Work from Irreversible Heat Engines

The general existence of a maximum for available work when there is a temperature difference between reservoirs and a closed cyclical system working at steady-state conditions is demonstrated. There is also a maximum for efficiency with internal irreversibility. Dependence of the maxima on entropy generation is demonstrated and the variations of the maxima with temperature in heating and cooling fluid of the engine are described. The maximum work per cycle is estimated from an exergy balance for an open system comprising two heat sources which are input- and output-cooled and heated fluids.