Transient Free Convection Generated by a Heated Vertical Plate in a Rectangular Cavity

Abstract

The effects of aspect ratio on the transient free convection generated by a heated vertical plate in a rectangular cavity is investigated for the characteristics and rates of heat transfer from the plate into the surrounding fluid medium. The plate is assumed to be an isothermal plate at a high temperature, suddenly immersed in air at a lower temperature inside the cavity whose walls are also assumed to be adiabatic. The full two-dimensional time-dependent partial differential forms of the conservation equations of continuity, momentum, and energy governing the flow field are cast and solved by a numerical method employing the finite-difference scheme. During the initial short period, heat flow is found to be by conduction irrespective of aspect ratio. The conduction regime is found to be more prolonged for tall enclosures. Shortly after conduction sets in the convection indicated by increase in the heat transfer coefficient following a temporal minimum in the coefficient at the end of the conduction regime. The rate of heat transfer by convection is found to increase with aspect ratio. At large times the temperature field stratifies and the heat transfer to the medium approaches zero, the velocity field decaying gradually and the flow approaches its eventual quiescence.