Heat and Mass Transfer and Thermo Physical Analysis of Water Distillation Using Passive Solar Still

Abstract

The demand of fresh water is becoming an increasingly important issue across the world. To alleviate this problem, a single slope single basin solar still was designed and tested. Top glass cover 9° slope ensures a very good transmission of solar radiation inside the still. In this paper a review of factors that improve the performance of the still is presented. Energy balances are made for each element of the still; solar time, direction of beam of radiation, clear sky radiation, optical properties of the cover, convection outside the still, convection and evaporation inside are accounted. Theoretical analysis of the heat and mass transfer mechanisms inside the solar still has been developed to find out heat transfer coefficients such as internal and external heat transfer modes and thermo physical properties such as dynamic viscosity, density, thermal conductivity, latent heat of evaporation and saturated vapor pressure for passive solar distillation system. Heat transfer coefficients were estimated for the present system since the still efficiency depends on heat transfer modes. It is also suggested that the water temperature plays a vital role in the distillate output since it increases significantly with the rise of basin water temperature. It is also found that the rise in water temperature increases the evaporative heat transfer coefficient value significantly.