Heat exchanger and refrigeration cycle apparatus

A heat exchanger comprising:

• a first header and a second header extending in a first direction and arranged apart from each other in a second direction perpendicular to the first direction;
• and
• a plurality of heat-transfer members arranged apart from each other in the first direction,
• each of the plurality of heat-transfer members having a first end in the second direction connected to the first header and a second end in the second direction connected to the second header,
• an internal space, through which a first heat exchange medium flows, of each of the first header, the second header, and the plurality of heat-transfer members being separated from an external space through which a second heat exchange medium flows,
• the internal space of the first header communicating with the internal space of the second header through the internal space of each of the plurality of heat-transfer members,
• the heat exchanger further comprising:
• at least one heat-transfer promotion member;
• and
• at least one positioning member,
• the at least one heat-transfer promotion member
• being located in the external space,
• being arranged in a central region between two heat-transfer members adjacent to each other in the first direction among the plurality of heat-transfer members, and
• extending in a third direction perpendicular to the first direction and the second direction,
• the at least one positioning member
• being located in the external space,
• positioning the at least one heat-transfer promotion member with respect to the first header, the second header, and the plurality of heat-transfer members, and
• being arranged only on a downstream side in the third direction in which the second heat exchange medium flows, relative to the internal space of each of the plurality of heat-transfer members.