Convective heat transfer and entropy generation analysis of non-Newtonian power-law fluid flows in parallel-plate and circular microchannels under slip boundary conditions

摘要

This study deals with convective heat transfer and entropy generation analysis of slip flow of non-Newtonian power-law fluids through parallel-plate and circular microchannels. The microchannels were subjected to uniform heat flux boundary condition at the wall. The governing equations relevant to both hydrodynamically and thermally fully developed laminar flows were analytically solved using non-linear slip boundary condition while also including viscous dissipation. Analytical closed form solution of the velocity profiles, temperature distributions, Nusselt number, entropy generation rate and Bejan number in terms of different parameters such as slip coefficient, power-law index and Brinkman number were obtained. The results indicate that increase of the slip coefficient leads to an increase in Nusselt number and a decrease in average entropy generation rate. The effect of slip coefficient on Bejan number is strongly affected by Brinkman number. Low values of either power law index or Brinkman number result in better working performance of microfluidic systems. Under same conditions, parallel-plate microchannel produce more entropy than circular microchannel. Viscous dissipation significantly affects heat transfer and entropy generation characteristics and cannot be neglected. The results of current study are helpful in deep understanding of flow and heat transfer rates and also designing more thermally efficient microfluidic devices which utilize non-Newtonian fluids.