Evaluation of overall thermal performance for conjugate natural convection in a trapezoidal cavity with different surface corrugations

Abstract

The effects of various surface corrugations and wall materials of the thick base wall of a trapezoidal cavity on conjugate natural convection have been examined in this study. Pinewood, plexiglas, dry concrete and glass fiber are considered as the materials of the solid bottom wall. In this cavity, both sidewalls are kept adiabatic, while the top wall is kept isothermally cold, and isothermal heating is applied at the bottom wall. Four types of regular surface corrugation, such as flat, rectangular, sinusoidal, and triangular-shaped corrugated surfaces are considered at the inner side of the base wall. The mathematical solutions of Navier-Stokes and thermal energy equations are obtained using Galerkin finite element method. Parametric simulation is carried out by varying Rayleigh number within laminar regime. The computed results are presented in terms of isotherm and streamline plots. The average Nusselt numbers along the solid-fluid interface, the average fluid temperature inside the cavity and the overall thermal performance ratio are also observed to assess the impact of wall materials and shapes of corrugation on convective heat transfer mechanism. From the viewpoint of overall heat transfer performance, the present results reveal that the surface material as well as the shape of the corrugation plays critically on the heat transfer enhancement of the trapezoidal cavity.