1. Underwood Equations – (L/D)min
We have looked at one limiting condition, Nmin, determined using the Fenske method at total reflux conditions.
The other limiting condition for multi-component systems is the solution for the minimum reflux ratio, (L/D)min, which gives us an infinite number of stages.
This method is known as the Underwood method or the Underwood equations.
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2. Underwood Equations – (L/D)min
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3. 1st Underwood Equation – φ Roots
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4. Underwood Equations – Cases
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5. Underwood Equations – Case A Methodology
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6. Underwood Equations – Case A Methodology (continued)
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7. Underwood Equations – Case A Methodology (continued)
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8. Underwood Equations – Case B Methodology
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9. Underwood Equations – Case B Methodology (continued)
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10. Underwood Equations – Case B Methodology (continued)
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11. Underwood Equations – Case C Methodology
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12. Underwood Equations – Case C Methodology (continued)
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13. Underwood Equations – Case C Methodology (continued)
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14. Gilliland Correlation – N and NF
Empirical relationship which relates the number of stages, N, at finite reflux ratio, (L/D)actual to the Nmin and (L/D)min.
Nmin is determined from the Fenske equation.
(L/D)min is determined from the Underwood equations.
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15. Gilliland Correlation
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16. Gilliland Correlation – Curve Fits
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17. Gilliland Correlation – NF
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