the same as that in the cooling operation, and thus a detailed description of the flow of the refrigerant is omitted.

Next, a configuration of the controller 30 illustrated in FIG. 1 will be described. FIG. 2 is a functional block diagram illustrating an example configuration of the controller illustrated in FIG. 1.

The controller 30 includes a refrigeration cycle control unit 51, a determination unit 52, a timer 53, a first defrosting unit 54, and a second defrosting unit 55. Regarding the controller 30, various functions are implemented by an arithmetic unit, such as a microcomputer, executing software. Furthermore, the controller 30 may be constituted by hardware, such as a circuit device, that implements various functions. A set temperature Ts1 is input to the controller 30 via a remote controller not illustrated in the figure by a user that uses the load side unit 20a. A set temperature Ts2 is input to the controller 30 via a remote controller not illustrated in the figure by a user that uses the load side unit 20b. Incidentally, in the refrigeration cycle apparatus 1 illustrated in FIG. 1, a location where the controller 30 is installed is not limited to the illustrated location, and the controller 30 may be provided in the heat source side unit 10, or may be provided in the load side unit 20a or 20b.

The refrigeration cycle control unit 51 controls the flow switching device 5 in accordance with an operation mode of the refrigeration cycle apparatus 1. The refrigeration cycle control unit 51 controls an operating frequency of the compressor 2 and opening degrees of the expansion valves 22a and 22b by using detected values received from the room temperature sensors 23a and 23b and the set temperatures Ts1 and Ts2. Specifically, the refrigeration cycle control unit 51 controls the operating frequency of the compressor 2 and the opening degrees of the expansion valves 22a and 22b so that the detected value of the room temperature sensor 23a approaches the set temperature Ts1 and the detected value of the room temperature sensor 23b approaches the set temperature Ts2.

While the refrigeration cycle apparatus 1 is performing the heating operation, the refrigeration cycle control unit 51 monitors the temperature Te of refrigerant received from the heat exchanger temperature sensor 11 and determines whether or not the temperature Te of refrigerant is not more than a predetermined temperature threshold T0. The temperature threshold T0 is, for example, 0 degrees C. When the temperature Te of refrigerant reaches not more than the temperature threshold T0, the refrigeration cycle control unit 51 controls the flow switching device 5 to switch between the flow passages and also transmits, to the determination unit 52, defrosting start information representing that the defrosting operation has been started. When the refrigeration cycle control unit 51 receives defrosting completion information from the determination unit 52, the refrigeration cycle control unit 51 controls the flow switching device 5 to switch between the flow passages and switches the operation mode from the defrosting operation to the heating operation.

The timer 53 measures a time period and provides measurement time information to the determination unit 52. The determination unit 52 determines, in accordance with at least either a time period that has elapsed since the start of defrosting or the temperature Tn2 of refrigerant detected by the refrigerant temperature sensor 12, a point in time when defrosting targets to be defrosted are switched. When the determination unit 52 receives the defrosting start information from the refrigeration cycle control unit 51, the determination unit 52 transfers the defrosting start information to the first defrosting unit 54 and also monitors a time t1 representing a time period that has elapsed since the start of defrosting. The determination unit 52 determines whether or not the time t1 is not less than a predetermined time threshold tth1. The time threshold tth1 is set to a time before defrosting of the first heat source side heat exchanger 3 is completely finished. When the time t1 reaches not less than the time threshold tth1, the determination unit 52 transmits, to the second defrosting unit 55, switching instruction information representing an instruction for switching between states of the opening-and-closing valve 7.

Furthermore, after the determination unit 52 transmits the switching instruction information to the second defrosting unit 55, the determination unit 52 monitors the temperature Tn2 of refrigerant received from the refrigerant temperature sensor 12 and determines whether or not the temperature Tn2 of refrigerant is not less than a predetermined temperature threshold Tb. The temperature threshold Tb is, for example, 7 degrees C. When the temperature Tn2 of refrigerant reaches not less than the temperature threshold Tb, the determination unit 52 transmits, to the refrigeration cycle control unit 51, defrosting completion information representing that defrosting has been completed.

When the first defrosting unit 54 receives the defrosting start information from the determination unit 52, the first defrosting unit 54 switches the opening-and-closing valve 7 from an open state to a closed state. When the second defrosting unit 55 receives the switching instruction information from the determination unit 52, the second defrosting unit 55 switches the opening-and-closing valve 7 from the closed state to the open state.

Here, an example of hardware of the controller 30 illustrated in FIG. 2 will be described. FIG. 3 is a hardware configuration diagram illustrating an example configuration of the controller illustrated in FIG. 2. In the case where various functions of the controller 30 are executed by hardware, the controller 30 illustrated in FIG. 2 is constituted by a processing circuit 31 as illustrated in FIG. 3. Functions of the refrigeration cycle control unit 51, the determination unit 52, the timer 53, the first defrosting unit 54, and the second defrosting unit 55 that are illustrated in FIG. 2 are implemented by the processing circuit 31.

In the case where each function is executed by hardware, the processing circuit 31 corresponds, for example, to a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or a combination of these. Functions of units that are the refrigeration cycle control unit 51, the determination unit 52, the timer 53, the first defrosting unit 54, and the second defrosting unit 55 may be implemented by respective processing circuits 31, or the functions of the units may be implemented by one processing circuit 31.

Furthermore, an example of other hardware of the controller 30 illustrated in FIG. 2 will be described. FIG. 4 is a hardware configuration diagram illustrating another example configuration of the controller illustrated in FIG. 2. In the case where various functions of the controller 30 are executed by software, the controller 30 illustrated in FIG. 2 is constituted by a processor 71 and a memory 72 as illustrated in FIG. 4. Functions of the refrigeration cycle control unit 51, the determination unit 52, the timer 53, the first defrosting unit 54, and the second defrosting unit 55 are implemented by the processor 71 and the memory 72. FIG. 4 illustrates that the processor 71 and the memory 72 are connected to each other in such a manner that they can communicate with each other.

In the case where each function is executed by software, the functions of the refrigeration cycle control unit 51, the determination unit 52, the timer 53, the first defrosting unit 54, and the second defrosting unit 55 are implemented by software, firmware, or a combination of software and firmware. Software and firmware are written as programs and stored in the memory 72. The processor 71 reads out a program stored in the memory 72 and executes the program to thereby implement a function of each unit.

As the memory 72, for example, non-volatile semiconductor memories, such as a Read Only Memory (ROM), a flash memory, an Erasable and Programmable ROM (EPROM), and an Electrically Erasable and Programmable ROM (EEPROM), are used. Furthermore, as the memory 72, a volatile semiconductor memory, such as a Random Access Memory (RAM), may be used. Additionally, as the memory 72, detachable recording media, such as a magnetic disk, a flexible disk, an optical disc, a Compact Disc (CD), a Mini Disc (MD), and a Digital Versatile Disc (DVD), may be used.

Next, the operation of the refrigeration cycle apparatus 1 in Embodiment 1 will be described. FIG. 5 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus illustrated in FIG. 1. FIG. 5 illustrates an example of an operation procedure in the case where the refrigeration cycle apparatus 1 performs the defrosting operation. Assume that the refrigeration cycle apparatus 1 is performing the heating operation before starting the operation procedure illustrated in FIG. 5 and the opening-and-closing valve 7 is in an open state.

The refrigeration cycle control unit 51 determines whether or not the temperature Te of refrigerant received from the heat exchanger temperature sensor 11 has reached not more than the temperature threshold T0 (step S101). When the temperature Te of refrigerant reaches not more than the temperature threshold T0 in step S101, the refrigeration cycle control unit 51 determines that frost has adhered to the heat source side heat exchanger 15 and controls the flow switching device 5 to switch between the flow passages (step S102). Thus, the refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the heat source side heat exchanger 15. Furthermore, the refrigeration cycle control unit 51 transmits defrosting start information to the determination unit 52 in step S102.

When the determination unit 52 receives the defrosting start information from the refrigeration cycle control unit 51, the determination unit 52 transfers the defrosting start information to the first defrosting unit 54 and also monitors the time t1 measured by the timer 53. When the first defrosting unit 54 receives the defrosting start information from the determination unit 52, the first defrosting unit 54 closes the opening-and-closing valve 7 (step S103). The determination unit 52 determines whether or not the time t1 has reached not less than the time threshold tth1 (step S104). When the time t1 reaches not less than the time threshold tth1 in step S104, the determination unit 52 transmits switching instruction information to the second defrosting unit 55.

When the second defrosting unit 55 receives the switching instruction information from the determination unit 52, the second defrosting unit 55 opens the opening-and-closing valve 7 (step S105). After the determination unit 52 transmits the switching instruction information to the second defrosting unit 55, the determination unit 52 determines whether or not the temperature Tn2 of refrigerant received from the refrigerant temperature sensor 12 has reached not less than the temperature threshold Tb (step S106). When the temperature Tn2 of refrigerant reaches not less than the temperature threshold Tb, the determination unit 52 determines that defrosting of the heat source side heat exchanger 15 has been completed and transmits defrosting completion information to the refrigeration cycle control unit 51.

When the refrigeration cycle control unit 51 receives the defrosting completion information from the determination unit 52, the refrigeration cycle control unit 51 controls the flow switching device 5 to switch between the flow passages (step S107). Thus, the refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the load side units 20a and 20b. The operation mode of the refrigeration cycle apparatus 1 returns from the defrosting operation to the heating operation.

Thus, the first heat source side heat exchanger 3 is intensively defrosted from the time when the refrigeration cycle apparatus 1 starts defrosting until the time when the time t1 reaches the time threshold tth1. Then, the refrigeration cycle apparatus 1 starts to defrost the second heat source side heat exchanger 4 before defrosting of the first heat source side heat exchanger 3 is completed, and the flow of refrigerant to the first heat source side heat exchanger 3 is continued. Subsequently, the determination unit 52 determines, in accordance with a temperature Tn2 of refrigerant downstream of the second heat source side heat exchanger 4, whether or not defrosting of the second heat source side heat exchanger 4 has been completed. When it is determined, in accordance with the temperature of refrigerant downstream of the second heat source side heat exchanger 4, that defrosting of the second heat source side heat exchanger has been completed, defrosting of the first heat source side heat exchanger 3 has been also completed.

Incidentally, in the example configuration illustrated in FIG. 1, although the refrigerant temperature sensor 12 is provided in the second liquid pipe 44b, the refrigerant temperature sensor 12 may be provided in the liquid pipe 47 near the confluence of the first liquid pipe 44a and the second liquid pipe 44b. In this case, in step S104 illustrated in FIG. 5, the determination unit 52 determines whether or not the temperature Tn2 of refrigerant is not less than a predetermined temperature threshold Ta. As a result of a determination made in step S104, when the temperature Tn2 of refrigerant is not less than the temperature threshold Ta, the determination unit 52 only has to transmit the switching instruction information to the second defrosting unit 55. The relationship between the temperature thresholds Ta and Tb is, for example, Ta>Tb. Even when the refrigeration cycle apparatus 1 proceeds to the operation of step S105 owing to the relationship of Ta>Tb before defrosting of the first heat source side heat exchanger 3 is completely finished, the refrigerant also flows through the first heat source side heat exchanger 3, and thus the defrosting is performed. Furthermore, when the refrigerant temperature sensor 12 is provided in the liquid pipe 47, the timer 53 does not have to be provided in the controller 30.

The refrigeration cycle apparatus 1 in Embodiment 1 includes the compressor 2, the expansion valve 22a, the load side heat exchanger 21a, the flow switching device 5, the heat source side heat exchanger 15, the opening-and-closing valve 7, and the controller 30. The heat source side heat exchanger 15 includes the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 connected in parallel between the flow switching device 5 and the expansion valve 22a. The opening-and-closing valve 7 is provided on downstream of the second heat source side heat exchanger 4 through which refrigerant flows during the defrosting operation. When the defrosting operation is performed, the controller 30 controls the flow switching device 5 so that the refrigerant discharged from the compressor 2 flows into the heat source side heat exchanger 15. The controller 30 includes the first defrosting unit 54, the determination unit 52, and the second defrosting unit 55. When the defrosting operation is started, the first defrosting unit 54 switches the opening-and-closing valve 7 from an open state to a closed state. The determination unit 52 determines a point in time when defrosting targets to be defrosted are switched. The second defrosting unit switches the opening-and-closing valve 7 from the closed state to the open state in accordance with the point in time determined by the determination unit 52.

In Embodiment 1, the first defrosting unit 54 closes the opening-and-closing valve 7 when defrosting is started, and thus the refrigerant discharged from the compressor 2 flows intensively to the first heat source side heat exchanger 3 of two heat source side heat exchangers. Subsequently, the second defrosting unit 55 opens the opening-and-closing valve 7. Thus, the refrigerant flows to the second heat source side heat exchanger 4 and also flows to the first heat source side heat exchanger 3. When the refrigerant flows to the two heat source side heat exchangers, most of the heat of the refrigerant is consumed in the second heat source side heat exchanger 4, and also frost remaining in the first heat source side heat exchanger 3 melts. Thus, the heat of the refrigerant is kept from being uselessly consumed in comparison with a case where two heat source side heat exchangers connected in series are simultaneously defrosted. Consequently, the two heat source side heat exchangers can be efficiently defrosted.

(Modification 1)

Modification 1 is the case where the refrigerant temperature sensor 12 is not provided in the refrigeration cycle apparatus 1 illustrated in FIG. 1. In Modification 1, components that are the same as components described with reference to FIGS. 1 to 5 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of a refrigeration cycle apparatus in Modification 1 will be described. FIG. 6 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus in Modification 1. FIG. 7 is a functional block diagram illustrating an example configuration of the controller in Modification 1.

In a heat source side unit 10a in a refrigeration cycle apparatus 1a, the refrigerant temperature sensor 12 illustrated in FIG. 1 is not provided. After the determination unit 52 transmits the switching instruction information to the second defrosting unit 55, the determination unit 52 determines whether or not the time t1 measured by the timer 53 is not less than a predetermined time threshold tth2. The relationship between the time thresholds tth1 and tth2 is tth1<tth2. When the time t1 reaches not less than the time threshold tth2, the determination unit 52 transmits the defrosting completion information to the refrigeration cycle control unit 51.

The operation of the refrigeration cycle apparatus 1a in Modification 1 will be described with reference to FIG. 5. Here, an operation different from the operations illustrated in FIG. 5 will be described, and a detailed description of operations similar to the operations described with reference to FIG. 5 is omitted.

In step S106, the determination unit 52 determines whether or not the time t1 measured by the timer 53 has reached not less than the time threshold tth2. As a result of a determination made in step S106, when the time t1 reaches not less than the time threshold tth2, the determination unit 52 transmits the defrosting completion information to the refrigeration cycle control unit 51.

In Modification 1, even when the refrigerant temperature sensor 12 is not provided, effects of Embodiment 1 can be obtained.

(Modification 2)

Modification 2 is the case where a flow control valve and a refrigerant temperature sensor are provided in the first liquid pipe 44a in the refrigeration cycle apparatus 1 illustrated in FIG. 1. In Modification 2, components that are the same as components described with reference to FIGS. 1 to 7 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of a refrigeration cycle apparatus in Modification 2 will be described. FIG. 8 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus in Modification 2. FIG. 9 is a functional block diagram illustrating an example configuration of the controller in Modification 2. As illustrated in FIG. 8, in the first liquid pipe 44a in a heat source side unit 10b in a refrigeration cycle apparatus 1b, a refrigerant temperature sensor 12a and a flow control valve 9 are provided. The refrigerant temperature sensor 12a detects a temperature Tn1 of refrigerant that flows through the first liquid pipe 44a. The flow control valve 9 can be switched, of a closed state and an open state, from one state to the other state.

Furthermore, the flow control valve 9 can adjust a flow rate of refrigerant that circulates by changing its opening degree. As illustrated in FIG. 9, the controller 30 in Modification 2 does not include the timer 53 illustrated in FIG. 2. Regarding the temperature Tn1 of refrigerant, the controller 30 stores, in advance, the temperature threshold Ta as a criterion value for determining a point in time when defrosting targets to be defrosted are switched. Values of Ta and Tb may be the same or may be different.

Next, the operation of the refrigeration cycle apparatus 1b in Modification 2 will be described. FIG. 10 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus illustrated in FIG. 8. Assume that the refrigeration cycle apparatus 1b is performing the heating operation before starting the operation procedure illustrated in FIG. 10 and the flow control valve 9 and the opening-and-closing valve 7 are in an open state. Operations of steps S201 and S202 illustrated in FIG. 10 are similar to the operations of steps S101 and S102 described with reference to FIG. 5, and thus a detailed description thereof is omitted.

After a determination is made in step S201, when the determination unit 52 receives defrosting start information from the refrigeration cycle control unit 51, the determination unit 52 transfers the defrosting start information to the first defrosting unit 54 and also monitors the temperature Tn1 of refrigerant detected by the refrigerant temperature sensor 12a. When the first defrosting unit 54 receives the defrosting start information from the determination unit 52, the first defrosting unit 54 closes the opening-and-closing valve 7 (step S203). The determination unit 52 determines whether or not the temperature Tn1 of refrigerant has reached not less than the temperature threshold Ta (step S204). When the temperature Tn1 of refrigerant reaches not less than the temperature threshold Ta in step S204, the determination unit 52 transmits switching instruction information to the second defrosting unit 55.

When the second defrosting unit 55 receives the switching instruction information from the determination unit 52, the second defrosting unit 55 opens the opening-and-closing valve 7 (step S205) and closes the flow control valve 9 (step S206). After the determination unit 52 transmits the switching instruction information to the second defrosting unit 55, the determination unit 52 determines whether or not the temperature Tn2 of refrigerant detected by a refrigerant temperature sensor 12b has reached not less than the temperature threshold Tb (step S207). When the temperature Tn2 of refrigerant reaches not less than the temperature threshold Tb, the determination unit 52 determines that defrosting of the heat source side heat exchanger 15 has been completed and transmits defrosting completion information to the second defrosting unit 55 and the refrigeration cycle control unit 51.

When the second defrosting unit 55 receives the defrosting completion information from the determination unit 52, the second defrosting unit 55 opens the flow control valve 9 (step S208). When the refrigeration cycle control unit 51 receives the defrosting completion information from the determination unit 52, the refrigeration cycle control unit 51 controls the flow switching device 5 to switch between the flow passages (step S209). Thus, the refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the load side units 20a and 20b. The operation mode of the refrigeration cycle apparatus 1 returns from the defrosting operation to the heating operation.

Incidentally, in step S206 illustrated in FIG. 10, although the second defrosting unit 55 closes the flow control valve 9, the second defrosting unit 55 does not completely close the flow control valve 9 and may reduce the opening degree of the flow control valve 9 to cause a little refrigerant to circulate. In this case, in step S208, the second defrosting unit 55 opens the flow control valve 9 fully.

In Modification 2, valves that shut off flows of refrigerant are provided in the respective liquid pipes of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 that are connected in parallel. In the defrosting operation, the refrigeration cycle apparatus 1b in Modification 2 performs opening and closing control of each valve to first intensively defrost the first heat source side heat exchanger 3 and then to intensively defrost the other second heat source side heat exchanger 4, and thus defrosting can be performed reliably and efficiently.

Furthermore, the determination unit 52 determines, by using the temperature Tn1 of refrigerant, a point in time when an object to be mainly defrosted is switched from the first heat source side heat exchanger 3 to the second heat source side heat exchanger 4. For this reason, the determination unit 52 can determine whether or not frost has remained in the first heat source side heat exchanger 3 more accurately than by using the time t1 measured by the timer 53. Furthermore, in Modification 2, the timer 53 does not have to be provided in the controller 30.

(Modification 3)

Modification 3 is the case where three or more heat source side heat exchangers are connected in parallel in the refrigeration cycle apparatus 1 illustrated in FIG. 1. In Modification 3, components that are the same as components described with reference to FIGS. 1 to 10 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of a refrigeration cycle apparatus in Modification 2 will be described. FIG. 11 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus in Modification 3. As illustrated in FIG. 11, in a heat source side unit 10c in a refrigeration cycle apparatus 1c, a third heat source side heat exchanger 8 connected in parallel with the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 is provided. The third heat source side heat exchanger 8 is connected to the gas pipe 41 via a third gas pipe 43c and is connected to the liquid pipe 47 via a third liquid pipe 44c.

In the third liquid pipe 44c, a refrigerant temperature sensor 12c and a second flow control valve 9b are provided. The refrigerant temperature sensor 12c detects a temperature Tn3 of refrigerant that flows through the third liquid pipe 44c. The determination unit 52 compares the temperature Tn3 of refrigerant with a predetermined temperature threshold Td and switches between defrosting targets to be defrosted when the temperature Tn3 of refrigerant reaches not less than the temperature threshold Td. Incidentally, configurations of a first flow control valve 9a and the second flow control valve 9b are similar to the configuration of the flow control valve 9, a configuration of the refrigerant temperature sensor 12c is similar to the configuration of the refrigerant temperature sensor 12, and thus a detailed description of these is omitted.

The operation of the refrigeration cycle apparatus 1c in Modification 2 will be described with reference to FIG. 10. Here, an operation different from the operations illustrated in FIG. 10 will be described, and a detailed description of operations similar to the operations described with reference to FIG. 10 is omitted. As a default state, the opening-and-closing valve 7, the first flow control valve 9a, and the second flow control valve 9b are in an open state.

In step S203, when the first defrosting unit 54 receives the defrosting start information from the determination unit 52, the first defrosting unit 54 maintains the first flow control valve 9a in the open state and closes the opening-and-closing valve 7 and the second flow control valve 9b. In step S206, the second defrosting unit 55 closes the first flow control valve 9a. In step S207, when the temperature Tn2 of refrigerant reaches not less than the temperature threshold Tb, the determination unit 52 transmits switching instruction information to the second defrosting unit 55. When the second defrosting unit 55 receives the switching instruction information from the determination unit 52 after step S206, the second defrosting unit 55 closes the opening-and-closing valve 7 and opens the second flow control valve 9b.

After the determination unit 52 transmits the switching instruction information to the second defrosting unit 55 in accordance with a result of a determination made in step S207, the determination unit 52 determines whether or not the temperature Tn3 of refrigerant detected by the refrigerant temperature sensor 12c has reached not less than the temperature threshold Td. When the temperature Tn3 of refrigerant reaches not less than the temperature threshold Td, the determination unit 52 determines that defrosting of the heat source side heat exchanger 15 has been completed and transmits defrosting completion information to the second defrosting unit 55 and the refrigeration cycle control unit 51. Subsequently, the controller 30 performs the operations of steps S208 and S209.

Although FIG. 11 illustrates the case where three heat source side heat exchangers are connected in parallel, the number of heat source side heat exchangers connected in parallel may be four or more. In this case, a flow control device and a refrigerant temperature sensor are provided on a liquid pipe of each heat source side heat exchanger. Furthermore, in the refrigeration cycle apparatus 1c illustrated in FIG. 11, the determination unit 52 may determine, in accordance with the time t1 measured by the timer 53 illustrated in FIG. 2, a point in time when defrosting targets to be defrosted are switched. In this case, the refrigerant temperature sensors 12a to 12c do not have to be provided.

In Modification 3, even when the number of heat source side heat exchangers connected in parallel is three or more, defrosting can be efficiently performed.

Embodiment 2

A refrigeration cycle apparatus in Embodiment 2 is a refrigeration cycle apparatus in which a header is provided for a heat source side heat exchanger, and the header splits refrigerant that circulates into streams and merges streams of the refrigerant. In Embodiment 2, components that are the same as components described in Embodiment 1 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of the refrigeration cycle apparatus in Embodiment 2 will be described. FIG. 12 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus according to Embodiment 2. A refrigeration cycle apparatus 1d includes a heat source side unit 10d. In the heat source side unit 10d, a first gas header 61 is provided on a first gas pipe 43a side of the first heat source side heat exchanger 3, and a first liquid header 62 is provided on a first liquid pipe 44a side of the first heat source side heat exchanger 3. Furthermore, in the heat source side unit 10d, a second gas header 63 is provided on a second gas pipe 43b side of the second heat source side heat exchanger 4, and a second liquid header 64 is provided on a second liquid pipe 44b side of the second heat source side heat exchanger 4.

FIG. 13 is a side view illustrating an example configuration of the first heat source side heat exchanger illustrated in FIG. 12. FIG. 14 is a side view illustrating an example configuration of the second heat source side heat exchanger illustrated in FIG. 12. For convenience of explanation, FIGS. 13 and 14 illustrate the X axis and the Z axis to define directions. A direction opposite to a Z-axis arrow illustrated in FIGS. 13 and 14 is a gravity direction. Solid line arrows illustrated in FIGS. 13 and 14 represent directions in which refrigerant flows when the refrigeration cycle apparatus 1 performs the cooling operation and the defrosting operation. Dashed line arrows illustrated in FIGS. 13 and 14 represent directions in which refrigerant flows when the refrigeration cycle apparatus 1 performs the heating operation.

As illustrated in FIG. 13, the first heat source side heat exchanger 3 includes a plurality of heat-transfer tubes 45a and a plurality of heat-transfer fins 46a. The first gas pipe 43a is connected to the first gas header 61. A position at which the first gas pipe 43a is connected to the first gas header 61 is a middle portion of the height that is the length of the first gas header 61 in a direction (Z-axis arrow direction) perpendicular to the ground. The middle portion is not limited to the exact middle position of the height of the first gas header 61 and includes a certain range of heights based on the middle position. The first liquid pipe 44a is connected to a lower portion of the first liquid header 62. When the refrigeration cycle apparatus 1 performs the cooling operation and the defrosting operation, the first gas header 61 splits refrigerant flowing in from the first gas pipe 43a into streams flowing through the plurality of heat-transfer tubes 45a. When the refrigeration cycle apparatus 1 performs the heating operation, the first gas header 61 merges streams of refrigerant flowing in from the plurality of heat-transfer tubes 45a and causes the refrigerant to flow to the first gas pipe 43a.

As illustrated in FIG. 14, the second heat source side heat exchanger 4 includes a plurality of heat-transfer tubes 45b and a plurality of heat-transfer fins 46b. The second gas pipe 43b is connected to the second gas header 63. A position at which the second gas pipe 43b is connected to the second gas header 63 is a middle portion of the height that is the length of the second gas header 63 in a direction (Z-axis arrow direction) perpendicular to the ground. The middle portion is not limited to the exact middle position of the height of the second gas header 63 and includes a certain range of heights based on the middle position. The second liquid pipe 44b is connected to a lower portion of the second liquid header 64. When the refrigeration cycle apparatus 1 performs the cooling operation and the defrosting operation, the second gas header 63 splits refrigerant flowing in from the second gas pipe 43b into streams flowing through the plurality of heat-transfer tubes 45b. When the refrigeration cycle apparatus 1 performs the heating operation, the second gas header 63 merges streams of refrigerant flowing in from the plurality of heat-transfer tubes 45b and causes the refrigerant to flow to the second gas pipe 43b.

In Embodiment 2, the height of the first heat source side heat exchanger 3 is equal to the height of the second heat source side heat exchanger 4, and the number of the heat-transfer tubes 45a is equal to the number of the heat-transfer tubes 45b. Although FIGS. 13 and 14 illustrate the case where the number of the heat-transfer tubes 45a and the number of the heat-transfer tubes 45b are 13, the numbers of the heat-transfer tubes 45a and the heat-transfer tubes 45b are not limited to 13.

The operation of the refrigeration cycle apparatus 1d in Embodiment 2 is similar to the operation procedure described with reference to FIG. 5, and thus a detailed description thereof is omitted.

To explain functions and effects achieved by the refrigeration cycle apparatus 1d in Embodiment 2 in an easy-to-understand fashion, a configuration of a refrigeration cycle apparatus in a comparative example will be described. FIG. 15 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus in the comparative example. Components that are the same as components described with reference to FIGS. 1 and 12 are denoted by the same reference signs, and a detailed description thereof is omitted.

As illustrated in FIG. 15, a refrigeration cycle apparatus 100 in the comparative example includes a heat source side unit 110, the load side units 20a and 20b, and a controller 130. On the basis of a direction in which refrigerant flows during the defrosting operation, a refrigerant temperature sensor 121 is provided in the liquid pipe 47 downstream from a position at which the first liquid pipe 44a and the second liquid pipe 44b are joined. The refrigerant temperature sensor 121 detects a temperature Tr of refrigerant that flows through the liquid pipe 47 and transmits information on the temperature Tr of refrigerant to the controller 130. A hardware configuration of the controller 130 is similar to the configuration described with reference to FIGS. 3 and 4, and thus a detailed description thereof is omitted.

In comparison with the configuration illustrated in FIG. 12, the opening-and-closing valve 7 illustrated in FIG. 1 is not provided in the second liquid pipe 44b in the heat source side unit 110 illustrated in FIG. 15. When the refrigeration cycle apparatus 100 performs the defrosting operation, the controller 130 compares the temperature Tr of refrigerant with a predetermined temperature threshold Tc. Subsequently, when the temperature Tr of refrigerant reaches not less than the temperature threshold Tc, the controller 130 determines that defrosting has been completed. The temperature threshold Tc is, for example, 10 degrees C. The relationship between the temperature thresholds Tb and Tc is Tc>Tb. Furthermore, when the temperature threshold Tc is compared with the temperature threshold Ta described in Modification 2, the relationship of Ta<Tc is established.

Next, the operation of the refrigeration cycle apparatus 100 in the comparative example illustrated in FIG. 15 will be described with reference to FIG. 16. FIG. 16 is a flowchart illustrating an example of an operation procedure performed by the refrigeration cycle apparatus in the comparative example illustrated in FIG. 15. Assume that the refrigeration cycle apparatus 100 is performing the heating operation before starting the operation procedure illustrated in FIG. 16.

The controller 130 determines whether or not the temperature Te of refrigerant has reached not more than the temperature threshold T0 (step S1001). When the temperature Te of refrigerant reaches not more than the temperature threshold T0 in step S1001, the controller 130 determines that frost has adhered to the heat source side heat exchanger 15 and controls the flow switching device 5 to switch between the flow passages (step S1002). Thus, the refrigerant discharged from the compressor 2 flows through the flow switching device 5 and flows into the heat source side heat exchanger 15.

Subsequently, the controller 130 determines whether or not the temperature Tr of refrigerant is not less than the temperature threshold Tc (step S1003). When the temperature Tr of refrigerant reaches not less than the temperature threshold Tc in step S1003, the controller 130 determines that defrosting of the heat source side heat exchanger 15 has been completed and controls the flow switching device 5 to switch between the flow passages (step S1004). The operation mode of the refrigeration cycle apparatus 100 returns from the defrosting operation to the heating operation.

While the refrigeration cycle apparatus 100 is performing the defrosting operation, in the first heat source side heat exchanger 3 illustrated in FIG. 13, gaseous refrigerant flows into the middle portion of the first gas header 61 from the first gas pipe 43a. The gaseous refrigerant having flowed into the first gas header 61 is split into streams flowing through the plurality of heat-transfer tubes 45a, and the refrigerant is likely to accumulate in a lower heat-transfer tube 45a in the first heat source side heat exchanger 3 due to pressure loss. As in the first heat source side heat exchanger 3, in the second heat source side heat exchanger 4 illustrated in FIG. 14, refrigerant is likely to accumulate in a lower heat-transfer tube 45b in the second heat source side heat exchanger 4 in the defrosting operation.

FIG. 17 includes graphs illustrating an example of the relationship between a refrigerant flow rate and a position of a heat source side heat exchanger during the defrosting operation. In FIG. 17, the horizontal axis represents refrigerant flow rate, and the vertical axis represents height Hu of a heat-transfer tube 45a in a vertical direction (Z-axis arrow direction) of the first heat source side heat exchanger 3 illustrated in FIG. 13. In the vertical axis in FIG. 17, among the plurality of heat-transfer tubes 45a in the first heat source side heat exchanger 3, the height of a lowermost heat-transfer tube 45a is denoted by Hu1, the height of an uppermost heat-transfer tube 45a is denoted by Hun. In FIG. 17, a solid line graph represents the case of the refrigeration cycle apparatus 1d in Embodiment 2, and a dashed line graph represents the case of the refrigeration cycle apparatus 100 in the comparative example illustrated in FIG. 15. Furthermore, the second heat source side heat exchanger 4 also has a tendency similar to that of the graphs illustrated in FIG. 17, and thus a description of the case of the second heat source side heat exchanger 4 is omitted here.

In the defrosting operation performed by the refrigeration cycle apparatus 100 in the comparative example, when refrigerant is split into streams flowing through the first heat source side heat exchanger and the second heat source side heat exchanger, a refrigerant flow rate in a lower section in the heat source side heat exchanger 15 is smaller than that in an upper section as represented by the dashed line graph in FIG. 17. This is because, in the case where refrigerant is split into streams flowing through a plurality of heat-transfer tubes from a middle portion of a header as described with reference to FIGS. 13 and 14, the flow of refrigerant deteriorates due to pressure loss and the refrigerant is likely to accumulate in the lower section.

Because of this, in the refrigeration cycle apparatus 100 in the comparative example, in consideration of a flow rate of refrigerant that flows to a lower heat-transfer tube in the heat source side heat exchanger 15, it takes a long time for defrosting of the heat source side heat exchanger 15 to be completed, and the temperature threshold Tc is set to a high value. As a result, as represented by the dashed line graph in FIG. 17, the refrigerant uselessly flows in the upper section until defrosting of the lower heat-transfer tube in the heat source side heat exchanger 15 is completed.

On the other hand, in the refrigeration cycle apparatus 1d in Embodiment 2, as represented by the solid line graph in FIG. 17, refrigerant flow rates are less affected by differences in the heights of the heat-transfer tubes 45a in the first heat source side heat exchanger 3 than those in the comparative example, and the plurality of heat-transfer tubes 45a allow the refrigerant to uniformly flow therethrough. Thus, the temperature threshold Tb can be set to a temperature lower than the temperature threshold Tc, and defrosting can be performed more efficiently than in the comparative example.

The refrigeration cycle apparatus 1d in Embodiment 2 includes the first gas header 61 and the second gas header 63. In the defrosting operation, the first gas header 61 splits refrigerant flowing into the first heat source side heat exchanger 3 into streams flowing through the plurality of heat-transfer tubes 45a, and the second gas header 63 splits refrigerant flowing into the second heat source side heat exchanger 4 into streams flowing through the plurality of heat-transfer tubes 45b. The first gas pipe 43a is connected to the middle portion in the gravity direction of the first gas header 61, and the second gas pipe 43b is connected to the middle portion in the gravity direction of the second gas header 63.

In Embodiment 2, in the defrosting operation, as described in Embodiment 1, when the opening degree of the opening-and-closing valve 7 is adjusted, flow rates of respective refrigerant streams that flow to the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4 are increased. In Embodiment 2, accumulation of refrigerant in a lower section in the heat source side heat exchanger caused by differences in the heights of the heat-transfer tubes is inhibited, and a flow rate of refrigerant in the lower section increases. As a result, frost having adhered to the lower section in the heat source side heat exchanger can be removed reliably and efficiently. The temperature thresholds Ta and Tb can be set to a value smaller than the temperature threshold Tc in the comparative example, and thus a defrosting time period is reduced in comparison with that in the comparative example, thereby enabling efficient defrosting.

Embodiment 3

A refrigeration cycle apparatus in Embodiment 3 is a refrigeration cycle apparatus in which the number of heat-transfer tubes in the first heat source side heat exchanger is different from the number of heat-transfer tubes in the second heat source side heat exchanger. In Embodiment 3, components that are the same as components described in Embodiments 1 and 2 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of the refrigeration cycle apparatus in Embodiment 3 will be described. FIG. 18 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus according to Embodiment 3. A refrigeration cycle apparatus 1e includes a heat source side unit 10e. The first heat source side heat exchanger 3 provided in the heat source side unit 10e includes a first division heat exchanger 3-1 and a second division heat exchanger 3-2 that are connected in parallel.

The first gas pipe 43a is split into gas branch pipes 43a-1 and 43-2. The gas branch pipe 43a-1 is connected to the first division heat exchanger 3-1, and the gas branch pipe 43a-2 is connected to the second division heat exchanger 3-2. The first liquid pipe 44a is split into liquid branch pipes 44a-1 and 44a-2. The liquid branch pipe 44a-1 is connected to the first division heat exchanger 3-1, and the liquid branch pipe 44a-2 is connected to the second division heat exchanger 3-2.

In the first division heat exchanger 3-1, the first gas header 61 is provided on a gas branch pipe 43a-1 side, and the first liquid header 62 is provided on a liquid branch pipe 44a-1 side. In the second division heat exchanger 3-2, a first gas header 65 is provided on a gas branch pipe 43a-2 side, and a first liquid header 66 is provided on a liquid branch pipe 44a-2 side. A configuration of the first gas header 65 is similar to that of the first gas header 61, a configuration of the first liquid header 66 is similar to that of the first liquid header 62, and thus a detailed description of these is omitted.

FIG. 19 is an external perspective view illustrating an example configuration of the heat source side unit illustrated in FIG. 18. FIG. 20 is an external perspective view of the heat source side unit illustrated in FIG. 18 as seen from a direction different from that in FIG. 19. The first division heat exchanger 3-1 and the second division heat exchanger 3-2 have the same height that is the length in a direction (Z-axis arrow direction) perpendicular to the ground, and the height is denoted by L1. When the height of the second heat source side heat exchanger 4 is denoted by L2, the relationship between the heights L1 and L2 is L2<L1. In example configurations illustrated in FIGS. 19 and 20, for example, the relationship of L2=L1×(⅔) is established.

FIG. 21 is a schematic view illustrating the layout of the heat source side heat exchangers in the heat source side unit illustrated in FIG. 20 as seen from above. The first division heat exchanger 3-1 and the second division heat exchanger 3-2 as seen from above are L-shaped as illustrated in FIG. 21. The second heat source side heat exchanger 4 as seen from above is linear-shaped as illustrated in FIG. 21. In an example configuration illustrated in FIG. 21, although the first division heat exchanger 3-1 is L-shaped, if the first division heat exchanger 3-1 is straightened into a linear shape, the linear length of the first division heat exchanger 3-1 is equal to the linear length of the second heat source side heat exchanger 4.

FIG. 22 is a side view illustrating an example configuration of the first division heat exchanger illustrated in FIG. 19. The second division heat exchanger 3-2 has the same configuration as the first division heat exchanger 3-1, and thus the second division heat exchanger 3-2 is not illustrated in FIG. 22. Furthermore, FIG. 22 illustrates the first division heat exchanger 3-1 obtained by straightening the L-shaped first division heat exchanger 3-1 illustrated in FIG. 21 into a linear shape. FIG. 23 is a side view illustrating an example configuration of the second heat source side heat exchanger illustrated in FIG. 20. For convenience of explanation, FIGS. 22 and 23 illustrate the X axis and the Z axis to define directions. However, an X-axis arrow does not have to correspond to X-axis arrows illustrated in FIGS. 19 and 20.

The number of heat-transfer tubes 45a in the first division heat exchanger 3-1 illustrated in FIG. 22 is 13. The number of heat-transfer tubes 45b in the second heat source side heat exchanger 4 illustrated in FIG. 23 is 9. The number of heat-transfer tubes 45a in the first division heat exchanger 3-1 is larger than the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4. A ratio of the number of heat-transfer tubes 45a in the first division heat exchanger 3-1 to the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4 is a value close to a ratio of the height L1 of the first heat source side heat exchanger 3 to the height L2 of the second heat source side heat exchanger 4 (L1:L2)=3:2.

In Embodiment 3, assuming that the length of the heat-transfer tubes 45a illustrated in FIG. 22 is equal to the length of the heat-transfer tubes 45b illustrated in FIG. 23, the number of heat-transfer tubes to be defrosted in the first heat source side heat exchanger 3 is compared with that in the second heat source side heat exchanger 4. From the ratio of L1/L2, the number of heat-transfer tubes 45a in the first division heat exchanger 3-1 is (3/2) times the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4. The number of heat-transfer tubes 45a in the first division heat exchanger 3-1 is equal to the number of heat-transfer tubes 45a in the second division heat exchanger 3-2, and thus the number of heat-transfer tubes 45a in the first heat source side heat exchanger 3 is three times the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4. Incidentally, the numbers of heat-transfer tubes 45a in the first division heat exchanger 3-1 and the second division heat exchanger 3-2, and the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4 are not limited to the numbers illustrated in FIGS. 22 and 23.

The operation of the refrigeration cycle apparatus 1e in Embodiment 3 is similar to the operation procedure described with reference to FIG. 5, and thus a detailed description thereof is omitted.

Referring to FIG. 5, the opening-and-closing valve 7 is closed from the start of the defrosting operation based on the operation of step S102 until the time when the time t1 reaches the time threshold tth1, and thus the first heat source side heat exchanger 3 is intensively defrosted. Subsequently, the opening-and-closing valve 7 is opened, and defrosting of the second heat source side heat exchanger 4 is started, while the refrigerant also flows to the first heat source side heat exchanger 3. The amount of refrigerant that flows to the first heat source side heat exchanger 3 is greater than the amount of refrigerant that flows to the second heat source side heat exchanger 4. For this reason, even if the number of heat-transfer tubes 45a in the first heat source side heat exchanger 3 is larger than the number of heat-transfer tubes 45b in the second heat source side heat exchanger 4, the refrigeration cycle apparatus 1e can time the completion of defrosting of the first heat source side heat exchanger 3 to coincide with a point in time when defrosting of the second heat source side heat exchanger 4 is completed.

In the refrigeration cycle apparatus 1e in Embodiment 3, the number of heat-transfer tubes 45a in the first heat source side heat exchanger 3 is larger than the number of heat-transfer tubes in the second heat source side heat exchanger 4. In Embodiment 3, the amount of refrigerant that flows to the first heat source side heat exchanger 3 is greater than the amount of refrigerant that flows to the second heat source side heat exchanger 4, and thus the completion of defrosting of the first heat source side heat exchanger 3 can be timed to coincide with a point in time when defrosting of the second heat source side heat exchanger 4 is completed.

(Modification 4)

A refrigeration cycle apparatus in Modification 4 is a refrigeration cycle apparatus in which, in the refrigerant circuits 60a and 60b illustrated in FIG. 18, the flow control valve 9 is provided in the first liquid pipe 44a. In Modification 4, components that are the same as components described with reference to FIGS. 18 to 23 are denoted by the same reference signs, and a detailed description thereof is omitted.

A configuration of the refrigeration cycle apparatus in Modification 4 will be described. FIG. 24 is a refrigerant circuit diagram illustrating an example configuration of the refrigeration cycle apparatus in Modification 4. In a heat source side unit 10f in a refrigeration cycle apparatus 1f, the flow control valve 9 is provided in the first liquid pipe 44a.

Incidentally, the operation of the refrigeration cycle apparatus 1f is similar to the procedure illustrated in FIG. 10 except that a point in time when defrosting targets to be defrosted are switched is determined in accordance with the time t1 measured by the timer 53 in step S207 illustrated in FIG. 10, and thus a detailed description thereof is omitted. The refrigerant temperature sensor 12 may be provided in the liquid pipe 47 near the confluence of the first liquid pipe 44a and the second liquid pipe 44b in place of the second liquid pipe 44b.

In Modification 4, valves that shut off flows of refrigerant are provided in the respective liquid pipes of the first heat source side heat exchanger 3 and the second heat source side heat exchanger 4. In the defrosting operation, the refrigeration cycle apparatus 1f in Modification 4 performs opening and closing control of each valve to first defrost the first heat source side heat exchanger 3 and then to defrost the other second heat source side heat exchanger 4, and thus defrosting can be performed reliably and efficiently.

Although, in Embodiment 3, the description based on the refrigeration cycle apparatus 1d described in Embodiment 2 has been given, Embodiment 3 may be applied to the refrigeration cycle apparatus 1 described in Embodiment 1. Furthermore, in each of Embodiments 2 and 3, among Modifications 1 to 3, any Modifications may be combined.

Claims

1. A refrigeration cycle apparatus comprising:

a compressor configured to compress and discharge refrigerant;

an expansion valve configured to reduce pressure of the refrigerant to cause the refrigerant to expand;

a load side heat exchanger connected to the expansion valve;

a four-way valve connected to the compressor and the load side heat exchanger;

a heat source side heat exchanger including a first heat source side heat exchanger and a second heat source side heat exchanger connected in parallel between the four-way valve and the expansion valve;

a gas pipe configured to join a first gas pipe connected to the first heat source side heat exchanger and a second gas pipe connected to the second heat source side heat exchanger to allow the first gas pipe and the second gas pipe to communicate with the flow switching device;

a first gas header configured to split the refrigerant flowing into the first heat source side heat exchanger including a plurality of first heat-transfer tubes from the compressor via the four-way valve into streams flowing through the plurality of first heat-transfer tubes;

a second gas header configured to split the refrigerant flowing into the second heat source side heat exchanger including a plurality of second heat-transfer tubes from the compressor via the four-way valve into streams flowing through the plurality of second heat-transfer tubes;

an opening-and-closing valve provided on downstream of the second heat source side heat exchanger through which the refrigerant flows during a defrosting operation; and

a controller configured to, when the defrosting operation is performed, control the four-way valve so that the refrigerant discharged from the compressor flows into the heat source side heat exchanger,

wherein

a number of the plurality of first heat-transfer tubes is larger than a number of the plurality of second heat-transfer tubes,

the first gas pipe is connected to a middle portion in a gravity direction of the first gas header,

the second gas pipe is connected to a middle portion in the gravity direction of the second gas header, and

the controller is configured to

switch the opening-and-closing valve from an open state to a closed state when the defrosting operation is started,

determine a point in time when defrosting targets to be defrosted are switched, and

switch the opening-and-closing valve from the closed state to the open state in accordance with the point in time determined.

2-3. (canceled)

4. The refrigeration cycle apparatus of claim 1, further comprising

a temperature sensor provided on the downstream of the second heat source side heat exchanger and configured to detect a temperature of the refrigerant,

wherein the controller is configured to

determine, as the point in time, a time when a value detected by the temperature sensor reaches not less than a predetermined temperature threshold.

5. The refrigeration cycle apparatus of claim 1, further comprising

a flow control valve provided on downstream of the first heat source side heat exchanger through which the refrigerant flows during the defrosting operation,

wherein, when the defrosting operation is started, the controller is configured to maintain the flow control valve in an open state and switch the opening-and-closing valve from an open state to a closed state, and

wherein, in accordance with the point in time determined, the controller is configured to switch the flow control valve from the open state to a closed state and switch the opening-and-closing valve from the closed state to the open state.

6. The refrigeration cycle apparatus of claim 5, further comprising

a temperature sensor provided on the downstream of the first heat source side heat exchanger and configured to detect a temperature of the refrigerant,

wherein the controller is configured to

determine, as the point in time, a time when a value detected by the temperature sensor reaches not less than a predetermined temperature threshold.

7. The refrigeration cycle apparatus of claim 1,

wherein the controller further includes a timer configured to measure a time period, and

wherein the controller is configured to

determine, as the point in time, a time when a time period measured from start of the defrosting operation by the timer reaches not less than a predetermined time threshold.

8. The refrigeration cycle apparatus of claim 1, further comprising:

a third heat source side heat exchanger connected in parallel with the first heat source side heat exchanger and the second heat source side heat exchanger between the four-way valve and the expansion valve;

a first flow control valve provided on downstream of the first heat source side heat exchanger through which the refrigerant flows during the defrosting operation; and

a second flow control valve provided on downstream of the third heat source side heat exchanger through which the refrigerant flows during the defrosting operation,

wherein, when the defrosting operation is started, the controller is configured to

maintain the first flow control valve in an open state and switch the opening-and-closing valve and the second flow control valve from an open state to a closed state,

wherein, in accordance with the point in time determined, the controller is configured to

switch the first flow control valve from the open state to a closed state and switch the opening-and-closing valve from the closed state to the open state, and

wherein, after switching the opening-and-closing valve from the closed state to the open state, in accordance with the point in time determined, the controller is configured to

switch the opening-and-closing valve from the open state to the closed state and switch the second flow control valve from the closed state to the open state.