Abstract: A heat exchanger wherein the pipe member is formed in a single stage to reduce the height of the heat exchanger in the thickness direction to enable the heat exchanger to be mounted below the floor of an automobile and wherein the pipe member is prevented from being broken. The heat exchanger includes: fin members formed as corrugated fins and having engagement recesses formed in curved sections; and a pipe member formed by connecting straight pipe sections by U-shaped bend sections, the straight pipe sections being arranged by means of the fin members.

Abstract: Soot adhering to the inner surface of a heat transfer pipe can be removed without lowering the heat transfer efficiency that is the inherent object of the heat transfer pipe or without stopping the cooling operation of the heat transfer pipe. Further, this soot removal can be effected when the amount of soot adhering to the inner surface of the heat transfer pipe is small, thus minimizing the soot-caused lowering in the heat transfer efficiency of the heat transfer pipe. A heat transfer pipe (1) wherein the inner peripheral surface of an element pipe (2) through which fluid can flow is formed with longitudinal grooves (4) as recessed grooves (3) of cross-section with a given depth such that the longitudinal grooves are parallel with the pipe axis and circumferentially continuous, and a partition wall (5) of given thickness is formed between the longitudinal grooves (4): and a heat exchanger incorporating this heat transfer pipe (1).