Heat exchanger, refrigeration cycle apparatus, and method for manufacturing heat exchanger

A method for manufacturing a heat exchanger, the heat exchanger comprising:

• a plurality of flat heat-transfer tubes arranged side by side such that an outer lateral wall of each of the flat heat-transfer tubes faces an outer lateral wall of an adjacent one of the flat heat- transfer tubes;
• and
• a corrugated fin having a wavy shape and provided between each adjacent two of the plurality of flat heat-transfer tubes,
• wherein the corrugated fin is joined to the outer lateral walls of each adjacent two of the plurality of flat heat-transfer tubes at apexes of the wavy shape,
• wherein the corrugated fin includes fins connecting the apexes and being side by side in an axial direction of the plurality of flat heat-transfer tubes,
• wherein defining a direction in which the plurality of flat heat-transfer tubes are side by side as a side-by-side direction and a longitudinal direction of a cross section of each of the plurality of flat heat-transfer tubes as a depthwise direction, the fin has a plurality of heat-transfer promoters arranged side by side in the depthwise direction,
• wherein the plurality of heat-transfer promoters each have a transfer-promoting projection projecting from a surface of the fin and an open part provided in the fin,
• wherein the fin has, between the plurality of heat-transfer promoters, frost-growing areas whose width is defined in the depthwise direction,
• wherein the frost-growing areas each have a through-hole continuous with the open part of a corresponding one of the plurality of heat-transfer promoters,
• the method comprising:
• forming the corrugated fin from a flat plate;
• and
• joining the apexes of the corrugated fin to the flat heat-transfer tubes, and
• wherein the forming of the corrugated fin includes:
• punching the through-holes in the plate and forming the heat-transfer promoters by deforming at least one of flat portions at edges of each of the through-holes such that the at least one flat portion is moved in a direction perpendicular to a surface of the plate;
• folding the plate having the through-holes and the heat-transfer promoters into a wavy shape;
• and
• cutting the plate into pieces each having a predetermined length, the cutting being performed after the folding.