Modeling of heat transfer through a liquid droplet
In dropwise condensation, the released latent heat passes through the static and sliding droplets to the condensing surface at a rate limited by various thermal resistances. In the present work, numerical simulation of heat transfer through a droplet is carried for one under static and sliding condition. 3-D governing equations with appropriate boundary conditions are solved for the surface, promoter layer and droplet included within the computational domain. Simulations are carried out using an in-house CFD solver. The simulation results are validated against the available data and are found in good agreement. The observations of the present work are: (a) heat transfer through the droplet achieves steady state over a timescale of micro-seconds, (b) the heat fluxes of deformed and equivalent spherical-cap droplet are found to be equal, (c) Marangoni convection is significant for Ma ≥ 2204, (d) convection is the dominant mode of heat transfer during drop slide-off (e) constriction resistance is insignificant for a copper surface of thickness ≤ 2 mm, (f) average heat flux increases with increasing contact angle, interfacial heat transfer coefficient, degree of subcooling and Reynolds number; however, it decreases with increasing Prandtl number of the liquid. These results are useful for sensitivity analysis of various thermal resistances in the mathematical modeling of dropwise condensation underneath inclined surfaces.