Crimp angle

Mellapak (Fig. 8.11 a). Mellapak has grooved and perforated surfaces. Adjacent elements are rotated 90°. The crimp angle is 45°, and the crimp apex is sharp. Mellapak is available in several types. The Mellapak number denotes the nominal surface area of the packing per unit volume (m2/m3). The suffix denotes the angle of orientation to the vertical axis Y signifies 45°, X signifies 60°. For instance, Mellapak 250.Y has a surface area of 250 m2/m3, and a 45° angle of orientation to the vertical axis. Mellapak is available in metals and plastics from Sulzer Chemtech in Switzerland. 

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. 

Crimp heights and specific surface area are listed in Table 8.1. The 4 in added in Eq. (9.35) gives this rule a conservative bias. Eliminating the 4 from Eq. (9.35) will improve the fit of this rule to data, and for a crimp angle of 45° will make it practically identical to Harrison and France s. However, the author feels that just like in the Porter and Jenkins rule (above), the conservative bias is needed to render the rule suitable for design. 

Force balance model is capable of predicting the irttemal mechanical parameters of the plain woven fabrics in a similar yam prrllout test based on the force distribution concepts. These parameters are yam-to-yam friction coef ftierrt, normal load at crossovers, lateral forces, lateral strairr, weave angle variatiorrs, arrd pullout force. Crimp angle of yams within the fabric 9 in (Figure 3)), its elastic modulus and linear density and fabric deformation data (a in (Figure 1(a))) are the required empirical factors of force balance model. The main equations of this model are presented in (Table 1) [10] ... 

Variation of crimp angle for the opposed yam due to fabric deformation by angle a during pullout test (Figure la) 0 = arctan(tan0 cos a) (7)... 

Form W process Wet cross-linking is achieved with formaldehyde solutions in aqueous hydrochloric acid. The tear strength decreases only slightly and the wet crimp angle is good. 

Form D process The unswollen cellulose is cross-linked in formaldehyde in 76% glacial acetic acid + a little HCl. Wet and dry crimp (crease) angles are good, but the tensile strength decreases. The crimp angle is a traditional measure of the quality of a natural fiber. 

Fabric crimp angle n. The maximum acute angle of a single weaving yarn s direction measured from a plane parallel to the surface of the fabric. 

The maximum crimp angle a is calculated at the middle plait length from the derivative of the BY cosine path, as shown by Eq. (10.26). 

The third gap describes the separation between the BYs and MEYs at the braid diameter. This gap depends on the BYs crimped section projected on the cylindrical surface having a diameter equal to the braid mid-diameter. This BY section has a width equal to the BY width at pitch, but the perpendicular direction is the BY thickness at pitch (1>byp) projected on the crimp angle. This gap is the difference between the circumference of the braid divided by half the number of BYs, the width of the MEY, and the distance between two parallel lines enclosing the crimped section of the BYs ( byp// iri Figure 10.20). The following equation (10.31) is used to calculate the parallel gap (Gappy//)-... 

Figure 10.19. Yam position in fabric, considering inclined tube geometry. is crimp angle, d is...

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