Heat exchanger

A heat exchanger comprising:

• heat transfer tubes disposed along a predetermined direction;
• and
• a header that retains longitudinal ends of the heat transfer tubes, wherein
• the header comprises:
• a first member comprising a main wall portion that has through holes through which the longitudinal ends respectively pass;
• a second member defining insertion spaces that communicate with the heat transfer tubes at the longitudinal ends;
• and
• a third member facing the longitudinal ends,
• the second member comprises:
• a pair of side plates disposed in a width direction of the header and that define the insertion spaces therebetween;
• and
• partition plates, each connected to the pair of side plates, that separate adjacent ones of the insertion spaces,
• the pair of side plates are spaced apart from the heat transfer tubes,
• the insertion spaces are individually separated from each other by the partition plates,
• the heat exchanger further comprises a pair of outer side plates respectively covering the pair of side plates from outside in the width direction of the header, and
• the second member is thicker in a longitudinal direction of the heat transfer tubes than is the third member.