Performance of a siphon-like water supplying solar distiller with helium gas enhancing the reverse film evaporation process

The multistage solar desalination method based on the interface local thermal method is an attractive and efficient desalination method. However, there are still problems such as the upward diffusion of water vapor in the air and the downward irradiation of solar light, which make the multistage device fail to effectively condense and interface salt crystallization cannot be effectively eliminated, hindering the development of large-scale and sustainable applications of this technology. Here, we use a cheap nanofiber super-hydrophilic material to promote the flow of seawater at the interface and promote the discharge of salt crystallization under the siphon-like effect. At the same time, the water vapor‑helium space is constructed by filling helium to promote the downward diffusion of water vapor in the space and solve the problem of insufficient multistage condensation. In this work, a two-stage and three-stage reverse mass transfer solar seawater desalination system with solar hot film evaporation was built, and the corresponding theoretical calculation and experimental verification were carried out. The experimental results show that under sunlight irradiation of 800 W m⁻², the three-stage experimental system filled with helium can effectively enhance the condensation of water so that the GOR value of the system vapor is 1.54, the first-stage evaporation efficiency reaches 67.9 %, and the water productivity reaches 1.85 kgm⁻²h⁻¹. In this study, injecting low molecular weight gas to achieve efficient condensation of the system to improve the performance of the interfacial evaporation desalination system provides a new method and reference.