Numerical and experimental analysis of the effect of fin inclination angle on the performance of a double-slope solar still

Desalination is an essential process for providing fresh water in regions with limited access to natural water resources, and solar stills represent a promising, low-cost solution. However, one of the major limitations of solar stills is their low productivity, which restricts their efficiency in large-scale water production. This study aims to optimize the performance of a double-slope solar still by investigating the effect of fin inclination angles on heat transfer and overall efficiency. The novelty of this work lies in the evaluation of five different fin angles (18 degrees, 34 degrees, 45 degrees, 75 degrees, and 90 degrees), a parameter that has not been widely explored in previous studies, to determine the optimal angle for improving solar still performance. The study uses the commercial computational fluid dynamics (CFD) software "Ansys Fluent" to develop a three-dimensional numerical model. This model employs the Volume of Fluid (VOF) method to simulate the water-vapor mixture, the Discrete Ordinates (DO) model to simulate heat transfer due to solar radiation, and laminar flow model. The model is validated against experimental data, including measurements of solar radiation, wind speed, and temperatures of key components of the solar still. The results showed that the absorber reached a maximum temperature of 62.5 degrees C at 13:00, and the best fin inclination angle for maximizing efficiency was found to be 45 degrees. At this angle, the water temperature increased by 22.24 %, compared to a 9.39 % increase at a 18 degrees angle. These findings demonstrate that optimizing fin angle can significantly improve heat transfer, thereby enhancing the efficiency of solar stills and addressing the challenge of low productivity in solar desalination systems.