Analytical study of natural convection in a heated vertical channel

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.In the present work, natural convection of air in heated vertical channels is studied. On the basis of the conception of induced-forced analogy, a simple and efficient analytical method of heat transfer and flow calculations is developed. General heat-transfer correlations in the form Nu = Nu(Re,Pr) are obtained for the air flow. The velocity (Reynolds number) is obtained by solving a momentum equation for induced convection taking into account energy balance for this case. It is shown that the developed method is simple and clear when applied to the problem under consideration. In this calculation, the initially known heat input (heat transfer rate or wall temperature) and hydraulic parameters are used. The developed method is applied to the problem natural convection of air in a symmetrically or asymmetrically heated vertical channel, which has allowed us to make a comparison with the literary data. The analogy and difference between the natural convection in a heated channel and a heated vertical plate in an infinite volume is demonstrated. A criterion of transition between the two is presented, and it is shown that this transition is smooth.