The Effect of Initial Turbulence on Heat Transfer of a Flate Plate

Abstract

The effect of initial turbulence on the surface heat transfer was investigated in the case of a smooth flat plate. The initial turbulence was introduced by a screen, and the percentage turbulence √( 2)/U was measured accurately by a hot-wire anemometer in the boundary layer and in the main flow. On the other hand, the change of the temperature difference between air and a plate, during the plate being cooled, was measured in the same condition, and from its result the local heat transfer coefficient on the surface was calculated. Thus, we were able to make clear the relation between initial turbulence and heat transfer. Surface heat transfer becomes better with the enlargement of the initial turbulence and the increasing of heat transfer coefficient was remarkable within the range of small initial turbulence. In the rage of larger initial turbulence than 7∼8%, the local heat transfer coefficient increased no more, and its value was 55% larger compared with the case of the smallest initial turbulence.