Experimental investigation of the steam condensation with air and helium

Condensation of steam coming out from the coolant pipe during a loss of coolant accident (LOCA) plays a key role in removing heat from the primary containment of the nuclear reactor. The presence of air and helium reduces the overall heat transfer coefficient substantially. Condensation experiments in the presence of non-condensable gases (e.g. air, helium) were conducted to evaluate the heat removal capacity of a vertical mounted smooth tube.The influences of various parameters, especially the wall subcooling, on the steam condensation heat transfer with non-condensable gases have been obtained for the wall subcooling ranging from 20 to 70 degrees C, total pressure ranging from 2.0X105 Pa to 7.0X105 Pa and air mass fraction ranging from 0.10 to 0.95. The empirical correlations for the heat transfer coefficient, consisting of the mass fraction of the non-condensable gases (air/air helium), total pressure, wall subcooling, and helium mole fraction in non-condensable gases, have been developed based on the experimental results. The relative error of proposed correlations with experimental data is less than 10%. The helium stratification on the condensation has been researched from the distribution of helium fraction and the bulk temperature at different axial positions. It shows that the helium stratification can be ignored when the helium mole fraction in non-condensable gases is less than 35%.