Angle, structured packings

Proc., 65(3), 45 (1986)] is preferred. To use this and alternate models, dimensional characteristics of structured packing must be defined. Figure 14-51 shows nomenclature and definitions of key dimensions. Not shown, but also important, is the angle the corrugations make with the horizontal (usu y 45 or 60°). Then the Rocha et al. predictive equation is ... 

This polymer crystallizes in three polymorphs. The threefold helical structure packs in a trigonal unit-cell with a = 14.3 A (1.43 nm) and c = 28.7 A (2.87 nm). The 8-fold helical structure occurs in a tetragonal unit-cell with a = 13.8 A (1.38 nm) and c = 78.2 A (7.82 nm). Axial periodicity in both cases is similar [h = 9.6 A (960 pm) and 9.8 A (980 pm), respectively], but the helix twist-angle is different (120 and 45°, respectively). Distribution of the charged side-groups in these helices was discussed. An orthorhombic form, with a twofold helical structure, has a repeat of 18.6 A (1.86 nm). 

FIG. 14-60 Effect of structured packing surface areas, loads, and inclination angle on packing efficiency. Efficiency expressed as number of theoretical stages per meter, the reciprocal of HETP. Sulzer data, chlorobenzene-ethylbenzene, 100 mbar, at total reflux 250-mm-diameter test column. (Reprinted courtesy of Sulzer... 

The angle of rotation and the element height therefore affect the extent of vapor and liquid spread in a structured packing. For this reason, element height is relatively short (typically 6 to 12 in) and the angle of rotation is around 90°. 

Harrison and France (52) presented the only published rule of thumb for structured packings efficiency. This rule states that HETP is 9 in for Winch crimp height, 18 in for 1/2-inch crimp, and 33 in for 1-in crimp. The author found this rule to do well when the crimp angle is 45°, but to be less satisfactory for other angles. Basad on data in Chap. 11, the author proposes an alternative rule of thumb. 

Angle of inclination of the structured packing flow channel from the horizontal. Valuss listed in Table 8.1, degress... 

Figure 13.51. Effect of corrugation angle on the mass transfer performance of a high-area structured packing, operated at total reflux. Bl-400 has the standard 45-degree angle, whereas 400.60 has a 60-degree angle (with the horizontal). Cyclohexane/n-heptane, column diameter = 0.43m, bed height = 3.3 m. (Olujic et al., 2000).

FIGURE 12.68 Efficiency comparison, two structured packings with 45° and 60° corrugation angles. Same conditions as for Figure 12.67. (Z. Olujic et al., 2000. Chem. Eng. Proc. 39 335.)... 

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