Theoretical investigation of stable dropwise condensation heat transfer on a horizontal tube

The heat transfer model of stable dropwise condensation for saturated vapor on a horizontal tube is developed based on previous theoretical models. Through a comprehensive analysis of all the contributing thermal resistances, the convection effect inside the droplet itself is taken into consideration in the model. For the stable dropwise condensation process in dynamic conservation, a method of double integration of heat flux through numerous inclined plates with different inclination angles is introduced to obtain the overall heat flux through the horizontal tube surface. The model can predict the variation of heat transfer of stable dropwise condensation with different contact angles outside a horizontal tube. The influences of contact angle, temperature difference, and other typical parameters on both a single droplet and the whole condensation process are discussed. The results indicate that a high contact angle can cause a size reduction of falling droplets from condensing surface and thus taking more heat away. The adsorbed condensate film adds an extra thermal resistance and its thickness plays a significant role on the dropwise condensation heat transfer.