Abstract
The convective heat transfer, which is 25 to 35 % of all heat dissipation of a human body, causes upward natural convection around a human body. This natural convection causes unevenness of the convective heat transfer over a body surface. The present paper studies the characteristics of the natural convection and the range of the unevenness in the natural convection heat transfer by using a thermal manikin. The thermal manikin was constructed of heated cylindrical parts, which simulated corresponding parts of a standing human body. The characteristics of the natural convection was examined by the flow visualization technics of infrared thermogram and smoke wire photography. The natural convection heat transfer coefficient was estimated from the surface temperature of various locations on the manikin. The flow visualization technics indicated that the flow of a velocity of 10 to 15 cm/s existed already at a height of 12 cm over the floor. The flow remained as laminar until a height of about 80 cm over the floor, then it converted into turbulent flow. A flow of a velocity of 40 cm/s at the maximum was observed at a level of the head of the manikin. A steep change with the height was found in the natural convection heat transfer coefficient along the legs and the arms. The highest natural convection heat transfer coefficient was found at the lowest temperature measuring points on the legs. The average heat transfer coefficient over the manikin was between 3.35 and 3.93 W/m2K according to its heat production. This means that the lower part of a leg has about 30% higher natural convection heat transfer coefficient than the average of the body.
