Liquid/liquid phase separation heat transfer at the microscale

An experimental study of liquid/liquid phase separation heat transfer at the microscale using triethylamine (TEA)/water solvent mixture is reported here. The mixture, 32.1% mass fraction of TEA, was introduced into a 22 mm long, 2 mm wide, and 0.4 mm deep microchannel. When heated above the critical temperature, the mixture separated into distinct immiscible liquid phases. Through flow visualization, the two-phase flow patterns were determined to be predominantly mist flow, elongated droplet flow, and annular flow. Increased heat transfer coefficients of up to about 250% and reduced pressure drop were observed between cases of phase separation flow and single phase mixture flow, demonstrating the potential for applying this type of solvent mixture to miniature heat sinks. A first-order computational fluid dynamics (CFD) model was used to reveal the mechanisms controlling the hydrodynamics and thermodynamics processes. It was determined that the latent heat of mixing associated with the phase separation process contributed to the enhanced heat transfer. The self-propelled motion of components driven by chemical potential gradient further boosted the heat transport. Reduced viscosities of both phases led to the reduced pressure drop.