A climate-control system is provided that includes a variable-capacity compressor unit and a control module controlling the compressor unit. The compressor unit is operable in a first capacity mode and in a second capacity mode that is higher than the first capacity mode. The control module may be configured to switch the compressor unit among a shutdown state, the first capacity mode and the second capacity mode based on a demand signal and a number of times that the compressor unit has been switched into the shutdown state within a predetermined time period.

An air conditioner and a method of controlling an air conditioner are provided. The method of controlling an air conditioner may include determining whether a low-load condition is satisfied on the basis of a number of indoor devices or a temperature of external air, performing a low-load operation of a compressor at a predetermined frequency when the low-load condition is satisfied, detecting whether an operation pressure is out of a target pressure value or range while the low-load operation is performed, and bypassing a refrigerant from the compressor to a gas/liquid separator via an injection passage when the operation pressure is out of the target pressure value or range.

A closed cooling system for cooling a fluid of an open fluid system including a first heat exchanger and a compressor facilitating circulation of a refrigerant in the closed cooling system, where the refrigerant facilitates providing a solid state cooling bank which is thermally coupled to the open fluid system thereby cooling fluid conducted through the open fluid system.

An air-conditioning apparatus includes indoor units including a plurality of use side heat exchangers that exchange heat between air and a heat medium, and a heat medium relay unit having a plurality of heat exchangers related to heat medium. A plurality of pumps deliver the heat medium involved in heating or cooling performed by the plurality of heat exchangers related to heat medium to each passage and circulate the heat medium. A plurality of heat medium flow switching devices perform switching so that the heat medium from a selected passage flows into and flows out of each use side heat exchanger. An expansion tank is connected to a passage alleviates a pressure change caused by a volumetric change of the heat medium, and a pressure equalizing pipe connects each inlet passage or each outlet passage of the heat medium sending devices.

In various implementations, compressor operation in an air conditioner may be managed by maintaining oil viscosity, a temperature differential, compressor sump temperature, and/or suction pressure. Properties of the air conditioner or portions thereof, such as the compressor, may be determined. To manage compressor operations, operation(s) of the air conditioner may be adjusted based on one or more of the determined properties.

A heat pump system for conditioning regeneration air from a space is provided. The heat pump system is operable in a winter mode and/or a summer mode, and may be selectively operated in a defrost mode or cycle. During a defrost mode, hot refrigerant may be used to directly and sequentially defrost the regeneration air heat exchanger. A compressor may be configured to be overdriven during a defrost cycle.

In various implementations, compressor operation in an air conditioner may be managed by maintaining oil viscosity, a temperature differential, compressor sump temperature, and/or suction pressure. Properties of the air conditioner or portions thereof, such as the compressor, may be determined. To manage compressor operations, operation(s) of the air conditioner may be adjusted based on one or more of the determined properties.

A method of operating a refrigeration cycle apparatus uses a compressor to compress a coolant. The compressed coolant is fed to a condenser for release of heat, the condensed coolant is later fed to a primary side of an internal heat exchanger for release of heat, and the cooled coolant is guided through an expansion device. The coolant expanded in the expansion device is fed to an evaporator for absorption of heat, the evaporated coolant is later fed to a secondary side of the internal heat exchanger for absorption of heat, and the heated coolant is fed to the compressor. For suction gas temperature control, an amount of heat transferred from the primary side to the secondary side of the internal heat exchanger is controlled with the aid of an additional expansion device arranged parallel to the heat exchanger and between the condenser and the evaporator.

A refrigeration circuit device includes a compressor for compressing a refrigerant, As viewed in the refrigerant flow direction, a condenser is connected downstream of the compressor, a first expansion device is connected downstream of the condenser, a heat exchanger is connected downstream of the first expansion device, a second expansion device is connected downstream of the heat exchanger, an evaporator is connected downstream of the second expansion device, and the compressor is connected downstream of the evaporator. The heat exchanger is configured for connection to an electronic device that is to be cooled, is configured as an internal heat exchanger for additional transfer of heat to the refrigerant, and includes a primary side, connected on one side to the first and on the other side to the second expansion device, and a secondary side, connected on one side to the evaporator and on the other side to the compressor.

A cryogenic refrigeration system and method are disclosed. The cryogenic refrigeration system comprises: a refrigerator unit comprising an expansion unit and a variable speed compressor configured to compress refrigerant. The variable speed compressor is configured to receive refrigerant from the refrigerator unit via a lower pressure line and to supply compressed refrigerant to the refrigerator unit via a higher pressure line. There is also control circuitry configured to control the variable speed compressor to maintain a power consumption of the variable speed compressor below a predetermined threshold value, by during cooldown controlling the compressor to initially operate at a reduced frequency and later increasing a frequency of operation of the variable speed compressor such that the variable speed compressor operates at a higher frequency.