Natural Convection in a Tilted Rectangular Enclosure with a Single Discrete Heater

Abstract. The effect of inclination angle on the steady laminar freeconvection in a rectangular enclosure (aspect ratio = 5), which isdiscretely heated by an isoflux flush mounted small heater (L / H =0.125) is studied numerically. The local and average Nusselt numbersare compared at inclination angles from 0 (bottom heating) to 180o(top heating), for modified Rayleigh numbers 102 . Ra* . 106. Thetwo-dimensional mass, momentum and energy equations with Boussinesqapproximation are solved for the present configuration where thesidewalls are adiabatic and the heat sink is isothermal. Forward timecentral space implicit finite difference scheme is employed to solvethe coupled governing equations. Numerical results demonstrate thestrong dependence of streamlines and isotherms on both inclinationangle and Rayleigh number. Unlike fully heated enclosures the endeffects of the discrete concentrated heat source enhances convectionand increases the average Nusselt number as compared to that forthermally full active wall. The effect of the orientation angle on theflow structure and associated transition between unicellular and multiplecell flow is presented. The maximum Nusselt number is foundclose to the vertical orientation while the minimum is at the horizontalposition with fluid heated from the top for which convection is effectualand the average Nusselt number is greater than unity.