Pressure drop Across tube banks

Ishehara, K,J. W. Palen, andj. Taborek, Critical Review of Correlations for Predicting Two-Phase Flow Pressure Drop Across Tube Banks, Heat Trans. Eng.,Y. 1, No. 3,Jan.-March (1980). 

The gas pressure drop across the bank of finned tubes... 

For pressure drop inside tubes, d is 0.046 and F is the fluid-flow path length. Across tubes banks, a is 0.75 and F is the product of the number of tube rows and the number of fluid passes across the tube bank. The physical property term is again tabulated after being normalised so that the lowest value is approximately unity. 

Figure 10-142. Pressure drop in fluid flowing across tube banks with segmental baffles. (Used by permission Buthod, A. P. Oil Gas Journal, V. 58, No. 3, 1960. PennWell Publishing Company. All rights reserved.)...

Any suitable correlation for the cross-flow friction factor can be used for that given in Figure 12.36, the pressure drop across the ideal tube bank is given by ... 

Most of the pressure drop will occur in the convection section. The procedures for estimating the pressure drop across banks of tubes can be used to estimate the pressure drop in this section, see Section 12.9.4 and Volume 1, Chapter 9. 

A simpler method due to Kem (1950, pp. 147-152) nominally considers only the drop across the tube banks, but actually takes account of the added pressure drop through baffle windows by employing a higher than normal friction factor to evaluate pressure drop across the tube banks. Example 8.8 employs this procedure. According to Taborek (HEDH, 1983, 3.3.2), the Kern predictions usually are high, and therefore considered safe, by a factor as high as 2, except in laminar flow where the results are uncertain. In the case worked out by Ganapathy (1982, pp. 292-302), however, the Bell and Kem results are essentially the same. 

APj = ideal pressure drop across the tube bank jf = shell-side friction factor ... 

PRESSURE DROP FOR FLOW ACROSS TUBE BANKS SINGLE-PHASE FLUIDS 7.79... 

Consider the causes of the pressure drop, and select equations to calculate each. The pressure drop for fluids flowing across tube banks may be determined by calculating the following components ... 

In an industrial facility, air is to be preheated before entering a furnace by geo-u thermal water at 120°C flowing through the tubes of a tube bank located in a S duct. Air enters the duct at 20°C and 1 atm v/ith a mean velocity of 4.5 m/s, H and flows over the tubes in normal direction. The outer diameter of the tubes is 1.5 cm, and the lubes are arranged in-line with longitudinal and transverse pilches of Sr = Sf = 5 cm. There are 6 rows in the flow direction with 10 tubes i in each row, as shown in Fig. 7-28. Determine the rate of heat transfer per unit 3 length of the tubes, and the pressure drop across the tube bank. 

For this square in-line tube bank, the friction coefficient corresponding to Reo = 5086 and SJD = 5/1.5 = 3.33 is, from Fig. 7-27a. f 0.16. Also, X = 1 for the square arrangements. Then the pressure drop across the tube bank becomes... 

Air is to be heated by passing it over a bank of 3-m-long tubes inside which steam is condensing at 100°C. Air approaches the tube bank in the normal direction at 20 C and I aim with a mean velocity of 5.2 m/s. The outer diameter of the tubes is 1.6 cm, and die lubes are arranged staggered with longitudinal and transverse pitches of = Sj = 4 cm. There are 20 row.s in the flow direction with 10 tubes in each row. Determine (a) the rate of heat transfer, (f ) and pressure drop across the tube bank, and (c) the rate of condensation of steam inside the tubes. 

In this equation, N is the nnmber of major restrictions in the tube bank (i.e., the nnmber of times the flow reaches its maximnm velocity in flowing throngh the tube bank). In the 30° and 90° arrangements, N is equal to the number of tube rows crossed in the bank for the 45° and 60° layonts, N is one less than the number of rows crossed. The term Ap is the frictional pressure drop across the tube bank. 

Equation 8.16 is a simplified equation which is based upon equipment with a certain amount of fouling present on the shell side. Consequently, it may predict values of pressure drop higher than actually present for certain applications. A more rigorous method for calculating pressure drop across banks of tubes is presented here. The pressure drop for fluids flowing across the tube banks may be determined by calculating the following components ... 

A large process plant air cooler may have 10, 20, 30, or more banks of air coolers, arranged in parallel. Figure 19.6 shows such an arrangement. Let s assume that the inlet header is oversized and has zero pressure drop. Let s also assume that the outlet header is oversized and also has no AP. The pressure drop across the tube side of all such air coolers arranged in parallel is then identical. 

Wang et al, (2010a) calibrated the inertial resistance factor, C2/, used in the porous media model in a bench scale set-up using membrane bundles with the same packing density as the Siemens Memcor Memjet BIOR HF membranes that are used in the full-scale plant being modelled. The pressure drops across the membrane bundle for flow directions perpendicular and parallel to the membrane bundle and at different fluid viscosities were measured for various liquid velocities. The empirical correlations used for modelling the pressure drop caused by tube banks were found to underestimate the pressure drop caused by the HF bundles (Fig. 15.10). 

Turbulent Flow The correlation by Grimison (Trans. ASME, 59, 583—.594 [1937]) is recommended for predicting pressure drop for turbulent flow (Re > 2,000) across staggered or in-hne tube banks for tube spacings [(a/Dt), (b/Dt)] ranging from 1.25 to 3.0. The pressure drop is given by... 

E/ig. Exp. Sta. Bull., 2 [1950]) recommend the following equations for pressure drop with laminar flow (Re, < 100) of liquids across banks of plain tubes with pitch ratios P/D( of 1.25 and 1..50 ... 

Bergelin, O. P, W. L. Lafferty,Jr., M. D. Leighton, R. L. Pigford, Heat Transfer and Pressure Drop during Viscous and Turbulent How across Baffled and UnbafUed Tube Banks, University of Delaware, Eng. Exp. Sta., Newark, Del. Bui. No. 4 (1958). 

---