Film condensation of steam flowing on a hydrophobic surface

Nano-engineered surfaces have recently been studied as a promising solution for several heat transfer applications. In particular, the modification of surface wetting properties for condensation heat transfer is an extremely interesting field of research. In the present work, an aluminum substrate has been modified to obtain a hydrophobic surface and the influence of the wetting properties during condensation of pure steam on a vertical surface is investigated. Condensation tests, at heat flux between 250 and 500 kW m−2 and vapor velocity between 2.2 m s−1 and 6.4 m s−1, have been performed on multiple samples, both hydrophilic (advancing contact angle <90°) and hydrophobic samples, with advancing contact angle ≈140°. The condensation mode during the present test runs is purely filmwise, even on the hydrophobic surfaces, due to the complete flooding of the surface. The results of filmwise condensation on the hydrophobic surfaces display higher heat transfer coefficients compared to the untreated hydrophilic plate.