Estimating density, viscosity and thermal conductivity

[Mark Rice]

Homework Statement

Hi there, I am designing a heat exchanger and I am really struggling to find out how to fairly accurately estimate the density, viscosity and thermal conductivity of a gaseous mixture at ~~20bar. There is 8 components in the mixture: methane, ethane, ethene, ethlyene oxide, CO2, water, argon and O2.

Homework Equations

PV=znRT (for denisty),
k_mix = k_a M_a + k_bM_b + k_nM_n (for themal conductivity of mix

I have all the pure component values of density, viscosity and thermal conductivity from NIST at the correct P and T.

The Attempt at a Solution

My initial thought was to just simply do a weighted average of the sum of (properties*molefraction) however I feel this may not be that accurate. I have looked through perry's engineering handbook and some design textbooks and can't find a reliable method to work out these properties. I then tried to use the ideal gas law with the compressibility factor however the values this gave me Z was almost = 1 and my density values were way too low (I know what the values should be roughly as I have modeled it on design software).

Thanks,

 

[Chestermiller]

See Transport Phenomena by Bird et al for mixing rules.