Refrigeration Cycle Apparatus

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.

The present disclosure relates to a refrigeration cycle apparatus.

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.

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.

is a schematic configuration diagram of a refrigeration cycle apparatusaccording to a first embodiment.

The refrigeration cycle apparatusincludes a refrigerant circuitand a control unit. The refrigerant circuitmainly includes a compressor, a switching mechanism, a first decompression means or first decompressor, a second decompression means or second decompressor, a first valve, a second valve, a third valve, a fourth valve, a first heat exchanger, a second heat exchanger, an internal heat exchanger, an economizer heat exchanger, an accumulator, a liquid refrigerant flow path, an injection flow path, a first branch flow path, and a second branch flow path.

The refrigeration cycle apparatusperforms the heating operation and the cooling operation. In more detail, the refrigeration cycle apparatuscauses the refrigerant circuitto perform a refrigeration cycle to heat or cool water circulating in a water circuit, performing the heating operation and the cooling operation for a target space by using this water.

In an implementation, the refrigerant circuitis 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.

The compressorcompresses a low-pressure refrigerant to a high-pressure refrigerant in the refrigeration cycle. In more detail, the compressoris 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 compressorincludes a casing, a first compression element, a second compression element, a drive motor, a first suction part, a second suction part, and a discharge part

The casingaccommodates the first compression elementand the second compression element. The first compression elementand the second compression elementare coupled to a single drive shaft. During the operation of the compressor, the drive motorrotationally drives the first compression elementand the second compression elementvia the drive shaft. In other words, the compressorhas a single-shaft two-stage compression structure. The number of rotations of the drive motoris controlled by the control unit.

The first suction partsuctions the low-pressure refrigerant from the refrigerant circuit. The second suction partsuctions the intermediate-pressure refrigerant from the refrigerant circuit. The discharge partdischarges the high-pressure refrigerant to the refrigerant circuit. The second suction partis one example of a suction part.

The second suction partincludes a check valve that allows inflow of the refrigerant from the outside to the inside of the casing, and regulates outflow of the refrigerant from the inside to the outside of the casing

The first compression elementcompresses the refrigerant suctioned by the first suction partto the intermediate pressure and discharges the compressed refrigerant to the second compression element. The second compression elementcompresses both the intermediate-pressure refrigerant discharged by the first compression elementand the intermediate-pressure refrigerant suctioned by the second suction partto high pressure and discharges the compressed refrigerant to the discharge part

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

The switching mechanismswitches the direction in which the refrigerant flows in the refrigerant circuitbetween two states. The switching mechanismis a four-way switching valve. The switching mechanismincludes a first port P, a second port P, a third port P, and a fourth port P.

The switching mechanismswitches between a first state (state indicated by the broken lines in) and a second state (state indicated by the solid lines in). In the first state, the switching mechanismallows communication between the first port Pand the second port P, and allows communication between the third port Pand the fourth port P. In the second state, the switching mechanismallows communication between the first port Pand the fourth port P, and allows communication between the second port Pand the third port P. The state of the switching mechanismis controlled by the control unit.

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

The first heat exchangercauses mutual heat exchange between the refrigerant flowing through the refrigerant circuitand the water circulating through the water circuit. The first heat exchangerfunctions as a radiator for the refrigerant in the heating operation, and as an evaporator for the refrigerant in the cooling operation. The first heat exchangerincludes a refrigerant flow pathand a water flow path. Note thatshows only a part of the water circuit.

The refrigerant flow pathis provided in the refrigerant circuit. The water flow pathis provided in the water circuit. The refrigerant flowing through the refrigerant flow pathexchanges heat with the water flowing through the water flow path. The water that has exchanged heat with the refrigerant circulates through the water circuitto heat or cool the air in the target space.

Hereinafter, for convenience of description, in the cooling operation, the end of the refrigerant flow pathinto which the refrigerant flows is referred to as a first end, and the end of the refrigerant flow pathfrom which the refrigerant flows out is referred to as a second end

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

The second heat exchangercauses mutual heat exchange between the refrigerant flowing through the refrigerant circuitand the air at the installation location of the second heat exchanger. The second heat exchangerfunctions as an evaporator for the refrigerant in the heating operation, and as a radiator for the refrigerant in the cooling operation. The second heat exchangerincludes a refrigerant flow path.

The refrigerant flow path of the second heat exchangeris provided in the refrigerant circuit. The refrigerant flowing through the refrigerant flow path of the second heat exchangerexchanges heat with the air at the installation location of the second heat exchanger.

Hereinafter, for convenience of description, in the heating operation, the end of the refrigerant flow path of the second heat exchangerinto which the refrigerant flows is referred to as a first end, and the end of the refrigerant flow pathfrom which the refrigerant flows out is referred to as a second end

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

Hereinafter, for convenience of description, the first heat exchangerand the second heat exchangermay collectively be referred to as a main heat exchanger.

The liquid refrigerant flow pathis a refrigerant flow path that connects the first endof the refrigerant flow pathof the first heat exchangerto the first endof the refrigerant flow path of the second heat exchanger.

The first decompressordecompresses the refrigerant passing through to low pressure. The first decompressoris provided in the liquid refrigerant flow path. The opening degree of the first decompressoris controlled by the control unit.

In an implementation, the first decompressoris an electric expansion valve.

The internal heat exchangeris a precooling heat exchanger that cools the refrigerant flowing from the main heat exchangerthat functions as a radiator to the main heat exchangerthat functions as an evaporator. The internal heat exchangerincludes a first heat transfer tubeand a second heat transfer tube. The internal heat exchangercauses mutual heat exchange between the refrigerant passing through the first heat transfer tubeand the refrigerant passing through the second heat transfer tube

The refrigerant flowing from the main heat exchangerthat functions as an evaporator to the first suction partof the compressorpasses through the first heat transfer tube. One end of the first heat transfer tubeis connected to the third port Pof the switching mechanism. The other end of the first heat transfer tubeis connected to the first suction partof the compressorvia the accumulator.

The refrigerant flowing from the main heat exchangerthat functions as a radiator to the main heat exchangerthat functions as an evaporator passes through the second heat transfer tube. Both ends of the second heat transfer tubeare connected to the liquid refrigerant flow pathbetween the first heat exchangerand the first decompressor.

As will be described in detail later, the refrigerant flows through the first heat transfer tubeand the second heat transfer tubeof the internal heat exchangerin the heating operation (in other words, flows through the internal heat exchanger), and does not flow through the second heat transfer tubein the cooling operation.

Each of the first branch flow pathand the second branch flow pathis a refrigerant flow path that branches from the liquid refrigerant flow pathbetween the first heat exchangerand the first decompressor, and connects to the second heat transfer tube. The first branch flow pathbranches from the liquid refrigerant flow pathat a position closer to the first heat exchangerthan the second branch flow path(in other words, at a position spaced apart from the first decompressor).

One end of the second heat transfer tubeis connected to the end of the first branch flow pathon the opposite side of the liquid refrigerant flow path. The other end of the second heat transfer tubeis connected to the end of the second branch flow pathon the opposite side of the liquid refrigerant flow path.

Hereinafter, for convenience of description, a portion at which the first branch flow pathbranches from the liquid refrigerant flow pathmay be referred to as a first branch portion, and a portion at which the second branch flow pathbranches from the liquid refrigerant flow pathmay be referred to as a second branch portion

The injection flow pathis a refrigerant flow path that branches from the liquid refrigerant flow pathand connects to the first suction partand the second suction partof the compressor.

In the present embodiment, the injection flow pathincludes a first part, a second part, a third part, and a fourth part

The first partis a flow path that branches from the liquid refrigerant flow pathand is shared with the first branch flow pathover a predetermined length.

The second partis a flow path that allows the refrigerant flowing through the first partto flow into a first heat transfer tubeof the economizer heat exchanger(described later). The second partis connected to the end of the first parton the opposite side of the branch portion from the liquid refrigerant flow path. The first heat transfer tubeof the economizer heat exchangeris provided in the middle of the second part

The third partis a flow path that allows the refrigerant flowing through the first heat transfer tubeof the economizer heat exchangerto flow into the first suction partof the compressor. The third partconnects the end of the second parton the opposite side of the first partto the first suction partof the compressor.

The fourth partis a flow path that allows the refrigerant flowing through the first heat transfer tubeof the economizer heat exchangerto flow into the second suction partof the compressor. The fourth partconnects the end of the second parton the opposite side of the first partto the second suction partof the compressor.

The second decompressordecompresses the refrigerant that passes through the injection flow pathto intermediate pressure. The second decompressoris provided in the second partof the injection flow path, between the connection part with the first partand the economizer heat exchanger. The opening degree of the second decompressoris controlled by the control unit.

In an implementation, the second decompressoris an electric expansion valve.

The economizer heat exchangercauses mutual heat exchange between the refrigerant that has passed through the injection flow pathand has been decompressed by the second decompressor, and the refrigerant flowing from the main heat exchangerthat functions as a radiator to the main heat exchangerthat functions as an evaporator. The economizer heat exchangerincludes the first heat transfer tubeand a second heat transfer tube. The economizer heat exchangercauses mutual heat exchange between the refrigerant passing through the first heat transfer tubeand the refrigerant passing through the second heat transfer tube

The refrigerant that flows through the injection flow pathpasses through the first heat transfer tube. The first heat transfer tubeis provided in the injection flow path. One end of the first heat transfer tubeis connected to the second decompressorvia the injection flow path. The other end of the first heat transfer tubeis connected to the first suction partand the second suction partof the compressorvia the injection flow path.

The refrigerant that flows through the first branch flow pathpasses through the second heat transfer tube. The second heat transfer tubeis provided in the first branch flow path. One end of the second heat transfer tubeis connected to the first valvevia the first branch flow path. The other end of the second heat transfer tubeis connected to the second heat transfer tubeof the internal heat exchangervia the first branch flow path.

As will be described in detail later, the refrigerant passes through the first heat transfer tubeand the second heat transfer tubeof the economizer heat exchangerin the heating operation (in other words, passes through the economizer heat exchanger), and does not flow through the economizer heat exchangerin the cooling operation.