Energy and exergy analysis of conventional and modified solar still integrated with sand bed earth: Study of heat and mass transfer

Experimental and theoretical evaluation of solar-earth water still suitable for coastal areas or swamps has been investigated. Relative analysis of energy and exergy of MSSIE and CSS have been done by using Dunkle, Clark, Kumar & Tiwari, Tsilingiris and modified Spalding's mass transfer theory reported in this paper. Clark model overestimates theoretical yield throughout the experimentation and it gives 285.02% and 82.4% higher distillate output as compared to experimental result in case of MSSIE and CSS respectively during peak hours. It has been observed that internal efficiency gradually increases till 16:00 h and reaches a value of 25.55% & 25.29% for MSSIE and CSS respectively. For MSSIE the maximum value of exergy as predicted by Clark model is 5.015% at 15:00 h which is 141.1% and 64.9% higher than Kumar & Tiwari and Dunkle models respectively. For CSS maximum exergy efficiency as predicted by Clark is 1.656% at 15:30 h which is 26.9% and 66.53% higher than Kumar & Tiwari and Dunkle models respectively. Numerical results obtained from Kumar & Tiwari model gives good agreement with the experimental result as it predicts only 11.9% higher value in case of MSSIE and 12.31% higher in case of CSS.