Available mixing rules for vapor conductivity

You can use one of the following mixing rules to calculate the bulk vapor thermal conductivity of a Fluid Type.

SimSci Mixing Rule

where

lm is the vapor thermal conductivity of the mixture

li is the vapor thermal conductivity of pure component i

yi is the molar composition fraction of component i in the vapor phase

Mi is the molar mass of pure component i

This is the default mixing rule.

Molar Average

Logarithmic Molar Average

Power Molar Average

where

r is an exponent that you specify in the Fluid Editor

Lambda Mixing Rule

Wassiljewa-Mason-Saxena Mixing Rule

TRAPP (transport property prediction)[2,3]

We evaluate the vapor thermal conductivity based on the deviations in a reference fluid, which we assume to be the pure vapor of a reference component, R. We use the following equations to calculate the vapor thermal conductivity of the mixture (lm):

where

lm0 is the vapor thermal conductivity of the mixture at low pressure and temperature, which we calculate by using the vapor thermal conductivities from the Lee-Kesler equation of state (EOS) and the SimSci mixing rule

Ci are a set of constant coefficients taken from literature[4]

rc,R is the density of reference component R at its critical temperature and pressure

rc,i is the density of component i at its critical temperature and pressure

MR is the molar mass of reference component R

Pisat is the vapor pressure of component i at the system temperature (T)

PRsat(T0) is the vapor pressure of reference component R at temperature T0

risat is the saturated liquid density of component i at the system temperature (T)

rRsat(T0) is the saturated liquid density of reference component R at T0

wi is the acentric factor of component i

wR is the acentric factor of reference component R

Zc,i is the critical compressibility factor of component i

Zc,R is the critical compressibility factor of reference component R

Because we evaluate the vapor pressure and saturated liquid density of the reference fluid at T0, we must iteratively solve for fi.

Typically, you use this mixing rule for systems of non-polar components at high pressures.

References

1. Mason, E. A.; Saxena, S. C. Approximate Formula for the Thermal Conductivity of Gas Mixtures. Phys. Fluids 1958, 1 (5), 361–369.

2. Leland, T. W.; Rowlinson, J. S.; Sather, G. A. Statistical Thermodynamics of Mixtures of Molecules of Different Sizes, Trans. Faraday Soc. 1968, 64, 1447-1460. DOI: 10.1039/TF9686401447

3. Ely, J. F.; Hanley, H. J. M. Prediction of Viscosity and Thermal Conductivity in Hydrocarbon Mixtures- Computer Program TRAPP. Proceedings of the 60th Annual Convention of the Gas Processors Association, San Antonio, TX, USA, Mar 23, 1981.

4. Reid, R. C.; Prausnitz, J. M.; Poling, B. E. The Properties of Gases and Liquids, 5th ed.; McGraw-Hill: New York, 1977; pp. 572-577.