Effective tubes

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. 

The effective tube surface is usually evaluated on the outside tube surface. Use net tube length. 

A = (fti external finned surface per ft length from Table 10-39 or other specific tube data) (U, net effective tube length) (N number of tubes) (10-5)... 

Effective Tube Length for U-Tube Heat Exchangers... 

The effective tube length, L, of the bundle for surface area calculations is the mean of the tube lengths between the outside tubes and the inside tubes. See Figure 10-27A. 

To more easily determine the effective tube lengths for U-tubes, the correction chart shown in Figure 10-27B is convenient. The chart is based on many actual U-tube bundle layouts. Values read from the chart are not more than 1 % lower than those obtained by calculations, except where the curve is extrapolated to lower tube counts. Such extrapolations result in errors of 3%, 4%, and higher, giving larger values than those calculated. This does not apply to higher tube count extrapolations. The chart is limited to -in. and... 

Inside Tube Effective Tube LengthiMean Tube Length)... 

Assume effective tube length = 11 ft. 2 142 Thus, the number of tubes required = 678) ... 

Figure 10-27B. Effective tube length correlations for calculating outside surface areas of U-tube bundles (two or four passes). (Used by permission D. L Whitley and E. E. Ludwig, Chemical Engineering. V. 67, No. 6 1960. McGraw-Hill, Inc. All rights reserved.)...

Calculate the net available area in the assumed unit, using only the effective tube length. 

N, = number of effective tubes for condensation L = tube length, ft W = condensate flow rate, Ib/hr... 

It is convenient to use 20 mm OD, 16 mm ID tubes, 4.88 m long which, allowing for the tube-sheets, would provide an effective tube length of 4.83 m. Thus ... 

Emerson, W. H. (1973) Conference on Advances in Thermal and Mechanical Design of Shell and Tube Exchangers, NEL Report No. 590. (National Engineering Laboratory, East Kilbride, Glasgow, UK). Effective tube-side temperature in multi-pass heat exchangers with non-uniform heat-transfer coefficients and specific heats. 

A P Effective tube-plate design pressure difference ML- T-2... 

Allowing for the tube sheet thickness, the effective tube length (L,) is 1.8 m. 

The first phenomenological model for description of polymer dynamics in concentrated solutions and melts was proposed in 1971 by P.de Gennes [50]. In this classical work, it was assumed that due to entanglements, the chain motions in the direction normal to the chain contour are blocked up and only tangential ones are possible. This kind of chain motion in the effective tube was called reptation. In the absence of external fields, the chain can escape from the tube by either of the free tube ends. 

Auxiliary calculations for tube area and effective tube emissivity ... 

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