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

The effect of inclination angle on the steady laminar free convection in a rectangular enclosure (aspect ratio = 5), which is discretely heated by an isoflux flush mounted small heater (L / H = 0.125) is studied numerically. The local and average Nusselt numbers are compared at inclination angles from 0 (bottom heating) to 180o (top heating), for modified Rayleigh numbers 102 ≤ Ra* ≤ 106. The two-dimensional mass, momentum and energy equations with Boussinesq approximation are solved for the present configuration where the sidewalls are adiabatic and the heat sink is isothermal. Forward time central space implicit finite difference scheme is employed to solve the coupled governing equations. Numerical results demonstrate the strong dependence of streamlines and isotherms on both inclination angle and Rayleigh number. Unlike fully heated enclosures the end effects of the discrete concentrated heat source enhances convection and increases the average Nusselt number as compared to that for thermally full active wall. The effect of the orientation angle on the flow structure and associated transition between unicellular and multiple cell flow is presented. The maximum Nusselt number is found close to the vertical orientation while the minimum is at the horizontal position with fluid heated from the top for which convection is effectual and the average Nusselt number is greater than unity.