With excellent capability for heat removing and compression resistance, condensers with horizontal in-tubes condensation have been used in some current designs for nuclear plant safety systems, especially for passive containment cooling system (PCCS). To confirm the thermal-hydraulic behavior of the horizontal condensers in PCCS when LOCA happens, the study on condensation of steam in the presence of non-condensable gases in tubes is prior to be investigated. An experimental investigation on forced convection condensation of steam/air mixtures in a horizontal tube was presented. The experimental data was obtained under the inlet mixtures velocity ranging from 17.27-36.88m/s, inlet noncondensable gas mass fraction ranging from 5%-32%, total pressure ranging from 0.15-0.4MPa and local inner wall subcooling ranging from 20.5-78.7K. The influences of inlet air mass fraction, velocity and pressure of the bulk mixture gases and inner wall subcooling on local condensation heat transfer were analyzed. A correlation for evaluating the local condensation heat transfer coefficient along the tube has been developed which shows a great agreement with the experiment results with an error of ±20%.
