Numerical Investigation on Unstable Direct Contact Condensation of Steam in Subcooled Water

Abstract

Stable direct contact condensation of choked steam jets in subcooled water has been the focus of researchers during the last three decades. Comparatively fewer works were reported on unstable direct contact condensation of steam jets which typically occurs at low steam mass flux and low pool subcooling. The focus of this paper is on the study of unstable direct contact condensation of steam jets in subcooled water occurring at low steam mass flux using numerical techniques. A two-fluid modeling approach has been adopted with a thermal phase change model for capturing the condensation phenomena. The numerical results are compared with the available experimental data, and a reasonable agreement (average discrepancy was around 15% for overall heat transfer coefficients and 11% for average time periods) was observed. Attempts were made to understand the unstable nature of the steam jets under the simulated conditions. The effect of pool subcooling on plume shapes, heat transfer coefficients and pressure amplitudes were examined. Finally, semi-empirical models available in the literature were compared with the simulation data, and the results were analyzed. The outcome of the article will be useful in understanding the flow physics, and characterization and design recommendations for direct contact condensers operating in the unstable oscillatory regime.