Investigation of liquid evaporation regulation by porous media in a high-voltage electrostatic field

Precise control of liquid evaporation is critically important for engineering applications such as seawater desalination, industrial cooling, and wastewater treatment; however, the coupling mechanisms among electrocapillarity/electrowetting, applied fields, solutes, and porous media remain incompletely understood. To address this, we built an experimental platform that integrates a high-voltage electrostatic system, optical visualization, and porous-substrate assemblies. Using deionized water and 1–5 wt. % NaCl solutions as working fluids and hydrophilic carbon cloths of different morphologies as substrates, we systematically investigated the effects of electrode type, porous-media morphology, NaCl concentration, and applied DC field on liquid evaporation and quantitatively analyzed the responses of key metrics such as evaporation number and capillary rise height. Results show that, under an applied electric field, the T-shaped carbon cloth exhibited the largest capillary-rise enhancement (up to 685%). NaCl concentration is significantly and negatively correlated with evaporation rate: under identical field and substrate conditions, the evaporation number decreases monotonically with increasing salt concentration. Nevertheless, the cylindrical carbon cloth maintained the highest evaporation efficiency across the entire salt range, with an average evaporation-number enhancement of 21.13% over the 3.5–8.5 kV interval. This study is the first to systematically investigate and experimentally quantify the internal control mechanisms governing pre-crystallization stage evaporation under the coupled influences of porous medium morphology, electric field strength, and salt concentration, and it identifies optimal parameter combinations and substrate configurations, providing quantitative experimental evidence and theoretical support for evaporation-based treatment of saline wastewater.