A dropwise condensation model using a nano-scale, pin structured surface

Abstract

In this paper, a dropwise condensation model using innovative “nano-scale, pin structured surfaces” is presented. The surfaces are porous surfaces oriented with nano- or sub micro-scale pins randomly designed or structurally arranged on extended and/or porous surfaces. These surfaces can promote a dropwise condensation showing a higher heat transfer rate than that of “filmwise” condensation by increasing the number of nucleation sites on the condenser surface and providing tunable surface properties such as surface wetting conditions. The developed model is consisted of a heat flux estimation of a single condensate drop based on thermal resistance analysis and a population theory for small and large condensate drops. The results of heat flux of a single condensate drop indicate that a smaller condensate drop with higher contact angle has a higher condensation heat flux; however, when it combined with population theory, a hemispherical shape of condensate with Wenzel surface wetting mode and a higher pin density can increase dropwise condensation heat transfer rates. In addition, a thinner nano- or sub micro-scale pins surfaces is required to increase condensation heat fluxes, when it is applied.