Thermal modeling based on solar fraction and experimental study of the annual and seasonal performance of a single slope passive solar still: The effect of water depths

This paper reports on the annual as well as seasonal performance analysis for different water depths in a single slope passive solar still of cover inclination of 30°. The experiments were conducted through out the year from June 2004 to May 2005 on six clear days of every month for 24 hours a day, for six different water depths. This experimental set up has been installed at the IIT Delhi, New Delhi, India the latitude of which is 28.35′N. The lower depth has been found giving the highest annual yield. Increasing the water depth decreases the yield of the still up to depths of about 0.1 m but at greater depths than this the yield becomes almost constant. The developed thermal model has validated the hourly yield for various water depths in summer and winter. The various modes of internal energy transfer within still have been evaluated and compared relatively for different depths and seasons. The dominance of evaporative fraction within 32–37°C has been noticed depending on the water depth under consideration. The concept of solar fraction and hourly values of solar azimuth and altitude angles has been used in thermal modeling to predict different parameters. The experimental value of yield of different water depth has been compared with the theoretical values obtained by thermal modeling and found in agreement. The effect of various parameters like ambient air velocities, basin absorptivity have been found and compared for the different water depths in still. The above results reported in detail within this paper have been found in accordance to the results obtained by earlier researchers.