Seal strips

It is assumed that process conditions and physical properties are known and the following are known or specified tube outside diameter D, tube geometrical arrangement (unit cell), shell inside diameter D shell outer tube limit baffle cut 4, baffle spacing and number of sealing strips N,. The effective tube length between tube sheets L may be either specified or calculated after the heat-transfer coefficient has been determined. If additional specific information (e.g., tube-baffle clearance) is available, the exact values (instead of estimates) of certain parameters may be used in the calculation with some improvement in accuracy. To complete the rating, it is necessary to know also the tube material and wall thickness or inside diameter. 

Sealing. strips. These longitudinal strips either extend from baffle to baffle or may be inserted in slots cut into the baffles. 

When tubes are omitted from the tube layout to provide entrance area about an impingement plate, the need for sealing strips or other devices to cause proper bundle penetration by the shell-side fluid is increased. 

For many years atactic polypropylene was an unwanted by-product but today it finds use in a number of markets and is specially made for these purposes rather than being a by-product. In Europe the main use has been in conjuction with bitumen as coating compounds for roofing materials, for sealing strips where it confers improved aging properties and in road construction where it improves the stability of asphalt surfaces. Less important in Europe but more important in USA is its use for paper laminating for which low-viscosity polymers are used, often in conjunction with other resins. Limestone/atactic... 

It is stated that modem passenger and military aircraft each use about 1000 lb of silicone rubber. This is to be found in gaskets and sealing rings for jet engines, ducting, sealing strips, vibration dampers and insulation equipment. 

Figure 9-6LL. Montz-Nutter high-efficiency structured packing assembly (Type with wiper bands and seal strip). Used by permission of Nutter Engineering, Harsco Corp., Bull. B-1.

Figure 10-147. Shell-side jn factors for bundles. One sealing strip per 10 rows of tubes and TEMA clearances. (Source Engineering Data Book, 2" Ed., 1960. Wolverine Tube, Inc. Used by permission Kern, D. Q., and Kraus, A. D. Extended Surface Heat Transfer, p. 506, 1972. McGraw-Hill, Inc. All rights reserved.)...

This approach will give more satisfactory predictions of the heat-transfer coefficient and pressure drop than Kern s method and, as it takes into account the effects of leakage and bypassing, can be used to investigate the effects of constructional tolerances and the use of sealing strips. The procedure in a simplified and modified form to that given by Bell (1963), is outlined below. 

The method is not recommended when the by-pass flow area is greater than 30% of the cross-flow area, unless sealing strips are used. 

This factor corrects for the main bypass stream, the flow between the tube bundle and the shell wall, and is a function of the shell to bundle clearance, and whether sealing strips are used ... 

Ns = number of sealing strips encountered by the bypass stream in the cross-flow zone,... 

Where no sealing strips are used, Fb can be obtained from Figure 12.34. 

The correction factor for exchangers without sealing strips is shown in Figure 12.37. 

Very low, sealing strips needed try one strip for each five vertical rows. 

The substrate was Valencia orange leaves, with 2500 leaves per sample selected in a carefully prescribed manner (4). The trees involved were field sprayed in a conventional manner with 4 pounds of a 25% wettable powder of parathion, then sampled after 7 days and again after 11 days. Each sample was mixed thoroughly and subsampled into 125-leaf units in 2-quart Mason jars. To all units were added 250 ml. of benzene each, and they were sealed, stripped for various lengths of time, then restripped with fresh benzene, again for various lengths of time. The strip solutions were analyzed in the usual manner. 

The U.S. rubber processing industry encompasses a wide variety of production activities ranging from polymerization reactions closely aligned with the chemical processing industry to the extrusion of automotive window sealing strips. The industry is regulated by seven Standard Industrial Classification (SIC) codes [1] ... 

Q- FLARE CASE R- CLOSING COVER (TOP) S- SEALING STRIP... 

Shell-side seal strips. See if you cannot find an old tube bundle lying around your plant. Many such bundles have pairs of metal strips set around the edge of the tube bundle. These metal strips are typically V4 in thick and 4 in wide. They extend down the length of the tubes. As seen in Fig. 19.4, they are inserted in grooves cut in the tube support baffles. These seal strips often increase heat-transfer efficiency by 5 to 10 percent. 

The function of seal strips is to interfere with, and hence reduce, the fluid flow through the bypass area. Often, one pair of seal strips is used for every 18 in of shell ID (inner diameter). These seal strips encourage good shell-side cross-flow velocity and also help reduce localized fouling, caused by low velocity. 

Figure 19.4 Seal strips reduce bypassing around tube bundle.

Sealing strips required 1 every 3 vertical tube rows -In/outlet branch nominal pipe size 4, schedule number 80 heat-transfer coefficient 570 W/(mJK)... 

This suggests that sealing strips are required assume one every three vertical rows (i.e. Ns/Ncv = 0.33). The bypass factor (Fb) is then predicted by the formula (from Ref. E2 p.556) ... 

Apparatus without evaporation (sealed strip). To seal the paper, either a nonconducting solid (K22) or a nonconducting liquid immiscible with water can be used. 

N, IVc, IVnu IVp. K, IVh. IVs. N Proportionality coefficient, dimensionless group Grashof number, L p P Af/)U Nusselt number, hD/k or hL/k Peclet number, DGc/k Prandtl number, c A/k Reynolds number, DG/ l Stanton number, Number of sealing strips Dimensionless Dimensionless... 

For the thermal insulation of roofs, there is a difference between fiat roof and steep roof insulation. The insulation of a nonventilated flat roof is done with EPS insulation elements, which could, also, be pre-laminated with a sealing strip. Steep roof insulation is used in attic conversions for residential purposes. There is a difference between insulation under, on and between the rafters. For the between-rafter insulation, different systems are used to make installation very easy. Slabs from the Styrotect [125] system, tongued and grooved, are cut to size, fitted together and laid between the rafters. Also special wedge systems or the use of elasticated slabs are possible. 

Stream C is the main bypass stream and will be particularly significant in pull-through bundle exchangers, where the clearance between the shell and bundle is of necessity large. Stream C can be considerably reduced by using sealing strips horizontal strips that block... 

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