**CARBONDIOXIDE or R744**

CARBONDIOXIDE and R744 both provide high accuracy thermodynamic properties for carbon dioxide using the fundamental equation of state developed by:

R. Span and W. Wagner

*"**A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures up to 800 MPa"*,

J. Phys. Chem, Ref. Data, Vol. 25, No. 6, 1996.

The values of specific enthalpy and entropy are, by default, referred to values of 0 at 298.15 K and 101.325 kPa in the ideal gas state. The reference state can be changed using the $Reference directive.

__Viscosity is determined using the correlation provided in:__

Laesecke, A. and Muzny,C.D.,

"Reference Correlation for the Viscosity of Carbon Dioxide"

*J Phys Chem Ref Data*.* 2017 ; 46:*

doi:10.1063/1.4977429

The viscosity correlation is valid for temperature between 220 K and 700 K for pressures up to 800 MPa.

This correlation replaced the correlation from: Fenghour, A., Wakeham, W.A., and Vesovic, V.,*J. Phys. Chem Ref, Data, Vol. 27, No. 1, 1998 *in version 11.595

__Thermal conductivity is determined in the manner described by:__

Huber, M.L., Sykioti, E.A., Assael, M.L, and Perkins R.A.,

"Reference Correlation of the Thermal Conductivity of Carbon Dioxide from the Triple Point to 1100 K and up to 200 MPa"

* J. Phys Chem Ref Data. 2016 March ; 45(1)*

doi:10.1063/1.4940892

This correlation replaced the correlation from: Vesovic et al., "The Transport Properties of Carbon Dioxide," *J. Phys. Chem Ref, Data, Vol. 19, No. 3, 1990.*

__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 Poin*t"

International Journal of Thermophysics, Vol. 9, No. 4, 1988

The sublimation pressure curve (valid for temperatures between 70 K and 216.592 K) is determined from R. Span and W. Wagner

The melting pressure curve (valid for temperatures between 216.592 K and 270 K) is determined from R. Span and W. Wagner

Note: Properties for solid carbon dioxide between 2 K and the triple-point temperature are available in the Incompressible substances library with substance name CO2_solid. The reference state for the solid values of specific internal energy, enthalpy and entropy are consistent with the default reference state for fluid CarbonDioxide allowing them to be used without shifting the reference state. For example, the specific enthalpy change of sublimation at the triple point can be determined with the following equations.

$Load Incompressible

T_t=**t_triple**(** CarbonDioxide**)

P=**p_sublimation**(** CarbonDioxide**,

DELTAh_sub=**enthalpy**(** CarbonDioxide**,

Note that CarbonDioxide and R744 provide thermodynamic properties assuming real fluid behavior. Use CO2 for ideal gas properties of carbon dioxide consistent with reference states used in combustion calculations.