Combined forced convection and surface radiation between two parallel plates

Purpose - This paper's aim is to investigate the effect of surface radiation on the developing laminar forced convection flow of a transparent gas between two vertical parallel plates. The walls are heated asymmetrically, this enhances the effect of radiation even with the two walls having low values of emissivity. Design/methodology/approach - Numerical techniques were used to study the effect of the controlling parameters on wall temperatures, fluid temperature profiles, and Nusslet number. Findings - The values of the radiation number at which surface radiation can engender symmetric heating (and hence maximum average Nusslet number on the heated wall and maximum reduction in the maximum heated wall temperature are achieved) are obtained. Threshold values of the radiation number at which radiation effects can be neglected are obtained. Research limitations/implications - Boundary-layer flow model is used. Practical implications - The implications include design of high-temperature gas-cooled heat exchangers, advanced energy conversion devices, advanced types of power plants, and many others. Originality/value - Though a number of analyses of internal flows including radiation effect have been made, most have been directed at the simplest case of the prescribed uniform (isothermal) temperature boundary condition. The available literature that deals with the problem with prescribed heat flux at the walls is limited to fully developed flow or specifying the convection coefficient a priori. The lack of both theoretical and experimental data concerning combined forced convection and surface radiation developing flows between two parallel and its practical importance motivated the present work.