Condensate Removal Mechanisms in a Constrained Vapor Bubble Heat Exchanger
Microgravity experiments on the constrained vapor bubble heat exchanger (CVB) are being developed for the space station. Herein, ground-based experimental studies on condensate removal in the condenser region of the vertical CVB were conducted and the mechanism of condensate removal in microgravity was found to be the capillary force. The effects of curvature and contact angle on the driving forces for condensate removal is studied. The Nusselt correlations are derived for the film condensation and the flow from the drop to the meniscus at the moment of merging. These new correlations scale as forced convection with h?L1/2 or h?L1/2cd. For the partially wetting ethanol system studied, the heat transfer coefficient for film condensation was found to be 4.25  104 W/m2K; for dropwise condensation at moment of merging it was found to be 9.64  104 W/m2K; and for single drops it was found to be 1.33  105 W/m2K.
capillary force dropwise condensation interferometry