Autodifferentiated thermal properties¶

This study obtains homogeneous-state thermal properties from the implemented thermodynamic potential with PyTorch autodiff. The experimental comparisons focus on the Joule-Thomson coefficient; the final figure demonstrates the other available properties without treating them as additional validation data.

CO2 Joule-Thomson coefficient¶

CO2 Joule-Thomson property curves

CO2 Joule-Thomson parity and error

The first comparison separates experiment, the independently reported Peng-Robinson calculation, and torch-flash. The parity and signed-error panels make the pressure-dependent discrepancy visible.

Propane Joule-Thomson coefficient¶

Propane Joule-Thomson validation

The propane curves follow the experimental vapor branch over all reported isotherms. Explicit vapor-root selection avoids switching to a liquid or metastable branch during numerical differentiation.

Homogeneous-state property profiles¶

Autodifferentiated thermal-property profiles

These profiles demonstrate enthalpy, internal energy, entropy, heat capacities, Joule-Thomson coefficient, and speed of sound from supplied homogeneous states. Additive enthalpy and entropy reference choices do not affect the derivative properties.

Sources: Pedersen, Christensen, and Shaikh (2024), Chapter 8; Wang, Wang, and Sun (2017), CO2 measurements; and Sage, Kennedy, and Lacey (1936), propane measurements.