Theoretical analysis of water distillation using solar still.

In developing countries, lack of safe and unreliable drinking water constitutes a major problem. To alleviate this problem, a solar still was designed and tested in Mubi, Adamawa State of Nigeria. The radiation from the sun evaporates water inside the solar still at a temperature higher than the ambient. The principle of operation is the greenhouse effect provided with the glass cover. Energy balances are made for each element of the still; solar time, direction of beam of radiation, clear sky radiation, optical properties of the cover, convection outside the still, convection and evaporation inside are accounted. Theoretical analysis of the heat and mass transfer mechanisms inside this solar still has been developed. The measured performance was then compared with results obtained by theoretical analysis. The results clearly show that the instantaneous efficiency increases with the increase of solar radiation and with the increase of feed water temperature. The distillation efficiency of the still is 99.64% as compared to the theoretical analysis.   Key words: Solar still, greenhouse effect, ambient, convection, evaporation, feed water.