**HYDROGEN**

HYDROGEN provides high accuracy thermodynamic properties for normal hydrogen (Molar mass =2.01594 kg/kmol) using the Fundamental Equation of State, as described by:

Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen

J. W. Leachman, R. T Jacobsen, S. G. Penoncello, and E. W. Lemmon

J. Phys. Chem. Ref. Data 38, 721 (2009)

**Reference State **

** ** h = 3932 kJ/kg, s = 53.37 kJ/kg-K at 298.15 K, 101.325 kPa. The reference state can be changed using the $Reference directive.

**Range of applicability for equation of state**:

13.957 < T < 1000 K

0 < P < 2000 MPa

Note that HYDROGEN provides thermodynamic properties assuming real fluid behavior. The reference state for this formulation is NOT consistent with the enthalpy of formation reference for which specific enthalpy would be 0 at 25C. Use H2 for ideal gas properties of hydrogen consistent with reference states used in combustion calculations.

__Viscosity is determined from:__

"Correlation for the Viscosity of Normal Hydrogen Obtained from Symbolic Regression"

Chris D. Muzny, Marcia L. Huber, and Andrei F. Kazakov

*J. Chem. Eng. Data* 2013, 58, 969-979, 2013

The correlations are valid for temperatures between the triple point and 1000 K at pressures up to 200 MPa.

Note that there are several errors in this paper. The exponent in equation (7) should be -i (not -1). A factor of Avogrado's number, 0.6022137 is missing in equation (6). Also, density appearing in the second term on the right side of equation (9) should be in molar units.

__Thermal conductivity is determined from: __

"Correlation of the Thermal Conductivity of Normal and Parahydrogen from the Triple Point to 1000 K and up to 100 MPa"

M.J. Assael, J.A.M. Assael, M.L. Huber, R.A. Perkins, and Y. Takata

*J. Phys. Chem. Ref. Data*, Vol. 40, No. 3, 2011

__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