Critical temperature shift modeling of confined fluids using pore-size-dependent energy parameter of potential...

Area of Science:

• Thermodynamics
• Fluid Mechanics
• Materials Science

Background:

• Fluid behavior and critical properties change within nanoscale porous media due to the critical shift phenomenon or pore proximity effect.
• Existing models based on Lennard-Jones potential functions offer limited accuracy in predicting these pore-confined properties.

Purpose of the Study:

• To develop a novel cubic equation of state (EOS) for modeling Kihara fluids under adsorption conditions.
• To accurately predict the critical temperature shift and phase behavior of fluids in porous media.

Main Methods:

• Derived a cubic EOS incorporating adsorption for Kihara fluids with a temperature-dependent attractive term.
• Developed a new adjustment method ensuring reliable adherence to bulk critical conditions on a thermodynamic basis.
• Introduced a variable energy parameter in the potential function, dependent on pore size, linking macroscopic and microscopic corresponding states theories.

Main Results:

• The Kihara potential, unlike Lennard-Jones, demonstrates flexibility in fitting variable energy parameters for accurate predictions.
• The proposed model successfully predicts phase behavior and critical properties of confined fluids.
• Application to a ternary system reduced prediction errors by over 6% compared to the Lennard-Jones model.

Conclusions:

• The developed model provides a thermodynamically sound and accurate approach to predicting critical shifts in porous media.
• Varying the energy parameter with pore size is crucial for accurate modeling of confined fluid behavior.
• The Kihara potential offers superior flexibility for modeling fluid properties in nanoscale confinement.