Thermal convective transport of nanofluids in a microannulus under electromagnetohydrodynamic and time-periodic pressure gradient

Abstract

The study of the unsteady flow and heat transfer characteristics of nanofluids in microannulus is crucial for the optimal design and precise operation of microfluidic systems, and microfluidic technology has an important application value in microelectronic engineering. In this article, a theoretical analysis of the heat transfer characteristics of unsteady flow of Water-Al2O3 nanofluids through a microannulus under the coupling of an alternating electric field, a magnetic field, and a time-periodic pressure gradient is presented. Both the thermally completely developed flow assumption and the Debye–Hückel linear approximation are taken into consideration. The microannulus wall is subjected to a consistent heat flow while taking into account the effects of Joule heating and viscous dissipation. A semi-analytical solution of the temperature field is efficiently obtained using the Green’s function method. In addition, the Nusselt number and total entropy generation are further analyzed. The results show that the nanoparticle volume fraction and dimensionless frequency have a significant effect on the heat transfer characteristics of nanofluids. The increase of dimensionless frequency decreases the convective heat transfer and improves the cooling performance of microannulus. On the contrary, increasing the nanoparticle volume fraction improves the heat transfer performance of microannulus. Therefore, the results of this study can be used for electronic cooling of compact and micro-sized circuits. This study is instructive for unsteady flow and heat transfer of nanofluids in microchannels.