VLE Thermodynamic Consistency: EOS Test background

Test 5: EOS (Equation of State) Test. The consistency test uses the the Universal Mixing Rule (UMR) described by Voutsas et al. (reference 32), which incorporates an activity coefficient model in a cubic equation of state. In TDE, the UNIQUAC activity coefficient model is used with the Peng-Robinson EOS .

This test is applied automatically only to P-T-x-y data sets with pressures > 1 MPa. Numerical criteria are calculated as for the Van Ness test. The key difference is that deviations in the critical region are not considered because the model is known to not represent the data well in this region. The excluded property value are displayed in orange on the plots.

After completion of the fitting process, the following criteria are applied:


where N is the number of properties values, the superscript exp indicates experimental data, and the superscript cal indicates values calculated with the NRTL equation. If Δp and Δy are less than 1, the data set passes the test.

The quality factor for the Van Ness Test is calculated as follows:

Ftest5 = 2/(Δp + Δy) with the limits 1 ≤ Δp ≤ 10, 1 ≤ Δy ≤ 10.

EOS Test Results: Output screen details