C2H4
C2H4 provides ideal gas thermodynamic properties for ethylene over the temperature range from 200 K to 6000 K based on property information from McBride et al, 2002. The reference state for specific enthalpy is based on the enthalpy of formation relative to the elements at 25 C. The reference state for specific entropy is based on the Third Law of Thermodynamics. The reference values are from:
Bonnie J. McBride, Michael J. Zehe, and Sanford Gordon
"NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species"
NASA/TP-2002-211556, Sept. 2002
https://www.grc.nasa.gov/WWW/CEAWeb/
Transport data were fit from the tabular data provided by: P.E. Liley and P.D. Desai, "Thermophysical Properties of Refrigerants", ASHRAE, 1993, ISBN 1-1883413-10-9 for temperatures between 270 K and 475 K.
Note that C2H4 provides thermodynamic properties assuming ideal gas behavior. Use ethylene to provide real fluid properties in the subcooled, saturated mixture, and superheated regimes.