Analysis of experiments for the effect of noncondensable gases on steam condensation over a vertical tube external surface under low wall subcooling

Experimental investigations have been conducted to study the steam heat removal capacity with noncondensable gases (e.g. air, helium) under low wall subcooling over a vertical tube external surface. The effect of the wall subcooling on the steam condensation heat transfer coefficients has been researched by experiments when the pressure and the air mass fractions are stable. At the air/steam cases, condensation heat transfer coefficient has been obtained under the wall subcooling degree ranging from13 to 25 °C, total pressure ranging from 0.4 MPa to 0.6 MPa and air mass fraction ranging from 0.07 to 0.52. Under the same pressure and noncondensable gases mass fraction, the effect of wall subcooling on condensation heat transfer coefficient with noncondensable gases is stronger than that with pure steam. The empirical correlation is developed for the heat transfer coefficient which covered all data points within 15%. Under air/helium/steam cases, the effect of helium (simulating hydrogen) on the heat transfer coefficient is investigated under the wall subcooling degree ranging from 18 to 27 °C, total pressure ranging from 0.53 MPa to 0.6 MPa, steam mass fraction ranging from 0.6 to 0.92 and helium volume fraction in noncondensable gases keeping 0.3. None of the experimental conditions is found the helium stratification. The condensation heat transfer coefficient that got from steam/air/helium condition is about 20% lower than that got from air/steam cases.