HETP Prediction—Data interpolation

Interpolation of experimental HETP data ie the most reliable means of obtaining design HETP values. This is hardly surprising, and can even be anticipated in an area where our understanding of the theory is so poor that rules of thumb can do better than theoretical models. The author fesls that it is always best to derive HETP from experimental data, and to check it against a rule of thumb. 

Eckert (72), Chen (98), and Vital et al. (120) tabulated experimental HETP data for various random packings. The author extended thess tabulations and included data published for structured packings. Chapter 11 presents this collection of published HETP data and a detailed procedure for interpolating such HETP data. 

A prerequisite to any interpolation of packing data is thorough familiarity with the factors that affect HETP. These factors are listed in Sec. 9.1.3, and elaborated on in various other sections (which are re- 

Maldistribution in packed columns may cause a severe reduction in column efficiency. For 1-in packings, HETP may increase fay a factor as high as 2 or 3 due to maldistribution (116,131,132). 

137) added lateral mixing (Sec. 9.2.3.) to the model. Lateral deflection of liquid by the packing particles tends to homogenize the liquid, thus counteracting the channeling and pinching effect. 

---

HETP Prediction HETP can be predicted from mass-transfer models, rules of thumb, and data interpolation. 

Eckert (6) was first to tabulate HETP data in a format suitable for interpolation. Vital, Grossel, and Olsen (65) recommended such data over predictive methods, subject to availability of data for a system similar to that considered. The author concurs with this recommendation. In this chapter, Eckert s table is updated and largely expanded, and new tables and charts are edded for structured packings. 

If you reached this step, interpolation of the data in this chapter cannot answer your problem. Check if proprietary data banks or the packing supplier have the data you are missing. If you cannot obtain these data, consider an alternative packing for which HETP can be predicted with confidence for your system. 

---