Conjugate heat transfer analysis of U-bend/turn microchannel: A computational approach

Abstract

A three-dimensional numerical study for conjugate heat transfer analysis of the U-bend microchannel (UMC) involving single-phase laminar flow has been performed to evaluate the fluid flow and heat transfer characteristics. Three different geometry configurations are considered for the UMC with aconstant hydraulic diameter of 0.4 mm and radius of curvature of the U bend R = 2 mm, 3 mm, and 4 mm. Comparison of UMC is done with equivalent length (along center) straight microchannel (SMC) with total channel length L = 36.2 mm, 39.4 mm, and 42.5 mm, respectively, for three different Reynolds numbers of 50, 100, and 200 at a constant applied heat flux of 50,000 W/m2. The performance evaluation factor (PEF) value indicate an improvement in heat transfer rate for the UMC compared to SMC. Parameters such as the local Nusselt number, average Nusselt number, and total pressure drop are evaluated. It is observed that bending effect improved overall performance of UMC over SMC by 33% for R = 4 mm at a Reynolds number of 200. Qualitative picture of the impact of curvature on the performance of UMC in the form of velocity and temperature contours are also presented. It is also found that performance of UMC with low radius of curvature can be improved with high pumping power, since the pressure drop is unavoidable. So, it is better to use channels with high radii of curvature at relatively low Reynolds number