On effect of wind speed on passive solar still performance based on inner/outer surface temperatures of the glass cover

The thermal performance of a passive single basin solar still was investigated by computer simulation using the climatic conditions of Jeddah (lat. 21 degrees 42' N, long. 39 degrees 11' E), Saudi Arabia under the two conditions: (a) the temperatures of the inner T(gi) and outer T(go) surfaces of the still cover are equal and (b) the temperatures of the inner T(gi) and outer T(go) surfaces of the still cover are not equal. Effect of wind speed V on the daily productivity P(d) of the still for these conditions was studied. It was indicated that for the condition T(gi) = T(go), there is a critical mass (depth) of basin water beyond which P(d) increases as V increases until a typical velocity V(t). For basin water masses less than the critical mass, P(d) was found to decrease with increasing V until V(t). After V(t), the change in P(d) becomes insignificant. When T(gi) not equal T(go), P(d) was found to be less dependent on wind speed V for all investigated values of mass of basin water m(w) in the range 0 < m(w) <= 100 kg. The rate of heat transfer by forced convection due to wind should be estimated on the basis of the temperature of the upper surface of the still cover. (C) 2011 Elsevier Ltd. All rights reserved.