Research on direct contact condensation of steam-air mixture in subcooled water

An experimental research was conducted on direct contact condensation of steam-air mixture in subcooled water flow in a rectangular channel. The inlet parameters including steam mass flux, water mass flux and water temperature were tested respectively in the range of 150~400 kg/(m²s), 6000~8000 kg/(m²s) and 30℃. Three different flow patterns for pure steam jet in water flow were observed as bubble flow, oscillation jet and stable jet by using a high speed camera through the visualization window. The effect of air mass fraction on flow patterns, wall temperature and pressure distributions was discussed, the results indicated that: with the increase of air mass fraction, the condensation of steam on the interface was hindered, the interface size of bubble flow and oscillation jet enlarged while that of stable jet changed a little, the mixture layer thickened and large amount of gas bubbles gathered at the steam region tail. Moreover, as air mass fraction increased, the upper wall temperatures decreased while the bottom wall temperatures and pressures increased. The peak of bottom wall pressure distributions moved away from the steam nozzle outlet, indicating that the interface size enlarged.