Effect of hydrophobic coating on optimization of dropwise condensation of steam on hybrid surfaces

Dropwise condensation of pure vapor on hybrid surfaces, characterized by alternate hydrophobic-hydrophilic regions, is numerically investigated via phenomenological, Lagrangian modelization of dropwise condensation on hydrophobic regions. The drop size distribution over the hydrophobic domain, which knowledge is crucial for development of accurate simplified, statistically based models, is computed. Comparison with literature correlations shows that the theoretical correlation for size distribution of small droplets gives an inaccurate estimate, while the improved correlation, derived from the droplet population balance, better describes the numerical size distribution and, if incorporated in the statistically based model, allows to accurately predict the condensing flux.