An outdoor unit for a heat pump includes a refrigerant circuit, the outdoor unit including a compressor, a discharge pipe of the refrigerant circuit connected to a discharge side of the compressor, a bottom plate, the bottom plate having a base and an outer flange protruding upward from an outer edge of the base, a heat source heat exchanger supported on the bottom plate, a liquid refrigerant pipe of the refrigerant circuit connected to the heat source heat exchanger, and a defrosting bypass pipe connected at one end to the discharge pipe and at the opposite end to the liquid refrigerant pipe, the defrosting bypass pipe being arranged between an inner side of the flange and an outer side of the heat source heat exchanger.

A passive heat recovery or defrosting apparatus features an evaporator, a condenser, and vapour and liquid conveyance lines connected therebetween. The vapour and liquid conveyance lines respectively connect to upper and lower ends of the evaporator and condenser. The evaporator and/or condenser has a ring-shaped body for fitting around or inline with a pipe to achieve heat exchange relation with a fluid passing therethrough. The evaporator is installed on or inside a warm pipe or duct (e.g. waste drain pipe, clothes dryer exhaust duct, flue pipe, or indoor section of a sewer vent stack) at a lower elevation than the condenser. The condenser is placed on an outdoor end of either a sewer stack or air intake duct for defrosting purposes, or is placed on a water supply line or air intake of a hot water tank, clothes dryer, etc. Working fluid circulates passively between the evaporator and condenser.

A refrigeration system includes a first compressor system, a second compressor system, a first conduit, a heat exchanger, a second conduit, and a third conduit. The first compressor system includes a plurality of first compressors. The second compressor system includes a plurality of second compressors. The first conduit is configured to provide refrigerant from the first compressor system to the second compressor system. The second conduit is fluidly coupled to the first conduit and configured to provide the refrigerant from the first compressor system to the heat exchanger. The third conduit is configured to provide the refrigerant from the second compressor system to the heat exchanger.

An outdoor unit control unit 200 has a defrosting operation condition table 300a that defines a defrosting operation interval time Tm in accordance with a total sum of rated capacity of indoor units 5a to 5c and a refrigerant pipe length as lengths of a liquid pipe 8 and a gas pipe 9. The outdoor unit control unit 200 uses the total sum of the rated capacity of indoor units 5a to 5c input by using an installation information input unit 250 and refers to the defrosting operation condition table 300a, so as to determine the defrosting operation interval time Tm. Then, the outdoor unit control unit 200 forcibly performs a defrosting operation when the defrosting operation interval time Tm elapses without establishment of a defrosting operation start condition since the last defrosting operation is terminated.

If an exterior heat exchanger is sensed to be frosted while a heat pump device is operating in a first heating operation mode in which two interior heat exchangers are used, the operation modes are switched into a second heating operation mode in which one interior heat exchanger is used, and then switched into a defrosting operation mode.

A refrigerating cycle apparatus includes: a compressor that compresses and discharges refrigerant; a radiator that makes the refrigerant discharged out of the compressor to radiate heat; a pressure reducing device that decompresses the refrigerant flowing out of the radiator; an evaporator that evaporates the refrigerant decompressed by the pressure reducing device; and a decompression control part that controls operation of the pressure reducing device. The decompression control part controls the operation of the pressure reducing device in a manner that a physical quantity which has correlation with a pressure of the refrigerant in the evaporator approaches a predetermined defrosting standard value when a time-priority defrosting mode is set.

A refrigerator and a control method, device and system thereof are included. The method includes detecting and confirming that the cumulative running time of a compressor is no less than a running time threshold, and an ice maker is currently in a working state, and controlling the ice maker to perform a defrosting operation after a current ice making period is ended, the running time threshold being a time difference between the defrosting period of the refrigerator and the ice making period of the ice maker.

An absorption heat pump having a generator, a heat source to heat the generator to drive coolant vapor out of solution, a condenser for cooling the coolant vapor and an expansion valve that expand the coolant fluid as well as an evaporator for at least partial evaporation of the expanded coolant fluid against a medium which is connected to at least one absorber which absorbs the expanded coolant fluid. A hot gas line which branches off from a line for coolant vapor upstream of the condenser and is fluid-connected to the evaporator such that it bypasses the condenser and the expansion valve, a defrosting valve being provided in the hot gas line, by means of which the flow of coolant vapor through the hot gas line can be controlled. The absorption heat pump is operated in a cyclic circulation process.

A refrigerating and air-conditioning apparatus performs a defrosting operation. The refrigerating and air-conditioning apparatus includes a refrigerant circuit, a temperature sensor, and a heat generation control unit. In the refrigerant circuit, a compressor, a first heat exchanger, an expansion device, a second heat exchanger, and a four-way valve are connected to each other by pipes to allow refrigerant to circulate through the refrigerant circuit. The temperature sensor measures a temperature of the compressor. The heat generation control unit increases a temperature of the compressor when the heat generation control unit detects a decrease in a value measured by the temperature sensor in a defrosting operation performed on the first heat exchanger.

A method includes measuring a saturated suction temperature, receiving actual temperature value reflective of the measured saturated suction temperature, and determining whether the actual temperature value is less than a first pre-determined minimum threshold temperature value. If the actual temperature value is less than the first pre-determined minimum threshold temperature value, initiating a timer to operate for a pre-determined time interval. Determining whether the actual temperature value is less than a second pre-determined minimum threshold temperature value and if the actual temperature value is less the second pre-determined minimum threshold temperature value, initiating the timer to operate for a modified time interval. If the timer has expired, the operation of the compressor is modified.