Numerical and experimental investigation on condensate droplet detachment of solar still

•A numerical model is adopted to reveal the droplet behavior on lower surface of solar still.•Critical radius and travel distance of droplet before detachment are numerically investigated.•Average experimental values of Vc and Dd are 49.3 μL and 19.2 mm at β = 30°, θ0 = 120°.•An optimized surface featuring hydrophilic-hydrophobic patterns is proposed and evaluated.