Turbine Model by F.D. Drake, 1988

     A standard thermodynamic is employed to simulate the preformance of a 
back-pressure or of a condensing steam turbine, with or without an electricity
generator.  In a condensing turbine, the steam is expanded from the high inlet
pressure to a very low pressure (Pcond < 1 atm), which is maintained at the
turbine outlet by a steam condenser.  Extraction of a constant or variable 
fraction of the inlet mass flow at various pressures is often used to
provide heat for feedwater preheating or cogeneration applications.  
     In contrast, the steam leaving a back-pressure turbine is superheated  so 
that it can be used for a second useful purpose like driving another low 
pressure turbine or a heating load.
     In both turbine types, two modes of calculation are possible: if the power
output is given, the model calculates the required steam mass flow rate.  In 
cogeneration systems, which are usually tracking the heat demand, the available
steam serves as the input to calculate the maximum possible power production.  

"Evaluating Cogeneration Options for a Campus Heating and Cooling Plant"
Drake F.D. M.S. Thesis 1988