An air-conditioning apparatus reduces occurrence of refrigerant accumulation on a downstream side of an evaporator to favorably circulate refrigerant. The air-conditioning apparatus includes: a main circuit in which a compressor, a refrigerant-flow switching device, a load-side heat exchanger, a load-side expansion device and three heat-source-side heat exchangers are connected by pipes to circulate refrigerant; and a heat-exchanger flow-passage switching device which performs switching to apply a first series refrigerant passage in the case where the three heat-source-side heat exchangers are used as condensers, and switching to apply a parallel refrigerant passage in the case where the three heat-source-side heat exchangers are used as evaporators. In the first series refrigerant passage, on an upstream side, the first and second heat-source-side heat exchangers are connected parallel to each other, and on a downstream side, the third heat-source-side heat exchanger is located. In the parallel refrigerant passage, first to third heat-source-side heat exchanger are connected parallel to each other.

A refrigerant flow path switching unit, disposed between a heat source unit and a utilization unit and that switches a refrigerant flow in the utilization unit, includes: a flow path switching valve; a case that houses the flow path switching valve; and an electric component box that houses an electric component that controls the flow path switching valve. At least two surfaces of the case include a box attachment part that is configured to attach the electric component box to the case.

An air conditioner may include a first compressor that compresses a refrigerant; a second compressor that compresses the refrigerant; an indoor heat exchanger that performs heat exchange between the refrigerant and air; a first four-way valve having a port connected to the first compressor; a first outdoor heat exchanger connected to a port of the first four-way valve; a first valve connected to a port of the first four-way valve; a second four-way valve having a port connected to the second compressor; a second outdoor heat exchanger connected to a port of the second four-way valve; a second valve connected to a port of the second four-way valve; a first valve pipe that connects a port of the first four-way valve and a port of the second four-way valve; a second valve pipe that connects the first valve and the second valve; and a third four-way valve having a port connected to the first valve pipe, a port connected to the second valve pipe, a port connected to the first compressor and the second compressor, and a port connected to the indoor heat exchanger.

A multi-air conditioner for heating and cooling may include at least one indoor unit, an outdoor unit, and at least one leak shut-off valve. The at least one indoor unit is installed in an indoor space and includes an indoor heat exchanger and an indoor expansion valve. The outdoor unit is connected to the at least one indoor unit via a refrigerant pipeline and includes an outdoor heat exchanger, a compressor, an outdoor expansion valve, and a four-way valve. The outdoor unit may decrease a pressure of the refrigerant pipeline when a refrigerant leak occurs from the refrigerant pipeline. The at least one leak shut-off valve is provided on the refrigerant pipeline and blocks a flow of refrigerant in the refrigerant pipeline when a refrigerant leak from the refrigerant pipeline occurs in the indoor space.

When performing dehumidification heating of a space to be air-conditioned, a refrigeration cycle device is switched to a refrigerant circuit in which a flow of a refrigerant flowing out of an interior radiator is branched, and one of the branched refrigerants is decompressed by an interior expansion valve to evaporate in an interior evaporator, while the other of the branched refrigerants flows into a high-pressure side refrigerant passage of an internal heat exchanger and is then decompressed by an exterior expansion valve to evaporate in an exterior heat exchanger. Further, in the refrigerant circuit, a flow of the refrigerant flowing out of the interior evaporator and a flow of the refrigerant flowing out of the exterior heat exchanger are merged into a low-pressure side refrigerant passage of the internal heat exchanger. Thus, the refrigerant flowing into the interior evaporator is prevented from becoming a liquid-phase refrigerant having an unnecessarily high degree of supercooling, thereby achieving appropriate dehumidification heating.

A dry-cooling system useful in absorbing heat from a heat source and related dry cooling methods including a depolymerization cooling unit (DCU) in fluid communication with a polymerization heating unit (PHU). The DCU includes a DCU heat exchanger which receives a polymer and a catalyst, wherein contact of the polymer and the catalyst within the DCU heat exchanger causes an endothermic reaction, converting the polymer to a monomer and drawing heat from a first heat source. The monomer is then withdrawn from the DCU. The PHU includes a PHU heat exchanger, which receives the monomer, wherein contact of the monomer with the catalyst causes an exothermic reaction within the PHU heat exchanger, converting the monomer to the polymer. The polymer is then withdrawn from the PHU for conveyance back to the DCU, and the cycle is repeated.

An air conditioner includes an outdoor unit including a compressor for compressing a refrigerant and an outdoor heat exchanger for exchanging heat between the refrigerant and outside air. A ventilation device is connected to the outdoor unit through a liquid refrigerant pipe, a high-pressure refrigerant pipe, and a low-pressure refrigerant pipe. The ventilation device supplies the outside air to an indoor space, and discharges indoor air to the outside. The ventilation device includes a case, a main heat exchanger, a recovery heat exchanger, a refrigerant distributor, and a re-heat heat exchanger. A liquid refrigerant pipe valve is disposed in the liquid refrigerant pipe for controlling an amount of refrigerant.

An air conditioning system includes a bypass passage and a cooling-heating switching mechanism. The bypass passage is configured to be at least a part of a flow passage connecting a third port to a refrigerant inlet of a compressor. A second expansion valve opens and closes the bypass passage. The cooling-heating switching mechanism includes check valves and four-way valves. The four-way valve causes a refrigerant outlet of the check valve to communicate with one of the refrigerant inlet and a refrigerant outlet of the compressor. The four-way valve causes a refrigerant inlet of the check valve to communicate with one of the refrigerant inlet and the refrigerant outlet of the compressor and causes a port to communicate with the other of the refrigerant inlet and the refrigerant outlet.

The air-conditioning apparatus includes: a refrigerant cycle circuit through which a heat source side refrigerant circulates; a plurality of heat medium cycle circuits through which a heat medium circulates, the plurality of heat medium cycle circuits including a plurality of use-side heat exchangers, the heat medium exchanging heat with the heat source side refrigerant of the refrigerant cycle circuit in intermediate heat exchangers; and a heat medium distribution device provided in one of the plurality of heat medium cycle circuits to which a plurality of the use-side heat exchangers are connected, the heat medium distribution device controlling flow rates of the heat medium of the plurality of use-side heat exchangers connected to the heat medium cycle circuit.

A heat pump performs a simultaneous air-conditioning and heating operation through the addition of a flow path switching apparatus. The heat pump may include a plurality of outdoor units, a plurality of indoor units, and a plurality of flow path switching apparatuses that switch a flow path between an outdoor unit and an indoor unit. A refrigerant flow path may be formed from the outdoor unit to the indoor unit via a high-pressure gas pipe. The flow path switching apparatuses may switch a flow path so that a refrigerant flow path is formed from the indoor unit to the outdoor unit via a low-pressure gas pipe. The heat pump may further include an indoor unit mode controller that is connected to the plurality of outdoor units through a liquid pipe, and which is connected to each of the plurality of flow path switching apparatuses.