Thermodynamically admissible diffuse interface model for nanoscale transport of dense fluids

We investigate the interfacial fluid dynamics and heat transfer at nanoscales using an improved diffuse interface approach for liquid–vapour interfaces in non-equilibrium. Conventional Navier–Stokes–Korteweg (NSK) formulations often fail to accurately capture transport phenomena across extremely thin interfaces due to underestimation of interface resistances. In this work, we improve the NSK model by adding a production term in the momentum equation based on higher-order corrections. To enhance interface resistances, viscosity and thermal conductivity are made dependent on the density gradient, increasing resistance only within the interface region. The gradient-based coefficients are determined by fitting to solutions of the Enskog–Vlasov equation for Couette flow of Struchtrup & Frezzotti (2022 J. Fluid Mech. , vol. 940, p. A40). Applying these fitted equations to pure heat conduction and planar evaporation problems shows that the model accurately captures interfacial transport, making it a useful tool for studying nanoscale evaporation, thermal management and the droplet dynamics on solid surfaces.