Evaluation of heat transfer and pressure drop in a mini-channel using transverse rectangular vortex-generators with various non-uniform heights

In recent years, the use of vortex-generators in low scale channels has been examined by several researchers. However, non-uniform vortex-generators have not yet been investigated, and this is the main motivation behind the current numerical study. Hence, simulations are carried out for water flow through a mini-channel equipped with various non-uniform transvers vortex-generators (TVGs). Also, experiments are conducted to validate the obtained results. The findings reveal the following trends: (i) non-uniform TVGs affect temperature contours and flow fields of water, (ii) the fluid mixing generated by long TVGs is greater than that of short TVGs, particularly at the upstream, (iii) when Reynolds number is large enough, the TVGs create 3D swirl flows which intensify the heat transfer effectively, (iv) locating long TVGs at the upstream of mini-channel enhances the thermal performance as well as the pressure drop, (v) maximum values of 0.63 and 2.06 are recorded for the relative ratios of Nusselt number and friction factor through the model with long to short arrangement of TVGs, (vi) at lower Reynolds number region, the best overall hydrothermal performance is seen for the model with long to short arrangement of TVGs, while at higher Reynolds number region, it belongs to the uniform model, (vii) maximum values of 0.49 and 1.43 are recorded for the considered performance indexes at Reynolds number of 50.