ICONE19-43772 DROPLET DEPOSITION RATE IN VERTICAL ANNULAR TWO-PHASE FLOW

Abstract

Droplet entrainment and deposition phenomena plays important role in dynamics of annular two-phase flow. Modeling of these phenomena is essential for the estimation of dryout margins in light water reactors and boilers. In this study, the droplet entrainment and deposition rates are measured in adiabatic vertical annular two-phase flow. Two types of experiments are performed: air-water and organic fluid (Freon-113) experiments. Liquid film extraction technique is used for the measurement of entrainment fraction (i.e., amount of entrained droplets), droplet entrainment rate, and deposition rate. Additionally, in air-water experiments, liquid film thickness is measured using ring type conductance probes. This paper presents analysis of the deposition rate data. Several mechanistic and empirical correlations are available for prediction of droplet deposition rate; however, due to lack of complete understanding of the deposition phenomenon, the mechanistic correlations are still not as accurate as the empirical correlation. Assessment of the most recently published empirical deposition rate correlation (Okawa, et al., 2005) using the experimental data obtained in this study and the data available in literature shows that the correlation could not predict the data correspond to high gas velocity conditions and in a transition region between the low and high droplet concentrations. The experimental data indicates that the deposition rate approaches a maximum limiting value at high gas velocity; however, the correlation predicted continuously increasing or decreasing deposition rates. Detailed understanding of the deposition mechanism under high gas velocity is developed based on the study of droplet dynamics.