A heat exchanger provided with tubes 210 through which a medium flows
and
tanks 300 to which the ends of the tubes are connected to perform heat exchange
of the medium with heat conducted to the tubes, wherein the tanks each provided
with an end plate 320 having holes 321 for connection of the ends
of the tubes and a tank plate 310 to which the end plate is fitted; and
when it is assumed that a cross section of the tank in its longitudinal direction
has a passage area X and a total wetted perimeter length Y for the medium, they
have a relationship of X=aY2/4 and 0.9a1.0.
