Equivalent diameter heat exchanger tubes

When points for 20-ft-long tubes do not appear in Fig. 11-41, use 0.95 times the cost of the equivalent 16-ft-Iong exchanger. Length variation of steel heat exchangers affects costs by approximately 1 per square foot. Shell diameters for a given surface are approximately equal for U-tube and floating-head construc tion. 

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.)...

The outer and inner tubes extend from separate stationary tube sheets. The process fluid is heated or cooled by heat transfer to/from the outer tube s outside surface. The overall heat transfer coefficient for the O.D. of the inner tube is found in the same manner as for the double-pipe exchanger. The equivalent diameter of the annulus uses the perimeter of the O.D. of the inner tube and the I.D. of the inner tube. Kem presents calculation details. 

Steady two-phase flow. In rod (or tube) bundles, such as one usually encounters in reactor cores or heat exchangers, the pressure drop calculations use the correlations for flow in tubes by applying the equivalent diameter concept. Thus, in a square-pitched four-rod cell (Fig. 3.51), the equivalent diameter is given by... 

Calculate the equivalent diameter of the annular space of a double tube-type heat exchanger. The outside diameter of the inner tube d is 4.0 cm and the inside diameter of the outer tube is 6.0 cm. 

In the case where the fluid flow is parallel to the tubes, as in a shell-and-tube heat exchanger without transverse baffles, the equivalent diameter d of the shell side space is calculated as mentioned above, and h at the outside surface of tubes can be estimated by Equation 5.8a with the use of d. ... 

The equations presented here can also be used to predict heat-transfer coefficients for the shell side of shell-and-tube heat exchangers in which the baffles have been designed to produce flow parallel to the axis of the tube. For such cases, the diameter that should be used is the equivalent diameter... 

Several types of internals have been proposed so far. Some studies are presented by Volkct al. (VI2) and Grekelet al. (G15), who studied several arrangements of tubular internals and baffle trays. Volk suggested vertical tubes to increase the contact efficiency. For fluidized beds with diameter of 5-198 inches, conversions for beds of the same equivalent diameter (cf. Section I,C) were found equal. A large heat-exchange surface in the fluid bed is necessary for non-isothermal reactions, so the use of vertical tubes is quite practical. 

FLOW OUTSIDE TUBES PARALLEL TO AXIS. Some membrane separators have bundles of hollow fibers in a shell-and-tube arrangement with liquid or gas flowing parallel to the tube axis on the outside of the tubes. The external flow passages are irregular in shape and not uniform, since the fibers are not held in position as are the tubes in a heat exchanger. Empirical correlations for the external mass-transfer coefficient have been proposed using an equivalent diameter to calculate the Reynolds number. For a bundle of fibers with diameter d packed in a shell with c void fraction, the equivalent diameter is... 

Assumed the established model use single U-tube heat exchanger, because of the small pitch in two pipes, will interfere each other, could cause heat change different of the outside pipe and concrete. To simplify the calculation, instead the two pipe of U-tube of an equivalence pipe. Its equivalent diameter D =->j2D (Bose JE,1993), D is the diameter of one of the U-tube. Consider that the heat change of equivalence pipe wall and concrete is uniform ... 

As mentioned earlier, the high porosity of the Chart-flo unit, together with the ability to use low hydraulic diameters, gives it advantages over several other CHEs in terms of compactness. For clean stream duties, the volume of a Chart-flo heat exchanger could be as low as 5% of that of the equivalent shell and tube heat exchanger. 

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