Influence of finite size of ions on thermal transport of a simultaneous electrokinetic-pressure driven flow of power-law fluids in a slit microchannel.

At high values of interfacial electrokinetic potentials, the effects of finite ionic sizes are consequential and must be taken in the purview. This paper addresses the non-trivial implications of steric effects on thermal transport of an electroosmotic-pressure driven flow within a microchannel under an imposed heat flux. The ion size is introduced into the modified Poisson-Boltzmann equation by the steric factor, which allows considering the ions as point charges or finite sizes. The non-linear, non-dimensional form of the electrokinetic potential, momentum, and energy equations are numerically solved in a spatial scheme discretized into the non-equally spaced elements. Our main point here is that the intricate physical interplay among zeta potential, pressure gradient, and steric effects has a considerable impact on the temperature distribution. Results indicated that by decreasing the surface cooling, the effect of ion finite size is significantly intensified while other factors become of peripheral importance. Also, unfavourable pressure gradients tend to mask the effect of additional heat generated by increasing the channel aspect ratio. Finally, adverse pressure gradients generated higher velocity gradients at the surface, results in a higher convective cooling and consequently an improved thermal dissipation. [Display omitted] • At low surface cooling, the role of ion size on heat rejection intensifies. • Negative pressure wipes out extra heat arisen from increasing the channel size. • Shear-thinning fluid velocity is largely altered by ionic size in adverse pressure. • S v does not affect the temperature of shear-thinning fluid in adverse pressures. [ABSTRACT FROM AUTHOR]