Abstract

Condensation heat transfer coefficients are rather low compared to thin film evaporation. Therefore, it can be a limiting factor for desiging a heat transfer equipment. In the present work, heat transfer characteristics of water vapor condensation phenomena were experimentally studied on a vertically aligned smooth copper substrate for a range of pressures and temperatures for two different liquid wettability conditions. Since the heat transfer performance is dominated by the phase change process at the solid-vapor interface along with the liquid formation mechanism. A specifically prepared perfluoro-silane fluid was applied over the surface to increase droplet contact angle with the objective of a strong promotion of dropwise condensation (DWC). Compared to heat transfer results measured at an untreated copper surface, heat transport is augmented with a thin layer of perfluoro-silane coating over the same substrate during condensation. In the present work, the effect of saturation pressure on the condensation process at both surfaces has been investigated by analyzing heat transfer coefficients. The results obtained experimentally show an increase in contact angle with the surface coating. A heat transfer augmentation of about 28 % over uncoated surfaces was obtained and surfaces did not show any degradation after 40 hours of operation. Finally, current results are compared with heat transfer values reported in open literature.

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