high temperature but the air which passes through the unfinned passages 11 1 11 3 is only slightly heated and so because many layers of high temperature air and relatively low temperature air flow into the mixing chamber 4 it is easy to mix the air the temperature of hot water which flows upward in the heat pipe 7 gradually decreases because of the heat exchanging process further since the area of the heat radiating fins 12 1 12 4 of the air heating passages 10 1 10 4 becomes gradually greater downwardly air which passes through the air heating passage 10 4 becomes heated to a higher temperature than that passing through passage 10 3 while air through passage 10 3 is heated more than that through 10 2 air through passage 10 2 is heated more than that through passage 10 1 this means that the contacting area between the heat pipe and the air gradually increases from the top of exchanger h to the bottom thereof and so the many air layers flowing into mixing chamber 4 are formed to vary from a higher temperature near the bottom to a lower temperature near the top as the result it is easy to mix the air even though the mixing chamber 4 has a comparatively small volume chamber the upper hot air having a temperature lower than the lower hot air of the mixing chamber is blow out toward and around the head of the rider within the automobile from the side exit 16 and the lower hot air having a temperature higher than the upper hot air is blown out toward and around the feed of the rider within the automobile from lower exit 17 the hot air from the upper exit 15 is.