  On the assumption that experimentally validated tabulated thermodynamic
properties of saturated fluids published by the National Institute of Standards
and Technology are accurate, a theoretical thermodynamic cycle can be
demonstrated that produces a net-negative entropy generation to the universe.
The experimental data on the internal energy can also be used to obtain a
simple, empirical equation for the change in internal energy of a real fluid
undergoing isothermal expansion and compression. This demonstration provides
experimental evidence to the theory that temperature-dependent intermolecular
attractive forces can be an entropic force that can enhance the thermodynamic
efficiency of a real-fluid macroscopic heat engine to exceed that of the Carnot
efficiency.
