Thermo-Mechanical Exergy of a Substance Below Environmental Pressure

In this work, we demonstrate why classical thermo-mechanical exergy functions are incorrect below the environmental reference pressure, since they result in too small or even negative values. We present new derivations for thermo-mechanical exergy for fluids at any temperature or pressure above or below the environmental reference temperature and pressure. We then present new pressure-enthalpy-exergy diagrams of real chemicals to visually demonstrate the results.