Baffle designs, heat exchanger

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 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). 

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. 

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. 

Figure 1.7 Simple detail of shell-and-tube heat exchanger. The water box may be designed for as many as eight passes, and a variety of configurations of shell-side baffles may be used to improve heat transfer, (a) Several water box arrangements for tube-side cooling, (b) Assembly of simple two-pass exchanger with U-tubes. [Fig. 38.2, The Nalco Water Handbook, 1st ed. (1979), reprinted with permission from McGraw-Hill, Inc.)...

Industry sets limits that bound our degrees of freedom and thus tend to shorten our design case study load. We are all aw are of such limits and this last category is included primarily for completeness. Examples include minimum industrial thickness for carbon steel plate, and maximum baffle cut for shell and tube heat exchangers. 

There are many text books that describe the fundamental heat transfer relationships, but few discuss the complicated shell side characteristics. On the shell side of a shell and tube heat exchanger, the fluid flows across the outside of the tubes in complex patterns. Baffles are utilized to direct the fluid through the tube bundle and are designed and strategically placed to optimize heat transfer and minimize pressure drop. 

As mentioned above batch crystallizers are usually simple vessels provided with some means of mechanical agitation or particulate fluidization. These have the effect of reducing temperature and concentration gradients, and maintain crystals in suspension. Baffles may be added to improve mixing and heat exchange or vacuum systems may be added, as appropriate. Various design combinations are available and some are illustrated in Figure 7.1. 

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. 

At the first level of detail, it is not necessary to know the internal parameters for all the units, since what is desired is just the overall performance. For example, in a heat exchanger design, it suffices to know the heat duty, the total area, and the temperatures of the output streams the details such as the percentage baffle cut, tube layout, or baffle spacing can be specified later when the details of the proposed plant are better defined. It is important to realize the level of detail modeled by a commercial computer program. For example, a chemical reactor could be modeled as an equilibrium reactor, in which the input stream is brought to a new temperature and pressure and the... 

Reppich, M. and S. Zagermann. A New Design Method for Segementally Baffled Heat Exchangers. Comput Chem Eng 19 (Suppl) S137-S142 (1995). 

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