A method of operating a thermal system including at least a compressor, a condenser, a flow control valve, and at least one heat exchanger connected in a closed fluid loop charged with refrigerant. The method includes: regulating refrigerant pressure at a selected point within the fluid loop using a pressure regulating apparatus including: a main pressure regulator including a dome in fluid communication with a diaphragm that seals directly against at least one process void and at least one vent void; and a pilot pressure regulator in fluid communication with the dome so as to provide fluid thereto at a setpoint pressure. The setpoint pressure is maintained by the pilot pressure regulator utilizing refrigerant tapped from the fluid loop The refrigerant is tapped from a point upstream of the main pressure regulator and tapped refrigerant is returned to the fluid loop downstream of the main pressure regulator.

A refrigeration cycle device that includes a main refrigerant circuit and a sub-refrigerant circuit cools or heats a main refrigerant that flows between a main heat-source-side heat exchanger and a main usage-side heat exchanger by causing a sub-usage-side heat exchanger to function as an evaporator or a radiator of a sub-refrigerant. A first main expansion mechanism and a second main expansion mechanism that decompress the main refrigerant are provided on an upstream side and a downstream side of the sub-usage-side heat exchanger of the main refrigerant circuit.

A refrigeration cycle apparatus includes: a refrigeration cycle circuit in which a compressor, a condenser, a first expansion valve, and an evaporator are connected by refrigerant pipes; an injection pipe having a refrigerant inflow side end and a refrigerant outflow side end, the refrigerant inflow side being connected between the condenser and the first expansion valve, the refrigerant outflow side end being connected to a suction side of the compressor; a second expansion valve provided at the injection pipe; and a controller that controls a rotation speed of the compressor and an opening degree of the second expansion valve. In the case of reducing a heat-exchange capability of the evaporator when the rotation speed of the compressor is a specified rotation speed, the controller performs a low load operation during which refrigeration is caused to flow through the injection pipe.

Device for a climate control system of a motor vehicle. The device includes a refrigeration circuit with a compressor for the two-stage compression of the refrigerant and injection of refrigerant at an intermediate pressure level, at least one heat exchanger operated as a condenser/gas cooler, a first internal heat exchanger, at least a first heat exchanger operated as an evaporator, which is situated upstream from a first expansion element in the flow direction of the refrigerant, as well as a first flow path and a second flow path, each of which extends from a branching point to the compressor. The refrigeration circuit is designed with a second internal heat exchanger. The first internal heat exchanger is arranged at least with a low-pressure side inside the first flow path and the second internal heat exchanger is arranged at least with an intermediate pressure side inside the second flow path.

A part of a gas-phase mixed refrigerant compressed by a compressor (20) is condensed by a first condenser (21). Then, the mixed refrigerant is separated by a first gas-liquid separator (22) into a gas-phase first fluid portion (I) and a liquid-phase second fluid portion (II) which has been condensed into a liquid phase. A part of the gas-phase first fluid portion (I) is further condensed by a second condenser (23). Then, the first fluid portion is further separated by a second gas-liquid separator (24) into a gas-phase third fluid portion (III) and a liquid-phase fourth fluid portion (IV) which has been condensed into a liquid phase. Thereafter, the gas-phase third fluid portion (III) is condensed and then expanded.

A cooling system is designed to operate in two different modes. Generally, in the first mode, when parallel compression is needed, certain valves are controlled to direct gaseous refrigerant from a tank to a compressor in the system and to direct refrigerant from low side heat exchangers towards other compressors. In this manner, a compressor in the system is transitioned to be generally a parallel compressor. In the second mode, when parallel compression is not needed, the valves are controlled to return the refrigerant flow back to normal.

A controller for a refrigeration system includes a processing circuit having one or more processors and memory. The processing circuit is configured to calculate a superheat of a gas refrigerant exiting a first side of a subcooler based on a measured temperature and a measured pressure of the gas refrigerant and compare the calculated superheat to a superheat threshold. In response to a determination that the calculated superheat is less than the superheat threshold, the processing circuit closes an expansion valve to restrict a flow of the gas refrigerant through a second side of the subcooler. In response to a determination that the calculated superheat is equal to or greater than the superheat threshold, the processing circuit operates the expansion valve to drive a temperature of a subcooled liquid refrigerant exiting the second side of the subcooler to a subcooled liquid temperature setpoint.

A refrigeration system and a control method thereof. The refrigeration system includes a compressor and a condenser, and further includes a first throttling device for receiving liquid refrigerant from the condenser; an ejector having a high-pressure fluid inlet, a fluid suction inlet and a fluid outlet, the high-pressure fluid inlet of the ejector is connected to the first throttling device, the fluid outlet of the ejector is connected to a flash tank, a gas-phase outlet of the flash tank is connected to a compressor inlet, a liquid-phase outlet of the flash tank is connected to an evaporator via a second throttling device, and the evaporator is connected to the fluid suction inlet of the ejector; and a controller configured to control an opening of the first throttling device based on a pressure difference between the fluid outlet and the fluid suction inlet of the ejector.

A multi-stage refrigeration system (100) includes: a refrigeration loop (110), which includes a gas suction port of a multi-stage compressor (111), a condenser (112), a first throttling element (113), an evaporator (114) and an exhaust port of the multi-stage compressor which are sequentially connected through pipelines; an economizer branch (120), which includes an economizer (121), a second throttling element (122) and a first control valve (123), the economizer having an economizer liquid inlet connected to the condenser via the first throttling element, an economizer liquid outlet connected to the evaporator via the second throttling element, and an economizer exhaust port connected to an intermediate stage of the multi-stage compressor via a control valve; and a bypass branch (130), which is joined to the evaporator from the downstream of the second throttling element and connected to the condenser via the first throttling element, and on which a second control valve (131) is arranged.

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.