Analysis of convective heat transfer in non-Newtonian fluids by applying the field synergy principle approach

The present paper is intended to evaluate the local convective heat transfer of power-law fluids through a circular channel, accounting for the asymmetric heating that may occur in some practical applications. The temperature distribution within the fluid is analytically determined by assuming that the wall of the channel could be partially heated by a constant heat flux. The effects of asymmetric heating and the flow behavior index on the average performance of the heat transfer device are evaluated in terms of average Nusselt number, while the local phenomena are investigated by adopting the field sinergy principle approach. The results in terms of average Nusselt number highlight that the convective heat transfer coefficient decreases as the portion of the heated wall increases, while it increases as the flow behavior index decreases. This trend is motivated by analyzing the heat transfer phenomenon by means of the field sinergy principle approach; indeed, this analysis reveals that synergy between the velocity vector and the temperature gradient is better when the wall is heated only for a small portion and for shear thinning fluid.