Convective heat transfer and entropy generation analysis on Newtonian and non-Newtonian fluid flows between parallel-plates under slip boundary conditions

Abstract

In this study, convective heat transfer and entropy generation in Newtonian and non-Newtonian fluid flows between parallel-plates with velocity slip boundary condition were analytically investigated for both isoflux and isothermal thermal boundary conditions. Accordingly, the governing equations of hydrodynamically and thermally fully developed laminar flows were analytically solved using wall slip boundary conditions while also including viscous dissipation. As a result of this analysis, some closed form expressions for velocity, local and mean temperature distributions, Nusselt number, entropy generation and Bejan number in terms of different parameters such as slip coefficient, power-law index, and Brinkman number were obtained. According to the results, it was found that heat transfer characteristics of non-Newtonian micro flows are strongly influenced by these governing parameters. The derived expressions can be also generalized to Newtonian fluids and to macro scale by letting the power-law index equal to unity and the slip coefficient equal to zero, respectively. The results indicated that an increase in the slip coefficient leads to an increase in both Nusselt number and Bejan number, whereas it gives rise to a decrease in global entropy generation rate. Brinkman number and power-law index had opposite effects on Nusselt number, Bejan number, and entropy generation rate compared to slip coefficient.