Combined effects of a microchannel with porous media and transverse vortex generators (TVG) on convective heat transfer performance

Abstract

The three-dimensional heat transfer and pressure drop of fluid flow within a microchannel with transverse vortex generator and porous medium are numerically investigated. A total of 14 cases with various designs of vortex generator, semi-porous, and completely porous material were studied in detail. Further, the performance is compared between microchannel with different heights and the number of transverse vortex generators, as well as a semi-porous microchannel with a vortex generator. The finite volume method is used to solve the governing equations based on the three-dimensional volume averaging method for single-phase laminar flow. The Darcy-Forchheimer model is applied to solve the flow in a porous medium. The computational domain includes a stainless steel rectangular microchannel with a vortex generator and/or the insertion of porous media. The numerical results indicate that the convective heat transfer coefficient increases with increasing height and the number of transverse vortex generators. Compared to the empty microchannel, the heat transfer coefficient is 12 times higher with a completely filled porous media and 2.6 times higher with eight vortex generators with 12.5% of the channel height. While pursuing a high heat transfer coefficient, the pressure drop of the fluid flow often also increases. Therefore, a thermal performance ratio is defined to normalize the change of heat transfer coefficient and pressure drop. The final combined results show that the microchannel with vortex generator and with top-and-bottom inserted porous media has the highest thermal performance ratio at low and high Reynolds number, respectively. Lastly, detail cross-sectional and down-the-channel flow streamlines and temperature distributions are shown to identify the fundamental mechanism of heat transfer. The findings of this study provide a comprehensive insight into designing an effective microchannel with optimal convective heat transfer and reasonable pressure drop.