Thermal modeling of double slope solar still by using inner glass cover temperature

Expressions for water and glass temperatures, hourly yield and instantaneous efficiency for double slope solar distillation systems have been derived. The analysis is based on the basic energy balance for the systems. A computer model has been developed to predict the performance of the still based on both, the inner and the outer glass temperatures of the solar still. In the present work two sets of values of C and n (Cinner, ninner and Couter, nouter), obtained from the experimental data under Indian climatic conditions, have been used. It is concluded that (i) there is a significant effect of operating temperature range on the internal heat transfer coefficients and (ii) by considering the inner glass cover temperature there is reasonable agreement between the experimental and predicted theoretical results.