ABSTRACT CTS-9632685 The proposed project is to investigate condensation in micro grooves that are 5 to 500 mm wide. Prior studies have shown that when micro grooves with such small dimensions are involved, the condensation rate could not be completely explained by models which only take into account gravitational and capillary forces. The proposed work is to incorporate interfacial forces in a model and conduct heat transfer experiments to determine the individual roles of gravitational, surface tension, and interfacial forces, and verify the model. By using micro grooves of different widths and apex angles, the dominance of the different forces could be revealed. The working fluids to be used are ultra-pure water and methanol.