A cooling system includes a compressor that compresses a refrigerant, a heat exchanger that cools the refrigerant from the compressor, heat exchangers that use the refrigerant cooled by the heat exchanger, a refrigerant passage that supplies the refrigerant from the heat exchanger to a battery and supplies this refrigerant to the compressor, and an expansion valve provided on the refrigerant passage upstream of the battery, and processing circuitry that maintains an opening degree of the expansion valve constant when the battery temperature is within a first region, and sets the opening degree of the expansion valve when the battery temperature is within a second region higher than the first region.

A cooling system includes a compressor that compresses a refrigerant, a heat exchanger that cools the refrigerant from the compressor, heat exchangers that use the refrigerant cooled by the heat exchanger, a refrigerant passage that supplies the refrigerant from the heat exchanger to a battery and returns this refrigerant to the compressor, and an expansion valve provided on the refrigerant passage upstream of the battery, and processing circuitry maintains an opening degree of the expansion valve constant when the battery temperature is within a first region, increases the opening degree of the expansion valve as the battery temperature rises when the battery temperature is within a second region, and maintains the opening degree of the expansion valve at a large opening degree when the battery temperature is within a third region.

A cooling system includes a compressor that compresses a refrigerant in two stages using first and second compressors, a heat exchanger that cools the refrigerant from the compressor, heat exchangers that use the refrigerant from the heat exchanger, a refrigerant passage that supplies the refrigerant from the heat exchanger to a battery and supplies this refrigerant to the first compressor, refrigerant passages that supply the refrigerant from the heat exchangers to the second compressor, an expansion valve provided on the refrigerant passage, and an expansion valve provided on the refrigerant passage, and a control device performs control to increase the opening degree of the expansion valve when the temperature of the refrigerant discharged from the second compressor is equal to or higher than a predetermined temperature.

A coolant circulation system that circulates a CO.sub.2 coolant to cool a motor in a vehicle includes a controller that performs a control such that an input coolant having an input pressure and being in a gas phase is outputted from upstream-side expansion valves, and the pressure of the input coolant is reduced by a downstream-side expansion valve into an output coolant having an output pressure. The controller estimates a corresponding pressure of the coolant at a corresponding point on a saturated vapor line located on a low pressure side of a local maximum pressure, a specific enthalpy at the corresponding point being equal to a specific enthalpy of the input coolant, sets the corresponding pressure to a target output pressure, and controls the downstream-side expansion valve such that its output pressure reaches the target output pressure.

A method for controlling a refrigeration system of a vehicle includes a circuit containing a refrigerant, a compressor, and first and second evaporators which are connected in parallel to the compressor, and a first expansion valve arranged upstream the first evaporator that regulates a pressure drop of the refrigerant before the first evaporator, and a second expansion valve arranged upstream the second evaporator that regulates a pressure drop of the refrigerant before the second evaporator, and a condenser arranged downstream the compressor between the compressor and the first and second expansion valves. The method includes controlling a total opening of the first expansion valve and the second expansion valve, based on a temperature and a pressure of the refrigerant which refrigerant temperature and refrigerant pressure are measured downstream the first and second evaporators at a position between the first and second evaporators and the compressor.

A system includes a refrigeration circuit, low-temperature circuit and controller. The refrigeration circuit includes: a tiller for absorbing heat from a colling water to a refrigerant; and a condenser for releasing heat from the refrigerant to an outside, and realizes a refrigeration cycle by circulating the refrigerant therethrough. The low-temperature circuit includes the tiller and an external heat exchanger for absorbing heat from an outside to the first heat medium, and circulate the cooling water therethrough. The controller can change a heat absorption amount of the refrigerant at the tiller. The controller controls the device so that a change in the heat absorption amount of the refrigerant at the first heat exchanger in accordance with a change in a temperature of the first heat medium is reduced, if the temperature of the cooling water flowing through the first heat exchanger changes by a reference value or more.