Numerical investigation on dynamic performance of hydrogel-based solar-driven seawater desalination system

Hydrogel-based interfacial solar evaporation is a promising pathway for sustainable seawater desalination, yet its optimization still relies heavily on empirical trial-and-error because the dynamic coupling among internal water transport, interfacial phase change, and salt accumulation remains insufficiently understood. In this study, a three-dimensional coupled heat–moisture–salt transport model is developed to investigate the internal mechanisms of hemispherical-capped hydrogel evaporators. The model is validated against experimental swelling and evaporation data. Results show that the hemispherical geometry markedly outperforms planar configurations, achieving an average evaporation flux of 4.21 kg·m⁻²·h⁻¹ and a volumetric water-processing rate of 412 kg·m⁻³·h⁻¹. The performance is found to be governed by the competition between effective evaporation-area gain and internal water-supply resistance. An optimal hemispherical radius of 9 mm and a hydrogel thickness of 7.5 mm are identified, corresponding to an area-averaged evaporation flux of 4.31 kg·m⁻²·h⁻¹ and a volumetric water-processing rate of 531 kg·m⁻³·h⁻¹ under the baseline condition. The influences of solar irradiance, incidence angle, ambient temperature, relative humidity, wind velocity, and feed salinity are further quantified. In particular, the optimized hemispherical structure maintains stable evaporation at salinity levels relevant to natural seawater. Overall, this work provides a validated theoretical framework for the mechanism-based design and practical optimization of high-efficiency solar-driven seawater desalination systems.