An Irreversible Heat Engine Working at the Reversible Efficiency

The thermodynamic analysis of the coupling of one cycle in the operation of a reversible heat engine with a work-degrading step in which the whole of the engine’s work output is frictionally degraded into heat at the temperature of its cold reservoir, allows identification of the fact that the engine’s reversibility is dependent on the continued availability of its work output. As long as this work remains available the engine will be reversible, this on reason of the fact that the initial condition can be restored via the simple expedient of using the said work to propel the inverse cycle. The moment this work becomes, for whatever reason, unavailable, restoration of the engine’s initial condition becomes impossible, and what was a reversible engine becomes irreversible. The inability of current thermodynamic terminology to deal with this situation is brought to light and a simple suggestion aimed at correcting this deficiency is advanced.