Abstract: A header includes a plurality of branch tubes and a header manifold. If refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold pass through a liquid-phase portion having a thickness ? [m] and reach a gas-phase portion. The thickness ? [m] of the liquid-phase portion is defined as ?=G×(1?x)×D/(4?L×ULS), where G is a flow speed [kg/(m2 s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ?L is a liquid density [kg/m3] of the refrigerant, ULS is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into a flow space of the header manifold. The reference apparent liquid speed ULS [m/s] is defined as G(1?x)/?L.

Abstract: An outdoor unit according to the present disclosure includes: a compressor that sucks refrigerant, compresses the sucked refrigerant, and discharges the compressed refrigerant; a first refrigerant flow switching device that switches a flow passage for the refrigerant between a flow passage for a cooling operation and a flow passage for a heating operation; a heat-source-side heat exchanger that causes heat exchange to be performed between the refrigerant and external fluid; a heat-source-side backflow prevention device and a connection pipe that are included in a flow passage for the refrigerant in which an outlet from which the refrigerant flows to an outside region and an inlet into which the refrigerant flows from the outside region are unchanged regardless of which of the cooling operation and the heating operation is performed; and a flow passage pipe through which part of the refrigerant having flowed from the inlet passes in the cooling operation.

Abstract: An air-conditioning apparatus includes an outdoor unit and a relay unit. The outdoor unit includes a compressor compressing and discharging refrigerant and a heat-source-side heat exchanger performing heat exchange between the refrigerant and outside air. The relay unit and the outdoor unit form a refrigerant circuit. The outdoor unit includes first and flow switching devices each switching an associated flow passage for the refrigerant between a plurality of flow passages, according to an operation mode. An outflow pipe and an inflow pipe through which refrigerant flows from the outdoor unit to the relay unit and from the relay unit into the outdoor unit, respectively, are between the outdoor unit and the relay unit. The first flow switching device is connected to the compressor, the second flow switching device, and the outflow pipe. The second flow switching device is connected to the first flow switching device and the inflow pipe.

Abstract: A heat exchanger includes a plurality of heat transfer tubes, a liquid header distributor, and a gas header distributor. The heat transfer tubes include U-shaped bent portions. The heat exchanger includes a heat exchanger core. A relationship between the liquid header distributor and the plurality of heat transfer tubes is established such that 9?? is satisfied, where Lh [m] is the length of the liquid header distributor, Lb [m] is the length of the shortest one of the heat transfer tubes, and ? is the ratio of the length Lb of the shortest heat transfer tube to the length Lh of the liquid header distributor and is expressed by ?=Lb/Lh.

Abstract: A heat exchanger includes first and second headers connected to end portions of heat transfer tubes. The second header includes a header pipe defining a flow space that communicates with the heat transfer tubes and, when the heat exchanger acts as an evaporator, allows refrigerant in a two-phase gas-liquid state to pass through the flow space into the heat transfer tubes. A bypass pipe is disposed between an entrance portion and the first header. The entrance portion has an entrance distance L between a connection end portion connected to a refrigerant pipe and a central axis of the bypass pipe. The entrance distance L of the entrance portion satisfies L?5di, where di is an inner diameter of a flow space of the header pipe on an orthogonal plane orthogonal to a direction of refrigerant flow. The bypass pipe is inserted in the flow space of the entrance portion.

Abstract: A header includes a plurality of branch tubes and a header manifold. If refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold pass through a liquid-phase portion having a thickness ? [m] and reach a gas-phase portion. The thickness ? [m] of the liquid-phase portion is defined as ?=G×(1?x)×D/(4?L×ULS), where G is a flow speed [kg/(m2s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ?L is a liquid density [kg/m3] of the refrigerant, ULS is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into a flow space of the header manifold. The reference apparent liquid speed ULS [m/s] is defined as G(1?x)/?L.

Abstract: An air-conditioning apparatus includes a refrigerant circuit in which an outdoor unit, at least one load-side expansion device, and at least one load-side heat exchanger are connected by pipes to allow refrigerant to circulate. The outdoor unit includes a compressor including an injection port allowing the refrigerant to flow into a suction chamber, a heat-source-side heat exchanger for heat exchange for the refrigerant, and an accumulator. The load-side heat exchanger transfers heat between a load and the refrigerant.

Abstract: A heat exchanger group includes a first heat exchanger, a second heat exchanger, and a third heat exchanger. In a cooling operation, refrigerant discharged from the compressor is divided into two. One refrigerant is delivered to the second heat exchanger, and the other refrigerant is delivered to the third heat exchanger. The second heat exchanger performs heat exchange to turn the refrigerant into two-phase refrigerant. The third heat exchanger performs heat exchange to turn the refrigerant into two-phase refrigerant. The refrigerant that has flowed through the second heat exchanger and the refrigerant that has flowed through the third heat exchanger meet, and the resultant refrigerant is delivered to the first heat exchanger. The first heat exchanger performs heat exchange, so that the two-phase refrigerant turns into liquid refrigerant and flows through the first heat exchanger.

Abstract: An air-conditioning apparatus includes a refrigerant circuit in which pipes sequentially connect a compressor, a flow switching device, a heat source side heat exchanger, an expansion device, a load side heat exchanger, and the flow switching device, and configured to perform a cooling operation and a heating operation switched by the flow switching device, an oil separator configured to separate refrigerating machine oil from refrigerant discharged from the compressor, a first bypass passage in which fluid flowing out of the oil separator flows, an auxiliary heat exchanger configured to cool the fluid, a first flow control device configured to control passing of the fluid, a second bypass passage in which liquid refrigerant or two-phase gas-liquid refrigerant flowing through one of the pipes connecting the heat source side heat exchanger and the expansion device flows, and a second flow control device configured to control passing of refrigerant.

Abstract: An air-conditioning apparatus is capable of performing a heating-defrosting operation where a specific one of a plurality of parallel heat exchangers is a heat exchanger to be defrosted and serves as a condenser while at least one parallel heat exchanger other than the heat exchanger to be defrosted serves as an evaporator. The air-conditioning apparatus includes a liquid refrigerant transporting unit for transferring liquid refrigerant from an accumulator to the heat exchanger to be defrosted. To perform the heating-defrosting operation, the air-conditioning apparatus supplies, to the heat exchanger to be defrosted, the liquid refrigerant transferred by the liquid refrigerant transporting unit.

Abstract: An 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 a plurality of heat source side heat exchangers are sequentially connected. When the plurality of heat source side heat exchangers are used as condensers, the first heat source side heat exchanger and the second heat source side heat exchanger are connected in series. When the plurality of heat source side heat exchangers are used as evaporators, the first heat source side heat exchanger and the second heat source side heat exchanger are connected in parallel. A distribution adjustment header on an inlet side of at least either the first heat source side heat exchanger or the second heat source side heat exchanger when the plurality of heat source side heat exchangers are used as evaporators.

Abstract: A heat exchanger includes a plurality of heat transfer tubes, a first header, a second header, and a plurality of fins. The heat exchanger constitutes a portion of a refrigeration cycle circuit in which refrigerant circulates. The second header includes a header pipe. The header pipe has an entrance portion. A bypass pipe is disposed between the entrance portion and the first header and configured to bypass refrigerant. The bypass pipe protrudes into the header pipe to be connected to the header pipe. The bypass pipe is provided with a flow control mechanism configured to control a flow rate of refrigerant.

Abstract: An air-conditioning apparatus is capable of efficiently performing defrosting operation without suspending a heating operation of an indoor unit. The air-conditioning apparatus includes a main circuit sequentially connecting, via a pipe, a compressor, indoor heat exchangers, first flow control devices, and a plurality of parallel heat exchangers connected in parallel to each other to allow refrigerant to circulate, first defrost pipes branching a part of the refrigerant discharged from the compressor and causing the part of the refrigerant to flow into one of the plurality of parallel heat exchangers to be defrosted, an interface heat exchanger located between the plurality of parallel heat exchangers, a first bypass pipe branching a part of the refrigerant discharged from the compressor and causing the part of the refrigerant to flow into the interface heat exchanger, and a second bypass pipe causing the part of the refrigerant flowing out of the interface heat exchanger to flow into the main circuit.

Abstract: An air-conditioning apparatus includes a selection unit and a determination unit, the selection unit selecting a reverse-defrosting operation mode or a heating-defrosting simultaneous operation mode, the reverse-defrosting operation mode being a mode in which all of parallel heat exchangers are defrosted by stopping a heating operation, the heating-defrosting simultaneous operation mode being a mode in which each parallel heat exchanger is sequentially defrosted while continuing a heating operation, the determination unit determining whether or not a defrosting operation is to be started, in which the determination unit is configured to start the defrosting operation in a state where the amount of frost deposited on the parallel heat exchangers is smaller in a case where the heating-defrosting simultaneous operation mode is selected than in a case where the reverse-defrosting operation is selected.

Abstract: An air-conditioning apparatus includes a refrigeration cycle circulating refrigerant and connecting a compressor, a heat-source-side heat exchanger, one or more of load-side expansion devices, and one or more of load-side heat exchangers by refrigerant pipes, a bypass having one end connected to a discharge side of the compressor of the refrigeration cycle and the other end connected to a suction side of the compressor of the refrigeration cycle to bypass a portion of the refrigerant discharged from the compressor, a first expansion device depressurizing the refrigerant flowing through the bypass, an auxiliary heat exchanger cooling the refrigerant depressurized at the first expansion device, a second expansion device controlling a flow rate of the refrigerant flowing from the auxiliary heat exchanger to the suction side of the compressor, and a controller controlling an opening degree of the second expansion device.

Abstract: An air-conditioning apparatus includes: a compressor allowing refrigerant injection thereto and compress and discharge the refrigerant at a high temperature; an indoor heat exchanger exchanging heat between air and refrigerant; a first flow rate control device adjusting and controlling a flow rate of refrigerant; and a plurality of outdoor heat exchangers being in parallel to exchange heat between outside air and refrigerant, a first defrosting pipe allowing a branched part of the refrigerant discharged from the compressor to pass and flow into the outdoor heat exchanger to be defrosted; a reducing device adjusting a pressure of refrigerant passing through the first defrosting pipe to a medium pressure; a second defrosting pipe from which the refrigerant having passed through the outdoor heat exchanger to be defrosted is injected into the compressor; and a reducing device adjusting a pressure of refrigerant passing through the second defrosting pipe to an injection pressure.

Abstract: A header includes a plurality of branch tubes and a header manifold. If refrigerant flowing into the header manifold forms a pattern of annular flow or churn flow, tips of the branch tubes inserted into the header manifold pass through a liquid-phase portion having a thickness ? [m] and reach a gas-phase portion. The thickness ? [m] of the liquid-phase portion is defined as ?=G×(1?x)×D/(4?L×ULS), where G is a flow speed [kg/(m2s)] of the refrigerant, x is a quality of the refrigerant, D is an inside diameter [m] of the header manifold, ?L is a liquid density [kg/m3] of the refrigerant, ULS is a reference apparent liquid speed [m/s] that is a maximum value within a range of variation in an apparent gas speed of the refrigerant flowing into a flow space of the header manifold. The reference apparent liquid speed ULS [m/s] is defined as G(1?x)/?L.

Abstract: An 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 a plurality of heat source side heat exchangers are sequentially connected. When the plurality of heat source side heat exchangers are used as condensers, the first heat source side heat exchanger and the second heat source side heat exchanger are connected in series. When the plurality of heat source side heat exchangers are used as evaporators, the first heat source side heat exchanger and the second heat source side heat exchanger are connected in parallel. A distribution adjustment header on an inlet side of at least either the first heat source side heat exchanger or the second heat source side heat exchanger when the plurality of heat source side heat exchangers are used as evaporators.

Abstract: A heat exchanger group includes a first heat exchanger, a second heat exchanger, and a third heat exchanger. In a cooling operation, refrigerant discharged from the compressor is divided into two. One refrigerant is delivered to the second heat exchanger, and the other refrigerant is delivered to the third heat exchanger. The second heat exchanger performs heat exchange to turn the refrigerant into two-phase refrigerant. The third heat exchanger performs heat exchange to turn the refrigerant into two-phase refrigerant. The refrigerant that has flowed through the second heat exchanger and the refrigerant that has flowed through the third heat exchanger meet, and the resultant refrigerant is delivered to the first heat exchanger. The first heat exchanger performs heat exchange, so that the two-phase refrigerant turns into liquid refrigerant and flows through the first heat exchanger.