Nucleate pool boiling heat transfer of acetone and HFE7200 on copper surfaces with nanoparticle coatings

Nucleate pool boiling performance of two well-wetting liquids, i.e., acetone and HFE7200, on three nanoparticle-coated surfaces were experimentally studied and compared with that of the smooth surface. Electrophoretic deposition was used to fabricate nano porous surfaces. Surface roughness, static and advancing contact angles, capillarity of the smooth and coated surfaces were characterized. Compared to the smooth surface, the nanoparticle-coated surfaces decreased the wall superheat by more than 50% for acetone and 65% for HFE7200 at the same heat flux level, and accordingly enhanced the heat transfer coefficient by up to 85% for acetone and up to 200% for HFE7200. Bubble departure diameters were measured and correlated with the advancing contact angle, the capillary length and the Jacob number. A new mechanistic heat transfer model was proposed based on the heat flux partition method. The advancing contact angle was suggested to be used for calculation of the active nucleation site density. Based on the mechanistic model, transient heat conduction on and around nucleation sites over the whole bubble cycle contributes the most (>70%) to the total heat flux, while microlayer evaporation contributes around 10-30% to the total heat flux, with negligible natural convection. The critical heat flux was not enhanced for the two well-wetting liquids. (C) 2019 The Authors. Published by Elsevier Ltd.