A control system and a control method, which can control an electronic expansion valve. The method comprises: acquiring a temperature signal of an electronic expansion valve outlet and a pressure signal of the electronic expansion valve outlet; determining a first current degree of superheat on the basis of the temperature signal of the electronic expansion valve outlet and the pressure signal of the electronic expansion valve outlet; and a processing unit controlling, according to the requirements of an upper computer or the requirements of a set condition, an electronic expansion value to operate one of a temperature control mode, a degree of superheat control mode and an opening control mode. The technical solution provided in the embodiments of the present invention improves the real-time performance and the accuracy of control of an electronic expansion valve.

A method of detecting electrical failure in a refrigeration system is provided. The method includes determining whether a present superheat of the refrigeration system is between a maximum superheat and a minimum superheat for the refrigeration system, the maximum superheat and the minimum superheat defining a normal operating range. The method also includes detecting an electrical property of an expansion valve assembly of the refrigeration system responsive to the superheat being outside the normal operating range. The method further includes determining whether the expansion valve assembly as experienced an electrical failure based on at least the electrical property. A signal indicating that the expansion valve has experienced an electrical failure is generated based on a determination that the expansion valve assembly has experienced the electrical failure.

Cooling systems and methods of operation are provided. The cooling system may comprise a two-phase pumped loop (TPPL). The two-phase pumped loop may include, a receiver, a pump downstream from the receiver, a heat load downstream from the pump, a TPPL tee downstream from the heat load, a TPPL check valve downstream from the TPPL tee, and a heat exchanger downstream from the TPPL check valve and upstream from the receiver. The cooling system may further include a vapor cycle system (VCS) loop. The vapor cycle system loop may include the receiver, a compressor downstream from a vapor outlet of the receiver, a compressor check valve downstream from the compressor and upstream of the heat exchanger, the heat exchanger, and the heat load downstream from a liquid outlet of the receiver.

A method of detecting electrical failure in a refrigeration system is provided. The method includes determining whether a present superheat of the refrigeration system is between a maximum superheat and a minimum superheat for the refrigeration system, the maximum superheat and the minimum superheat defining a normal operating range. The method also includes detecting an electrical property of an expansion valve assembly of the refrigeration system responsive to the superheat being outside the normal operating range. The method further includes determining whether the expansion valve assembly as experienced an electrical failure based on at least the electrical property. A signal indicating that the expansion valve has experienced an electrical failure is generated based on a determination that the expansion valve assembly has experienced the electrical failure.

A CO.sub.2 cooling system includes a compression stage in which CO.sub.2 refrigerant is compressed; a cooling stage in which the CO.sub.2 refrigerant releases heat; a CO.sub.2 liquid receiver in which the CO.sub.2 refrigerant is accumulated in liquid and gaseous states; an evaporation stage in which the CO.sub.2 refrigerant, having released heat in the cooling stage, absorbs heat. The evaporation stage has first and second evaporation sectors; a first metering device for feeding CO.sub.2 refrigerant into the first evaporation sector at a first pressure; and a second metering device for feeding CO.sub.2 refrigerant into the second evaporation sector at a second pressure. The first metering device and the second metering device are operated independently from one another. A plurality of CO.sub.2 transfer lines connects the compression stage, the cooling stage, the CO.sub.2 liquid receiver and the evaporation stage. The CO.sub.2 refrigerant is circulable in a closed-loop circuit.

A dynamic method of maintaining a predefined sub-cooling of a refrigerant exiting a condenser by dynamic control of the circulating mass of refrigerant, by transferring the refrigerant into or towards a receiver installed in parallel with the liquid connection between the condenser and the expansion valve, as a function of the difference in temperatures between the condensation temperature of the saturation liquid and the discharge temperature from the condenser.

A method of operating a refrigeration and heating system (2a, 2b) comprises: circulating a refrigerant through a refrigeration circuit (4) which comprises in the direction of flow of the circulating refrigerant: at least one compressor (6a, 6b, 6c); a refrigeration circuit side (8a) of a coupling heat exchanger (8); at least one gas cooler (10); at least one expansion device (12, 14); and at least one evaporator (16); circulating a heating fluid through a heating circuit (20) which comprises a heating circuit side (8b) of the coupling heat exchanger (8) and at least one heat consumer (22); wherein the coupling heat exchanger (8) is configured for transferring heat from the circulating refrigerant to the circulating heating fluid. The method further includes increasing the temperature of the refrigerant entering the at least one gas cooler (10) in order to meet increased heating demands by allowing at least a portion of the heating fluid to flow directly from an outlet to an inlet of the heating circuit side (8b) of the coupling heat exchanger (8) bypassing the at least one heat consumer (22) or by allowing at least a portion of the refrigerant circulating through the refrigeration circuit (4) to bypass the coupling heat exchanger (8).

A method for determining when to initiate a defrost mode of a heat pump includes monitoring a heating capacity of an evaporator of the heat pump during operation of the heat pump in a heating mode, determining a threshold associated with the heating capacity, and initiating a defrost mode when the heating capacity of the evaporator is less than or equal to the threshold.

A method of controlling injection into a compressor in a refrigeration cycle is described. A refrigeration cycle may comprise at least an economizer heat exchanger, a heat rejection heat exchanger, a first expansion device, and a compressor. A discharge port of the compressor is connected to the heat rejection heat exchanger via a discharge line and an injection port of the compressor is connected to the means for compressing. The economizer heat exchanger comprises a first path having an input connected to the heat rejection heat exchanger and an output connected to the first expansion device, and a second path having an input connected to the heat rejection heat exchanger via an economizer valve and an output connected to the injection port of the compressor via an injection line. The economizer valve is regulated based on a superheat level of the refrigerant in the economizer heat exchanger.

Methods and systems provided for determining a phase state and/or for determining a degree of subcooling in a fluid. An exemplary method for operating a refrigeration cycle includes flowing a refrigerant through a metering device and calculating a pressure differential of the refrigerant across the metering device. Further, the method includes determining whether the refrigerant is a saturated liquid based on the pressure differential. The method includes, when the refrigerant is not a saturated liquid, cooling the refrigerant upstream of the metering device.