Energy Efficiency Optimization of Superhydrophobic Surfaces for Enhanced Condensation Heat Transfer

The process of droplets jumping, against adhesive forces, from a solid surface upon coalescence has been studied in detail using experimentally-validated CFD modelling. Both Lattice Boltzmann and Volume of Fluid methods have been used to evaluate different kinematic conditions of coalescence inducing a jump velocity. Design of experiment techniques were used to establish near-optimal initial process parameters around which to focus the study. This multidisciplinary approach allows us to evaluate the jumping phenomenon for super-hydrophobic surfaces for which several input parameters may be varied, so as to improve the heat transfer exchange rate on the surface during condensation. Reliable conditions were found to occur for droplets within initial radius range of r=20-40 μm and static contact angle θs~160º. Moreover, the jumping phenomenon was observed for droplets with initial radius of up to 500 μm. Our study also shows that a critical contact angle for droplets to jump upon coalescence is θc~140º.