Transfer units AIChE correlations

Hughmark [181] has proposed empirical correlations for better fit of experimental data to transfer units and thus tray efficiency comparison with the AIChE method [2]. 

We use the AIChE correlation to illustrate the general approach, noting that the correlation was not developed specifically for valve trays (few methods were). In this model the number of transfer units is given by... 

AIChE Method. The AIChE correlation of the number of transfer units for the vapor phase on both bubble caps and sieve trays is... 

Chan and Fair Method. Chan and Fair (1984a) retained the AIChE (1985) procedure for calculation of the but developed an alternative correlation for the number of transfer units in the vapor phase Nj/ as follows ... 

SOLUTION We will begin by estimating the numbers of transfer units using the AIChE correlations. 

For the liquid-phase Chan and Fair make use of the AIChE correlation thus, N/ = 8.412, as calculated above. The overall number of transfer units follows from Eq. 12.1.17 as... 

Numerous attempts have been made to develop useful correlations for predicting fire efficiency of tray towers. The most comprehensive study was carried out under sponsorship of the American Insthute of Chemical Engineers (AIChE) and resulted in the publication of the AlChE bubble tray design manual. The AIChE prediction method, which is aimed primarily at bubble-cap trays, involves first estimating the number of gas-phase and liquid-phase transfer units, Nc and N, for the specific conditions on the tray, combining these to obtain the number of overall gas transfer units Nqc, and predicting the point efficiency by the relationship... 

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