Numerical Simulations of the Molecular Behavior and Entropy of Non-Ideal Argon

Abstract

A numerical model is built, simulating the principles of kinetic gas theory, to predict pressures of molecules in a spherical pressure vessel; the model tracks a single particle and multiplies the force on the spherical walls by a mole of molecules to predict the net pressure. An intermolecular attractive force is added for high-density simulations, to replicate a real fluid; the force is chosen to ensure the fluid matches the Peng-Robinson equation of state as it is compressed to a near supercritical density. The standard deviations of the molecule velocity with respect to temperature and density is studied to define the entropy. A parametric study of a Stirling cycle heat engine utilizing near-supercritical densities is modeled, to study how the temperature dependence of the attractive intermolecular Van der Waal forces can affect the net total entropy change to the surrounding environment. A practical, macroscopic-scale piston-cylinder engine was then built and demonstrated, utilizing a novel thermodynamic cycle that closely resembles the Carnot heat engine cycle, utilizing an arrangement of valves and pneumatic air to replicate the isothermal and isentropic compression and expansion of the working fluid. This heat engine cycle could be built without requiring advanced manufacturing, and utilized non-ideal carbon dioxide as the working fluid, to take advantage of the entropy effects of the Van der Waals forces demonstrated in the Argon simulations to boost the thermodynamic efficiency. This engine demonstrated this capability in a practical, macroscopic heat engine, and offers great opportunities to practical energy generation.