Thermal Modelling of Solar Still

Abstract

Supply of drinking water is a major problem in under-developed and in some developing countries. The use of solar energy for desalination purpose was one of the first processes developed for producing fresh water from salt water. The process is based on the use of solar thermal energy to evaporate water thus separating pure water from brine water. The solar stills are used as a good method for obtaining the fresh water for even small scale demand because of economical and technical advantages as it uses the inexpensive technology including the material prices and manufacturing. Hence for increasing the performance of solar still it is necessary to model and investigate the effect of different parameters as condensing cover. Present work aimed at modeling of single slope solar still using ANSYS CFX 13.0 to investigate the effect of different slopes on the yield. Three dimensional two phase model is developed for evaporation and condensation process to simulate the temperature distribution of water and gas phase and also the amount of fresh water productivity. Two condensing covers at inclination 150 and 300 slope studied to analyse the effect on rate of evaporation. Simulation is carried out from 40-600C with 20C interval. For 150 and 300 inclination various contours have been plotted and studied for each simulation. Simulation results have been compared with the available experimental data it was observed that fresh water production rate and water temperature are in good agreement. Simulation results are also used to calculate the convective and evaporative heat transfer coefficient based on two models and there results are compared with experimental data they are in good agreement with certain error. It was concluded that condensing cover at inclination 300 obtain the higher yield and high convective and evaporative heat transfer coefficient as compared to 150 slope.The condensing cover at 300inclination gives about 29.4% higher yield than 150 inclination. Hence CFD is powerful tool in design of solar still and studying effective parameters on the performance.