A computational model of a power plant steam condenser which incorporates the effects of air in-leakage and removal on the performance of the condenser is reported. The condenser interior space is modeled as a porous medium. A quasi-three-dimensional approach is taken in which the steady-stare steady-flow conservation equations for the steam-air mixture mass, momentum, thermal energy. and air mass fraction are solved for a series of two-dimensional grids perpendicular to the circulating water flow direction. The air removal system is explicitly modeled. The computational model is used to calculate the performance of the steam condenser of ct 750-MWe unit at 100 percent load. Some of the calculated variables are compared with measurements obtained in the condenser. The effects of changing various operating parameters on the condenser performance at 100 percent load are also studied.