An air conditioning system can be toggled between a heating mode, in which heat is withdrawn from a source (e.g., a geothermal source) and deposited into a conditioned space (e.g., a building), and a cooling mode, in which heat is withdrawn from the conditioned space and deposited into the source. The air conditioning system uses a combination of efficiency-enhancing technologies, including injection of superheated vapor into the system's compressor from an economizer circuit, adjustable compressor speed, the use of one or coaxial heat exchangers and the use of electronic expansion valves that are continuously adjustable from a fully closed to various open positions. A controller may be used to control the system for optimal performance in both the heating and cooling modes, such as by disabling the economizer circuit and vapor injection when the system is in the cooling mode.

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.

An air-conditioning apparatus includes a heat source unit, a plurality of indoor units, and a relay unit. The heat source unit includes a heat-source-side flow control valve connected to a heat-source-side heat exchanger, a bypass pipe connected in parallel to the heat-source-side heat exchanger, a bypass flow control valve provided in the bypass pipe, and a gas-liquid separating unit configured to, when refrigerant flows out to the high-pressure pipe, mix refrigerant in a liquid state flowing through the heat-source-side heat exchanger and refrigerant in a gas state flowing through the bypass pipe and cause mixed refrigerant to flow out to the high-pressure pipe, and configured to, when refrigerant flows in from the low-pressure pipe, separate the refrigerant flowing in from the low-pressure pipe into refrigerant in a liquid state flowing into the heat-source-side heat exchanger and refrigerant in a gas state flowing into the bypass pipe.

A refrigeration system comprises a variable speed compressor and a first evaporator. A second evaporator is operably coupled in series with the first evaporator. A first valve is coupled to the variable speed compressor and the first evaporator. A second valve is fluidly coupled to the second evaporator, and a pressure regulator is coupled to the second valve.

An air-conditioning apparatus includes heat-source-side units each including a compressor and a heat-source-side heat exchanger, a load-side heat exchanger and a load-side expansion device, a first header, a second header, bypass expansion devices, circuit switching units, discharge pressure sensors, bypass pressure sensors, and a controller configured to control, in a heat-source-side unit in defrosting mode, the circuit switching unit in such a manner that a portion of refrigerant discharged from the compressor flows into the heat-source-side heat exchanger and configured to control, in the heat-source-side unit in defrosting mode, an opening degree of the bypass expansion device in the heat-source-side unit in such a manner that a value representing a difference between a value obtained by the discharge pressure sensor and a value obtained by the bypass pressure sensor is equal to or greater than a predetermined value.

A refrigeration system comprises a variable speed compressor and a first evaporator. A second evaporator is operably coupled in series with the first evaporator. A first valve is coupled to the variable speed compressor and the first evaporator. A second valve is fluidly coupled to the second evaporator, and a pressure regulator is coupled to the second valve.

An air conditioning system can be toggled between a heating mode, in which heat is withdrawn from a source (e.g., a geothermal source) and deposited into a conditioned space (e.g., a building), and a cooling mode, in which heat is withdrawn from the conditioned space and deposited into the source. The air conditioning system uses a combination of efficiency-enhancing technologies, including injection of superheated vapor into the system's compressor from an economizer circuit, adjustable compressor speed, the use of one or coaxial heat exchangers and the use of electronic expansion valves that are continuously adjustable from a fully closed to various open positions. A controller may be used to control the system for optimal performance in both the heating and cooling modes, such as by disabling the economizer circuit and vapor injection when the system is in the cooling mode.

An air conditioner may include a case through which outdoor air flows into an indoor space is formed; a first heat exchanger that exchanges heat between the air and refrigerant; a second heat exchanger disposed downstream of the first heat exchanger, through which the refrigerant selectively flows, and that exchanges heat between the air and the refrigerant; a liquid pipe connected to each of the first and second heat exchangers; a high-pressure gas pipe connected to each of the first and second heat exchangers; a low-pressure gas pipe through which the gaseous refrigerant discharged from the first and second heat exchangers flows; a high-pressure gas pipe valve; a low-pressure gas pipe valve; an expansion valve installed in the liquid pipe; and a controller configured to control an opening degree of the low-pressure gas pipe valve, based on a temperature of the refrigerant flowing through the first heat exchanger.

An air-conditioning apparatus includes a primary-side circuit in which a compressor, a first flow switching device, an outdoor heat exchanger, a second flow switching device, a first expansion device, and a relay heat exchanger are connected by pipes and in which refrigerant circulates; a secondary-side circuit in which the relay heat exchanger, a pump, a plurality of indoor heat exchangers, and heat medium flow control devices are connected by pipes and in which a heat medium circulates; and a controller configured to control the first and second flow switching devices such that in cooling and heating operations, the refrigerant and a heat-source-side fluid flow through the outdoor heat exchanger in opposite directions and the refrigerant flows through the relay heat exchanger in a constant direction. The pump is installed such that the heat medium, the refrigerant flow, and air for an air-conditioning target space flow in particular directions.

A two-stage refrigeration apparatus (500) includes a first cycle (510) and a second cycle (520). The first cycle (510) includes a first compressor (511), a first condenser (512), a first expansion mechanism (513), and a first evaporator (514) that are arranged in such a manner as to be connected to the first cycle. A first refrigerant circulates through the first cycle. The second cycle (520) includes a second downstream-side condenser (523) and a second evaporator (527) that are arranged in such a manner as to be connected to the second cycle. A second refrigerant circulates through the second cycle. The first evaporator (514) and the second downstream-side condenser (523) constitute a cascade condenser (531). In the cascade condenser (531), heat is exchanged between the first refrigerant and the second refrigerant. At least one of the first refrigerant and the second refrigerant is a refrigerant mixture containing at least 1,2-difluoroethylene (HFO-1132(E)).