Experimental Investigation on the Pressure Oscillations Induced by Subsonic Steam Jets Under Different Vessel Pressures

Abstract

An experimental study has been conducted to investigate the characterisitcs of subsonic steam jet condensation pressure oscillations in the ranges of steam mass flux 50-90 kg/m 2 s, water temperature 20-90 ℃ and vessel pressure 0.1-0.4 MPa. High frequency dynamic pressure and high speed images of the steam bubble condensation process are recorded and analyzed. It is found that the steam bubble necking frequency increases with steam mass flux and decreases with water temperature. The vessel pressure also has an effect on the steam bubble necking frequency. The pressure oscillation intensity in the pipe increases with steam mass flux in condensation oscillation region but the trend is opposite in chugging region. The vessel pressure can strengthen the inner pipe pressure oscillation in chugging region. The pressure oscillation intensity in the pool increases initially but decreases rapidly then with the water temperature. The water temperature where the pressure oscillation intensity becomes maximum shifts lower with an increasing vessel pressure. An equation correlating the Strouhal number, Reynolds number and Jacob number is developed and can predict the experimental data obtained under 0.1 MPa vessel pressure with a deviation within ±10%. A dimensionless pressure term is added in the correlation to be applied for 0.2-0.4 MPa conditions and the maximum discrepancy between the predicted values and experimental results is within ±15%.

Keywords: Subsonic steam jet condensation, Pressure oscillation, Vessel pressure, Steam bubble, Oscillation frequency