Calculating mixture residual/departure enthelpy from EOS

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Discussion Overview

The discussion revolves around calculating mixture residual enthalpies and entropies, specifically in the context of vapor-liquid equilibrium (VLE) using equations of state (EOS). Participants seek algorithms or methods for these calculations, distinguishing them from pure-fluid approaches.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant expresses uncertainty about calculating mixture residual enthalpies and entropies, noting a lack of resources for mixtures compared to pure fluids.
  • Another participant suggests that Smith and Van Ness may contain relevant algorithms for residual enthalpy calculations for mixtures.
  • A participant mentions using linear mixing rules on critical parameters to derive effective critical parameters for calculating departure enthalpy as if it were a single fluid.
  • There is mention of encountering codes and texts that apply a quadratic mixing rule on the alpha function, leading to confusion about the validity of these steps.
  • One participant points out specific chapters in a reference that discuss mixing rules based on statistical thermodynamics, although this may not align with the original request for EOS methods.
  • Clarification is made that the original inquiry specifically seeks EOS methods rather than virial coefficient approaches.
  • A participant acknowledges the potential oversight in their previous review of the suggested chapters and expresses intent to revisit the material.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to calculating mixture residual enthalpies and entropies, with multiple competing views and methods being discussed.

Contextual Notes

Participants express uncertainty regarding the application of different mixing rules and the validity of various methods, indicating a need for further clarification and exploration of the topic.

Who May Find This Useful

Readers interested in thermodynamics, particularly those focused on mixture calculations in the context of vapor-liquid equilibrium and equations of state.

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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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
 
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!
 
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
 
Oops, forgot to specify. I wanted the EOS methods, not the virial coefficient ones, sorry.
 
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.
 
Thanks. Will try and give a look again, I may have been too tired and have missed it o_o thanks!
 

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