Natural Convection Heat Transfer from Horizontal Heated Plates in an Enclosure(Effects of Design Parameters)

The effect of design parameters on natural convection heat transfer from horizontal heated plates in an enclosure is investigated experimentally. Our experimental setup is described as follows: Two heated plates are arranged in the vertical direction. The temperature of the ceiling is maintained at a constant low temperature. The other sides satisfy the thermal insulation boundary condition. To clarify the effects of the design parameters, the relationship of heat transfer to the heat flux and the aspect ratio of the enclosure were examined. The results show that the flow characteristics have two distinctive patterns: one includes vortex motion, and the other comprises a flow along the heated surface. An increase in the heat flux promotes vortex motion and enhances heat transfer. The heat transfer is independent of the height of the adjacent air space. The heat transfer from the heated surface that gives rise to the vortex motion is not influenced by the enclosure diameter, whereas the heat transfer from the other surfaces increase linearly with the enclosure diameter. Nusselt number is expressed as a function of the modified Rayleigh number and the nondimensional enclosure diameter.