Hydrodynamic and thermal investigation of pulsating non-newtonian fluid flow

In this study, considering the power-law model, effect of pulsating inlet flow of non-Newtonian fluid in some basic geometries (planar, circular and concentric annular channels) on flow and heat transfer is analytically investigated. The flow is considered hydrodynamically and thermally fully developed and laminar. The uniform heat flux thermal boundary conditions are applied at the walls. Perturbation method based on the series expansion is used to solve the continuity, momentum and energy governing equations. In addition, the hydrodynamic development length is investigated numerically by considering the power-law model in laminar pulsating flow in a circular channel. The average velocity, maximum, minimum and average friction factors, dimensionless bulk and wall temperatures, and Nusselt number are obtained for different values of amplitude, frequency and power-law indexes for each geometry considered. As a general character, it is observed that the dimensionless frequency is effective on the friction factor for a specific range, and this range enlarges with an increase in the power-law index. It is determined that the effect of the amplitude on the friction factor changes according to the dimensionless frequency. It is also determined that as the dimensionless frequency increases, the averaged Nusselt number reaches a maximum value at a critical value of the dimensionless frequency and then decreases. While the related maximum value increases with the power-law index, it is not affected by the amplitude.