Experimental investigation and mathematical modelling of heat transfer coefficient in double slope solar still

Abstract

n this study, a double slope solar still has been designed and fabricated with the help of locally available materials for the climatic condition of Sultanpur, India. The experimental study was performed to investigate the effect of basin water, wind velocity on the heat transfer coefficient (convective, evaporative, and radiative) and yield of solar still. A mathematical model is developed to understand the impact of wind velocity and basin water depth in the double slope solar still on the heat transfer coefficient. It was found that the convective heat transfer coefficient depends upon the water mass and the temperature of basin mass, and glass cover temperature. The maximum value of hew (55.05 W/(m2K) and 31.80 W/(m2K)) and hcw , (2.48 W/(m2K) and 2.38 W/(m2K)) found for depths of 2 cm and 5 cm, respectively. The radiative heat transfer coefficient found to be a maximum of 8.31 W/(m2K) for 2 cm depth, and it increases as the condensation increases, because the glass surface temperature increases as vapour transfers its energy to the surface. On increasing the depth from 2 cm to 5 cm, the yield from the solar still decreases by 25.45 %. The maximum yield of 2.5 l/m2/day was found for a 2 cm water depth. The theoretical and experimental yield agreed with an error of 7.5 %, 3.25 %, 7.4 %, and 8.4 % for water depths of 2 cm, 3 cm, 4 cm, and 5 cm, respectively. It was also found that the yield from the solar still increases as the wind speed increase because this leads the faster condensation at the glass surface.