Intensification of heat and mass transfer by turbulent reactive phase change in a diffuse-interface framework

Reactive fluids undergoing turbulent phase change exhibit intrinsically coupled interfacial mass transfer, chemical conversion, and heat transport, which challenge conventional vapor–liquid equilibrium closures and strongly affect overall system performance. We develop a diffuse-interface framework for turbulent reactive multiphase flows. It couples reactive vapor–liquid equilibrium (RVLE) thermodynamics, two-scalar species transport of separate liquid- and vapor-phase concentrations, single-mixture momentum and enthalpy equations, and a Stefan-flow-based interfacial mass-transfer closure with resolved turbulence. The formulation is applied to turbulent reactive evaporation of a wall-bounded liquid N2O4 film into a vapor mixture undergoing the reversible gas-phase reaction N2O4⇌2NO2. The simulations indicate that rapid interfacial equilibration organizes the flow into distinct thermochemical layers: a phase-change-dominated region adjacent to the liquid side, a reaction-dominated vapor-rich region, and an intermediate layer in which both processes contribute comparably. Evaporation induces strong localized endothermic cooling, quantified here by a saturation-referenced thermal-reduction ratio IT,Γ. This ratio reaches an equilibrium-limit estimate of 58% at the highest reactivity level (αk=1, corresponding to the local-chemical-equilibrium limit), compared with about 12% at low reactivity. Turbulence wrinkles the interface, steepens vapor-side scalar gradients, enhances mixing, and strengthens the coupling between heat and mass transfer. These results show that turbulent reactive phase change is governed by the joint action of interfacial equilibration, chemical kinetics, latent heat, and turbulent mixing and is therefore not recovered by appending a reaction step to a non-RVLE model.