Numerical study on flow and thermal characteristics of a micro-channel separated heat pipe under various surface wettability

Abstract

This paper aims to investigate the influences of surface wettability under different contact angles on the thermal and flow characteristics of the refrigerant inside the evaporator of a micro-channel separate heat pipe (MCSHP). The outside louvered fins were simplified by an empirical model, and the inside refrigerant flow and heat transfer behavior was simulated by CFD. The simulation results were validated by previous experimental data. In the hydrophilic channels, there was lubricating liquid film between bubbles and wall surface, while the bubbles in the hydrophobic channels were more likely to contact with wall directly. The heat transfer rate, fluid velocity and initial nucleate spot decreased with the increase of contact angle. And the temperature and liquid fraction distribution along the X and Y axis also varied with contact angle. It could be concluded that hydrophilic surface could enhance the heat transfer rate, while hydrophobic surface could accelerate bubble nucleation. These results may have benefits on the optimization of the design and material selection of MCSHP.