Enhancing the Performance of a Double-Slope Solar Still Using Thin and Twisted Fins: A Numerical Study

Water scarcity is a global issue. Solar desalination systems, particularly double-slope solar stills (DSSS), offer an efficient, affordable approach to produce fresh water. This study systematically investigates the influence of fin geometry (thin vs. twisted) and fin number on the thermo-fluid behavior and productivity of DSSS under hot climatic conditions. Using ANSYS Fluent 2019 R1, the mass, momentum, and energy equations were discretised via the finite volume method to examine simultaneous heat, mass, and fluid flow inside the basin. Results show that using fins significantly enhances system performance. At peak time (12:00 PM), productivity improved from 0.8206 L/h (conventional) to 1.4928 L/h for thin fins (81.91% enhancement) and 1.9535 L/h for twisted fins (138.13% enhancement). Efficiency likewise improved from 28.543% to 59.810% and 80.500%, respectively. On a daily basis, productivity and efficiency increased from 3.514 to 8.761 L/m²·day and from 25.87% to 74.97% using 49 twisted fins, representing improvements of 149.32% and 189.68%. Twisted fins exhibit superior performance by enhancing internal mixing, reducing thermal boundary layer thickness, and improving vapor distribution. Ultimately, the best results were obtained with 49 twisted fins, demonstrating that sophisticated geometric modifications are essential to maximize DSSS productivity and efficiency.