Dynamic Simulations of Pressure-Drop Type Instabilities in a Two-Phase Upflow Boiling System Including the Effect of Thermal Non-Equilibrium

Two-phase flow pressure-drop type instabilities in a two-phase upflow boiling system has been studied theoretically. The drift-flux model is adopted in predicting the steady state characteristics of the boiling system, using the finite difference method. The dynamic simulation of the quasi-static pressure-drop type instability in the boiling system is presented. The thermal non-equilibrium effect between the two phases is included by assuming the temperature profile in the subcooled boiling region. By comparing the equilibrium theory, non-equilibrium theory and experiments, it is concluded that the models including the nonequilibrium effects fit better the experimental results of the steady state characteristics of the system, as well as the system stability boundary and oscillations characteristics (amplitude and period).