Calculating mixture residual/departure enthelpy from EOS

  • Thread starter maistral
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In summary, the conversation revolves around the topic of calculating mixture residual enthalpies/entropies for VLE. The individual has searched for information on the internet and found only pure-fluid residual enthalpy calculations. They are looking for a source that provides an algorithm for calculating residual enthalpies for mixtures. Chet suggests checking the book Smith and Van Ness, which mentions using linear mixing rules and effective critical parameters. However, the individual also comes across codes and texts that use quadratic mixing rules and is unsure of how to proceed. They mention needing enlightenment and Chet suggests chapters 11 and 14 in the book for an EOS example.
  • #1
maistral
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Good day.

I have no idea how to calculate mixture residual enthalpies/entropies. I have searched all over the internet and yeah, I keep on finding the pure-fluid residual enthalpy calculations.

Is there ANY possible source here where an algorithm for residual enthalpy calculations for MIXTURES (for VLE) is shown? Thanks!
 
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  • #2
maistral said:
Good day.

I have no idea how to calculate mixture residual enthalpies/entropies. I have searched all over the internet and yeah, I keep on finding the pure-fluid residual enthalpy calculations.

Is there ANY possible source here where an algorithm for residual enthalpy calculations for MIXTURES (for VLE) is shown? Thanks!
It might be in Smith and Van Ness.

Chet
 
  • #3
Oh hi again chet! :D Happy to see you.

SVNA tells me to apply linear mixing rules on the critical parameters to calculate an effective critical parameter, then use these parameters to calculate the departure enthalpy as if it was a single fluid.

Searching for the validity of such steps, I encountered some codes and texts that seemingly apply a quadratic mixing rule on the alpha function? I have no idea how they did it. I'm totally at a loss, I have no idea what to do. I need some enlightenment. Thanks a lot!
 
  • #4
I think chapters 11 and 14 have what you want, where they work with the second virial coefficient and have a theoretically based mixing rule, based on statistical thermodynamics.

Chet
 
  • #5
Oops, forgot to specify. I wanted the EOS methods, not the virial coefficient ones, sorry.
 
  • #6
maistral said:
Oops, forgot to specify. I wanted the EOS methods, not the virial coefficient ones, sorry.
They give an eos example in ch 14.
 
  • #7
Thanks. Will try and give a look again, I may have been too tired and have missed it o_o thanks!
 

1. How is residual enthalpy calculated from an EOS?

The residual enthalpy is calculated by subtracting the ideal enthalpy from the actual enthalpy of the mixture. The ideal enthalpy is calculated using the ideal gas law, while the actual enthalpy is determined from the EOS.

2. What is the purpose of calculating mixture residual enthalpy?

Calculating the mixture residual enthalpy allows scientists to understand the behavior of a mixture and how it deviates from ideal gas behavior. It can also provide information about the thermodynamic properties of the mixture.

3. How does the EOS affect the calculation of mixture residual enthalpy?

The EOS is used to determine the actual enthalpy of the mixture, which is necessary for calculating the residual enthalpy. The accuracy of the EOS will directly affect the accuracy of the calculated residual enthalpy.

4. Can mixture residual enthalpy be negative?

Yes, mixture residual enthalpy can be negative. This indicates that the actual enthalpy of the mixture is lower than the ideal enthalpy, meaning that the mixture is more stable than an ideal gas mixture.

5. How can mixture departure enthalpy be calculated?

Mixture departure enthalpy is calculated by subtracting the actual enthalpy of the mixture from the enthalpy of the pure components. This can provide information about the mixing behavior of the components in the mixture.

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