Development of A Two-Phase Navier-Stokes Equation Solver for Analysis of LWR Thermal Hydraulic Problems

This paper presents a computational fluid dynamic (CFD) model for analysis of fluid flow and heat transfer with phase change. This CFD model is based on the Navier-Stokes equations in conjunction with two-equation turbulence model. Using the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) scheme, the continuity, momentum, and energy equations for the liquid and vapor phases are discretized and solved simultaneously to calculate the temperature and flow fields. A novel energy-based algorithm is developed and used to track and delineate the dynamic liquid-vapor interfacial boundary. In the formulation of the governing equations the ensemble average geometrical void fraction is replaced by a dynamic vapor-phase fraction. The topology of the vapor-liquid interfacial boundary is identified by the value of the dynamic vapor-phase fraction. In order to accelerate the convergence of the SIMPLE algorithm for problems involving wall heat flux boundary condition, an efficient enthalpy-rebalancing scheme is developed and implemented. Using an adaptive relaxation scheme further accelerates the iterative solution process. The model is successfully used for simulation of a number two-phase flow and heat transfer problems including the film boiling on a cylindrical vertical wall. (author)