Abstract: A refrigerant circuit has a liquid passage that allows a receiver to communicate with a utilization heat exchanger, and a first expansion valve provided in the liquid passage. The controller opens the first expansion valve when the compression element is in the stopped state and a pressure in the receiver exceeds a predetermined first pressure.

Abstract: A heat source unit connected to a utilization-side unit and configured to perform a refrigeration cycle includes a low-stage compressor, a high-stage compressor, a four-way switching valve, a low-stage pipe, and a controller. The low-stage pipe is provided in parallel with the low-stage compressor, and the refrigerant flows therethrough while the low-stage compressor is stopped. The controller outputs an instruction signal for actuating the four-way switching valve, to the four-way switching valve while the low-stage compressor is stopped and the high-stage compressor is operating.

Abstract: A heat source unit connected to a utilization unit includes a compressor, a first heat exchanger, a first expansion valve, and a receiver. The heat source unit further includes a first cooler and a second cooler. The first cooler cools a primary refrigerant flowing from the receiver toward the utilization unit. The second cooler cools the primary refrigerant flowing from the first heat exchanger functioning as a radiator toward the first expansion valve, using a coolant other than outdoor air.

Abstract: A refrigeration apparatus is of a two-stage compression type for compressing a refrigerant to a supercritical region. The refrigeration apparatus includes a lower stage-side compression unit, a higher stage-side compression unit, an intermediate cooler, a heat source-side heat exchanger, a utilization-side heat exchanger, an economizer circuit, and a control unit. During a first operation in which the heat source-side heat exchanger functions as a radiator and the utilization-side heat exchanger functions as an evaporator, in a case where a discharge temperature which is a temperature of the refrigerant discharged from the higher stage-side compression unit is more than a first temperature, the control unit increases a cooling capacity of the intermediate cooler without increasing a refrigerant flow rate of the economizer circuit on condition that the intermediate cooler does not reach a maximum cooling capacity.

Abstract: A heat source unit connected to a utilization unit includes a compressor, a first heat exchanger, a first expansion valve, and a receiver. The heat source unit further includes a first cooler and a second cooler. The first cooler cools a primary refrigerant flowing from the receiver toward the utilization unit. The second cooler cools the primary refrigerant flowing from the first heat exchanger functioning as a radiator toward the first expansion valve, using a coolant other than outdoor air.

Abstract: A heat source unit connected to a utilization-side unit and configured to perform a refrigeration cycle includes a low-stage compressor, a high-stage compressor, a four-way switching valve, a low-stage pipe, and a controller. The low-stage pipe is provided in parallel with the low-stage compressor, and the refrigerant flows therethrough while the low-stage compressor is stopped. The controller outputs an instruction signal for actuating the four-way switching valve, to the four-way switching valve while the low-stage compressor is stopped and the high-stage compressor is operating.

Abstract: If a first condition that an intermediate pressure corresponding to a pressure of an intermediate flow path is greater than a predetermined value is satisfied in an operation in which first, second, and third compressors are operated, the control unit executes a first action of increasing the number of revolutions of the third compressor.

Abstract: A refrigerant circuit (11), in which carbon dioxide circulates as a refrigerant, includes a plurality of heat exchangers (12), a receiver (60), a degassing passage (61), and a degassing valve (62). The refrigeration system implements a first operation during which one of the plurality of heat exchangers (12) functions as a radiator while two of the plurality of heat exchangers (12) function as evaporators, and the refrigerant flows from the heat exchanger (12) functioning as a radiator into the receiver (60) and then flows from the receiver (60) into each of the two heat exchangers (12) functioning as evaporators. The control unit (15) changes the degassing valve (62) from a closed state to an open state when a pressure (RP) in the receiver (60) exceeds a first pressure (Pth1) set in advance, in the first operation.

Abstract: A refrigeration apparatus (1) includes a heat-source-side unit (10) using a refrigerant that works in a supercritical region. The heat-source-side unit (10) includes a compression element (20) configured to compress the refrigerant, a heat-source-side heat exchanger (24), an expansion valve (26) provided downstream of the heat-source-side heat exchanger (24), a receiver (25) provided downstream of the expansion valve (26), and a control unit (101). The control unit (101) performs a first operation for evaluating the amount of the refrigerant based on a high-pressure-side pressure, on a first condition that the internal pressure of the receiver (25) be equal to or less than a supercritical pressure.

Abstract: A refrigeration apparatus (1) includes a heat-source-side unit (10) using a refrigerant that works in a supercritical region. The heat-source-side unit (10) includes a compression element (20) configured to compress the refrigerant, a heat-source-side heat exchanger (24), an expansion valve (26) provided downstream of the heat-source-side heat exchanger (24), a receiver (25) provided downstream of the expansion valve (26), and a control unit (101). The control unit (101) performs a first operation for evaluating the amount of the refrigerant based on a high-pressure-side pressure, on a first condition that the internal pressure of the receiver (25) be equal to or less than a supercritical pressure.

Abstract: The heat source controller transmits the drive permission signal (SE) to the utilization controller when the compression element is drivable. The utilization controller opens a utilization expansion valve when heat exchange in a utilization heat exchanger is required, on condition that the utilization controller receive the drive permission signal (SE).

Abstract: If a first condition that an intermediate pressure corresponding to a pressure of an intermediate flow path is greater than a predetermined value is satisfied in an operation in which first, second, and third compressors are operated, the control unit executes a first action of increasing the number of revolutions of the third compressor.

Abstract: A refrigerant circuit (11), in which carbon dioxide circulates as a refrigerant, includes a plurality of heat exchangers (12), a receiver (60), a degassing passage (61), and a degassing valve (62). The refrigeration system implements a first operation during which one of the plurality of heat exchangers (12) functions as a radiator while two of the plurality of heat exchangers (12) function as evaporators, and the refrigerant flows from the heat exchanger (12) functioning as a radiator into the receiver (60) and then flows from the receiver (60) into each of the two heat exchangers (12) functioning as evaporators. The control unit (15) changes the degassing valve (62) from a closed state to an open state when a pressure (RP) in the receiver (60) exceeds a first pressure (Pth1) set in advance, in the first operation.

Abstract: A heat source-side unit (10) includes a heat source-side circuit (11). The heat source-side circuit (11) includes a compression unit (20) including a lower-stage compression element (23) and a higher-stage compression element (21), an intermediate heat exchanger (17) disposed on a refrigerant path between the lower-stage compression element (23) and the higher-stage compression element (21), and a bypass passage (23c) connected to a suction pipe (23a) and a discharge pipe (23b) each connected to the lower-stage compression element (23). At startup of the compression unit (20), a first action is performed for stopping the lower-stage compression element (23) and operating the higher-stage compression element (21). This configuration thus suppresses occurrence of liquid compression at startup of a compressor.

Abstract: A heat source controller performs a first operation when a compression element is in a stopped state and a pressure in a receiver exceeds a predetermined first pressure. The heat source controller allows an inlet of the compression element to communicate with the receiver, and drives the compression element in the first operation.

Abstract: A refrigeration apparatus includes a heat source-side unit and a utilization-side unit that are connected to each other, and performs a refrigeration cycle in which a high pressure of a refrigerant reaches or exceeds a critical pressure. The refrigeration apparatus also includes a control unit configured to perform a first action of returning the refrigerant to the heat source-side unit when a stop condition of the utilization-side unit is satisfied, and a second action of prohibiting the first action when a pressure at the heat source-side unit is equal to or more than the critical pressure of the refrigerant. This configuration suppresses damage to a refrigerant storage reservoir and the like in returning the refrigerant to the heat source-side unit.

Abstract: A flow path switching mechanism (70) includes first to fourth flow paths (71, 72, 73, 74) and opening and closing mechanisms (V1, V2, V3, V4, 75, 76) that can each open and close a corresponding one of the flow paths (71, 72, 73, 74). A first connection point (C1) connecting an inflow portion of the first flow path (71) and an inflow portion of the second flow path (72) is connected to a discharge portion of a compression unit (30). A second connection point (C2) connecting an outflow portion of the first flow path (71) and an inflow portion of the third flow path (73) is connected to a gas-side end of a heat source heat exchanger (22). A third connection point (C3) connecting an outflow portion of the second flow path (72) and an inflow portion of the fourth flow path (74) is connected to a gas-side end of a second utilization heat exchanger (85, 93).

Abstract: A refrigerant circuit of a refrigeration apparatus performs a refrigeration cycle in which a high pressure is equal to or greater than the critical pressure of a refrigerant. The refrigeration apparatus performs at least a heat application operation in which an indoor heat exchanger of the refrigerant circuit functions as a radiator. A controller of the refrigeration apparatus controls the opening degree of the indoor expansion valve of the refrigerant circuit so that the temperature of the refrigerant at the outlet of the indoor heat exchanger reaches a predetermined reference temperature, in the heat application operation.

Abstract: A multistage compression system uses refrigerant and oil. The multistage compression system includes a low-stage compressor that compresses the refrigerant, a high-stage compressor that further compresses the refrigerant compressed by the low-stage compressor, an oil return pipe that returns the oil discharged by the high-stage compressor to the low-stage compressor, and an oil discharge pipe that discharges the oil in the low-stage compressor. The low-stage compressor includes a compression part that compresses the refrigerant, a motor that drives the compression part, and a container that houses the compression part and the motor. The container forms a high-pressure space storing compressed refrigerant. Inside of the oil return pipe and inside of the oil discharge pipe are connected to the high-pressure space.

Abstract: An intermediate unit includes a liquid-side pipe, a first valve, and a refrigerant pressure sensor. The liquid-side pipe is connected to a liquid connection pipe connecting a heat source unit and a utilization unit together. A controller of the intermediate unit adjusts the opening degree of the first valve based on a value measured by the refrigerant pressure sensor. The pressure of a refrigerant to be sent through the liquid connection pipe from the intermediate unit to the utilization unit is adjusted by the first valve.