HETP Prediction—Rules of Thumb

Because there axe only few vmiables that significantly affect random-packing HETP (Sec. 9.1.3), and due to the unreliability of even the best mass transfer model, rules of thumb for HETP successfully compete with mass transfer models. It hu been the author s experience tliat rules of thumb for HETP prediction are more accurate and more reliable than mass transfer models. A similar conclusion was reached by Porter and Jenkins (127). 

T8d)le 9.2 lists the rules of thumb available in the published literature. Most are based on second- and third-generation random packings and should not be applied to first-generation packings. The majority of rules are in veiy dose agreement with each other. Porter 

Note 6 7 irrigation efSciency. 7. Same as general, but needs 

HETP (ft) = 4. Small column HETP(ft) - for bi viscosity systems. 8. For cdumn dieuneter 2 ft. 9. For odumn diameter 1-4 

For small-diameter columns, the rules of thumb presented by Frank (128), Ludwig (63), and Vital et al. (120) are identical. The author believes that for small columns, the more conservative value predicted from either the Porter and Jenkins or the Frank-Ludwig-Vital rule should be selected for design, Siimmarising 

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