Coupled heat-water-salt transport in 3D solar interfacial evaporator

3D solar interfacial evaporation exhibits a high evaporation rate and is thus a promising approach to address the global freshwater crisis. However, the absence of a comprehensive theoretical framework makes it challenging to optimize the evaporator to maximize the evaporation rate while preventing salt precipitation. To bridge this gap, we develop a theoretical model to describe the coupled heat–water–salt transport in 3D evaporators fully saturated with liquid. The model is validated through comparisons with experimental data. The temperature profile along the height of evaporator has a similar trend as that of local evaporation flux. At a salt mass fraction of 5%, the evaporator can achieve a height of up to 22 cm while remaining fully saturated and free from salt precipitation. The range of pore sizes required to achieve this maximum evaporator height has been identified. Under these conditions, the corresponding maximum evaporation rate can be 7 times higher than the solar-thermal limit. Both the maximum evaporator height and the maximum evaporation rate are linearly reduced with the increase of the salt concentration in the liquid reservoir. One effective strategy to increase the maximum height of evaporator is to increase the longitudinal dispersivity, which is dictated by the pore structures. These insights are essential to optimization of 3D evaporators. The theoretical model presented in this work provide a critical foundation for advancing solar interfacial evaporation technology.