Solaris 2019–India Renewable Energy Sustainable Climate 7-9 Feb 2019 Investigation of the performance of single slope solar still at different salt concentrations Pankaj Dumka, Prince Goyal, Kedar Mishra, Gaurav Goswami, Manishi Parashar, Dhananjay R. Mishra * Jaypee University of Engineering & Technology, Guna-473226, India * Corresponding author. Tel: +91-9893808251, E-mail: dhananjay.mishra@juet.ac.in Abstract: In this manuscript, an effort has been made to inspect the influence of salt concentration on the internal heat transfer coefficients in a single slope single basin conventional solar still. Experiments were performed with seven different salt concentrations (0, 0.5, 1, 1.5, 2, 2.5 and 3%) for different seven days in the month of April 2018 at Guna, India (77°19’ E, 24°39’ N). A numerical model proposed by Kumar & Tiwari has been used for theoretical calculations. It has been observed that at 1% salt concentration the evaporative heat transfer coefficient is highest when compared with 0, 0.5, 1.5, 2, 2.5 and 3%. The evaluated values of C and n at 1% salt concentration are 5.4891and 0.1308 respectively. Hence it is concluded that; feed water containing 1% of salt can improve the energy exchange mechanism in passive solar still remarkably. Keywords: Desalination, passive solar still, Salt concentration Nomenclature (Optional) ܣ ௦ Basin area…………………………… (m 2 ) C Constant  ௣ Specific heat at constant pressure…………………………………..(J/kg-K) D Characteristic length of solar still….. (m) G Acceleration due to gravity………(m 2 /s) Gr Grashof Number ℎ ௖௪ Convective heat transfer rate….. (W/m 2 K) ℎ ௘௪ Evaporative heat transfer coefficient…… ……………………………………………(W/m 2 K) ℎ ௥௪ Radiative heat transfer coefficient……… …………………………………………..(W/m 2 K) ℎ ଵ௪ Total internal heat transfer coefficient… …………………………………………..(W/m 2 -K) ܫ( ݐ) Incident solar radiation on inclined cover surface…………………………………….. (W/m 2 ) K Thermal conductivity of humid air…. (W/mK) L Latent heat of vaporization…….... (J/kg) ̇ ௘௪ Distillate output ……………….(kg/m 2 hr) N Constant Nu Nusselt Number  ௖௜ Saturated vapor pressure on inner glass surface………………………………………. (Pa)  ௧ Total atmospheric pressure………… (Pa)  ௪ Saturated vapor pressure on water surface……………………………………….. (Pa) Pr Prandtl Number ݍ̇ ௖௪ Convective heat transfer rate from water to glass cover……………………………...(W/m 2 )  ௔ Ambient Temperate…………………… ( o C)  ௖௜ Inner glass cover temperature………. ( o C)  ௪ Temperature of water surface……….. ( o C) Greek ߪStefan Boltzmann constant……… (W/m 2 K 4 ) μ Dynamic viscosity of humid air…... (Ns/m 2 ) ߝ ௘௙௙ Effective emissivity ߝ ௪ Emissivity of water surface ߝ ௖௜ Emissivity of Glass surface ߟ ௜ Instantaneous thermal efficiency 1. Introduction Rapid population growth and industrialization are one of the causes for continuous reduction of pure drinking water on the earth. Solar stills have been recognised long back as a cost- effective desalination devices. Wilson [1] in 1872 first used solar still to supply potable water to a nitrate mining community. But these passive solar stills suffer the major drawbacks of low distillate output and requirement of large surface area. In this view, various researchers have anticipated a different method for enhancing the productivity of passive distiller units. Mishra and Tiwari [2] have reported the enhancement of distillate yield by spreading coal and