Comparison of MARS-KS to SPACE for counter current flow limitation model

Abstract

In two phase flow, the counter current flow limitation (CCFL) occurs in a situation in which the liquid and gas flow in the opposite direction. When gas flows upward with small flow rate while the liquid flows downward, the interface between the liquid phase and the gas phase is smooth since the interaction between two flows is small. However, if the gas upward flow is large enough, the downward liquid flow decreases drastically or flows in the opposite direction due to interfacial drag. Various complex physical phenomena occur at the interface between the liquid phase and the gas phase. This is an important phenomenon which may occur during loss of coolant type accidents in a nuclear power plant. Therefore, CCFL is one of the thermal-hydraulic models which has significant effect on the reactor safety analysis code performance. In this study, the CCFL model will be evaluated for MARS-KS based on two-phase two-field governing equations and SPACE code based on two-phase three-field governing equations. This study is conducted by comparing MARS-KS code to SPACE code results of liquid upflow and liquid downflow rate for different gas flow rate for the famous Dukler’s CCFL experimental data.