New development in the theory of heat and mass transfer in solar stills

A single basin solar still with basin area of 0.98 × 0.98 m was constructed from galvanized iron sheets and an inclined glass cover. The still was provided with 525 W electrical heating tapes, fixed under the still basin for indoor steady state operation. The variation of basin temperature, glass temperature and evaporation rate were measured during both indoor and outdoor operation. The hourly variation of solar radiation, ambient temperature, and wind velocity were also taken during the outdoor measurements. Transient analysis of the still requires the evaluation of evaporative, convective and radiative heat transfer coefficients. The Dunkle model, which has been widely used for the prediction of the evaporative coefficient, was found to overpredict evaporation rates. The models developed in this work were found to provide better prediction for the evaporation rate measured in this work and in some previous works.