The effect of thermal radiation on the heat transfer characteristics of lid-driven cavity with a moving surface

Abstract

Purpose – There are industrial applications for varying speed lid-driven flow and heat transfer such as the float glass process where the glass film stretches or thickens depending on the desired thickness. Hence the tin cavity underneath or the nitrogen cavity above is being driven by a variable speed. The purpose of this paper is to simulate such behavior. Design/methodology/approach – Numerical solution of variable speed lid-driven cavity is carried out with thermal radiation being considered using control volume approach and staggered grid and applying the SIMPLE algorithm. Transient simulation is used for 2D model in the present study. Second order upwind schemes were used for discretization of momentum, energy equations and time. Findings – Under laminar conditions, thermal radiation plays a significant role in the heat transfer characteristics of the lid-driven cavity. This effect is more significant for blackbody radiation and decreases as the surface emissivity decreases. Nusselt number (Nu) behavior lies between these two limiting case profiles considering constant speed profiles of both maximum and minimum lid velocities, respectively. In addition, local Nu values at the tip where higher than those at the top of the cavity that is stagnant. Research limitations/implications – The study is limited to laminar flow case. Practical implications – The applications of this study can be found in float glass process where the glass film stretches or thickens depending on the desired thickness. Hence the tin cavity underneath or the nitrogen cavity above is being driven by a variable speed. Another application involves casting of plastic films. The molten polymer leaves the die with a considerable thickness and high temperature. The film is then trenched to reach its final thickness. In this case, usually there is no actual cavity above or below the film but one can approximate the problem as such. Other similar applications do exist in food drying and processing where the conveyer belt is in portions and their speed may not be the same in different section of the processing oven. Originality/value – To the best of the authors knowledge, no study in the literature addressed the effect of thermal radiation in lid-driven cavities with variable speed