A comparative numerical study of three similar passive solar stills: Single slope, V-type, and greenhouse

In this paper, three solar stills with similar geometries are numerically investigated for analysis and comparison. The solar stills include single slope, V-type, and greenhouse stills. Steady-state laminar flow numerical simulations with different water surface temperatures and cover glass temperatures are performed. Simulation results were confirmed with data from analytical and experimental models to ensure reliability. The results showed that the V-type still has a higher number of recirculation zones than that of single slope and greenhouse stills. These vortex regions are small, but the velocity magnitude is no less than the other two stills. This difference makes the freshwater yield and convection heat transfer coefficient of V-type still the largest. Daily freshwater productions of single slope, V-type, and greenhouse stills are 0.592, 0.673, and 0.623 kg/m2, respectively. Productivity at 15 PM is 2.5 times higher than the hours from noon to 14 PM. The natural convection heat transfer coefficient seemed to be unvaried with the temperature difference but changed strongly with the still geometry.