Enhancement of Thermal Efficiency on a Upstream Wedge Ribs Microchannel using Lattice Boltzmann Approach

Abstract

Numerical analysis of flow friction and thermal performances in upstream wedge ribs microchannel at the slip flow condition has been intended in the current study employing a Thermal Lattice Boltzmann Method (TLBM). A D2Q9 single relaxation time TLBM is used to investigate and discuss the thermal-fluid flow behavior namely the streamlines in terms of velocity vectors, isotherms in terms of temperature profiles, pressure gradient as well as friction coefficient for different Knudsen numbers (Kn) ranging from 0.01~0.10 with ribs height 20% of channel height. Finally, the overall performance enhancement ratio is calculated for wedge ribs microchannel to compare with smooth one. The results have been compared with previously published works and are found a very good agreement and thus the model has been used to predict the heat transfer and friction factor in wedge ribs microchannel. In this study, it is illustrated that the vortices are strongly influenced and the strength of vortices are decreased as the Kn increases and hence the pressure gradient also responsible for changing the Knudsen number. The flow friction, the average rate of heat transfer as well mass flow linearly decreased with increasing Kn but compare to smooth channel, the friction is significantly increased and the heat transfer rate as well mass flow decreased for upstream wedge ribs microchannel. Finally, the performance enhancement (PE) namely the thermal efficiency are calculated and it is found that the PE decreased slightly with Kn for upstream wedge ribs microchannel. However, compare to smooth one, the lower PE identified in the present study.