Figure 6.10 Fair's entrainment flooding correlation. (J. R. Fair, PetrolChem Eng. 33 (10), p. 45,1961, reprinted courtesy of Petroleum Engineer International, Dallas, Texas.

Fair's correlation applies to nonfoaming or low-foaming systems. For highly foaming systems, the capacity is lower. The correlation applies to sieve trays with holes Vz-in or smaller and where weir height does not exceed 15 percent of the tray spacing (18). Fair's correlation also applies to bubble-cap and valve trays (3,18,34). For bubble-cap and valve trays, the fractional hole areas used in the correction term are the ratio of the slot area to bubbling area, and the ratio of full valve-opening area to bubbling area, respectively (18). The correlation can also be used for dual-flow trays with fractional hole area greater than 0.2 (18).

When Fair's correlation was developed, little was known about the difference between spray and froth entrainment flooding, and the data base used was small and included both types. The author compared predictions from Fair's correlation to a much wider data bank available at present. The correlation predicted most of these data well, perhaps somewhat on the conservative side. However, the correlation has been less successful iii reliably predicting some of the effects (described above) of physical properties, operating variables, and tray geometry on entrainment flooding.

The Smith et al. correlation (20, Fig. 6.11). This is another early entrain-- ment flooding prediction method that has sometimes been recom-< mended (11). Compared to Fair's correlation, the Smith et al. correla-l tion is claimed (20) to be less conservative. It was derived from a small | base of field data for sieve, valve, and bubble-cap trays. Similar to i Fair's correlation, Smith's correlation uses CSB versus a flow parame-f ter plot, but here the dependence of CSB on the flow parameter is ' weaker, and there is no surface tension correction factor. CSB and ยป' "flood are both based on the net area and are evaluated from Fig. ' 6.11 and Eq. (6.9), respectively. The height over the weir, how, is ob-1 tained from Eq. (6.49).

; The Kister and Haas correlation (15). This is a recent correlation for ! entrainment flooding i f CSB = 0.144

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