Abstract The classical Hertz–Knudsen–Schrage (HKS) relations for mass and heat transfer across liquid-vapor interfaces are valid for ideal gas vapors only. We propose a generalization of the HKS relations towards non-ideal vapors based on equilibrium and non-equilibrium property relations for a van-der-Waals-like gas obtained from the Enskog–Vlasov kinetic equation, and determine the corresponding dimensionless resistivities for mass and heat transfer across an interface. Considering constant evaporation and accommodation coefficients, it is found that all resistivities decay towards the critical point.
Henning Struchtrup (2026) studied this question.