NATURAL CONVECTIVE COOLING OF A HORIZONTAL HEAT-CONDUCTING PLATE FACING UP IN AN OTHERWISE ADIABATIC CAVITY

The transient conjugate cooling of a thin horizontal plate enclosed in an adiabatic cavity is studied using asymptotic and numerical techniq ues. The upper surface of the plate is in contact with a fluid initial ly at rest. The most important parameter to be obtained is the nondime nsional cooling time, which depends on the aspect ratio of the plate E . the nondimensional longitudinal heat conductance of the plate alpha and the Prandtl number of the fluid Pi, for large values of the Raylei gh number of the laminar natural boundary layer flow induced by the de nsity changes. Both the thermally thin (alpha much greater than epsilo n(2)) and thick wail regimes (alpha similar to epsilon(2)) are conside red in this payer. A minimum nondimensional cooling Lime is achieved f or a thin plate (epsilon --> 0) for values of the nondimensional longi tudinal thermal conductance of the plate alpha, such as epsilon(2) muc h less than alpha much less than 1. That is, the process is faster if the longitudinal heat conduction through the wall is negligible. (C) 1 998 Elsevier Science Ltd. All rights reserved.