Murphree vapor efficiency equation

Combined with the above equation for E, the Murphree vapor efficiency is expressed as a function of Nqq. 

Equation (5.9-2) defines the Murphree vapor efficiency. an equivalent expression could be given in teims of liquid concentrations, but the vapor concentration basis is the one most used, and it is equivalent to its couaterpart dealing with the liquid. It should be noted thy the value or y is based on the exit concentration of the liquid and is silent ou the idea that liquid concentration can vary from point to point of the tray when liquid concentration gradients are severe, as in the case of very loug liquid flow pelhs. it is possible for the Muiphree efficiency to have a value greater than ]. 0,... 

To develop a simultaneous Newtonian procedure for multiconponent distillation, Naphtali and Sandholm 119711 first wrote the N(2C + 1) equations and variables consisting of conponent mass balances [essentially Eq. 16-131 but without substitution of the equilibrium K values for y ], the energy balances [essentially Eq. 16-2811. and equilibrium relationships including Murphree vapor efficiencies in functional matrix form. Their procedure is illustrated for the energy balance. Essentially, the functional matrix form for Eq. 16-281 is... 

We will now focus on case (1), namely the solution of equation (8.3.19) to develop the expression for Murphree vapor efficiency Emv for plate n under the condition of constant molar overflow this is the AIChE model. Equation (8.3.19) may be written as... 

As mentioned previously, the number of actual plates in an absoiber is related to the number of theoietical plates by a factor known as the plate efficiency. In its simplest definition, the overall plate efficiency is defined as the ratio of theoretical to actual plates required for a given separation. For individual plates, the Murphree vapor efficiency (Murphree, 1935) more closely relates actual performance to the theoretical-plate standard. It is d ined by the following equation ... 

Murphree vapor plate efficiency, see equation 82 poiat value of plate efficiency... 

Solving the problem defined in the following table will show the equations for estimating system physical properties and their relation to the calculation of Murphree vapor plate efficiencies ... 

Point efficiency (Murphree point efficiency). If the vapor and liquid compositions are taken at a point on the plate, equation 11.64 gives the local or point efficiency,... 

The column solution methods described in this chapter are based on an equilibrium stage model. Normally, the vapor and liquid leaving a tray are not at equilibrium due to imperfect mixing or insufficient residence time on the tray. Tray efficiencies, discussed in Chapter 14, are parameters that relate actual performance to equilibrium stage performance. By replacing the equilibrium relationship in the model with an equation based on the Murphree tray efficiency, the actual column performance can be calculated. The accuracy of the model obviously depends on the reliability of the tray efficiencies used in the calculations. 

First the equations for the modified Murphree plate efficiency are developed and then the corresponding equations for the Murphree plate efficiency are developed. Expressions for the vaporization efficiencies for each of these efficiencies are then presented. The section is concluded by the presentation of numerical examples for binary mixtures which demonstrate that essentially the same compositions of the vapor leaving a plate are predicted by vaporization efficiencies corresponding to the modified Murphree efficiency model as are predicted by the Murphree plate efficiencies. This result suggests that the correlations for the film coefficients developed by others4 for use with Murphree efficiencies may be used in the prediction of vaporization efficiencies for multi-component systems. 

Parameter defined by Equation 13.22 Parameter defined by Equation 13.23 Total number of components Component balance function on tray j Average heat capacity on tray j Enthalpy balance function on tray j Murphree tray efficiency in vapor terms Eugacity... 

For values of the Murphree plate vapor efficiency in commercial size towers, the following equation is recommended ... 

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