Modeling of Moist Air Condensation Underneath Engineered Surfaces

Abstract

Atmospheric moist air is a mixture of water vapor and air, incorporating various non-condensable inert gases such as Nitrogen, Oxygen, Argon, Carbon dioxide and Hydrogen. The ambient air contains 1.29×1013 m3 of fresh water in form of water vapor. Once extracted efficiently this amount of water is ample to accomplish all the basic requirements of life on Earth. The current water crises scenario necessitates the development of technologies for extracting potable water from ambient air. In this lieu, phenomena of condensing water vapors present in moist atmospheric air has gained substantial scientific and societal attention. The condensation of moist air is preferred in droplet mode over film mode, due to high transport coefficients associated with dropwise condensation. In addition to water harvesting applications, moist air condensation has wide applications in nuclear and thermal power plants, humidification and dehumidification devices, heating ventilation and air conditioning (HVAC), water purification and distillation units etc. Due to wide applicability of moist air condensation it is essential to understand the behaviors of all the performance parameters that governs the transport coefficents in moist air condensation process. In this context, present research was carried out to develop a holistic mathematical model for droplet condensation of moist air. In order to investigate the effect of various operating parameter on the heat transfer and condensation rates associated with moist air condensation. This study also reveals that convection dominate during droplet slide-off. The effect of constriction resistance is negligible for Cu surface with thickness less than 2 mm. Thin condensing surfaces with high contact angle and conductivity enhances the thermal rates of condensation process. newline