A heat pump system includes a first bypass pipe provided with a first bypass valve and connecting a liquid refrigerant pipe and a low-pressure refrigerant pipe, a refrigerant heat exchanger configured to cause a heat-exchange between refrigerant flowing in the liquid refrigerant pipe and refrigerant flowing in first bypass pipe, a second bypass pipe provided with a second bypass valve and connecting the liquid refrigerant pipe and the low-pressure refrigerant pipe, and a controller. The controller is configured to control opening degree of the first bypass valve based on detected superheated temperature of refrigerant flowing in the first bypass pipe, and detected discharge temperature of a compressor and control opening degree of the second bypass valve based on the detected discharge temperature.

An air-conditioning apparatus includes a bypass pipe through which part of refrigerant discharged from a discharge port of a compressor flows. Heating components provided on a substrate of the controller include a first heating component and a second heating component that generates a smaller amount of heat than the first heating component. The first heating component is provided such that a longitudinal direction of the first heating component is parallel to a flow direction of the refrigerant in the bypass pipe, the longitudinal direction being a direction in which long sides of the first heating component extend. The second heating component is provided such that a widthwise direction of the second heating component is parallel to the flow direction of the refrigerant in the bypass pipe, the widthwise direction being a direction in which short sides of the second heating component extend.

Provided is an air conditioner including a connection pipe connected to a refrigerant pipe disposed inside an outdoor heat exchanger that operates as a condenser during a cooling operation and as an evaporator during a heating operation, a header connected to the connection pipe, wherein a refrigerant separated from a two-phase refrigerant flowing through the refrigerant pipe flows through the header, a bypass pipe connected to the header to guide a flow of the refrigerant to a compressor, a flow rate control valve installed at the bypass pipe to control a flow velocity of the refrigerant, a subcooler configured to superheat the refrigerant flowing through the bypass pipe, and a controller configured to control an opening degree of the flow rate control valve.

A cooling device comprising a cooling circuit, is described. The cooling circuit further comprises a compressor adapted to compress cooling agent present in the cooling circuit during an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor; a condensing unit connected to the compressor by a first fluid line of the cooling circuit; and an evaporating unit, which is connected to the condensing unit by a second fluid line of the cooling circuit. The cooling circuit further comprises an expansion device arranged in the second fluid line; and an additional evaporator connected to the evaporating unit by a third fluid line of the cooling circuit, and connected to the compressor by a fourth fluid line of the cooling circuit.

A method for operating and controlling a vapor-compression cycle includes providing a system comprising an evaporator with a fan, a compressor, a condenser with a fan, an integrated expander, and a flash tank device with a vapor/liquid two-phase inlet and two outlets wherein a first outlet is a vapor outlet and a second outlet is a liquid outlet, and a metering valve; bringing a vapor-compression cycle up to steady-state at a fixed operating condition; opening the metering valve until the desired compressor suction superheat is achieved; and maintaining the desired degree of superheat by selectively increasing and decreasing superheat by reducing and increasing metering valve flow rate respectively.

Disclosed is a CO.sub.2 based refrigeration system including a condenser for transferring heat from a CO.sub.2 refrigerant of the refrigeration system to an air stream. The system further includes a metering device downstream of the condenser and a bypass arrangement. The metering device is configured to create a pressure drop so that part of the refrigerant liquifies, when received in a supercritical state, from the condenser such that a liquid component and a flash gas component are generated. The bypass arrangement includes a valve and a bypass line to allow the refrigerant to bypass the metering device.

Systems and methods for controlled subcooling of working fluid in a heating, ventilation, air conditioning and refrigeration (HVACR) system through a suction line heat exchanger are disclosed. The suction line heat exchanger may receive a first fluid flow travelling to a suction of the compressor in the HVACR system and second flow of working fluid that is travelling from a heat exchanger receiving the discharge of the compressor to an expansion device. Superheating of the first working fluid may be determined based on temperature measurements prior to and following the suction line heat exchanger. The superheating may be used to control the quantity of the second flow of working fluid introduced into the suction line heat exchanger, for example to maintain superheat that is below a threshold value. These systems may include chillers and heat pump systems, and methods may be applied to chillers or heat pump systems.

A refrigeration cycle apparatus includes a refrigerant circuit including a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger connected to each other via refrigerant pipes. The outdoor heat exchanger includes a heat transfer pipe, and a plurality of fins. The outdoor heat exchanger is configured so that a ratio of a heat capacity of the plurality of fins to a total of heat capacities of the heat transfer pipe and the plurality of fins is not more than 50%. The refrigeration cycle apparatus has a mixed defrosting operation mode in which a hot gas defrosting operation and a reverse-defrosting operation are performed in sequence. In the hot gas defrosting operation, hot gas discharged from the compressor is supplied to the outdoor heat exchanger. In the reverse-defrosting operation, refrigerant passing through the indoor heat exchanger is supplied from the compressor to the outdoor heat exchanger.

A refrigerant leakage determination system capable of detecting leakage of refrigerant without requiring complicated processing is provided. A refrigerant leakage determination system is a refrigerant leakage determination system of a refrigeration cycle apparatus that includes a refrigerant circuit including a heat-source-side heat exchanger and has, as operating modes, a normal mode in which the heat-source-side heat exchanger is caused to function as an evaporator and a defrosting mode in which the heat-source-side heat exchanger frosted during a normal operation is defrosted. The refrigerant leakage determination system includes a processor configured to acquire defrosting information regarding a relationship between a normal operation period and the number of defrosting operations, and memory that stores the defrosting information. The processor is further configured to determine, based on the acquired defrosting information, leakage of refrigerant in the refrigerant circuit.

Systems and methods for controlled subcooling of working fluid in a heating, ventilation, air conditioning and refrigeration (HVACR) system through a suction line heat exchanger are disclosed. The suction line heat exchanger may receive a first fluid flow travelling to a suction of the compressor in the HVACR system and second flow of working fluid that is travelling from a heat exchanger receiving the discharge of the compressor to an expansion device. Superheating of the first working fluid may be determined based on temperature measurements prior to and following the suction line heat exchanger. The superheating may be used to control the quantity of the second flow of working fluid introduced into the suction line heat exchanger, for example to maintain superheat that is below a threshold value. These systems may include chillers and heat pump systems, and methods may be applied to chillers or heat pump systems.