An apparatus includes a flash tank that stores a refrigerant, a first load that uses the refrigerant to cool a first space, second and third loads, first and second compressors, and a high side heat exchanger configured to remove heat from the refrigerant. During a first mode of operation: the second load uses the refrigerant to cool a second space, the third load uses the refrigerant to cool a third space, the second compressor compresses the refrigerant from the second and third loads, and the first compressor compresses the refrigerant from the first load and the second compressor. During a second mode of operation, the second compressor compresses the refrigerant from the second load and directs the compressed refrigerant to the third load to defrost the third load.

To provide a defrost system capable of preferable defrosting and prevention of generation of icicles on a casing without installing a brine circuit. A defrost system includes a thermosiphon defrost circuit that is provided by being branched from a circulation line, in which, at the time of defrosting, a CO.sub.2 refrigerant staying inside a fin-tube heat exchanger repeats a two-phase change of a gaseous form and reliquefaction, and which forms a CO.sub.2 circulation path together with the fin-tube heat exchanger; electromagnetic opening/closing valves that are closed at the time of defrosting and set the CO.sub.2 circulation path to a closed circuit; and a first electric heater arranged above the thermosiphon defrost circuit so as to be adjacent to the thermosiphon defrost circuit, and naturally circulates the CO.sub.2 refrigerant in the closed circuit at the time of defrosting.

An air source heat pump system includes at least one heat pump sub-system and at least one water tank. Each heat pump sub-system includes a refrigerant circulation path and a water supply circulation path. The refrigeration circulation path includes a compressor, a first heat exchanger, a first throttling device, and an evaporator that are sequentially connected to one another. The water supply circulation path includes a first supply pipe, a second supply pipe, a return pipe, and a waterway control valve. The first supply pipe and the second supply pipe are each communicated with an end of the first heat exchanger through the waterway control valve, and the return pipe is communicated with another end of the first heat exchanger. The return pipe is communicated with a water inlet of a corresponding water tank, and the second supply pipe is communicated with a water outlet of the corresponding water tank.

An air source heat pump system includes at least one heat pump sub-system and at least one water tank. Each heat pump sub-system includes a refrigerant circulation path and a water supply circulation path. The refrigeration circulation path includes a compressor, a first heat exchanger, a first throttling device, and an evaporator that are sequentially connected to one another. The water supply circulation path includes a first supply pipe, a second supply pipe, a return pipe, and a waterway control valve. The first supply pipe and the second supply pipe are each communicated with an end of the first heat exchanger through the waterway control valve, and the return pipe is communicated with another end of the first heat exchanger. The return pipe is communicated with a water inlet of a corresponding water tank, and the second supply pipe is communicated with a water outlet of the corresponding water tank.

A refrigeration system includes a dedicated defrost-mode compressor that delivers high pressure, high temperature refrigerant to one or more evaporators to defrost the evaporators.

A refrigeration system includes an expansion valve downstream of one or more medium temperature compressors. The expansion valve is configured to decrease pressure of a portion of refrigerant output by the one or more medium temperature compressors. When defrost operation of an evaporator is indicated, the refrigerant with decreased pressure from the expansion valve is provided to the evaporator for at least a period of time sufficient to defrost the evaporator.

An air conditioner and a control method thereof. The air conditioner includes an indoor unit including an indoor heat exchanger and an indoor fan, an outdoor unit connected to the indoor unit and including an outdoor heat exchanger, an outdoor fan, a compressor, an expansion valve, and a four-way valve, and at least one processor configured to perform a test operation by controlling the indoor unit and the outdoor unit. Based on an outdoor temperature being less than a predetermined reference temperature, the at least one processor is configured to determine whether the indoor unit and the outdoor unit operate normally, by continuously performing a heating operation and a defrosting operation during the test operation.

A system includes a flash tank, a first load, a second load, a first compressor, a second compressor, a first valve, and a second valve. The flash tank stores a refrigerant. The first and second loads use the refrigerant to cool first and second spaces. The first compressor compresses the refrigerant from the first load during a first mode of operation and a flash gas from the flash tank during a second mode of operation. The second compressor compresses a mixture of the refrigerant from the first and second loads during the first mode of operation. The first valve directs the flash gas from the flash tank to the first compressor during the second mode of operation. The second valve directs the compressed flash gas from the first compressor to the first load during the second mode of operation to defrost the first load.

Systems and methods have demonstrated the capability of rapidly cooling the contents of pods containing the ingredients for food and drinks.

A heat pump system and a control method therefor. The heat pump system includes a compressor; an indoor heal exchanger; an outdoor heat exchanger, including a first heat exchange portion and a second heat exchange portion, wherein a flow path switching device is provided between the first heat exchange portion and the second heat exchange portion to disconnect or communicate the first heat exchange portion and the second heat exchange portion; a first four-way valve; and a second four-way valve, configured to enable a high-temperature refrigerant to be input into the first heat exchange portion in a heating mode, so as to enable the heat pump system to operate in a heating and deicing mode.