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Two-phase behavior

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Two-phase behavior

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    1. Two-phase behavior

    2. Behavior in the two phase region

    4. Antoines Equation Antoines equation is used to predict the relationship between the T and P in the two phase region. P is usually called saturation pressure and T is usually called the vaporization temperature or vice-versa For propane, the Antoines constants are A = 6.80398, B =803.81, C= 246.99 (Psat in mmHg) Calculate the vapor pressure for propane at 100, 200, 300 K and the critical point 369.8 K. Compare to the values from the chart.

    5. Antoines Equation

    6. Gibbs Free energy

    7. Relationship of V and S

    9. Finding the slope of Psat vs Tvap

    10. Change in Psat with T

    11. Numerical (Easier) Estimating the slope of Psat vs Tvap at a particular T.

    12. DSvap Given the Antoines constants, one can calculate the way the saturation pressure changes with Tvap at any Tvap. One can use an EOS to estimate Vvap and Vliq at that temperature Tvap.(eg 10-24 PR) From the difference in Vvap and Vliq one can obtain Svap Sliq (DSvap)

    13. Shortcut Approximations Since Vliq << Vvap, a shortcut is to find only Vvap Since Vvap ~ RT/P

    14. Calculation of DSvap from dPsat/dTvap

    15. Calculation of DHvap Since along the two phase region:

    17. Clausius-Clapeyron Eq

    18. Clausius-Clapeyron

    20. Summary In the two phase region, there is an explicit relationship between P and T. As T increases so does the vapor pressure, according to Antoines equation. The relationship between Pvap and Tsat can be used to compute the difference in the vapor and liquid volumes, entropy, and enthalpy.

    21. Gibbs Phase Rule

    22. Single Phase

    23. 2-phase Region

    24. Two phase region

    25. 2 Components Two phases

    26. Phase Rule in Multicomponent Systems

    27. 3 phases

    28. Triple Point

    29. Stability Analysis

    30. Summary There is an explicit rule that relates the number of degrees of freedom of multiphase and multicomponent systems at equilibrium. This rule tells one how many of the intensive variables in a system can be independently specified, which keeps ones thoughts organized about systems

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