During heat applying operation, both an air-source heat exchanger that exchanges heat with the atmosphere as a heat source and an earth-source heat exchanger that uses geothermal heat as a heat source serve as evaporators to collect heat from the atmosphere and the geothermal heat. During defrosting operation, while a four-way valve is switched to cause the air-source heat exchanger to serve as a radiator, and the earth-source heat exchanger to serve as an evaporator to collect the geothermal heat, and the collected geothermal heat is collected in the main circuit via the sub-circuit.

A heat exchanger includes a plurality of heat exchange units each including a plurality of flat tubes, a plurality of fins, an upper header, and a lower header. In the plurality of heat exchange units, the upper headers are connected such that the upper headers communicate with each other, and the lower headers are connected such that the lower headers communicate with each other through an opening-closing valve. The heat exchanger has a configuration in which when the heat exchanger serves as a condenser, the opening-closing valve is controlled such that refrigerant in at least one of the plurality of heat exchange units flows in an upward direction, and refrigerant in the other one or the other ones of the plurality of heat exchange units flows in a downward direction.

An air-conditioning apparatus includes a refrigerant circuit and a controller. The refrigerant circuit includes a main circuit and a bypass circuit. The bypass circuit is connected, by a pipe, to each of a plurality of parallel outdoor heat exchangers via a defrosting refrigerant pressure-reducing device, a defrosting flow passage switching device, and a backflow prevention device. The controller switches a flow passage for use in introduction of refrigerant using the defrosting flow passage switching device, to select one of the plurality of parallel outdoor heat exchangers as a defrosting target to be defrosted; and supplies defrosting refrigerant whose pressure is reduced by the defrosting refrigerant pressure-reducing device to the selected one of the plurality of parallel outdoor heat exchangers.

An outdoor unit of an air-conditioner and two-pipe and three-pipe air-conditioning systems having the same are provided. The outdoor unit includes a compressor defining an outlet and an inlet; a first four-way valve defining a first valve communicated with the outlet, second and third ports communicated with the inlet; a second four-way valve defining second and third ports communicated with the inlet; an outdoor heat exchanger defining a first refrigerant valve Communicated with the fourth port of the first four-way valve; a first gas pipe defining a first end connected with the second and third ports of the first and second four-way valves and, the inlet; a second gas pipe defining a first end connected with the fourth port of the second four-way valve; a third gas pipe defining a first end connected with the outlet and a second end connected with the first port of the second four-way valve.

A multiple-evaporation cooling system in which the intermediate heat exchanger of first evaporation line includes at least a segment of the physically arranged expansion device in contact with at least a portion of the second row of evaporation and the intermediate heat exchanger's second evaporative line includes at least one expansion device segment physically disposed in contact with at least one portion of a first evaporation line. Considering the temperature of the intermediate heat exchanger of first evaporation line influences the temperature of the refrigerant flowing in the second line of evaporative expansion device and the temperature of the intermediate heat exchanger of the second evaporative line influences the temperature of the refrigerant flowing in the first line of evaporative expansion device. Features include varying the restriction of the respective expansion devices and then unduly inhibit mass transfer of refrigerant between at least two distinct evaporation.