A method for controlling a vapour compression system (1) is disclosed, the vapour compression system (1) comprising at least one expansion device (8) and at least one evaporator (9). For each expansion device (8), an opening degree of the expansion device (8) is obtained, and a representative opening degree, OD.sub.rep, is identified based on the obtained opening degree(s) of the expansion device(s) (8). The representative opening degree could be a maximum opening degree, OD.sub.max, being the largest among the obtained opening degrees. The representative opening degree, OD.sub.rep, is compared to a predefined target opening degree, OD.sub.target, and a minimum setpoint value, SP.sub.rec, for a pressure prevailing inside a receiver (7), is calculated or adjusted, based on the comparison. The vapour compression system (1) is controlled to obtain a pressure inside the receiver (7) which is equal to or higher than the calculated or adjusted minimum setpoint value, SP.sub.rec.

A refrigerant system includes a compressor configured to pressurize a refrigerant fluid. The compressor includes a sump portion. A heater is situated to heat at least the sump portion. A controller is configured to selectively operate the heater to apply heat to at least the sump portion while the compressor is off and continue operating the heater when the compressor turns on until a temperature of the compressor or a temperature of fluid discharged from the compressor satisfies at least one criterion.

A method of initiating a defrost cycle using a controller of a heat pump system includes measuring a temperature of an evaporator coil and determining whether the temperature of the evaporator coil is less than a freezing temperature. Responsive to a determination that the temperature of the evaporator coil is less than the freezing temperature, determining whether a current dew point temperature of air is greater than the temperature of the evaporator coil. Responsive to a determination that the current dew point temperature of air is greater than the temperature of the evaporator coil, calculating a frost-collection rate. Determining whether the frost-collection rate is greater than a frost-collection-rate threshold, and, responsive to a determination that the frost-collection rate is greater than the frost-collection-rate threshold, initiating a defrost cycle.

During a first cooling operation, a compressor is in an operational state, a liquid pump is in a non-operational state, and an amount of refrigerant allowing for existence of a liquid surface of the refrigerant in a refrigerant tank is accumulated in the refrigerant tank. During a second cooling operation, the compressor is in the non-operational state, the liquid pump is in the operational state, and the amount of the refrigerant allowing for the liquid surface of the refrigerant in the refrigerant tank is accumulated in the refrigerant tank.

Provided is an air-conditioning device that includes an outdoor unit and an indoor unit, the outdoor unit including a compressor, the indoor unit being connected to the outdoor unit, the air-conditioning device including a heating means provided to the compressor, and configured to heat refrigerant in the compressor, and a controller configured to control the heating means. The controller includes a heat load learning unit configured to learn a heat load based on temperature data and air conditioning data, a stagnation prevention control start timing estimation unit configured to estimate a stagnation prevention control start timing based on the heat load obtained by learning, the stagnation prevention control start timing being a timing at which a stagnation prevention control of heating the compressor is started, and a device control unit configured to control the heating means such that the stagnation prevention control is performed by the heating means at the stagnation prevention control start timing estimated.

A refrigeration system for a carbon dioxide based refrigerant fluid, wherein the refrigeration system includes a refrigerant circuit, the refrigerant circuit including a compression device, a heat rejecting heat exchanger, an ejector, a receiver, an expansion device, and a heat absorbing heat exchanger; wherein the ejector includes a primary inlet, a secondary inlet and an outlet; wherein the receiver includes an inlet, a liquid outlet and a gas outlet; wherein the ejector primary inlet is arranged to receive fluid from an outlet of the heat rejecting heat exchanger, the ejector secondary inlet is arranged to receive fluid from an outlet of the heat absorbing heat exchanger, and the ejector outlet is arranged to direct flow to the receiver inlet; wherein a suction inlet of the compression device is arranged to receive refrigerant fluid from the gas outlet of the receiver.

Thermal management systems include an open circuit refrigeration system featuring a first receiver configured to store a gas, a second receiver configured to store a liquid refrigerant fluid, an evaporator configured to extract heat from a heat load that contacts the evaporator, and an exhaust line, where the first receiver, the second receiver, the evaporator, and the exhaust line are connected to provide a refrigerant fluid flow path.

A refrigeration cycle device includes a compressor, an upstream branch portion, a heating portion, a decompression portion, a bypass passage, a bypass flow adjustment portion, and a mixing portion. The mixing portion mixes a bypass side refrigerant flowing out from the bypass flow adjustment portion with a decompression-portion side refrigerant flowing out from the decompression portion, and causes the mixed refrigerant to flow to a suction port side of the compressor. The mixing portion mixes the bypass side refrigerant and the decompression-portion side refrigerant such that an enthalpy difference obtained by subtracting an enthalpy of an ideal homogeneously mixed refrigerant from an enthalpy of a suction side refrigerant actually sucked into the compressor is equal to or less than a predetermined reference value.

The motor-driven compressor includes an electric motor, a housing, a compression portion, and an inverter device. The inverter device includes an inverter circuit, a current sensor, a coordinate converter, a speed controller, a current controller, a PWM controller, and a rotation angle estimator. The speed controller generates a d-axis current command value and a q-axis current command value such that a necessary torque to drive the electric motor occurs. The inverter device includes a heat-generating current command section that increases a temperature of the electric motor by changing the d-axis current command value and the q-axis current command value. The heat-generating current command section changes the d-axis current command value and the q-axis current command value so as to shift them in a direction in which a d-axis current value increases along a constant torque curve in a d-q coordinate system.

A method of controlling the temperature in cavities of a refrigerator (10) cooled by a refrigeration circuit having a compressor (18) and an evaporator (32) includes the steps of: monitoring the duty cycle of the compressor (18); determining whether the duty cycle is below a threshold; determining whether the temperature of the evaporator (32) is above a threshold; and if the duty cycle is below the threshold and if the evaporator temperature is above a threshold, activating the refrigeration circuit to start cooling of at least one of the refrigerator cavities. A refrigeration appliance (10) with a controller that activates the refrigeration circuit based on the monitored duty cycle of the compressor (18) and the evaporator temperature is also provided.