Triangular pitch

I Normal triangular pitch does not permit mechanical cleaning. With a wide triangular pitch, which is equal to 2 (tube diameter plus cleaning lane)/V, mechanical cleaning is possible on removahle bundles. This wide spacing is infrequently used. 

Tubes are most commonly arranged on an equilateral triangular pitch. Tubes are arranged on a square pitch primarily for mechanical cleaning purposes in removable-bundle exchangers. 

I Fixed-tube-sheet construction Anth Vi-in OD tube on i-Vift-in triangular pitch provides 36 percent more surface. 

Tubing The 25.4-mm (I-in) outside-diameter tube is most commonly used. Fin heights vary from 12.7 to 15.9 mm (0.5 to 0.625 in), fin spacing from 3.6 to 2.3 mm (7 to II per linear inch), and tube triangular pitch from 50.8 to 63.5 mm (2.0 to 2.5 in). Ratio of extended surface to bare-tube outside surface varies from about 7 to 20. The... 

Perforations are usually 0.32 to 0.64 cm Vh to Vi in) in diameter, set 1.27 to 1.81 cm to Vi in) apart, on square or triangular pitch. There appears to be relatively httle effect of hole size on extraction rate, except that with systems of high interfacial tension smaller holes will... 

Tube exteriors with triangular pitch cleanable chemically only chemically only chemically only chemically only chemically only... 

In Figure 3-5e the square-pitch layout has been rotated 45, yet it is es,sentially the same as Figure 3-5a. In Figure 3-5d a mechanically clean-able modification of triangular pitch is shown. If the tubes are spread wide enough, it is possible to allow the cleaning lanes indicated. 

Holes spaced closer than twice the hole diameter lead to unstable operation. The recommended spacing is 2.5 do to 5 do with 3.8 do being preferable [42]. Holes are usually placed on 60° equilateral triangular pitch with the liquid flowing norrrially to the rows. Holes should not be greater than 2.5-3 in. apart for effective tray action. 

In-Line Triangular Pitch, Apex Horizontal or at Right Angle to Oncoming Flow. Not as popular as the staggered triangular pitch coefficients not as high, but better than in-line square... 

In-Line Square Pitch. Popular for conditions requiring low-pressure drop and/or cleaning lanes for mechanical cleaning of outside of tubes coefficient lower than triangular pitch. 

Full Circle Tube Layouts Floating Head Exchanger -in. O.D. Tubes on -in. Triangular Pitch... 

Figure 10-56. Equivalent diameter for tubes on shell side of exchanger taken along the tube axis, (a) Square pitch, (b) triangular pitch on 60° equilateral angles. (Used by permission Kern, D. Q. Process Heat Transfer, V Ed., 1959. McGraw-Hill, Inc. All rights reserved.)...

Try 15.25-in. I.D. shell 4 pass, with 78 tubes total, 16-ft long on 1 Vr -in. triangular pitch. 

For a 4-pass, fixed tubesbeet unit, -in. tubes on /jg -in. triangular pitch, shell I.D. = 12-in., number of tubes = 84 ... 

Use two passes in tubes tubes on 1-in. triangular pitch. From the tube count in Table 10-9, a 29-in. I.D. shell will hold 646 tubes, including an allowance for tie rods. The number of tubes per pass = 646/2 = 323. 

V4 -in. tubes X 12 BWG steel for low pressure drop, easier cleaning on 1 Vj -in. triangular pitch, 4 ft long Assume tube sheets, each 1 Vj in. thick, then usable tube length = 3.75 ft. 

The approximate tube bundle diameter for tubes layed out on triangular pitch can be calculated from... 

Duplex tubes 1-in. O.D. X 16 ft, 0 in. long, 16 BWG steel outside, 16 BWG cupro-nickel inside No. = 578,1 V4 -in. triangular pitch Shell 36-in. O.D., 4 tube pass Film coefficients ... 

With a dean shell-side fluid, 1.25 triangular pitch may be used and, from equation 9.211 ... 

Square and equilateral triangular patterns are used triangular is preferred. The total hole area as a fraction of the perforated area Ap is given by the following expression, for an equilateral triangular pitch ... 

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