Thermal Conductivity Calculation in Organic Liquids: Application to Poly-α-Olefin

Area of Science:

• Computational materials science
• Tribology
• Lubricant chemistry

Background:

• Automotive lubricants require precise thermal property understanding for engine efficiency and longevity.
• Previous work focused on engine mechanical parts; this study addresses lubricant thermal conductivity.
• Poly-α-olefin base oil (PAO4) is a common lubricant base stock.

Purpose of the Study:

• To understand and predict the thermal conductivity of poly-α-olefin base oil (PAO4).
• To develop and validate a methodology for calculating thermal conductivity using non-equilibrium molecular dynamics.
• To compare simulation results with experimental data.

Main Methods:

• Non-equilibrium molecular dynamics (NEMD) simulations were employed.
• The sink and source method was used to impose a heat flux.
• Four different force fields (OPLS-AA, PCFF, COMPASS, and an in-house field) were evaluated.
• Simulations were conducted across a temperature range of 300 to 500 K.

Main Results:

• A detailed methodology for calculating thermal conductivity (κ) was established, accounting for system-specific constraints.
• Thermal conductivity values were computed for PAO4 using four force fields.
• Simulation results were compared against experimental data obtained via the laser flash method.
• Excellent agreement was observed at room temperature for the in-house force field.

Conclusions:

• Non-equilibrium molecular dynamics is a viable method for predicting lubricant thermal conductivity.
• The in-house force field demonstrated high accuracy in predicting PAO4 thermal conductivity at room temperature.
• Accurate thermal property prediction is crucial for optimizing lubricant performance in automotive engines.