Baffles in heat exchangers

There are many different arrangements of the shells, tubes and baffles in heat exchangers. Figure 3-6 is a list of TEMA standard cIassification.s for heat exchangers, which helps to describe the various options. These... 

Back-mix reactor design, 721, 728 Baffles in heat exchangers, 595, 610-612 pressure drop over, 599-602, 605-606 Bailee s liahihty, 263 Balance sheet, 140-142 Barometric-leg pumps, 523 Batch operation versus continuous, 35-36 Batch-reactor design, 721-727 Battery-limit additions, definition of, 167 Berl saddles, 688-690 cost of 710... 

The baffle patterns in the column can be segmental (simple) up to about 4-ft diameter column, and larger columns can use a disk and donut design as in heat exchangers, or the double segmented or even multi-segmented as in the layouts discussed under bubble caps earlier in this text. 

The presence of internals in a bed, such as baffles and heat exchangers, or variation in geometric configurations, such as tapered geometry, can affect the flow behavior. The classification scheme in Fig. 9.3 is, however, generally applicable to these situations. 

The pressure drop due to friction when a fluid is flowing parallel to and outside of tubes can be calculated in the normal manner described in Chap. 14 by using a mean diameter equal to four times the hydraulic radius of the system and by including all frictional effects due to contraction and expansion. In heat exchangers, however, the fluid flow on the shell side is usually across the tubes, and many types and arrangements of baffles may be used. As a result, no single... 

The most important choices in the design of batch reactors are reactor volume selection of the agitator speed of the agitator power consumption geometry of the tank, including baffles and heat exchange area (internal and external). 

In Table 17.22, two correlations are presented for shellside two-phase flow pressure drop estimation, based on modifications of the internal flow correlations. The first correlation uses the modified Chrisholm correlation [69, 79], and the second one [80] employs the modified Lockhart-Martinelli correlation. The first correlation is for horizontal crossflow (crossflow in a baffled horizontal heat exchanger with horizontal or vertical baffle cuts). The second one is for vertical crossflow (upflow in a horizontal tube bundle). 

In heat exchanger design it is desirable to place the maximum number of tubes in the enclosing shell. Basically, a shell and tube heat exchanger consists of (1) a tube bundle which is circular in cross section and contains many closely spaced tubes, (2) a hollow shell which encloses the tube bundle and (3) baffles equally spaced along the tube length which have segmented cutouts at the opposite sides of successive baffles to cause flow back and forth across the tube bundle. 

In the case of disc-and-donut-type heat exchangers, the baffles are in the shape of a disc-and-donut. Because of the shape of the baffles, gas distribution is almost uniform on the shell side in spite of any orientation of gas inlet and outlet nozzles (not very critical unlike segmental baffle-type heat exchangers). 

A wide variety of reactor designs and configurations are used to produce latexes. The most common reactors are simple impeller-stirred vessels with jackets for heat exchange. Removal of the heat of polymerization can also be achieved with internal coils or tube-baffles, with heat exchangers in external circulation loops, and with reflux condensers. Sometimes a combination of these techniques is employed. 

Bubble size control is achieved by controlling particle size distribution or by increasing gas velocity. The data as to whether internal baffles also lower bubble size are contradictory. (Internals are commonly used in fluidized beds for heat exchange, control of soflds hackmixing, and other purposes.)... 

Fig. 8. Shell-and-tube heat exchanger A, shell of high strength B, tube sheet C, tubes (normally small diameter tubes are seamless, but large diameter tubes (>1 in.) are welded tubes) D, boimets E, baffles to assure more efficient circulation by providing minimum clearance between tubes and tube holes...

A numerical study of the effect of area ratio on the flow distribution in parallel flow manifolds used in a Hquid cooling module for electronic packaging demonstrate the useflilness of such a computational fluid dynamic code. The manifolds have rectangular headers and channels divided with thin baffles, as shown in Figure 12. Because the flow is laminar in small heat exchangers designed for electronic packaging or biochemical process, the inlet Reynolds numbers of 5, 50, and 250 were used for three different area ratio cases, ie, AR = 4, 8, and 16. 

Several descriptions have been pubUshed of the continuous tar stills used in the CIS (9—11). These appear to be of the single-pass, atmospheric-pressure type, but are noteworthy in three respects the stills do not employ heat exchange and they incorporate a column having a bubble-cap fractionating section and a baffled enrichment section instead of the simple baffled-pitch flash chamber used in other designs. Both this column and the fractionation column, from which light oil and water overhead distillates, carboHc and naphthalene oil side streams, and a wash oil-base product are taken, are equipped with reboilers. 

Maximum shell-side heat-transfer rates in forced convection are apparently obtained by cross-flow of the flmd at right angles to the tubes. In order to maximize this type of flow some heat exchangers are built with segmental-cut baffles and with no tubes in the window (or the baffle cutout). Maximum baffle spacing may thus equal maximum unsupported-tube span, while conventional baffle spacing is hmited to one-h f of this span. 

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