Heat exchanger and air-conditioning apparatus including the heat exchanger

A heat exchanger comprising a plurality of heat exchange units configured to exchange heat between refrigerant and air,

• each of the plurality of heat exchange units including
• a plurality of flat tubes spaced from and parallel to each other and in which a refrigerant flow passage is formed through which refrigerant flows in an up-down direction,
• a plurality of fins provided between the plurality of flat tubes adjacent to each other,
• an upper header to which respective upper end portions of the plurality of flat tubes are connected, and
• a lower header to which respective lower end portions of the plurality of flat tubes are connected,
• in the plurality of heat exchange units, the upper headers being connected such that the upper headers communicate with each other, the lower headers being connected such that the lower headers communicate with each other through an opening-closing valve,
• wherein the heat exchanger includes a configuration in which when the heat exchanger serves as an evaporator, the opening-closing valve is controlled such that refrigerant in all the plurality of heat exchange units flows in an upward direction,
• the heat exchanger having a configuration in which when the heat exchanger serves as a condenser, the opening-closing valve is controlled such that:
• refrigerant in at least one of the plurality of heat exchange units flows in the upward direction, and refrigerant in an other one or other ones of the plurality of heat exchange units flows in a downward direction, and
• the refrigerant enters the heat exchanger at the lower header, and then flows, in this order, in the upward direction in the at least one of the plurality of heat exchange units, through the upper header, in the downward direction through the other one or other ones of the plurality of heat exchange units, and then exits the heat exchanger.