Experimental investigation on the interface shape of bubble condensation for vertical upward steam jet at low mass flux

Steam direct contact condensation in subcooled water is widely used in various industries. The steam-water interface shape is an essential parameter for direct contact condensation. An experimental study was carried out to investigate the flow patterns and interface shape of bubbling regime with a vertical upward steam jet. Steam mass flux and water temperature were 8.34–50.13 kg/(m²∙s) and 40–85°C, respectively. Three flow patterns such as chugging, smooth grown bubble, and rough grown bubble were found based on the dynamic behavior of steam-water interface. The bubble collapse frequency and the maximum bubble radius at the bubble growth stage were calculated. The bubble collapse frequency increased rapidly when the smooth grown bubble regime was transformed into the rough grown regime. When the water temperature was between 40-80°C, the maximum bubble radius initially increased, and then decreased with the increase of steam mass flux. A transition criterion from the smooth grown bubble regime to the rough grown bubble regime was given based on the theoretical analysis and experimental data.