Session 1 · optional reference
30 September 2026
Return to the 12-slide classroom deck.
Use these details when a question from your investigation needs them. They are outside the required 45–60 minute practice.
Choose one extension: compare liquid activity models, examine zero versus nonzero virial coefficients in Lab 09, or add the energy balance in Lab 07.
At fixed temperature and pressure, a stable equilibrium minimizes total Gibbs energy subject to material conservation.
\mu_i^L=\mu_i^V\quad\Longleftrightarrow\quad \hat f_i^L=\hat f_i^V
A calculation also needs a phase model, composition constraints and a stability check.
y_i\hat\phi_i P=x_i\gamma_i P_i^{sat}\phi_i^{sat}\Pi_i
Lab 01 uses ideal vapor. Lab 09 adds second-virial vapor corrections.
| Specified | Unknown boundary | Composition supplied |
|---|---|---|
| T | Bubble P | Liquid x |
| T | Dew P | Vapor y |
| P | Bubble T | Liquid x |
| P | Dew T | Vapor y |
A dew calculation generally needs an inner liquid-composition iteration because γ depends on x.
0.5=(1-0.493506)(0.388889)+(0.493506)(0.614035)
The rounded result closes the component-1 balance. Component 2 must close as well.
Also check x_1+x_2=y_1+y_2=1 and equality of component fugacities. A small balance residual alone does not validate the physical model.
One-parameter Margules, two-parameter Margules and NRTL share the same equilibrium criterion but predict different γ(x).
Hold the synthetic component properties and T fixed. Change only the liquid model or one interaction parameter.
A nonconvex liquid needs an LLE/VLLE stability analysis; it cannot simply be accepted as a stable VLE flash.
\ln\hat\phi_i=\frac{P}{RT}\left(2\sum_j y_j B_{ij}-B_{mix}\right) B_{mix}=\sum_i\sum_j y_i y_j B_{ij}
Lab 09 also evaluates pure saturated-vapor φ consistently. With all Bᵢⱼ=0, the ideal-vapor limit must be recovered.
Compare the same T, P, feed and liquid model. Change only the vapor description first.
Record differences in boundary pressures, phase compositions and β. Then examine the declared B(T) range and the truncation guard.
PR/SRK, dense vapor and virial adiabatic flash are outside these lab solvers.
H_{feed}=(1-\beta)H^L(T,x)+\beta H^V(T,y)
At specified pressure and feed enthalpy, T is another unknown. A TP flash at the feed temperature does not impose this energy balance.
Lab 07 uses synthetic caloric data. Independent practice only if the core TP calculation is secure.
Module reference deck · Lab assumptions and sources
The worked examples use synthetic inputs. Each lab states its supported models and validity limits.