It is unclear why GETEM provides cost estimates for two different types of shell & tube condensers: one for Non Condensable Gas (NCG) stage condensers and another for primary steam condensing. Without any further description of the design of these devices, they should be the same. The typical heat exchange area of an NCG condenser in GETEM is much smaller than a steam condenser, thus it is possible these exponential fits are the result of fitting different ranges of heat exchanger area data to an exponential regression model.