# Tag Info

If you call $\chi$ the exergy (availability) then $\chi = U + p_o V - T_o S$ where $p_o, T_o$ are the pressure and temperature of the environment (and are assumed to be constant). To find the maximum amount of useful work that can be extracted form the system it is sufficient to analyze reversible processes only so that $dU=TdS-pdV$ and then the exergy ...