REFRIGERATION CYCLE APPARATUS

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to International Application No. PCT/JP2023/009412, filed Mar. 10, 2023, the entire contents of each of which being incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus.

BACKGROUND

Patent Literature 1 (JP-2013-210132-A) discloses an air conditioning apparatus including an outdoor heat exchanger, an economizer heat exchanger, an internal heat exchanger, and an indoor heat exchanger to perform heating and cooling operations by switching these operations. The air conditioning as disclosed in Patent Literature 1 suppresses the refrigerant to the economizer heat exchanger and the internal heat exchanger during heating, with the aim of improving operational efficiency.

SUMMARY

A refrigeration cycle apparatus of a first aspect performs the heating operation and the cooling operation. The refrigeration cycle apparatus includes a compressor, a radiator, an evaporator, and an internal heat exchanger.

The internal heat exchanger includes a first heat transfer tube and a second heat transfer tube. A refrigerant flowing from a main heat exchanger that functions as an evaporator to the compressor passes through the first heat transfer tube. The refrigerant flowing from a main heat exchanger that functions as a radiator to the evaporator passes through the second heat transfer tube. The internal heat exchanger causes heat exchange between the refrigerant passing through the first heat transfer tube and the refrigerant passing through the second heat transfer tube. In the internal heat exchanger, the refrigerant does not flow through the second heat transfer tube in the cooling operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a refrigeration cycle apparatus 1.

FIG. 2 is a block diagram of a control unit 100.

FIG. 3 is a diagram illustrating a flow of a refrigerant in a heating operation of the refrigeration cycle apparatus 1.

FIG. 4 is a diagram illustrating the flow of the refrigerant in a cooling operation of the refrigeration cycle apparatus 1.

FIG. 5 is a schematic configuration diagram of a refrigeration cycle apparatus 1a.

FIG. 6 is a diagram illustrating the flow of the refrigerant in the heating operation of the refrigeration cycle apparatus 1a.

FIG. 7 is a diagram illustrating the flow of the refrigerant in the cooling and heating operations of the refrigeration cycle apparatus 1a.

DESCRIPTION OF EMBODIMENTS

First Embodiment

(1) Overall Configuration

FIG. 1 is a schematic configuration diagram of a refrigeration cycle apparatus 1 according to a first embodiment.

The refrigeration cycle apparatus 1 includes a refrigerant circuit 90 and a control unit 100. The refrigerant circuit 90 mainly includes a compressor 10, a switching mechanism 20, a first decompression means or first decompressor 41, a second decompression means or second decompressor 42, a first valve 51, a second valve 52, a third valve 53, a fourth valve 54, a first heat exchanger 61, a second heat exchanger 62, an internal heat exchanger 63, an economizer heat exchanger 64, an accumulator 80, a liquid refrigerant flow path 71, an injection flow path 72, a first branch flow path 73, and a second branch flow path 74.

The refrigeration cycle apparatus 1 performs the heating operation and the cooling operation. In more detail, the refrigeration cycle apparatus 1 causes the refrigerant circuit 90 to perform a refrigeration cycle to heat or cool water circulating in a water circuit 200, performing the heating operation and the cooling operation for a target space by using this water.

(2) Detailed Configuration

(2-1) Refrigerant Circuit 90

In an implementation, the refrigerant circuit 90 is charged with a flammable refrigerant. The flammable refrigerant is a refrigerant having flammability. The flammable refrigerant is a refrigerant such as, for example, a hydrocarbon-based refrigerant, R1234yf, R1234ze, and R32. Here, the flammable refrigerant is a refrigerant classified as highly flammable (A3) under ISO 817, and is R290 (propane) in the present embodiment.

(2-1-1) Compressor 10

The compressor 10 compresses a low-pressure refrigerant to a high-pressure refrigerant in the refrigeration cycle. In more detail, the compressor 10 is a two-stage compressor that suctions the low-pressure refrigerant in the refrigeration cycle, compresses the refrigerant to intermediate pressure in the refrigeration cycle, and then further compresses the intermediate-pressure refrigerant to high pressure for discharge.

The compressor 10 includes a casing 10a, a first compression element 10b, a second compression element 10c, a drive motor 10d, a first suction part 10e, a second suction part 10f, and a discharge part 10g.

The casing 10a accommodates the first compression element 10b and the second compression element 10c. The first compression element 10b and the second compression element 10c are coupled to a single drive shaft. During the operation of the compressor 10, the drive motor 10d rotationally drives the first compression element 10b and the second compression element 10c via the drive shaft. In other words, the compressor 10 has a single-shaft two-stage compression structure. The number of rotations of the drive motor 10d is controlled by the control unit 100.

The first suction part 10e suctions the low-pressure refrigerant from the refrigerant circuit 90. The second suction part 10f suctions the intermediate-pressure refrigerant from the refrigerant circuit 90. The discharge part 10g discharges the high-pressure refrigerant to the refrigerant circuit 90. The second suction part 10f is one example of a suction part.

The second suction part 10f includes a check valve that allows inflow of the refrigerant from the outside to the inside of the casing 10a, and regulates outflow of the refrigerant from the inside to the outside of the casing 10a.

The first compression element 10b compresses the refrigerant suctioned by the first suction part 10e to the intermediate pressure and discharges the compressed refrigerant to the second compression element 10c. The second compression element 10c compresses both the intermediate-pressure refrigerant discharged by the first compression element 10b and the intermediate-pressure refrigerant suctioned by the second suction part 10f to high pressure and discharges the compressed refrigerant to the discharge part 10g.

In an implementation, the structure of the compressor 10 may include the single-shaft two-stage compression structure. In an implementation, the structure of the compressor 10 may include, for example, a compression element driven by another drive motor.

(2-1-2) Switching Mechanism 20

The switching mechanism 20 switches the direction in which the refrigerant flows in the refrigerant circuit 90 between two states. The switching mechanism 20 is a four-way switching valve. The switching mechanism 20 includes a first port P1, a second port P2, a third port P3, and a fourth port P4.

The switching mechanism 20 switches between a first state (state indicated by the broken lines in FIG. 1) and a second state (state indicated by the solid lines in FIG. 1). In the first state, the switching mechanism 20 allows communication between the first port P1 and the second port P2, and allows communication between the third port P3 and the fourth port P4. In the second state, the switching mechanism 20 allows communication between the first port P1 and the fourth port P4, and allows communication between the second port P2 and the third port P3. The state of the switching mechanism 20 is controlled by the control unit 100.

In an implementation, the switching mechanism 20 may include the four-way switching valve. In an implementation, the switching mechanism 22 may be configured by combining a plurality of electromagnetic valves and refrigerant flow paths.

(2-1-3) First Heat Exchanger 61 and Second Heat Exchanger 62

The first heat exchanger 61 causes mutual heat exchange between the refrigerant flowing through the refrigerant circuit 90 and the water circulating through the water circuit 200. The first heat exchanger 61 functions as a radiator for the refrigerant in the heating operation, and as an evaporator for the refrigerant in the cooling operation. The first heat exchanger 61 includes a refrigerant flow path 61a and a water flow path 61b. Note that FIG. 1 shows only a part of the water circuit 200.

The refrigerant flow path 61a is provided in the refrigerant circuit 90. The water flow path 61b is provided in the water circuit 200. The refrigerant flowing through the refrigerant flow path 61a exchanges heat with the water flowing through the water flow path 61b. The water that has exchanged heat with the refrigerant circulates through the water circuit 200 to heat or cool the air in the target space.

Hereinafter, for convenience of description, in the cooling operation, the end of the refrigerant flow path 61a into which the refrigerant flows is referred to as a first end 61aa, and the end of the refrigerant flow path 61a from which the refrigerant flows out is referred to as a second end 61ab.

In an implementation, the first heat exchanger 61 is a plate-type heat exchanger. The capacity of the refrigerant flow path 61a is, for example, about 0.4 liters.

The second heat exchanger 62 causes mutual heat exchange between the refrigerant flowing through the refrigerant circuit 90 and the air at the installation location of the second heat exchanger 62. The second heat exchanger 62 functions as an evaporator for the refrigerant in the heating operation, and as a radiator for the refrigerant in the cooling operation. The second heat exchanger 62 includes a refrigerant flow path.

The refrigerant flow path of the second heat exchanger 62 is provided in the refrigerant circuit 90. The refrigerant flowing through the refrigerant flow path of the second heat exchanger 62 exchanges heat with the air at the installation location of the second heat exchanger 62.

Hereinafter, for convenience of description, in the heating operation, the end of the refrigerant flow path of the second heat exchanger 62 into which the refrigerant flows is referred to as a first end 62aa, and the end of the refrigerant flow path 61a from which the refrigerant flows out is referred to as a second end 62ab.

In an implementation, the second heat exchanger 62 is a microchannel-type heat exchanger. The capacity of the refrigerant flow path of the second heat exchanger 62 is, for example, about 2.5 liters, which is larger than the capacity of the refrigerant flow path 61a of the first heat exchanger 61.

Hereinafter, for convenience of description, the first heat exchanger 61 and the second heat exchanger 62 may collectively be referred to as a main heat exchanger 60.

(2-1-4) Liquid Refrigerant Flow Path 71

The liquid refrigerant flow path 71 is a refrigerant flow path that connects the first end 61aa of the refrigerant flow path 61a of the first heat exchanger 61 to the first end 62aa of the refrigerant flow path of the second heat exchanger 62.

(2-1-5) First Decompressor 41

The first decompressor 41 decompresses the refrigerant passing through to low pressure. The first decompressor 41 is provided in the liquid refrigerant flow path 71. The opening degree of the first decompressor 41 is controlled by the control unit 100.

In an implementation, the first decompressor 41 is an electric expansion valve.

(2-1-6) Internal Heat Exchanger 63

The internal heat exchanger 63 is a precooling heat exchanger that cools the refrigerant flowing from the main heat exchanger 60 that functions as a radiator to the main heat exchanger 60 that functions as an evaporator. The internal heat exchanger 63 includes a first heat transfer tube 63a and a second heat transfer tube 63b. The internal heat exchanger 63 causes mutual heat exchange between the refrigerant passing through the first heat transfer tube 63a and the refrigerant passing through the second heat transfer tube 63b.

The refrigerant flowing from the main heat exchanger 60 that functions as an evaporator to the first suction part 10e of the compressor 10 passes through the first heat transfer tube 63a. One end of the first heat transfer tube 63a is connected to the third port P3 of the switching mechanism 20. The other end of the first heat transfer tube 63a is connected to the first suction part 10e of the compressor 10 via the accumulator 80.

The refrigerant flowing from the main heat exchanger 60 that functions as a radiator to the main heat exchanger 60 that functions as an evaporator passes through the second heat transfer tube 63b. Both ends of the second heat transfer tube 63b are connected to the liquid refrigerant flow path 71 between the first heat exchanger 61 and the first decompressor 41.

As will be described in detail later, the refrigerant flows through the first heat transfer tube 63a and the second heat transfer tube 63b of the internal heat exchanger 63 in the heating operation (in other words, flows through the internal heat exchanger 63), and does not flow through the second heat transfer tube 63b in the cooling operation.

(2-1-7) First Branch Flow Path 73 and Second Branch Flow Path 74

Each of the first branch flow path 73 and the second branch flow path 74 is a refrigerant flow path that branches from the liquid refrigerant flow path 71 between the first heat exchanger 61 and the first decompressor 41, and connects to the second heat transfer tube 63b. The first branch flow path 73 branches from the liquid refrigerant flow path 71 at a position closer to the first heat exchanger 61 than the second branch flow path 74 (in other words, at a position spaced apart from the first decompressor 41).

One end of the second heat transfer tube 63b is connected to the end of the first branch flow path 73 on the opposite side of the liquid refrigerant flow path 71. The other end of the second heat transfer tube 63b is connected to the end of the second branch flow path 74 on the opposite side of the liquid refrigerant flow path 71.

Hereinafter, for convenience of description, a portion at which the first branch flow path 73 branches from the liquid refrigerant flow path 71 may be referred to as a first branch portion 73a, and a portion at which the second branch flow path 74 branches from the liquid refrigerant flow path 71 may be referred to as a second branch portion 74a.

(2-1-8) Injection Flow Path 72

The injection flow path 72 is a refrigerant flow path that branches from the liquid refrigerant flow path 71 and connects to the first suction part 10e and the second suction part 10f of the compressor 10.

In the present embodiment, the injection flow path 72 includes a first part 72a, a second part 72b, a third part 72c, and a fourth part 74d.

The first part 72a is a flow path that branches from the liquid refrigerant flow path 71 and is shared with the first branch flow path 73 over a predetermined length.

The second part 72b is a flow path that allows the refrigerant flowing through the first part 72a to flow into a first heat transfer tube 64a of the economizer heat exchanger 64 (described later). The second part 72b is connected to the end of the first part 72a on the opposite side of the branch portion from the liquid refrigerant flow path 71. The first heat transfer tube 64a of the economizer heat exchanger 64 is provided in the middle of the second part 72b.

The third part 73c is a flow path that allows the refrigerant flowing through the first heat transfer tube 64a of the economizer heat exchanger 64 to flow into the first suction part 10e of the compressor 10. The third part 73c connects the end of the second part 72b on the opposite side of the first part 72a to the first suction part 10e of the compressor 10.

The fourth part 74c is a flow path that allows the refrigerant flowing through the first heat transfer tube 64a of the economizer heat exchanger 64 to flow into the second suction part 10f of the compressor 10. The fourth part 74c connects the end of the second part 72b on the opposite side of the first part 72a to the second suction part 10f of the compressor 10.

(2-1-9) Second Decompressor 42

The second decompressor 42 decompresses the refrigerant that passes through the injection flow path 72 to intermediate pressure. The second decompressor 42 is provided in the second part 72b of the injection flow path 72, between the connection part with the first part 72a and the economizer heat exchanger 64. The opening degree of the second decompressor 42 is controlled by the control unit 100.

In an implementation, the second decompressor 42 is an electric expansion valve.

(2-1-10) Economizer Heat Exchanger 64

The economizer heat exchanger 64 causes mutual heat exchange between the refrigerant that has passed through the injection flow path 72 and has been decompressed by the second decompressor 42, and the refrigerant flowing from the main heat exchanger 60 that functions as a radiator to the main heat exchanger 60 that functions as an evaporator. The economizer heat exchanger 64 includes the first heat transfer tube 64a and a second heat transfer tube 64b. The economizer heat exchanger 64 causes mutual heat exchange between the refrigerant passing through the first heat transfer tube 64a and the refrigerant passing through the second heat transfer tube 64b.

The refrigerant that flows through the injection flow path 72 passes through the first heat transfer tube 64a. The first heat transfer tube 64a is provided in the injection flow path 72. One end of the first heat transfer tube 64a is connected to the second decompressor 42 via the injection flow path 72. The other end of the first heat transfer tube 64a is connected to the first suction part 10e and the second suction part 10f of the compressor 10 via the injection flow path 72.

The refrigerant that flows through the first branch flow path 73 passes through the second heat transfer tube 64b. The second heat transfer tube 64b is provided in the first branch flow path 73. One end of the second heat transfer tube 64b is connected to the first valve 51 via the first branch flow path 73. The other end of the second heat transfer tube 64b is connected to the second heat transfer tube 63b of the internal heat exchanger 63 via the first branch flow path 73.

As will be described in detail later, the refrigerant passes through the first heat transfer tube 64a and the second heat transfer tube 64b of the economizer heat exchanger 64 in the heating operation (in other words, passes through the economizer heat exchanger 64), and does not flow through the economizer heat exchanger 64 in the cooling operation.

(2-1-11) First Valve 51

The first valve 51 regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the economizer heat exchanger 64 in the first part 72a of the injection flow path 72. The first valve 51 is an on-off valve that switches between the open state and the closed state. The switching between the open state and the closed state of the first valve 51 is controlled by the control unit 100.

The first valve 51 is brought into the open state in the heating operation, and is brought into the closed state in the cooling operation.

(2-1-12) Second Valve 52

The second valve 52 regulates the inflow of the refrigerant flowing through the injection flow path 72 to the first suction part 10e of the compressor 10 in the third part 72c of the injection flow path 72. The second valve 52 is an on-off valve that switches between the open state and the closed state. The switching between the open state and the closed state of the second valve 52 is controlled by the control unit 100.

The second valve 52 is brought into the closed state in the heating operation, and is brought into the open state in the cooling operation.

(2-1-13) Third Valve 53

The third valve 53 regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the second heat transfer tube 63b in the second branch flow path 74. The third valve 53 is a check valve that regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the second heat transfer tube 63b, and allows the flow of the refrigerant from the second heat transfer tube 63b to the liquid refrigerant flow path 71.

(2-1-14) Fourth Valve 54

The fourth valve 54 regulates the flow of the refrigerant from the first branch portion 73a to the second branch portion 74a in the liquid refrigerant flow path 71. The fourth valve 54 is provided between the first branch portion 73a and the second branch portion 74a in the liquid refrigerant flow path 71. The fourth valve 54 is a check valve that regulates the flow of the refrigerant from the first branch portion 73a to the second branch portion 74a, and allows the flow of the refrigerant from the second branch portion 74a to the first branch portion 73a.

The third valve 53 is brought into the open state in the heating operation, and is brought into the closed state in the cooling operation.

(2-1-15) Accumulator 80

The accumulator 80 separates the refrigerant flowing out of the first heat transfer tube 63a and flowing into the first suction part 10e of the compressor 10 into a gas refrigerant and a liquid refrigerant. The accumulator 80 is provided in a refrigerant flow path that connects the other end of the first heat transfer tube 63a to the first suction part 10e of the compressor 10.

(2-2) Control Unit 100

The control unit 100 controls each device of the refrigerant circuit 90 to cause the refrigerant circuit 90 to perform the refrigeration cycle. The control unit 100 is electrically connected to the compressor 10, the switching mechanism 20, the first decompressor 41, the second decompressor 42, the first valve 51, and the second valve 52 to allow transmission and reception of signals.

The control unit 100 is implemented by a computer. The control unit 100 includes a control arithmetic device and a storage device. A processor such as a CPU or a GPU can be used for the control arithmetic device. The control arithmetic device reads a program stored in the storage device and performs predetermined arithmetic processing according to the program. Furthermore, the control arithmetic device can write an arithmetic result in the storage device and read information stored in the storage device according to the program.

(3) Overall Operation

The control unit 100 controls each device in the heating operation and the cooling operation, as will be described next. FIG. 3 is a diagram illustrating the flow of the refrigerant in the heating operation of the refrigeration cycle apparatus 1. FIG. 4 is a diagram illustrating the flow of the refrigerant in the cooling operation of the refrigeration cycle apparatus 1. FIGS. 3 and 4 show the refrigerant flow path through which the refrigerant flows with broken lines, and show the direction in which the refrigerant flows with arrows.

(3-1) Heating Operation

When execution of the heating operation is instructed for the refrigeration cycle apparatus 1, the control unit 100 controls each part of the refrigerant circuit 90 as follows.

The control unit 100 causes the compressor 10 to start operations, and controls the number of rotations of the drive motor 10d. The switching mechanism 20 is controlled to be in the first state. The opening degree of the first decompressor 41 is controlled. For example, the control unit 100 controls the opening degree of the first decompressor 41 such that the degree of subcooling of the refrigerant flowing out of the first end 61aa of the first heat exchanger 61 approaches a predetermined target degree of subcooling. The opening degree of the second decompressor 42 is controlled. For example, the control unit 100 controls the opening degree of the second decompressor 42 such that the degree of superheating of the refrigerant flowing out of the second decompressor 42 approaches a predetermined target degree of superheating. The first valve 51 is controlled to be in the open state. The second valve 52 is controlled to be in the closed state.

When the compressor 10 starts operations, the low-pressure gas refrigerant in the refrigeration cycle is suctioned from the first suction part 10e, and the intermediate-pressure gas refrigerant in the refrigeration cycle is suctioned from the second suction part 10f. The first compression element 10b compresses the low-pressure refrigerant suctioned by the first suction part 10e to the intermediate pressure and discharges the compressed refrigerant to the second compression element 10c. The second compression element 10c compresses both the intermediate-pressure refrigerant discharged from the first compression element 10b and the intermediate-pressure refrigerant suctioned by the second suction part 10f to high pressure in the refrigeration cycle, and discharges the compressed refrigerant as a gas refrigerant to the discharge part 10g.

The high-pressure gas refrigerant that has flowed out of the discharge part 10g passes through the switching mechanism 22 in the order of the first port P1 and the second port P2, and then flows into the refrigerant flow path 61a of the first heat exchanger 61 from the second end 61ab. The refrigerant that flows into the first heat exchanger 61 exchange heat with the water flowing through the water flow path 61b and condenses, becomes a high-pressure liquid refrigerant, and flows out of the first end 61aa. In other words, the first heat exchanger 61 functions as a radiator.

The high-pressure refrigerant that has flowed out of the first heat exchanger 61 flows through the liquid refrigerant flow path 71. Since the first valve 51 is in the open state and the fourth valve 54 is provided downstream of the first branch portion 73a, the refrigerant flowing through the liquid refrigerant flow path 71 flows into the injection flow path 72 at the first branch portion 73a without passing through the fourth valve 54. The refrigerant that has flowed into the injection flow path 72, after passing through the first valve 51 in the first part 72a, branches into the second part 72b of the injection flow path 72 and the first branch flow path 73.

The refrigerant that has flowed into the second part 72b of the injection flow path 72 is decompressed to the intermediate pressure when passing through the second decompressor 42. The intermediate-pressure refrigerant flows into the first heat transfer tube 64a of the economizer heat exchanger 64, causes mutual heat exchange with the refrigerant passing through the second heat transfer tube 64b of the economizer heat exchanger 64, and then flows out of the first heat transfer tube 64a.

Since the second valve 52 is in the closed state, the refrigerant that has flowed out of the first heat transfer tube 64a does not flow into the third part 72c of the injection flow path 72, but flows into the fourth part 72d of the injection flow path 72. The refrigerant that has flowed into the fourth part 72d is again suctioned into the compressor 10 from the second suction part 10f.

The refrigerant that has flowed into the first branch flow path 73 flows into the second heat transfer tube 64b of the economizer heat exchanger 64, causes mutual heat exchange with the refrigerant passing through the first heat transfer tube 64a of the economizer heat exchanger 64, and then flows out of the second heat transfer tube 64b.

The refrigerant that has flowed out of the second heat transfer tube 64b passes through the first branch flow path 73 and flows into the second heat transfer tube 63b of the internal heat exchanger 63. The refrigerant that has flowed into the second heat transfer tube 63b causes mutual heat exchange with the refrigerant passing through the first heat transfer tube 63a of the internal heat exchanger 63, and then flows out to the second branch flow path 74. The refrigerant that has flowed out to the second branch flow path 74 passes through the third valve 53 and flows into the liquid refrigerant flow path 71.

The refrigerant that has flowed into the liquid refrigerant flow path 71 is decompressed to low pressure while passing through the first decompressor 41, becomes a refrigerant in the gas-liquid two-phase state, and flows into the second heat exchanger 62 from the first end 62aa. The refrigerant that has flowed into the second heat exchanger 62 evaporates by mutual heat exchange with the air at the installation location of the second heat exchanger 62, becomes a low-pressure gas refrigerant, and flows out of the second end 62ab. In other words, the second heat exchanger 62 functions as an evaporator.

The low-pressure refrigerant that has flowed out of the second heat exchanger 62 passes through the switching mechanism 22 in the order of the fourth port P4 and the third port P3, and then flows into the first heat transfer tube 63a of the internal heat exchanger 63. The refrigerant that has flowed into the first heat transfer tube 63a causes mutual heat exchange with the refrigerant passing through the second heat transfer tube 63b of the internal heat exchanger 63, and then flows out of the first heat transfer tube 63a. The refrigerant that has flowed out of the first heat transfer tube 63a passes through the accumulator 80 and is again suctioned into the compressor 10 from the first suction part 10e.

In this way, the internal heat exchanger 63 and the economizer heat exchanger 64 are configured to allow the refrigerant to flow in the heating operation.

(3-2) Cooling Operation

When execution of the cooling operation is instructed for the refrigeration cycle apparatus 1, the control unit 100 controls each part of the refrigerant circuit 90 as follows.

The control unit 100 causes the compressor 10 to start operations, and controls the number of rotations of the drive motor 10d. The switching mechanism 20 is controlled to be in the second state. The opening degree of the first decompressor 41 is controlled. The control unit 100 controls, for example, the opening degree of the first decompressor 41 such that the degree of superheating of the refrigerant flowing out of the second end 61ab of the first heat exchanger 61 approaches a predetermined target degree of superheating. The second decompressor 42 is controlled such that the opening degree is fully open or nearly fully open (hereinafter simply referred to as fully open). The first valve 51 is controlled to be in the closed state. The second valve 52 is controlled to be in the open state.

When the compressor 10 starts operations, the low-pressure gas refrigerant in the refrigeration cycle is suctioned from the first suction part 10e. The first compression element 10b compresses the low-pressure refrigerant suctioned by the first suction part 10e to the intermediate pressure and discharges the compressed refrigerant to the second compression element 10c. The second compression element 10c compresses the intermediate-pressure refrigerant discharged from the first compression element 10b to high pressure in the refrigeration cycle, and discharges the compressed refrigerant as a gas refrigerant to the discharge part 10g.

Note that as will be described in detail later, in the cooling operation, a part of the injection flow path 72 becomes low pressure. Therefore, the check valve of the second suction part 10f regulates the outflow of the intermediate-pressure refrigerant from the inside to the outside of the casing 10a.

The high-pressure gas refrigerant that has flowed out of the discharge part 10g passes through the switching mechanism 22 in the order of the first port P1 and the fourth port P4, and flows into the refrigerant flow path of the second heat exchanger 62 from the second end 62ab. The refrigerant that has flowed into the second heat exchanger 62 condenses by mutual heat exchange with the air at the installation location of the second heat exchanger 62, becomes a high-pressure liquid refrigerant, and flows out of the first end 62aa. In other words, the second heat exchanger 62 functions as a radiator.

The high-pressure refrigerant that has flowed out of the second heat exchanger 62 flows through the liquid refrigerant flow path 71, is decompressed to low pressure when passing through the first decompressor 41, and is brought into a gas-liquid two-phase state. Since the third valve 53 is provided in the second branch flow path 74, the refrigerant flowing through the liquid refrigerant flow path 71 does not flow into the second branch flow path 74, but passes through the fourth valve 54.

Since the first valve 51 is in the closed state, the refrigerant that has passed through the fourth valve 54 flows into the first heat exchanger 61 from the first end 61aa without flowing into the first branch flow path 73. The refrigerant that has flowed into the first heat exchanger 61 causes mutual heat exchange with the water flowing through the water flow path 61b and evaporates, becomes a low-pressure gas refrigerant, and flows out of the second end 61ab. In other words, the first heat exchanger 61 functions as an evaporator.

The low-pressure refrigerant that has flowed out of the first heat exchanger 61 passes through the switching mechanism 22 in the order of the second port P2 and the third port P3, and then flows into the first heat transfer tube 63a of the internal heat exchanger 63. As will be described later, in the cooling operation, the refrigerant in the second heat transfer tube 63b is collected by the compressor 10. Therefore, the refrigerant that has flowed into the first heat transfer tube 63a flows out of the first heat transfer tube 63a without heat exchange. The refrigerant that has flowed out of the first heat transfer tube 63a passes through the accumulator 80 and is again suctioned into the compressor 10 from the first suction part 10e.

In the cooling operation, since the first valve 51 is in the closed state, the refrigerant flowing through the liquid refrigerant flow path 71 does not flow into the injection flow path 72. In the cooling operation, since the first valve 51 is in the closed state, the second valve 52 is in the open state, and the second decompressor 42 is fully open, the operation of the compressor 10 causes a portion of the injection flow path 72, the first heat transfer tube 64a and the second heat transfer tube 64b of the economizer heat exchanger 64, the second heat transfer tube 63b of the internal heat exchanger 63, and a portion of the first branch flow path 73 to be at low pressure. Here, a portion of the injection flow path 72 is specifically a portion between the first valve 51 and the first suction part 10e of the compressor 10. A portion of the first branch flow path 73 is specifically a portion between the first valve 51 and the third valve 53.

As a result, when switching from the heating operation to the cooling operation, the refrigerant remaining in a portion of the injection flow path 72, the first heat transfer tube 64a and the second heat transfer tube 64b of the economizer heat exchanger 64, the second heat transfer tube 63b of the internal heat exchanger 63, and a portion of the first branch flow path 73 flows into the compressor 10 via the first suction part 10e and is collected. FIG. 4 shows the refrigerant flow path through which the refrigerant to be collected flows with dot-and-dash lines.

In this way, the internal heat exchanger 63 is configured such that the refrigerant does not flow through the second heat transfer tube 63b in the cooling operation. The economizer heat exchanger 64 is configured such that the refrigerant does not flow in the cooling operation.

(4) Characteristics

(4-1)

The refrigeration cycle apparatus 1 performs the heating operation and the cooling operation. The refrigeration cycle apparatus 1 includes the compressor 10, the main heat exchangers 60 that function as a radiator and an evaporator (first heat exchanger 61 and second heat exchanger 62), and the internal heat exchanger 63.

The internal heat exchanger 63 includes a first heat transfer tube 63a and a second heat transfer tube 63b. The refrigerant flowing from the main heat exchanger 60 that functions as an evaporator to the compressor 10 passes through the first heat transfer tube 63a. The refrigerant flowing from the main heat exchanger 60 that functions as a radiator to the evaporator passes through the second heat transfer tube 63b. The internal heat exchanger 63 causes heat exchange between the refrigerant passing through the first heat transfer tube 63a and the refrigerant passing through the second heat transfer tube 63b. In the internal heat exchanger 63, in the cooling operation, the refrigerant does not flow through the second heat transfer tube 63b.

Generally, the amount of refrigerant charged into the refrigerant circuit of the refrigeration cycle apparatus including the internal heat exchanger (refrigerant charge amount) is determined by adding the capacity of the internal heat exchanger to the capacity of the heat exchanger that functions as a refrigerant radiator. For example, for the refrigeration cycle apparatus 1, the capacities of the first heat exchanger 61 and the second heat exchanger 62 that function as radiators are compared, and the refrigerant charge amount is determined by adding the capacity of the internal heat exchanger 63 to the second heat exchanger 62 having a larger capacity.

In the internal heat exchanger 63 of the refrigeration cycle apparatus 1, in the cooling operation, the refrigerant does not flow through the second heat transfer tube 63b. Therefore, the refrigerant charge amount in the refrigeration cycle apparatus 1 is determined solely based on the capacity of the second heat exchanger 62 that functions as a radiator in the cooling operation, without considering the capacity of the internal heat exchanger 63. Therefore, with the refrigeration cycle apparatus 1, the refrigerant charge amount is reduced as compared to the case where the internal heat exchanger 63 is caused to function (in other words, the refrigerant flows through the second heat transfer tube 63b) in the cooling operation.

In addition, in the refrigeration cycle apparatus, due to the climate of the installation location, either the heating operation or the cooling operation may be used more frequently than the other. For example, in a cold region, the opportunities for the refrigeration cycle apparatus to perform the cooling operation are fewer than when performing the heating operation. As a result, the annual power consumption of the refrigeration cycle apparatus installed in a cold region tends to be less affected by the power consumption in the refrigerant operation and tends to be influenced by the power consumption in the heating operation. For such a reason, although the refrigeration cycle apparatus 1 regulates the inflow of the refrigerant into the internal heat exchanger 63 in the cooling operation and limits the function, the influence of such an operation on the operational efficiency is limited.

For the above reason, the refrigeration cycle apparatus 1 can achieve both a reduction in the refrigerant charge amount and high operational efficiency.

(4-2)

The refrigeration cycle apparatus 1 further includes the liquid refrigerant flow path 71, the injection flow path 72, the second decompressor 42, and the economizer heat exchanger 64.

The liquid refrigerant flow path 71 connects the main heat exchanger 60 that functions as an evaporator to the main heat exchanger 60 that functions as a radiator. The injection flow path 72 branches from the liquid refrigerant flow path 71 and joins the compressor 10. The second decompressor 42 decompresses the refrigerant passing through the injection flow path 72. The economizer heat exchanger 64 causes mutual heat exchange between the refrigerant that has been decompressed by the second decompressor 42 and the refrigerant flowing from the radiator to the evaporator.

The refrigeration cycle apparatus 1, which includes the economizer heat exchanger 64, can operate with higher efficiency.

(4-3)

The economizer heat exchanger 64 is configured such that the refrigerant does not flow in the cooling operation.

Therefore, the refrigerant charge amount of the refrigeration cycle apparatus 1 is determined solely based on the capacity of the second heat exchanger 62 that functions as a radiator in the cooling operation, without considering the capacities of the internal heat exchanger 63 and the economizer heat exchanger 64. Therefore, with the refrigeration cycle apparatus 1, the refrigerant charge amount is reduced as compared to the case where the economizer heat exchanger 64 is caused to function in the cooling operation. This allows the refrigeration cycle apparatus 1 to achieve both a reduction in the refrigerant charge amount and high operational efficiency.

(4-4)

The internal heat exchanger 63 and the economizer heat exchanger 64 are configured such that the refrigerant flows in the heating operation.

The refrigeration cycle apparatus 1 can operate with higher efficiency in the heating operation because the internal heat exchanger 63 and the economizer heat exchanger 64 are caused to function.

(4-5)

The refrigeration cycle apparatus 1 further includes the first valve 51 that regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the economizer heat exchanger 64.

The first valve 51 regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the economizer heat exchanger 64 in the cooling operation.

(4-6)

The first valve 51 is a valve that switches between the open state and the closed state.

(4-7)

The first valve 51 is in the closed state in the cooling operation.

The first valve 51 can regulate the flow of the refrigerant from the liquid refrigerant flow path 71 to the economizer heat exchanger 64 in the cooling operation.

(4-8)

The refrigeration cycle apparatus 1 further includes the second valve 52 that regulates the inflow of the refrigerant flowing through the injection flow path 72 to the compressor 10.

The second valve 52 can regulate the flow of the refrigerant from the injection flow path 72 to the compressor 10.

(4-9)

The second valve 52 is a valve that switches between the open state and the closed state.

(4-10)

The second valve 52 is in the open state in the cooling operation.

By bringing the second valve 52 into the closed state, a part of the injection flow path 72, the first heat transfer tube 64a and the second heat transfer tube 64b of the economizer heat exchanger 64, the second heat transfer tube 63b of the internal heat exchanger 63, and the first branch flow path 73 are brought into low pressure. As a result, when switching from the heating operation to the cooling operation, the refrigerant remaining in a portion of the injection flow path 72, the first heat transfer tube 64a and the second heat transfer tube 64b of the economizer heat exchanger 64, the second heat transfer tube 63b of the internal heat exchanger 63, and the first branch flow path 73 flows into the compressor 10 and is collected. Therefore, the refrigeration cycle apparatus 1 suppresses a shortage of the refrigerant amount in the refrigerant circuit 90 in the cooling operation.

(4-11)

The refrigeration cycle apparatus 1 further includes the first branch flow path 73 and the second branch flow path 74 that branch from the liquid refrigerant flow path 71.

One end of the second heat transfer tube 63b is connected to an end of the first branch flow path 73 on the opposite side of the liquid refrigerant flow path 71, and the other end is connected to an end of the second branch flow path 74 on the opposite side of the liquid refrigerant flow path 71.

(4-12)

The second branch flow path 74 further includes the third valve 53 that regulates the flow of the refrigerant from the liquid refrigerant flow path 71 to the second heat transfer tube 63b.

The third valve 53 suppresses the inflow of the refrigerant into the second heat transfer tube 63b of the internal heat exchanger 63 in the cooling operation.

(4-13)

The third valve 53 is a check valve.

(4-14)

The refrigeration cycle apparatus 1 further includes the fourth valve 54. The fourth valve 54 is a check valve that regulates the flow of the refrigerant from the first branch portion 73a at which the first branch flow path 73 branches from the liquid refrigerant flow path 71 to the second branch portion 74a at which the second branch flow path 74 branches from the liquid refrigerant flow path 71.

The fourth valve 54 promotes the inflow of the refrigerant flowing out of a radiator into the first branch flow path 73 in the heating operation.

(4-15)

The economizer heat exchanger 64 causes mutual heat exchange between the refrigerant flowing through the injection flow path 72 and the refrigerant flowing through the first branch flow path 73.

The economizer heat exchanger 64 causes the refrigerant that has radiated heat in the first heat exchanger 61 that functions as a radiator to further radiate heat in the heating operation for subcooling. This allows the refrigeration cycle apparatus 1 to operate with higher efficiency.

(4-16)

The refrigerant used by the refrigeration cycle apparatus 1 is a flammable refrigerant (propane).

Since the refrigeration cycle apparatus 1 suppresses the amount of refrigerant charged in the refrigerant circuit 90, even if the refrigerant leaks, the amount of refrigerant leakage is suppressed. Therefore, even if the flammable refrigerant is used, the occurrence of accidents caused by the leakage is suppressed.

(5) Modification Examples

(5-1)

In an implementation, the heat source with which the refrigerant flowing through the refrigerant flow path 61a exchanges heat may be water; or heat may be exchanged with air in the target space. In this case, the first heat exchanger 61 is disposed in the target space.

(5-2)

In an implementation, the refrigerant that is charged in the refrigerant circuit 90 may be propane.

Second Embodiment

(1) Overall Configuration

FIG. 5 is a schematic configuration diagram of a refrigeration cycle apparatus 1a according to a second embodiment. The differences between the refrigeration cycle apparatus 1 and the refrigeration cycle apparatus 1a are the position of a first decompressor 41, and that a refrigerant circuit 90 of the refrigeration cycle apparatus 1a further includes a fifth valve 55, a sixth valve 56, and a third branch flow path 75.

Hereinafter, the differences between the refrigeration cycle apparatus 1 and the refrigeration cycle apparatus 1a will be mainly described. The same or corresponding characteristics between the refrigeration cycle apparatus 1 and the refrigeration cycle apparatus 1a are denoted with the same reference signs, and description thereof is omitted as appropriate.

(2) Detailed Configuration

(2-1) First Decompressor 41

The first decompressor 41 of the refrigeration cycle apparatus 1a decompresses the refrigerant passing through a second branch flow path 74 to low pressure. The first decompressor 41 of the refrigeration cycle apparatus 1a is provided between a second branch portion 74a of the second branch flow path 74 and a third valve 53.

(2-2) Third Branch Flow Path 75

The third branch flow path 75 is a refrigerant flow path that branches from the second branch flow path 74 between the first decompressor 41 and the third valve 53, and is connected to a portion of a liquid refrigerant flow path 71 on the opposite side of a fourth valve 54 with the second branch portion 74a interposed therebetween.

(2-3) Fifth Valve 55

The fifth valve 55 regulates the flow of the refrigerant from a connection part 75a of the third branch flow path 75 to the second branch portion 74a in the liquid refrigerant flow path 71. The fifth valve 55 is provided between the connection part 75a and the second branch portion 74a in the liquid refrigerant flow path 71. The fifth valve 55 is a check valve that regulates the flow of the refrigerant from the connection part 75a to the second branch portion 74a, and allows the flow of the refrigerant from the second branch portion 74a to the connection part 75a.

(2-4) Sixth Valve 56

The sixth valve 56 regulates the flow of the refrigerant from the second branch flow path 74 to the liquid refrigerant flow path 71 in the third branch flow path 75. The sixth valve 56 is provided in the third branch flow path 75. The sixth valve 56 is a check valve that regulates the flow of the refrigerant from the second branch flow path 74 to the liquid refrigerant flow path 71, and allows the flow of the refrigerant from the liquid refrigerant flow path 71 to the second branch flow path 74.

(3) Overall Operation

FIG. 6 is a diagram illustrating the flow of the refrigerant in the heating operation of the refrigeration cycle apparatus 1a. FIG. 7 is a diagram illustrating the flow of the refrigerant in the cooling operation of the refrigeration cycle apparatus 1a. FIGS. 6 and 7 show the refrigerant flow path through which the refrigerant flows with broken lines, and show the direction in which the refrigerant flows with arrows.

(3-1) Heating Operation

The difference between the flow of the refrigerant of the refrigeration cycle apparatus 1a in the heating operation and the flow of the refrigerant of the refrigeration cycle apparatus 1 in the heating operation is a path through which the refrigerant flows until the refrigerant having flowed out of the second heat transfer tube 63b of the internal heat exchanger 63 to the second branch flow path 74 flows into the second heat exchanger 62. Therefore, here, only the path of the refrigerant from after flowing out to the second branch flow path 74 until flowing into the second heat exchanger 62 will be described.

Since the sixth valve 56 is provided in the third branch flow path 75, the refrigerant that has flowed from the second heat transfer tube 63b of the internal heat exchanger 63 into the second branch flow path 74 does not flow into the third branch flow path 75. The refrigerant that has flowed into the second branch flow path 74 passes through the third valve 53 and the first decompressor 41, and flows into the liquid refrigerant flow path 71. The refrigerant that has flowed into the second branch flow path 74 is decompressed to low pressure when passing through the first decompressor 41, and is brought into a refrigerant of a gas-liquid two-phase state. The refrigerant that has flowed into the liquid refrigerant flow path 71 passes through the fifth valve 55 and flows into the second heat exchanger 62 from the first end 62aa.

(3-2) Cooling Operation

The difference between the flow of the refrigerant of the refrigeration cycle apparatus 1a in the cooling operation and the flow of the refrigerant of the refrigeration cycle apparatus 1 in the cooling operation is a path until the refrigerant that has flowed out of the second heat exchanger 62 passes through the fourth valve 54. Therefore, here, only the path of the refrigerant from after flowing out of the second heat exchanger 62 until passing through the fourth valve 54 will be described.

Since the fifth valve 55 is provided in the liquid refrigerant flow path 71, the high-pressure refrigerant that has flowed out of the second heat exchanger 62 flows into the third branch flow path 75.

The refrigerant that has flowed into the third branch flow path 75 passes through the sixth valve 56 and flows into the second branch flow path 74. Since the third valve 53 is provided in the second branch flow path 74, the refrigerant that has flowed into the second branch flow path 74 does not flow into the second heat transfer tube 63b of the internal heat exchanger 63. The refrigerant that has flowed into the second branch flow path 74 is decompressed to low pressure when passing through the first decompressor 41, and is brought into a refrigerant of a gas-liquid two-phase state. The refrigerant that has passed through the first decompressor 41 flows into the liquid refrigerant flow path 71 and passes through the fourth valve 54.

(4) Characteristics

(4-1)

The refrigeration cycle apparatus 1a further includes the first decompressor 41, the third branch flow path 75, the fifth valve 55, and the sixth valve 56.

The first decompressor 41 decompresses the refrigerant between the second branch portion 74a and the third valve 53 in the second branch flow path 74. The third branch flow path 75 branches from the second branch flow path 74 between the first decompressor 41 and the third valve 53, and is connected to a portion of the liquid refrigerant flow path 71 on the opposite side of the fourth valve 54 with the second branch portion 74a interposed therebetween. The fifth valve 55 regulates the flow of the refrigerant from a connection part 75a of the third branch flow path 75 to the second branch portion 74a in the liquid refrigerant flow path 71. The sixth valve 56 regulates the flow of the refrigerant from the second branch flow path 74 to the liquid refrigerant flow path 71 in the third branch flow path 75.

The fifth valve 55 and the sixth valve 56 are provided on a refrigerant flow path extending from an upstream side to a downstream side of the first decompressor 41 via the third branch flow path 75. Therefore, the fifth valve 55 and the sixth valve 56 reliably operate due to a pressure difference of the refrigerant generated between the upstream side and the downstream side of the first decompressor 41, suppressing the flow of the refrigerant in an unintended direction.

While the embodiments according to the present disclosure have been described above, it will be understood that various changes in forms and details can be made without departing from the gist and scope of the present disclosure recited in the claims. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated.

REFERENCE SIGNS LIST

• • 1 refrigeration cycle apparatus
  • 10 compressor
  • 20 switching mechanism
  • 41 first decompressor
  • 42 second decompressor
  • 51 first valve
  • 52 second valve
  • 53 third valve
  • 54 fourth valve
  • 55 fifth valve
  • 56 sixth valve
  • 61 first heat exchanger (radiator or evaporator)
  • 62 second heat exchanger (radiator or evaporator)
  • 63 internal heat exchanger
  • 63a first heat transfer tube
  • 63b second heat transfer tube
  • 64 economizer heat exchanger
  • 71 liquid refrigerant flow path
  • 72 injection flow path
  • 73 first branch flow path
  • 74 second branch flow path
  • 75 third branch flow path
  • 90 refrigerant circuit

CITATION LIST

Patent Literature

• Patent Literature 1: JP 2013-210132 A