Modeling and Simulation of Nucleate Boiling

This work investigates the modelization and simulation of liquid-vapor phase change in compressible flows. Each phase is modeled as a compress-ible fluid equipped with its own Equation of State (EOS). We suppose that inter-phase equilibrium processes in the medium operate at a short time-scale compared to the other physical phenomena such as convection or thermal diffusion. This assumption provides an implicit definition of an equilibrium EOS for the two-phase medium. Within this framework, mass transfer is the result of local and instantaneous equilibria between both phases. The overall model is strictly hyperbolic. We examine properties of the equilibrium EOS and we propose a discretization strategy based on a Finite-Volume relaxation method. This method allows to cope with the implicit definition of the equilibrium EOS, even when the model involves complex EOSs for the pure phases, including tabulated ones. We present two-dimensional numerical simulations that shows that the model is able to reproduce mechanism such as nucleation. 1 Phenomenon. In this talk we propose an approximation method for using general equations of state (EOS), including tabulated ones, in the numerical simulation of dynamical liquid-vapor phase change in pool boiling type flows. This phenomenon concerns various engineering fields such as the study of pressurized water reactors in the nuclear industry. Indeed, understanding the triggering of boiling crisis is a critical safety issue for the nuclear industry: when the transition occurs from nucleate boiling to film boiling in the vicinity of heating wall, the vapor acts as a thermal insulator and the wall temperature raises suddenly. If this phenomenon occurs, it may cause serious damages to the facility. 2 Model. We suppose that the medium is far from the critical point. Therefore both phases are modeled by compressible fluids equipped with an EOS given by a function (τα, εα) 7 → sα, where τα> 0, εα> 0 and sα denote respectively the specific volume, the specific internal energy and the specific entropy o