Parametric studies on dropwise condensation heat transfer
AuthorCheng, Kuok Kong
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Wettability of a solid surface with liquids could be tuned based on surface morphologies. This is significant in condensation heat transfer. Condensation is a critical heat transfer mechanism in industrial processes; Dropwise (DWC) and Filmwise (FWC) condensation processes are important and are focus of this study. There are few studies on surface morphology effect on wetting behavior of a solid in relation to condensation heat transfer. We conducted these studies to understand the phenomenon. Condensation heat transfer is affected by condensate droplets properties on the surface. Condensate drop sizes and mobility relationships are important to condensation heat transfer. Droplet sizes and mobility affect population density and condensation heat transfer coefficients directly. The goal of this study is to acquire the fundamental understanding of condensation heat transfer with relation to condensate droplet behavior. In order to achieve this goal, a liquid droplet wetting dynamic model was initially developed for predicting single drop behavior on different surfaces. Heat fluxes were then estimated by combining liquid droplet behavior models and heat transfer model. Condensation experiments were conducted to verify effectiveness of the model. Experimental results coupled with condensation models revealed relationships between wetting behaviors and condensation heat transfer. Contact angle hysteresis (CAH) remains low at both high and low droplet contact angle, i.e. whether the surface is hydrophilic or hydrophobic. CAH increases with degree of wetting, but coating thermal conductance also increases. Details of drop (DWC) and film-wise (FWC) condensation are presented.