LBM Simulation for Analyzing the Performance of Sawtooth Microchannels with Positive and Negative Ramps

This study investigates thermal and fluid behaviors in smooth microchannels under slip flow regime using an alternative numerical technique namely the thermal lattice Boltzmann method (TLBM). This method is based on D2Q9 model with lattice-BGK (Bhatnagar–Gross–Krook) approximations. In this procedure, an internal energy distribution function uses to calculate temperature, and a momentum distribution function to evaluate macroscopic quantities like density, pressure and velocity etc. With these macroscopic quantities, the important physical properties such as the average flow friction, mass flow rate, and the heat transfer rate are investigated and discussed for different governing parameters. The relative ramp heights (0\(\%\)–10\(\%\)) and Knudsen number (Kn) (0.01–0.10) are the most important parameters in this study. The average frictional resistance decrease with increasing Kn but increasing with ramps height, whereas the mass flow rate reduced both for ramps height and Kn. Moreover, the heat transfer rate decreased significantly with Kn and very slowly with ramps height. Another important properties, the combined effect of thermal and hydraulic properties called the coefficient of performance (COP) is studied to compare the efficiency of different microchannels. COP decreases with increasing ramp height as well as Kn. Optimal performance is observed with very low ramp heights. The microchannel with negative ramps perform better than positive ramps case. The COP of sawtooth microchannels is calculated to compare with the friction (pressure drop) and heat transfer of smooth microchannel. Finally, the obtained result is compared, and an excellent agreement is found with published work.