Heat transfer characteristics of a non-isothermal surface moving parallel to a free stream

Abstract

Heat transfer from a surface in motion relative to a quiescent or moving fluid occurs in many manufacturing processes such as hot rolling, continuous casting, extrusion, and drawing. In this study, an analysis has been carried out to predict thermal transport occurring in the boundary layer on a non-isothermal flat surface that moves in the same direction of the flowing surrounding fluid. The surface temperature is assumed to have a power-law variation,T w (x)=T ∞ +Ax m . The effect of various governing parameters, such as Prandtl number Pr, wall temperature exponentm, free stream velocityu∞, and the normalized velocity difference|u w −u ∞ |/u r , whereu r is the largest ofu∞ andu w , on the temperature profiles and the Nusselt number are clearly illustrated. For the same wall temperature exponent, Prandtl number, and normalized velocity difference, a higher value of Nusselt number results fromu w >u∞ than fromu w <u∞. To increase the velocity ratiosu ∞ /u r andu w /u r is found to increase the heat transfer rate. Also, increasing the values of the wall temperature exponent and Prandtl number produces higher heat transfer rates; while increasing the normalized velocity difference tends to reduce the heat transfer. Furthermore, increasing the values of free-stream velocity and Prandtl number is found to reduce the surface temperature for uniform surface heat flux.