MIXED CONVECTION FROM AN ISOLATED HEAT SOURCE IN A RECTANGULAR ENCLOSURE

Abstract

The mixed convection transport from an isolated thermal source, with a uniform surface heat flux input and located in a rectangular enclosure, is studied numerically. The enclosure simulates a practical system such as an oven or an air-cooled electronic device, where an airstream flows through the openings on the two vertical walls. The heat source represents a heater or an electronic component located in such an enclosure. The interaction of the cooling stream with the buoyancy-induced flow from the heat source is of interest in this work. Laminar, two-dimensional flow is assumed, and the problem lies in the mixed convection regime, governed by the buoyancy parameter GrIRe1 and the Reynolds number Re. Other significant variables include the locations of the heat source and the outflow opening. The inflow is kept at a fixed position. The mathematical model is developed with vorticity and stream function, along with temperature, as the dependent variables. The unsteady terms are retained in the vorticity and energy equations, while a Poisson equation is derived for the stream function. The control volume approach is used to derive the finite difference equations. The numerical scheme employs the alternating direction implicit ( ADI) method for time marching, while the stream function equation is solved at each time step by the successive overrelaxation ( SOR) method. The heat transfer from the source, for various values of the governing parameters, is computed, after the Navier-Stokes and the energy equations are solved to determine the flow and the temperature fields in the enclosure. The basic nature of the resulting interaction between the externally induced airstream and the buoyancy-driven flow generated by the source is investigated. The trends observed are also discussed in terms of heat removal from practical systems such as electronic circuitry.