Natural convection heat transfer characteristics of a protruding thermal source located on horizontal and vertical surfaces

Abstract

An experimental study of natural convection heat transfer from a heat source module of finite thickness, mounted on a vertical or horizontal surface, is carried out. This problem is of particular interest in the removal of thermal energy from heated elements in manufacturing and electronic systems. A wall plume, adjacent to the surface, arises if the heat source module is mounted on a vertical surface. A freely rising thermal is generated by the heat source when it is located on a horizontal surface. The temperature distributions in the flow and along the surface are measured. The results obtained indicate that the natural convection flow and the associated heat transfer characteristics vary strongly with the rate of energy input and the source thickness. A comparison between the free and wall plume circumstances indicates very different temperature distributions. While the resulting isotherms for the free plume case are symmetric about the source, those for the wall plume case are swept downstream of the source. It is found that conduction along the plate length is of considerable importance in the transport process. The downstream locations of the plate come under the effect of the wake for the wall plume case, whereas the region far from the source is free from the wake effect in the free plume circumstance which arises in the horizontal orientation. The interaction between the wakes generated by the three exposed surfaces of the heat source module is also found to have a significant effect on the flow. Thus, the heat transfer from a protruding heat source module cannot be accurately determined by assuming three heated, isolated surfaces. The results obtained are compared with those for a source of negligible thickness and the effect of a significant module thickness on the convective flow and transport is determined. The heat transfer coefficient for a protruding heat source module is found to depend on the ratio of the vertical to the horizontal surface areas of the module, exposed to the ambient medium. Several other interesting trends are observed in this investigation and discussed in terms of the underlying flow and thermal transport processes.