Developing a One-Dimensional, TwoPhase Fluid Flow Model in Simulink
Blacksburg, Virginia, (September 2013)Abstract
In this thesis, a one-dimensional, two-fluid model is developed in MATLAB-Simulink. The model features a mass, momentum, and energy balance for each fluid—an ideal gas and an incompressible liquid. The simulation may model a straight pipe section, or a pipe section that involves a cross-sectional area change. Rough models of interphase heat transfer and interphase friction are included. Currently, phase change is not modeled in the simulation Also, a single-fluid model was developed before the two-fluid model, as an intermediate step in developing the two-fluid model. The single-phase simulation applies a mass, momentum, and energy balance for the single fluid, and ideal gas. The single-fluid model was validated by incompressible flow, Fanno flow, and isentropic flow models. The incompressible model demonstrated the simulations ability to properly balance pressure and frictional forces. The Fanno flow model showed that the simulation could capture compressibility effects. The isentropic flow model validation verified that the simulation could model area change properly. The two-fluid model was validated using the Homogeneous Equilibrium Model (HEM). An analytical model of HEM flow with frictional pressure drop was developed to compare against the simulation results. To achieve the HEM, interphase effects were tuned so that the liquid and gas phases had similar temperatures and velocities. Under these conditions, the simulation matched the analytical model. The thesis goal is to create a solid foundation for an open-source, one-dimensional, two-fluid model that is easier to use and modify than current nuclear system analysis software.