Performance of single-pass aircooled or gascooled condensers with inertsAbstract. In single-pass gascooled condensers the accumulation of noncondensables within the tubes may cause the formation of a dead zone. This may also happen in condensers that are operating with excess vapour. Simple arithmetic expressions are developed to describe the dependency of excess vapour and size of the dead zone. More over, the solution enables the calculation of the twodimensional temperature and vapour flow distribution within the condenser.