Heat exchangers, baffles

Oil Scale Sludge hoaming Fouling of pipe work and heat exchangers Baffle separators Strainers Coagulation Diatomaceous earth... 

Water can be trapped behind heat exchanger baffles and then suddenly vaporized by circulation of hot oil. It can also be trapped in dead-ends and U-bends in pipework (see Section 9.1.1). Such U-bends can form when one end of a horizontal pipe is raised by thermal expansion. The trays in a distillation column were damaged during startup when hot gas met water, from previous steaming, dripping down the column [3J. Section 17.12 describes an incident somewhat similar to a foamover. 

Composition 60% copper and 40% zinc. It is used in the manufacture of screws, valve stems, brazing rods, condenser tubes, condenser heads, and heat exchanger baffles and plates. Muntz metal is strong, ductile, and corrosion resistant. 

Estimation of the mass-transfer coefficient in the dialysate outside the fibers is considerably more difficult because of the complex geometry. In a shell-and-tube heat exchanger, baffles are used to help direct the shell-side fluid to flow back and forth in directions largely normal to the tube length. It would... 

Many problems have plagued steam generators of nuclear power plants over the last decades. Therefore, Laborelec developed its own inspection equipment and services. These were extended to other components of nuclear plants like thimbles, guide cards and baffle bolts and to classical parts of power stations like turbines, alternators, heat exchangers and piping. 

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.)... 

Fypass Flow Effects. There are several bypass flows, particularly on the sheUside of a heat exchanger, and these include a bypass flow between the tube bundle and the shell, bypass flow between the baffle plate and the shell, and bypass flow between the shell and the bundle outer shroud. Some high temperature nuclear heat exchangers have shrouds inside the shell to protect the shell from thermal transient effects. The effect of bypass flow is the degradation of the exchanger thermal performance. Therefore additional heat-transfer surface area must be provided to compensate for this performance degradation. 

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. 

U-Tube Heat Excbajiger (Fig. 11-36J) The tube bundle consists of a stationaiy tube sheet, U tubes (or hairpin tubes), baffles or support plates, and appropriate tie rods and spacers. The tube bundle can be removed from the heat-exchanger shell. A tube-side header (stationary head) and a shell with integr shell cover, which is welded to the shell, are provided. Each tube is free to expand or contract without any limitation being placed upon it by the other tubes. 

The tube bundle is the most important part of a tubular heat exchanger. The tubes generally constitute the most expensive component of the exchanger and are the one most hkely to corrode. Tube sheets, baffles, or support plates, tie rods, and usually spacers complete the bundle. 

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. 

Certain corrosive conditions require that special consideration be given to complete drainage when the unit is talcen out of service. Particular consideration is required for the upper surfaces of tube sheets in vertical heat exchangers, for sagging tubes, and for shell-side baffles in horizontal units. 

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.)...

Carbon steel, low-alloy steels Transfer lines, beat exchanger shells, baffles, pump components, heat exchanger tubing, fan blades and shrouds, valves, screens, fasteners... 

An ethylene heat exchanger tube failed in service. The tube was severely thinned beneath a baffle and tore in half (Fig. 2.27). 

Figure 2.27 Close-up of severely thinned heat exchanger tube in a baffle.

Oil Expressed as oil or chloroform extractable matter, ppmw Scale, sludge and foaming in boilers impedes heat exchange undesirable In most processes Baffle separators, strainers, coagulation and filtration, diatomaceous earth filtration... 

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. 

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