Enhancement of Phase Change Heat Transfer by using Surface Energy Patterning Techniques

Using phase change of working fluid to remove heat in a heat exchanger device is a high efficiency method. When superheated vapor passes over a sub-cooled substrate, water droplets nucleate and grow by coalescence with the surrounding drops. The merging droplets exhibit two-dimensional random motion somewhat like the Brownian movements of colloidal particles. If surface energy patterns are designed on the substrate surface, the random condensing droplets will nucleate and grow to a certain size and move toward the more hydrophilic side of the surface. Powered by this forces, condenser surface will not grow into film-wise condensation situation. Thus condensation speeds are faster than those of typical surfaces without any surface modification. This effect has implications for passively enhancing heat transfer in heat exchangers or heat pipes