A multi-channel heat exchanger includes a plurality of heat exchange tubes, each heat exchange tube includes first to fourth heat exchange tube portions which are distributed along a direction from an airflow inlet side to an airflow outlet side. Each heat exchange tube portion includes at least two flow channels. The heat exchange tube has a cross section defined in a thickness direction and a width direction of the heat exchange tubes, and the cross section includes a flow section. A total area of a flow section of the first heat exchange tube portion is A1, a total area of a flow section of the fourth heat exchange tube portion is A4, and the total area A1 of the flow section of the first heat exchange tube portion is 1.05-1.4 times of the total area A4 of the flow section of the fourth heat exchange tube portion.

A heat exchanger includes: a header that extends in a horizontal direction; and heat transfer tubes that extends in a direction crossing the horizontal direction, that are disposed side by side in a longitudinal direction of the header, and that are connected to the header. The header includes a first space that causes a refrigerant to flow in a first direction along the longitudinal direction of the header, a second space that causes the refrigerant to flow in a second direction along the longitudinal direction of the header and opposite to the first direction, a circulation member extends in the longitudinal direction of the header and separates the first space from the second space, a first communication port, a second communication port, and an inflow port.

A heat exchanger includes: a header that extends in a horizontal direction; and heat transfer tubes that extends in a direction crossing the horizontal direction, that are disposed side by side in a longitudinal direction of the header, and that are connected to the header. The header includes a first space that causes a refrigerant to flow in a first direction along the longitudinal direction of the header, a second space that causes the refrigerant to flow in a second direction along the longitudinal direction of the header and opposite to the first direction, a circulation member extends in the longitudinal direction of the header and separates the first space from the second space, a first communication port, a second communication port, and an inflow port.

The disclosed technology includes systems and methods for controlling an air conditioning system. The method of controlling the air conditioning system can include receiving air temperature data from an air temperature sensor and determining that the air conditioning system should operate in a reheat mode based on the air temperature being less than a threshold air temperature. The method can include outputting a control signal to a first electronic expansion valve to close and thereby prevent refrigerant to flow through an outdoor condenser coil. The method can also include outputting a control signal to a second electronic expansion valve to open and thereby permit refrigerant to flow through a reheat coil.

The disclosed technology includes systems and methods for controlling an air conditioning system. The method of controlling the air conditioning system can include receiving air temperature data from an air temperature sensor and determining that the air conditioning system should operate in a reheat mode based on the air temperature being less than a threshold air temperature. The method can include outputting a control signal to a first electronic expansion valve to close and thereby prevent refrigerant to flow through an outdoor condenser coil. The method can also include outputting a control signal to a second electronic expansion valve to open and thereby permit refrigerant to flow through a reheat coil.

A heat exchanger according to the present disclosure includes a main heat exchange unit configured to exchange heat between air and refrigerant, and condense the refrigerant, a subcooling heat exchange unit configured to exchange heat between air and the refrigerant passing through the main heat exchange unit, and subcool the refrigerant passing through the main heat exchange unit, and a connection pipe configured to connect the main heat exchange unit and the subcooling heat exchange unit to allow the refrigerant to pass therethrough, wherein the connection pipe connects the main heat exchange unit on its outflow side to the refrigerant and the subcooling heat exchange unit on its inflow side to the refrigerant, such that when the main heat exchange unit condenses the refrigerant, the refrigerant from the outside flows into the downstream side of the main heat exchange unit and the subcooling heat exchange unit relative to a flow of the air, and flows out from the upstream side of the main heat exchange unit and the subcooling heat exchange unit relative to a flow of the air to form a counter flow in which a flow of the refrigerant is opposite to a flow of the air.

A heat exchanger includes a plurality of heat transfer parts arranged in a first direction and spaced apart from each other, the plurality of heat transfer parts extending in a second direction and allowing refrigerant to flow through inside the plurality of heat transfer parts; a first header extending in the first direction and connected to one end of each of the plurality of heat transfer parts; a second header extending in the first direction and connected to an other end of each of the plurality of heat transfer parts; and a support extending along the first direction and the second direction and having an opening, the support being located at at least one face of the plurality of heat transfer parts in a third direction that is perpendicular to the first direction and the second direction, the support being fixed to the first header and the second header.

A heat exchanger includes a plurality of heat transfer parts arranged in a first direction and spaced apart from each other, the plurality of heat transfer parts extending in a second direction and allowing refrigerant to flow through inside the plurality of heat transfer parts; a first header extending in the first direction and connected to one end of each of the plurality of heat transfer parts; a second header extending in the first direction and connected to an other end of each of the plurality of heat transfer parts; and a support extending along the first direction and the second direction and having an opening, the support being located at at least one face of the plurality of heat transfer parts in a third direction that is perpendicular to the first direction and the second direction, the support being fixed to the first header and the second header.

The disclosed technology includes devices, systems, and methods for heat pump systems configured to operate in low ambient temperatures. The disclosed technology can include a heat pump water heater system having an evaporator, a first compressor configured to compress refrigerant to a first pressure, and a second compressor configured to compress the refrigerant to a second pressure. The second pressure can be greater than the first pressure. The heat pump water heater system can include a preheater configured to receive the refrigerant at the first pressure and heat water and a condenser configured to receive the refrigerant at the second pressure and heat water. The water can be passed through the preheater before being passed through the condenser.

The disclosed technology includes devices, systems, and methods for heat pump systems configured to operate in low ambient temperatures. The disclosed technology can include a heat pump water heater system having an evaporator, a first compressor configured to compress refrigerant to a first pressure, and a second compressor configured to compress the refrigerant to a second pressure. The second pressure can be greater than the first pressure. The heat pump water heater system can include a preheater configured to receive the refrigerant at the first pressure and heat water and a condenser configured to receive the refrigerant at the second pressure and heat water. The water can be passed through the preheater before being passed through the condenser.