Tray Efficiency Types
Three types of tray efficiencies are provided. All of the models result in non-equilibrium products leaving the tray for which the efficiency is applied and should therefore be used with care to minimize inconsistencies in calculated results. See Tray Efficiency Models for the tray efficiency equation forms. None of the models correspond to the overall tray efficiency, which is defined as the number of theoretical trays in the column divided by the number of actual trays in the column.
Murphree Model
This model uses the classic equation developed by E. V. Murphree in 1925. It was designed for ease of use in classic McCabe-Thiele diagrams. There is a relationship between the Murphree efficiency and the overall tray efficiency when the column equilibrium and operating lines are both straight. However, the Murphree efficiency is not an overall tray efficiency model and values greater than 1.0 are possible for some types of columns. Murphree efficiencies have been measured and published in the literature for some types of separations.
Vaporization Model
For this model, the equilibrium K-value is scaled for a component or group of components. Quite simply, the equilibrium vapor leaving the tray is changed in quantity and the tray is no longer at true equilibrium conditions. This model is useful for tuning a column operation when a fractional tray is needed to match an operating temperature. It is best applied on a selective basis.
Equilibrium Model
This model is based on the Vaporization Model, and provides a way to modify vaporization efficiencies. The expression is compatible with the Vaporization Model and the two types of efficiencies may be used simultaneously. The equation for simultaneous use is:
where: 
, 
= Effective K-value and equilibrium K-value, respectively.
,
= equilibrium efficiency and vaporization efficiency, respectively.
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