Experimental and analytical study of interfacial area transport in rod bundle two-phase flow

The behavior of reactor systems is predicted using advanced computational codes in order to determine the safety characteristics of the system during various accidents and to determine the performance characteristics of the reactor. These codes generally utilize the two-fluid model for predictions of two-phase flows, as this model is the most accurate and detailed model which is currently practical for predicting large-scale systems. In the two-fluid model, it is important to give an accurate prediction of the interfacial area concentration due to the existence of the interfacial transfer terms. In order to achieve this goal, the interfacial area transport equation (IATE) has been developed. This research focuses on the study of the IATE in a scaled rod bundle geometry both in source and sink term modeling and experiment instrument development. By using conductivity probe in a scaled stainless steel rod bundle test section, an adequate local measurement database is established ranging from bubbly flow to churn turbulent flow regime in two pressure conditions. With proper interpolation method and area averaging, an accurate model of interfacial area source and sink terms is developed and benchmarked. Result shows that in most of the flow conditions, the relative error of interfacial area prediction is less than 15%. Since previously developed conductivity probe cannot catch the droplet information, the interfacial area concentration database from churn turbulent to annular flow regime is limited. In order to solve this problem, a droplet capable conductivity probe (DCCP) is developed and benchmarked for the measurement in churn turbulent to annular flow regime. Comparing with the high speed camera and flow rate measurements, the probe can measure the droplet fraction, velocity, interfacial area concentration, Sauter mean diameter and flow rate within ±5% error