A numerical study of natural convective heat transfer from an inclined plate with a 'WAVY' surface

摘要

Natural convective heat transfer from a wide isothermal plate which is, in general, inclined to the vertical has been numerically studied. The plate has a "wavy" surface, i.e. has a surface which periodically rises and falls. These waves are at right angles to the direction of flow over the surface and have a relatively small amplitude. Two types of wavy surface have been considered here - saw-tooth and sinusoidal. The flow has been assumed to be laminar and two-dimensional. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated by means of the Boussinesq type approximation. The governing equations have been written in dimensionless form and the resultant dimensionless equations have been solved using a finite-element method. Results have been obtained for a Prandtl number of 0.7. The parameters on the solution are the Grashof number based on the plate height, the angle of inclination of the plate, the form of the surface waviness (saw-tooth or sinusoidal) and dimensionless amplitude and pitch of the surface "waviness". Results have been obtained for Grashof numbers of up to 10{sup}7 for angles of inclination between +90°(horizontal, facing downwards) through 0° (vertical)to -90° (horizontal, facing upwards). The main result sought was the mean Nusselt number. The results indicate that in most cases the surface waviness decreases the mean heat transfer rate compared to that for a plane surface.