The air-conditioning apparatus includes the plurality of heat source apparatuses; a plurality of indoor units each including an indoor heat exchanger and each configured to perform one of cooling and heating operations; a relay device connected to the heat source apparatuses by a high pressure pipe and a low pressure pipe and configured to distribute refrigerant flowing therein from the heat source apparatuses to the plurality of indoor units; and a controller configured to control operations of the heat source apparatuses. The relay device includes a relay device temperature detecting unit configured to detect a temperature of the refrigerant flowing through the bypass pipe. During the heating main operation, the controller changes an opening degree of each of the outdoor side expansion devices based on the temperature detected by the relay device temperature detecting unit.

A heat pump system includes a first unit; a second unit connected to a first flow path of the first unit; and a third unit connected to a second flow path of the first unit and connected to the second unit. The heat pump system can operate in a cooling and water heating mode and a heating and water heating mode, wherein, in the cooling and water heating mode, the heat pump system is configured to switch a switching assembly to a first position and connect the at least one first heat exchangers and the second heat exchanger in series; in the heating and water heating mode, the heat pump system is configured to switch the switching assembly to a second position and connect the second heat exchanger and the at least one third heat exchangers in parallel.

A refrigeration cycle apparatus includes a main circuit through which refrigerant circulates and in which a compressor, a condenser, a first expansion device, a centrifugal gas-liquid separator that separates refrigerant into gas refrigerant and liquid refrigerant by using centrifugal force, and an evaporator are connected by refrigerant pipes; and a bypass that returns the gas refrigerant obtained through the separation by the gas-liquid separator to a suction side of the compressor. The gas-liquid separator includes a cylindrical container, an inflow pipe, a gas outflow pipe, and a liquid outflow pipe. The main circuit includes a second expansion device provided between the liquid outflow pipe of the gas-liquid separator and the evaporator. The gas refrigerant discharged from the gas outflow pipe of the gas-liquid separator flows into the bypass, and the bypass is provided with a third expansion device.

Provided is an air conditioning apparatus. The air conditioning apparatus includes an outdoor unit through which a refrigerant is circulated, an indoor unit through which water is circulated, and a heat exchange device including a heat exchanger in which the refrigerant and the water are heat-exchanged with each other. The heat exchanger includes a high-pressure guide tube, a low-pressure guide tube, a liquid guide tube, a bypass tube configured to connect a bypass branch point of the high-pressure gas tube of the outdoor unit to a bypass combination point of the liquid guide tube to bypass a high-pressure refrigerant existing in the high-pressure tube to the liquid guide tube, and a bypass valve installed in the bypass tube. The outdoor unit includes a first valve device configured to guide a refrigerant compressed in the compressor to the outdoor heat exchanger and a second valve device configured to guide the refrigerant compressed in the compressor to the high-pressure guide tube of the heat exchange device.

Proposed a gas heat-pump system including: a compressor compressing refrigerant and discharging the compressed refrigerant; an engine providing a drive force to the compressor; a radiator that cools coolant which is heated while passing through the engine; an indoor heat exchanger causing heat exchange to occur between indoor air and the refrigerant and thus cooling or heating an indoor space; an outdoor heat exchanger condensing the refrigerant; a four-way valve switching a flow direction of the refrigerant in such a manner that the refrigerant discharged from the compressor flows to the outdoor heat exchanger in a cooling operation mode and flows to the indoor heat exchanger in a heating operation mode; and a hot-water storage tank causing the heat exchange to occur between stored water and the refrigerant, and thus cooling the refrigerant in the cooling operation mode and heating the refrigerant in the heating operation mode.

An air conditioner includes a refrigeration cycle in which a first compressor and a second compressor are connected in parallel, and the first compressor, the second compressor, a first outdoor heat exchanger, a second outdoor heat exchanger, a first indoor heat exchanger, a second indoor heat exchanger, and expansion valves are connected. When the air conditioning apparatus is operated in a first operation mode in which the second outdoor heat exchanger and the first indoor heat exchanger are operated as condensers and the second indoor heat exchanger is operated as an evaporator, refrigerant discharged from the first compressor flows through the first indoor heat exchanger, the expansion valves, and the second indoor heat exchanger in order while bypassing the first outdoor heat exchanger and the second outdoor heat exchanger.

An air-conditioning apparatus includes a refrigerant circuit in which a compressor, a condenser, an expansion unit, and an evaporator are connected by a pipe and through which a working fluid obtained by adding a stabilizer to a refrigerant mixture containing CF.sub.3I flows. The pipe includes a riser gas pipe erected and extending from an outlet of the evaporator to an inlet of the condenser via the compressor. An inner diameter of the riser gas pipe is smaller than or equal to an upper-limit threshold value.

A refrigeration cycle apparatus includes a main circuit through which refrigerant circulates and in which a compressor, a condenser, a first expansion device, a centrifugal gas-liquid separator that separates refrigerant into gas refrigerant and liquid refrigerant by using centrifugal force, and an evaporator are connected by refrigerant pipes; and a bypass that returns the gas refrigerant obtained through the separation by the gas-liquid separator to a suction side of the compressor. The gas-liquid separator includes a cylindrical container, an inflow pipe, a gas outflow pipe, and a liquid outflow pipe. The main circuit includes a second expansion device provided between the liquid outflow pipe of the gas-liquid separator and the evaporator. The gas refrigerant discharged from the gas outflow pipe of the gas-liquid separator flows into the bypass, and the bypass is provided with a third expansion device.

The air-conditioning apparatus includes the plurality of heat source apparatuses; a plurality of indoor units each including an indoor heat exchanger and each configured to perform one of cooling and heating operations; a relay device connected to the heat source apparatuses by a high pressure pipe and a low pressure pipe and configured to distribute refrigerant flowing therein from the heat source apparatuses to the plurality of indoor units; and a controller configured to control operations of the heat source apparatuses. The relay device includes a relay device temperature detecting unit configured to detect a temperature of the refrigerant flowing through the bypass pipe. During the heating main operation, the controller changes an opening degree of each of the outdoor side expansion devices based on the temperature detected by the relay device temperature detecting unit.

A heat pump system includes a first air-conditioning apparatus, a ventilator, and a refrigerant circuit. The first air-conditioning apparatus includes a compressor, an outdoor-side heat exchanger, an expansion device, and an indoor-side heat exchanger, and air-conditions a first space. The ventilator includes a first auxiliary heat exchanger, and ventilates and air-conditions a second space different from the first space. In the refrigerant circuit, the compressor, the outdoor-side heat exchanger, the first auxiliary heat exchanger, the expansion device, and the indoor-side heat exchanger are sequentially connected by a refrigerant pipe to allow refrigerant to circulate. The first auxiliary heat exchanger is provided in a supply air passage in the ventilator.