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° 42′ N, long. 39° 11′ E), Saudi Arabia under the two conditions: (a) the temperatures of the inner Tgi and outer Tgo surfaces of the still cover are equal and (b) the temperatures of the inner Tgi and outer Tgo surfaces of the still cover are not equal. Effect of wind speed V on the daily productivity Pd of the still for these conditions was studied. It was indicated that for the condition Tgi = Tgo, there is a critical mass (depth) of basin water beyond which Pd increases as V increases until a typical velocity Vt. For basin water masses less than the critical mass, Pd was found to decrease with increasing V until Vt. After Vt, the change in Pd becomes insignificant. When Tgi ≠ Tgo, Pd was found to be less dependent on wind speed V for all investigated values of mass of basin water mw in the range 0 < mw ≤ 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.