Numerical Simulation of Turbulent Natural Convection in a Rectangular Enclosure with Localised Heating and Cooling

Abstract

This study involves simulation of turbulent natural convection in a rectangular enclosure with localised heating and cooling. Numerical simulation of turbulent natural convection has been studied in the past using the k-epsilon (k-ε), k-omega (k-ω) and k-ω-SST turbulence models. Further research showed that the k-ω SST model performed better in terms of convergence of time than the k-ε and k-ω models. The study of natural convections in an enclosure has several applications from natural space, warming of household rooms to sections of engineering and atomic installations. This study involves numerical simulation of natural convention flow in a rectangular enclosure full of air using the k-ω- SST model with an objective of establishing the best position of the heater and the cooler for better distribution of heat in the enclosure. The transfer of heat due to natural convection inside a rectangular closed cavity was modelled to include the effect of Rayleigh number greater than or equal to 109. The non-linear terms in averaged momentum and energy equation respectively were modeled using k-ω-SST model to close the governing equations. The cavity was maintained at 303K on a square hot section midway on the extreme lower boundary of one of the vertical walls and at 283K on a square (twice in length and width the lower one) cold section midway on the extreme upper boundary on the same wall. The remaining part of this wall and the other five walls were adiabatic. The vorticity-vector potential, energy and the two equations for k-ω-SST model with boundary conditions were solved using finite difference method and FLUENT.