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.

A refrigeration system operable in cooling mode and defrosting mode is provided. The refrigeration system includes a defrost line connecting a first reservoir to an evaporation stage for conveying at least part of the flash gas from the first reservoir to the evaporation stage when the refrigeration system is operating in defrosting mode. The flash gas thereby releases heat in the evaporation stage for defrosting the evaporation stage. The refrigeration system can also include a discharge line connecting the evaporation stage to a second reservoir.

A defrost system includes: a cooling device in a freezer, and includes a casing, a heat exchanger pipe with a difference in elevation in the casing, and a drain receiver unit below the heat exchanger pipe; a refrigerating device to cool and liquefy CO.sub.2 refrigerant; and a refrigerant circuit for permitting the cooled and liquefied CO.sub.2 refrigerant to circulate to the heat exchanger pipe. The defrost system includes a bypass pipe of the heat exchanger pipe to form a CO.sub.2 circulation path; an on-off valve in the heat exchanger pipe to be closed during defrosting so that the CO.sub.2 circulation path is a closed circuit; a pressure adjusting unit for adjusting pressure of the CO.sub.2 refrigerant during defrosting; and a brine circuit as a first heating medium, in which the defrost system permits the CO.sub.2 refrigerant to naturally circulate in the closed circuit during defrosting by a thermosiphon effect.

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.

Disclosed are a refrigerator cooling system and a method for defrosting a refrigerator. The refrigerator cooling system includes a refrigerant circulation flow path provided with a compressor, a condenser, a throttling device and an evaporator. The throttling device has a throttling working mode for cooling and a defrosting working mode not used for cooling. The throttling working mode and the defrosting working mode are switched with each other. The condenser has a first heat release mode corresponding to the throttling working mode and a second heat release mode corresponding to the defrosting working mode, and a heat release amount of a refrigerant flowing through the condenser in the second heat release mode is lower than a heat release amount of the refrigerant flowing through the condenser in the first heat release mode.

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.

A heat pump air conditioning system and a control method. The heat pump air conditioning system includes: a compressor; an indoor unit heat exchanger, an outdoor unit heat exchanger and a throttling device; a refrigerant circulation loop, connecting the compressor, the indoor unit heat exchanger, the outdoor unit heat exchanger and the throttling device in series; the heat storage module, disposed in the refrigerant circulation loop and configured to absorb heat from refrigerant in the refrigerant circulation loop and store heat when heat storage is required, and to heat the refrigerant in the refrigerant circulation loop when the outdoor unit heat exchanger defrosting is required. The heat pump air conditioning system can store excess heat of the system for defrosting when indoor heat load is low, and release heat for defrosting by means of the heat storage module during a defrosting process while continuing supplying heat to a room.

A heat pump air conditioning system and a control method. The heat pump air conditioning system includes: a compressor; an indoor unit heat exchanger, an outdoor unit heat exchanger and a throttling device; a refrigerant circulation loop, connecting the compressor, the indoor unit heat exchanger, the outdoor unit heat exchanger and the throttling device in series; the heat storage module, disposed in the refrigerant circulation loop and configured to absorb heat from refrigerant in the refrigerant circulation loop and store heat when heat storage is required, and to heat the refrigerant in the refrigerant circulation loop when the outdoor unit heat exchanger defrosting is required. The heat pump air conditioning system can store excess heat of the system for defrosting when indoor heat load is low, and release heat for defrosting by means of the heat storage module during a defrosting process while continuing supplying heat to a room.

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.

A refrigeration system operable in cooling mode and defrosting mode is provided. The refrigeration system includes a defrost line connecting a first reservoir to an evaporation stage for conveying at least part of the flash gas from the first reservoir to the evaporation stage when the refrigeration system is operating in defrosting mode. The flash gas thereby releases heat in the evaporation stage for defrosting the evaporation stage. The refrigeration system can also include a discharge line connecting the evaporation stage to a second reservoir.