Heat Source Unit and Refrigeration Apparatus

The present application is a bypass continuation of PCT international application No. PCT/JP2024/001188, filed on Jan. 18, 2024, which claims benefit of Japanese patent application No. 2023-021806, filed on Feb. 15, 2023, the contents of each are incorporated herein by reference in their entirety.

The present disclosure relates to a heat source unit and a refrigeration apparatus.

Patent Document 1 discloses a heat source unit for a refrigeration apparatus. The heat source unit is connected to a utilization-side unit and performs a refrigeration cycle. The heat source unit includes devices such as a compressor, an outdoor heat exchanger, and a receiver.

A first aspect of the present disclosure is directed to a heat source unit connected to a utilization-side unit and configured to perform a refrigeration cycle. The heat source unit includes: a heat-source-side circuit including a compression element with one or more compressors, a heat-source-side heat exchanger, an expansion valve, and a receiver; and a controller configured to control the expansion valve, wherein in the heat-source-side circuit, the expansion valve is located between the heat-source-side heat exchanger and the receiver, and while the compression element is stopped, the controller controls the expansion valve based on one or both of a refrigerant pressure in the receiver and a refrigerant pressure in the heat-source-side heat exchanger.

Embodiments will be described with reference to the drawings. The following embodiments are merely exemplary ones in nature, and are not intended to limit the scope, applications, or use of the invention.

A first embodiment will be described. A refrigeration apparatus () according to this embodiment can cool an object to be cooled, and can condition indoor air. The object to be cooled herein includes air in facilities such as a refrigerator, a freezer, and a show case.

As illustrated in, the refrigeration apparatus () includes a heat source unit () placed outside, air-conditioning units () configured to perform air-conditioning of an indoor space, and cooling units () configured to cool inside air. The refrigeration apparatus () according to this embodiment includes one heat source unit (), a plurality of cooling units (), and a plurality of air-conditioning units (). The refrigeration apparatus () may include one cooling unit () or one air-conditioning unit ().

In the refrigeration apparatus (), the heat source unit (), the cooling units (), the air-conditioning units (), and the connection pipes (,,,) connecting those units (,,) constitute a refrigerant circuit ().

In the refrigerant circuit (), a refrigerant circulates to create a refrigeration cycle. The refrigerant in the refrigerant circuit () of this embodiment is carbon dioxide. The refrigerant circuit () is configured to perform the refrigeration cycle where the high pressure is higher than or equal to the critical pressure of the refrigerant.

The refrigerant charged in the refrigerant circuit () is not limited to carbon dioxide. The refrigerant circuit () may be charged with the so-called chlorofluorocarbon refrigerant.

In the refrigerant circuit (), the plurality of air-conditioning units () are connected to the heat source unit () through a first liquid connection pipe () and a first gas connection pipe (). In the refrigerant circuit (), the plurality of air-conditioning units () are connected in parallel to each other.

In the refrigerant circuit (), the plurality of cooling units () are connected to the heat source unit () through a second liquid connection pipe () and a second gas connection pipe (). In the refrigerant circuit (), the plurality of cooling units () are connected in parallel to each other.

The heat source unit () includes an outdoor fan () and an outdoor circuit (). The outdoor circuit () includes a compression element (C), a flow path switching mechanism (), an outdoor heat exchanger (), a first outdoor expansion valve (), a receiver (), a subcooling heat exchanger (), an intercooler (), and a bypass pipe (). The outdoor circuit () is a heat-source-side circuit. The heat source unit () includes a controller ().

The compression element (C) compresses a refrigerant. The compression element (C) includes a high-stage compressor (), a first low-stage compressor (), and a second low-stage compressor (). The high-stage compressor (), the first low-stage compressor (), and the second low-stage compressor () are rotary compressors each including a compression mechanism that is driven by a motor. The compressors (,,) are hermetic scroll compressors, for example. The high-stage compressor (), the first low-stage compressor (), and the second low-stage compressor () are configured as capacity-variable-type compressors each including a compression mechanism of which the rotational speed can be changed.

The compression element (C) performs two-stage compression. The first low-stage compressor () compresses the refrigerant sucked from the air-conditioning units () or the outdoor heat exchanger (). The second low-stage compressor () compresses the refrigerant sucked from the cooling units (). The high-stage compressor () sucks and compresses the refrigerant discharged from the first low-stage compressor () and the refrigerant discharged from the second low-stage compressor ().

The high-stage compressor () is connected to a high-stage suction pipe () and a high-stage discharge pipe (). The high-stage discharge pipe () is a discharge pipe through which the refrigerant discharged from the high-stage compressor () flows. The first low-stage compressor () is connected with a first low-stage suction pipe () and a first low-stage discharge pipe (). The first low-stage suction pipe () is a suction pipe through which the refrigerant sucked into the first low-stage compressor () flows. The second low-stage compressor () is connected with a second low-stage suction pipe () and a second low-stage discharge pipe (). In the compression element (C), the first low-stage discharge pipe () and the second low-stage discharge pipe () are connected to the high-stage suction pipe ().

The second low-stage suction pipe () is connected to the second gas connection pipe (). The second low-stage compressor () communicates with the cooling units () through the second gas connection pipe (). The first low-stage suction pipe () communicates with the air-conditioning units () through the flow path switching mechanism () and the first gas connection pipe ().

The compression element (C) includes a first low-stage pipe () and a second low-stage pipe (). The first low-stage pipe () is a pipe through which the refrigerant flows to bypass the first low-stage compressor (). One end of the first low-stage pipe () is connected to the first low-stage suction pipe (), and the other end of the first low-stage pipe () is connected to the first low-stage discharge pipe (). The first low-stage pipe () is provided in parallel with the first low-stage compressor (). The second low-stage pipe () is a pipe through which the refrigerant flows to bypass the second low-stage compressor (). One end of the second low-stage pipe () is connected to the second low-stage suction pipe (), and the other end of the second low-stage pipe () is connected to the second low-stage discharge pipe (). The second low-stage pipe () is in parallel with the second low-stage compressor ().

The flow path switching mechanism () is a mechanism configured to switch the flow paths in the refrigerant circuit () through which the refrigerant flows. The flow path switching mechanism () includes a first pipe (), a second pipe (), a third pipe (), a fourth pipe (), a first switching valve (), and a second switching valve ().

The inflow end of the first pipe () and the inflow end of the second pipe () are connected to the high-stage discharge pipe (). The outflow end of the third pipe () and the outflow end of the fourth pipe () are connected to the first low-stage suction pipe ().

The first switching valve () and the second switching valve () each switch the flow path of the refrigerant sucked into the first low-stage compressor () and the flow path of the refrigerant discharged from the high-stage compressor (). The first switching valve () and the second switching valve () are four-way switching valves each having four ports.

The first port of the first switching valve () is connected to the outflow end of the first pipe (). The second port of the first switching valve () is connected to the inflow end of the third pipe (). The third port of the first switching valve () is closed. The fourth port of the first switching valve () is connected to one end of a first outdoor gas pipe (). The other end of the first outdoor gas pipe () is connected to the first gas connection pipe ().

The first port of the second switching valve () is connected to the outflow end of the second pipe (). The second port of the second switching valve () is connected to the inflow end of the fourth pipe (). The third port of the second switching valve () is connected to a second outdoor gas pipe (). The fourth port of the second switching valve () is closed.

The first switching valve () and the second switching valve () each switch between a first state (the state indicated by the solid lines in) and a second state (the state indicated by the broken lines in). In the switching valves (,) in the first state, the first port communicates with and the third port, and the second port communicates with the fourth port. In the switching valves (,) in the second state, the first port communicates with the fourth port, and the second port communicates with the third port.

In the flow path switching mechanism (), the first switching valve () and the second switching valve () may be three-way valves each having three ports.

The outdoor heat exchanger () serves as a heat-source-side heat exchanger. The outdoor heat exchanger () is a fin-and-tube air heat exchanger. The outdoor fan () is disposed near the outdoor heat exchanger (). The outdoor fan () transfers outdoor air. The outdoor heat exchanger () exchanges heat between the refrigerant flowing therein and the outdoor air transferred by the outdoor fan ().

The gas end of the outdoor heat exchanger () is connected with the second outdoor gas pipe (). The liquid end of the outdoor heat exchanger () is connected with an outdoor flow path (O).

The outdoor flow path (O) includes a first outdoor pipe (o), a second outdoor pipe (o), a third outdoor pipe (o), a fourth outdoor pipe (o), a fifth outdoor pipe (o), a sixth outdoor pipe (o), a seventh outdoor pipe (o), and an eighth outdoor pipe (o).

One end of the first outdoor pipe () is connected to the liquid end of the outdoor heat exchanger (). The other end of the first outdoor pipe (o) is connected with one end of the second outdoor pipe (o) and one end of the third outdoor pipe (o). The other end of the second outdoor pipe (o) is connected to the top of the receiver ().

One end of the fourth outdoor pipe (o) is connected to the bottom of the receiver (). The other end of the fourth outdoor pipe (o) is connected with one end of the fifth outdoor pipe (o) and the other end of the third outdoor pipe (o). The other end of the fifth outdoor pipe (o) is connected with one end of the sixth outdoor pipe (o) and one end of the eighth outdoor pipe (o).

The other end of the eighth outdoor pipe (o) is connected to the first liquid-side trunk pipe () of the second liquid connection pipe (). The eighth outdoor pipe (o) is a liquid pipe through which a liquid refrigerant downstream of the receiver () flows. The other end of the sixth outdoor pipe (o) is connected to the first liquid connection pipe (). One end of the seventh outdoor pipe (o) is connected to an intermediate portion of the sixth outdoor pipe (o). The other end of the seventh outdoor pipe (o) is connected to an intermediate portion of the second outdoor pipe (o).

The first outdoor pipe (o) of the outdoor circuit () is provided with the first outdoor expansion valve (). The third outdoor pipe (o) of the outdoor circuit () is provided with a second outdoor expansion valve (). The first outdoor expansion valve () and the second outdoor expansion valve () are electronic expansion valves of which the opening degree is variable. The first outdoor expansion valve () and the second outdoor expansion valve () are expansion valves provided in the outdoor circuit () as a heat-source-side circuit.

The receiver () serves as a container that stores the refrigerant. The receiver () is provided downstream of the first outdoor expansion valve (). In the receiver (), the refrigerant is separated into a gas refrigerant and a liquid refrigerant. The top of the receiver () is connected with the other end of the second outdoor pipe (o) and one end of a venting pipe () described later.

The receiver () is covered with a thermal insulator (). One of the examples of the thermal insulator () is glass wool. By covering the receiver () with the thermal insulator (), it is possible to reduce the amount of heat transferred from the outdoor air to the refrigerant in the receiver () in a situation such as summer in which the outdoor air temperature is high.

The outdoor circuit () includes an intermediate injection circuit (). The intermediate injection circuit () is a circuit configured to supply the refrigerant decompressed by the first outdoor expansion valve () to the high-stage suction pipe (). The intermediate injection circuit () includes the venting pipe () and an injection pipe ().

One end of the injection pipe () is connected to an intermediate portion of the fifth outdoor pipe (o). The other end of the injection pipe () is connected to the high-stage suction pipe (). The injection pipe () is provided with a decompression valve (). The decompression valve () is an expansion valve of which the opening degree is variable.

The venting pipe () is a pipe configured to send the gas refrigerant of the receiver () to the high-stage suction pipe (). The venting pipe () serves as a venting passage. Specifically, one end of the venting pipe () is connected to the top of the receiver (). The other end of the venting pipe () is connected to an intermediate portion of the injection pipe (). The venting pipe () is connected with a venting valve (). The venting valve () is an electronic expansion valve of which the opening degree is variable.

The outdoor circuit () includes the subcooling heat exchanger (). The subcooling heat exchanger () is a heat exchanger configured to cool the refrigerant (mainly the liquid refrigerant) separated in the receiver (). The subcooling heat exchanger () is placed downstream of the receiver (). The subcooling heat exchanger () has a first flow path () and a second flow path (). The subcooling heat exchanger () exchanges heat between the refrigerant flowing through the first flow path () and the refrigerant flowing through the second flow path ().

In the subcooling heat exchanger (), the refrigerant flowing through the first flow path () is cooled. The first flow path () is connected to an intermediate portion of the fourth outdoor pipe (o) serving as a liquid pipe through which the liquid refrigerant in the outdoor circuit () flows.

The second flow path () is included in the intermediate injection circuit (). Specifically, the second flow path () is connected to part of the injection pipe () downstream of the decompression valve (). The refrigerant that has been decompressed at the decompression valve () flows through the second flow path ().

The intercooler () is connected to an intermediate flow path (). One end of the intermediate flow path () is connected to the first low-stage discharge pipe () and the second low-stage discharge pipe (). The other end of the intermediate flow path () is connected to the high-stage suction pipe ().

The intercooler () is a fin-and-tube air heat exchanger. A fan () is disposed near the intercooler (). The intercooler () exchanges heat between the refrigerant flowing therein and the outdoor air transferred from the fan ().

The outdoor circuit () has a first check valve (CV), a second check valve (CV), a third check valve (CV), a fourth check valve (CV), a fifth check valve (CV), a sixth check valve (CV), a seventh check valve (CV), an eighth check valve (CV), and a ninth check valve (CV). The check valves (CVto CV) allow the refrigerant to flow in the directions indicated by the respective arrows shown in, and disallow the refrigerant to flow in the directions opposite thereto.

The first check valve (CV) is connected to the high-stage discharge pipe (). The second check valve (CV) is connected to the second low-stage discharge pipe (). The third check valve (CV) is connected to the first low-stage discharge pipe (). The fourth check valve (CV) is connected to the second outdoor pipe (o). The fifth check valve (CV) is connected to the third outdoor pipe (o). The sixth check valve (CV) is connected to the sixth outdoor pipe (o). The seventh check valve (CV) is connected to the seventh outdoor pipe (o). The eighth check valve (CV) is connected to the second low-stage pipe (). The ninth check valve (CV) is connected to the first low-stage pipe ().

The heat source unit () includes various sensors. The sensors include a high-pressure sensor (), an intermediate-pressure sensor (), a first low-pressure sensor (), a second low-pressure sensor (), a liquid refrigerant pressure sensor (), and a high-stage suction temperature sensor ().

The high-pressure sensor () is connected to the high-stage discharge pipe (). The high-pressure sensor () detects the pressure of the refrigerant discharged from the high-stage compressor () (the pressure (HP) of the high-pressure refrigerant).

The intermediate-pressure sensor () is connected to part of the intermediate flow path () downstream of the intercooler (). The intermediate-pressure sensor () detects the pressure of the refrigerant in the intermediate flow path (). In other words, the intermediate-pressure sensor () detects the pressure of the refrigerant between the high-stage compressor () and the set of the second low-stage compressor () and the first low-stage compressor () (the pressure (MP) of the intermediate-pressure refrigerant).

The first low-pressure sensor () is connected to the second low-stage suction pipe (). The first low-pressure sensor () detects the pressure of the refrigerant sucked by the second low-stage compressor () (the pressure (LP) of the first low-pressure refrigerant).

The second low-pressure sensor () is connected to the first low-stage suction pipe (). The second low-pressure sensor () detects the pressure of the refrigerant sucked by the first low-stage compressor () (the pressure (LP) of the second low-pressure refrigerant).