Tubular heat exchanger

The Tube Wall Tubular heat exchangers are built using a number of circular (or noncircular) tubes thus, the heat-transfer rate across tubular walls, following Fourier s law of heat conduction, becomes... 

Air preheat temperature requirements of 2250—2300 K are anticipated for natural gas-fired systems, and about 2000 K for oil or coal-fired systems (11). Use of 32—40% oxygen enrichment lowers the preheat temperature requirement to a moderate 900—1000 K, which can be attained with conventional metal-type tubular heat exchangers. Depending on the cost of oxygen, this is a viable alternative to the use of separately fired high temperature preheaters. 

Medium Pressure Synthesis. Pressures of 500—2000 kPa (5—20 atm) were typical for the medium pressure Fischer-Tropsch process. Cobalt catalysts similar to those used for the normal pressure synthesis were typically used at temperatures ranging from 170 to 200°C ia tubular "heat exchanger" type reactors. 

Patrick M. Bernhagen/ P.E./ B.S.M.E./ Senior Mechanical Engineer Fo.ster Wheeler USA Corporation, American Society of Mechanical Engineers. (Compact and Non-Tubular Heat Exchangers)... 

TABLE 11-3 Typical Overall Heat-Transfer Coefficients in Tubular Heat Exchangers... 

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. 

The best known use of the hairpin is its operation in true counter-current flow which yields the most efficient design for processes that have a close temperature approach or temperature cross. However, maintaining countercurrent flow in a tubular heat exchanger usually implies one tube pass for each shell pass. As recently as 30 years ago, the lack of inexpensive, multiple-tube pass capability often diluted me advantages gained from countercurrent flow. 

By virtue of its chemical and thermal resistances, borosilicate glass has superior resistance to thermal stresses and shocks, and is used in the manufacture of a variety of items for process plants. Examples are pipe up to 60 cm in diameter and 300 cm long with wall tliicknesses of 2-10 mm, pipe fittings, valves, distillation column sections, spherical and cylindrical vessels up 400-liter capacity, centrifugal pumps with capacities up to 20,000 liters/hr, tubular heat exchangers with heat transfer areas up to 8 m, maximum working pressure up to 275 kN/m, and heat transfer coefficients of 270 kcal/hz/m C [48,49]. 

Dowtherm A will be used at 620°F (326.67°C) in a horizontal tubular heat exchanger. 

Economizer. The economizer is a tubular heat exchanger used to recover heat from the exhaust gases from boilers or some processes. It is used in boilers to recover much of the sensible heat for use in preheating the boiler feedwater. An increase in boiler efficiency of 4-6 per cent is typical. The design and materials of construction depend on the application. 

In forming a comparison between plate and tubular heat exchangers there are a number of guidelines which will generally assist in the selection of the optimum exchanger for any application. In summary, these are ... 

When mild steel construction is acceptable and when a closer temperature approach is not required, the tubular heat exchanger will often be the most economic solution since the plate heat exchanger is rarely made in mild steel. 

The resistance of titanium in nitric acid is good at most concentrations and at temperatures up to boiling . Thus tubular heat exchangers are used in ammonium nitrate production for preheating the acid prior to its introduction into the reactor via titanium sparge pipes. In explosives manufacture, concentrated nitric acid is cooled in titanium coils and titanium tanks are... 

Tucker, G. and Heydon, G Trans.I.Chem.E. 76 Part C (1998) 208. Food particle residence time measurement for the design of commercial tubular heat exchangers suitable for processing suspensions of solids im liquids,... 

TWo tubular heat exchangers are available each with a 0.44 m i.d. shell fitted with 166 tubes, 19.0 mm o.d. and 15.0 mm i.d., each 5.0 m long. The tubes are arranged in two passes on 25 mm square pitch with a baffle spacing of 150 mm. There are two passes on the shell side and operation is to be countercurrent. With benzene passing through the tubes, the anticipated film coefficient on the tube side is 1000 W/m2K. 

BS 3274 (British Standards Institution, Londonl British Standard 3274 I960 Tubular heat exchangers for general purposes. 

It is desired to warm an oil of specific heat 2.0 kJ/kg K from 300 to 325 K by passing it through a tubular heat exchanger with metal tubes of inner diameter 10 mm. Along the outside of the tubes flows water, inlet temperature 372 K and oudet temperature 361 K. 

Example 8.9 Find the temperature distribution in a laminar flow, tubular heat exchanger having a uniform inlet temperature and constant wall temperature Twall- Ignore the temperature dependence of viscosity so that the velocity profile is parabolic everywhere in the reactor. Use art/P = 0.4 and report your results in terms of the dimensionless temperature... 

Distillation columns, vessels and tubular heat exchangers, though non-proprietary items, will be designed to conform to recognised standards and codes this reduces the amount of design work involved. 

TEMA (1999) Standards of the Tubular Heat Exchanger Manufactures Association, 8th edn (Tubular Heat Exchanger Manufactures Association, New York). 

Figure 31 (Liu, Liu, Li and Kwauk, 1986) shows a cylindrically shaped shallow fluid bed tubular heat exchanger. Solid particles are fluidized with a small stream of activating gas Ga, so as to insure maximal heat transfer between the particles and the exchanger tube wall. The waste gas Gw, from which heat is to be extracted, passes through the solid...

Liu, D., Liu, J., Li, T., and Kwauk, M., Shallow-Fluid-Bed Tubular Heat Exchanger, Fifth Int. Fluidization Conf, p. 401M08, Elsinore, Denmark... 

Figure 8.4. Example of tubular heat exchangers (see also Fig. 8.14). (a) Double-pipe exchanger, (b) Scraped inner surface of a double-pipe exchanger, (c) Shell-and-tube exchanger with fixed tube sheets, (d) Kettle-type reboiler, (e) Horizontal shell side thermosiphon reboiler, (f) Vertical tube side thermosiphon reboiler, (g) Internal reboiler in a tower, (h) Air cooler with induced draft fan above the tube bank, (i) Air cooler with forced draft fan below the tube bank.

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