Pressure-driven phase change model for interfacial mass transfer in air-water systems

The Lee model uses saturation temperature as the only criterion for phase change and does not consider the dynamic influence of vapour partial pressure. This paper addresses the dry air-water system at 0-60°C by incorporating a vapour pressure gradient source term via a user-defined function within the VoF interface capture framework. This construct enhances the gas-liquid mass transfer model by dynamically updating the saturated vapour pressure via temperature-dependent expressions. The simultaneous coupling of temperature and humidity gradients enables a more comprehensive characterization of the thermodynamics of low temperature evaporation, thus broadening the applicability of the model and enabling it to better approximate real-world physical processes. Systematic investigation of the mass transfer characteristics of the phase change mass transfer coefficient, β, over five orders of magnitude (from 10⁻¹-10⁻⁵) revealed the behavior of the key control mechanisms. In the high phase change mass transfer coefficient region (β > 10⁻³), the evaporation mass transfer rate is primarily controlled by the vapour pressure difference, whereas in the low phase change mass transfer coefficient region (β < 10⁻³), the evaporation mass transfer process is dominated by β. Using parameter inversion with independent experimental data, the optimal range for the phase change mass transfer coefficient, β, in low temperature evaporation simulations of dry air-water single-pore bubble systems was determined to be 10⁻⁴-10⁻⁵. The developed model provides an optimized framework for simulating phase change mass transfer in low temperature evaporation processes.