A drift-flux analysis of the diversely heated channel using the Broyden method

Abstract

In this paper, a Drift-Flux model is presented for the analysis of the thermal-hydraulic behavior of a vertical boiling channel with various wall thermal fluxes. Detail treatment and simulation of the two-phase flow phenomena are critical to the safety analysis of nuclear power reactors. Four principal conservation equations in the Drift-Flux model are discretized using the mesh staggered finite volume technique. Broyden method is then invoked for solving the non-linear system of equations. To investigate the boiling phenomena, a code is developed based on the aforementioned approach. In the first step, the code is validated by 4 different experimental benchmarks with constant heat fluxes. Numerical results show very good agreement with those experimental data. For the next step, the sub-cooled fluid behavior exposed to variable wall heat fluxes is studied. The effect of heat flux function on the shape and quantity of thermal-hydraulic parameters e.g. void fraction, pressure, liquid temperature, fluid enthalpy and volumetric mass transfer rate along the channel is then investigated in detail. Furthermore, on the mechanism of the void fraction evolution akin to changes in the amount and the form of volumetric mass transfer rate along the tube is focused. The Broyden scheme exploited in this study proved to be much faster than the Newton method solved through either the LU factorization or the inverse of Jacobian matrix.