Twu-Sim-Tassone equation of state: Difference between revisions

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:<math>Z_c = \frac{p_cv_c}{RT_c} =  0.296296  </math>
:<math>Z_c = \frac{p_cv_c}{RT_c} =  0.296296  </math>


it better represents  the compressibility than many of than the [[Redlich-Kwong equation of state]]s, including the Soave modified version, and the [[Peng and Robinson equation of state]].
it better represents  the compressibility than many of than the [[Redlich-Kwong equation of state]]s, including the [[Redlich-Kwong equation of state#Soave modification | Soave modified version]], and the [[Peng and Robinson equation of state]].


The equation follows the general cubic form resulting in the equation (Eq. 2):
The equation follows the general cubic form resulting in the equation (Eq. 2):
Line 9: Line 9:
:<math>p=\frac{RT}{V_m-b}-\frac{a}{(V_m-0.5b)(V_m+3b)}</math>
:<math>p=\frac{RT}{V_m-b}-\frac{a}{(V_m-0.5b)(V_m+3b)}</math>


Where <math>V_m</math> is the molar volume, and <math>a</math> and <math>b</math> are the attractive and repulsive parameters akin to those of the [[Van der Waals equation of state]].  Relations exists between <math>a</math> and <math>b</math> and the critical parameters <math>T_c</math> and <math>P_c</math> in the forms (Eqs. 3 and 4):
where <math>V_m</math> is the molar volume, <math>R</math> is the [[molar gas constant]], <math>T</math> is the [[temperature]], <math>p</math> is the [[pressure]], and <math>a</math> and <math>b</math> are the attractive and repulsive parameters akin to those of the [[Van der Waals equation of state]].  Relations exists between <math>a</math> and <math>b</math> and the critical parameters <math>T_c</math> and <math>p_c</math> in the forms (Eqs. 3 and 4):


:<math>a_c=0.470507  \frac{ R^2T_c^2}{P_c}</math>
:<math>a_c=0.470507  \frac{ R^2T_c^2}{p_c}</math>
:<math>b_c=0.0740740  \frac{ RT_c}{P_c}</math>
 
:<math>b_c=0.0740740  \frac{ RT_c}{p_c}</math>


==References==
==References==

Revision as of 17:33, 7 November 2011

Twu, Sim and Tassone presented a cubic equation of state for accurate representation of hydrocarbons that has become known as the Twu-Sim-Tassone or TST equation of state[1]. With a critical compressibility factor of (Eq. 5)

it better represents the compressibility than many of than the Redlich-Kwong equation of states, including the Soave modified version, and the Peng and Robinson equation of state.

The equation follows the general cubic form resulting in the equation (Eq. 2):

where is the molar volume, is the molar gas constant, is the temperature, is the pressure, and and are the attractive and repulsive parameters akin to those of the Van der Waals equation of state. Relations exists between and and the critical parameters and in the forms (Eqs. 3 and 4):

References

  1. ↑ Chorng H. Twu, Wayne D. Sim and Vince Tassone "A versatile liquid activity model for SRK, PR and a new cubic equation-of-state TST", Fluid Phase Equilibria 194-197 pp. 385-399 (2002)
Related reading
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