ISOBUTANE and R600a
ISOBUTANE (also referred to as R600a) provides high accuracy thermodynamic and transport properties for isobutane (R600a, CAS# 75-28-5, Molar mass =58.122 g/mol) using the Fundamental (or Helmholtz Free Energy) Equation of State formulated by:
D. Bucker and W. Wagner
"Reference Equations of State for the Thermodynamic Properties of Fluid Phase n-Butane and Isobutane"
J. Phys. Chem. Ref. Data, Vol. 35, No. 2, 2006
The equation of state is valid for temperatures between 113.73 K (the triple point temperature) and 575 K at pressures up to 70 MPa.
The default reference state is the IIR standard for which: h=200.0 kJ/kg, s=1.0 kJ/kg-K. The reference state can be changed using the $Reference directive.
(Versions prior to 12.010 used the equation of state provided by: Miyamoto, H., and Watanabe, K.,"A thermodynamic property model for fluid-phase isobutane," Int. J. Thermophys., 23(2):477-499, 2002.)
Viscosity information is provided by:
Sebastian Herrmann and Eckhard Vogel
"New Formulation for the Viscosity of Isobutane"
Journal of Physical and Chemical Reference Data 47, 043103 (2018)
https://doi.org/10.1063/1.5057413
(Versions prior to 11.620 used: B.A. Younglove and J.F. Ely, "Thermophysical Properties of Fluids. II Methane, Ethane, Propane, Isobutane and Normal Butane",
J. Phys. Chem. Ref. Data Vol. 16, No. 4, 1987.)
Thermal conductivity data are provided by:
R. Perkins,
"Measurement and correlation of the thermal conductivity of isobutane from 114 K to 600 K at pressures to 70 MPa,"
J. Chem. Eng. Data 47 (2002).
Surface tension data are provided through a correlation developed by:
G.R. Somayajulu
"A Generalized Equation for Surface Tension from the Triple Point to the Critical Point"
International Journal of Thermophysics, Vol. 9, No. 4, 1988
The melting temperature line is provided by D. Bucker and W. Wagner