Entropy production and lost work for some irreversible processes

In this paper we analyse in depth the Lost Work in an irreversible process (i.e. IRREV REV Lost ) W =W -W . This quantity is also called ‘degraded energy’ or ‘Energy unavailable to do work’. Usually in textbooks one can find the relation Lost U W º TDS . Here we show that Lost W can be expressed in terms of internal and external Entropy production, int p and ext p , quantities which enable to write down in a simple way the Clausius inequality. We will show that º + B A Endo ext ext B A Lost sys T T W dp d p int , where sys T is the temperature of the system during the corresponding quasi-static process and ext T is the temperature of the external heat source during the related Endo-reversible process. Endo ext dp is the infinitesimal entropy production in each infinitesimal step of such Endoreversible process. Examples are given for elementary processes.