Convection cooling of a continuously moving surface in manufacturing processes

An analysis of flow and heat transfer from a heated flat surface continuously moving in a parallel free stream of non-Newtonian fluid has been performed. This kind of problem is of practical interest in materials processing. The surface temperature is assumed to have a power-law variation. Three surface heating conditions of uniform wall temperature (UWT), variable wall temperature (VWT), and uniform surface heat flux (UHF) are considered in this study. Numerical solutions for the momentum and thermal transport between the continuous surface and the flowing non-Newtonian fluid are generated by using a finite-difference method. Velocity and temperature profiles are presented at selected values of free stream velocity using the power-law viscosity index. The friction factor and Nusselt number are illustrated for a wide range of governing parameters. For the same normalized velocity difference, the Nusselt number is increased for a shear thinning fluid but decreased for a shear thickening fluid, as compared to the Newtonian fluid. An increase in the ratio of the free stream velocity U∞ to the wall velocity Uw results in an increase in the heat transfer rate, but a decrease in the friction factor. For the same values of power-law viscosity index and the normalized velocity difference, higher values of friction factor and Nusselt number are obtained from Uw>U∞ than from Uw