Visualization of bubble collapse phenomenon by direct contact condensation at steam bubble including non-condensable gas

Abstract

Direct contact condensation (DCC) is a phenomenon that occurs when steam is injected into a subcooled water pool and is an integral part of many industrial devices. However, the actual phenomenon involves non-condensable gases in the steam, and there has been insufficient research on how non-condensable gases affect direct contact condensation. Therefore, the purpose of this study was to clarify the bubble collapse behavior of vapor bubbles containing non-condensable gas by DCC, and the bubble collapse behavior was confirmed using a high-speed video camera. The images show periodic bulging and necking, and the contraction speed at the point of necking was slower in the bubble plume with a higher air mass fraction. The number of microbubbles produced in the rising bubble plume was suppressed in the high air mass fraction plume. Thus, there is a negative correlation between the contraction rate of the bubble plume and the size of the generated bubbles.