Interplay of high zeta potential and steric factor on the slip thermofluidics of power law fluids through narrow confinements

Thermal transport in a non-Newtonian fluid flow through a parallel plate microchannel is investigated with an emphasis on the effects of high zeta potential and steric factor. The fluid viscosity is modelled using the power law and the flow is driven by a combination of electric field and pressure gradient in the form of a dimensionless flow actuation coefficient. The effects of joule heating, viscous dissipation and slip length at the wall are considered. A semi-analytical formulation for the temperature profile is de-veloped which is solved numerically using the Galerkin Finite Element method. We find that the Nusselt number increases as the flow behaviour index is increased. Velocity slip is also found to have a positive impact on convective heat transfer. However, as the zeta potential and steric factor increase, the Nusselt number begins to decline as there is an increase in viscous dissipation. We highlight the importance of considering variable electrical conductivity in evaluating the effect of joule heating at high zeta potential and moderate steric factor. In this regime, joule heating dominates advective transport and heat flow is reversed which may be detrimental or even damaging to microfluidic devices. A comprehensive thermal map is developed for a wide range of zeta potentials and steric factors. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Thermal transport in a non-Newtonian fluid flow through a parallel plate microchannel is studied with a focus on the effects of high zeta potential and steric factor. The flow behavior is modeled using a power law and is driven by a combination of electric field and pressure gradient. The study considers the impacts of joule heating, viscous dissipation, and slip length at the wall. A semi-analytical formulation for the temperature profile is developed and solved numerically. The results show that the Nusselt number increases with the flow behavior index and that velocity slip has a positive impact on convective heat transfer. However, as the zeta potential and steric factor increase, the Nusselt number starts to decrease due to increased viscous dissipation. The study emphasizes the importance of considering variable electrical conductivity in evaluating the effect of joule heating in high zeta potential and moderate steric factor conditions. A comprehensive thermal map is developed for a wide range of zeta potentials and steric factors.