Heat Exchanger Tube Bundles

Example 3.11 Atmospheric air (p = 0.1 MPa) is to be heated in a tube bundle heat exchanger from 10 °C to 30 °C. The exchanger consists of 4 neighbouring rows and zr rows of tubes aligned one behind the other. The outer diameter of the tubes is 25 mm, their length 1.5m, the longitudinal pitch is the same as the transverse pitch s /d = sq/d = 2. The wall temperature of the tubes is 80 °C with an initial velocity of the air of 4m/s. Calculate the required number zr of tube rows. 

Fig. 4.40 Paddle wheel reactor with a tube bundle heat exchanger in the gas space after [622].

The first four types of heat exchangers are especially popular in the petroleum industry. The double-pipe heat exchanger is only used for heating high viscosity materials such as vacuum residue or bitumen. Figure 5.21 shows an example of the horizontal tube-bundle heat exchanger. 

Type Pfaudlcr type UB, hairpin tube bundle heat exchanger Heat transfer area 5 ft ... 

The tube-bundle heat exchanger (Figure 2.3.1-4a), in various construction variations, can be regarded as the standard heat exchanger. 

Thbe evaporators with thermosiphon circulation or continuous flow evaporators are mainly used in rectification facilities. Falling film evaporators or film evaporators are seldom used. The vapor is condensed in a horizontal liquid-cooled tube bundle heat exchanger or air-cooled finned-tube heat exchangers [2.135]. 

Figure 2.13 Schematic display of a tube bundle heat exchanger with manifold for flow distribution, consisting of baffle and flow straightener.

Both the Hoechst Tropfapparat and the Proabd are tube bundle crystallization equipment run in the same way, as mentioned above. In principle, every plate or tube bundle heat exchanger can be used as static solid layer crystallizer however, a few special geometrical considerations have to be obeyed. 

They can be used to measure the thickness of the wall of a pipe and situate pitting or local corrosion in two dimensions. Possible applications for probing tube bundle heat exchangers (e.g. the Probolog). 

Fouling is a common cause of increased head losses and deterioration of the through-tube bundle heat exchange coefficient. 

Figure 3.3.1 Tube bundle heat exchanger. Tube bundle heat exchanger.

The U-tube bundle has the advantage of providing minimum clearance between the outer tube hmit and the inside of the shell for any of the removable-tube-bundle constructions. Clearances are of the same magnitude as for fixed-tube-sheet heat exchangers. 

Figure 10-4G. Twisted tubes with heat exchanger bundle arrangements. (Used by permission Brown Fintube Co., A Koch Engineering Co., Bui. B-100-2.)...

Design for Heat Transfer Coefficients by Forced Convection Using Radial Low-Fin tubes in Heat Exchanger Bundles... 

Process (12). The reactor is a horizontal pressure vessel called Contactor and containing an inner circulation tube, a heat exchanger tube bundle to remove the heat of reaction, and a mixing impeller in one end. The hydrocarbon feed and recycle acid enter on the suction side of the impeller inside the circulation tube. This design ensures the formation of a fine acid-continuous emulsion. The high circulation rate prevents significant temperature differences within the reactor. The reactor is shown schematically in Fig. 11. 

For reactors of a larger diameter (e.g. more than 600 mm) it is more advisable to use a bundle of small tubes as heat exchangers. Such a distribution of heat exchange surfaces virtually does not inhibit fluidising and ensures that the heat is efficiently withdrawn from the whole surface of the apparatus. It should be also kept in mind that tube bundles allow one to select the reaction space and place rotating gas distribution devices between sections this considerably increases the coefficient of heat transfer and ensures a more uniform gas distribution in the reaction zone. 

In contrast, Dunlap and Rushton [34] succeeded to correlate their measurements at cooling and heating in a vessel with a turbine stirrer and pipe bundle heat exchangers with Vis-0 4 because a thick boundary layer developed around the tubes. 

Fig. 5.2. Several concentric tube heat exchanger configurations, (a) simple heat exchanger (b) multiple-tube heat exchanger (c) concentric tube with a wire spacer or turbulator and (d) bundle heat exchanger. LP refers to the general location of low-pressure flow and HP refers to the normal location of high-pressure flow.

In petrochemical plants, fans are most commonly used ia air-cooled heat exchangers that can be described as overgrown automobile radiators (see HeaT-EXCHANGEtechnology). Process fluid ia the finned tubes is cooled usually by two fans, either forced draft (fans below the bundle) or iaduced draft (fans above the bundles). Normally, one fan is a fixed pitch and one is variable pitch to control the process outlet temperature within a closely controlled set poiat. A temperature iadicating controller (TIC) measures the outlet fluid temperature and controls the variable pitch fan to maintain the set poiat temperature to within a few degrees. 

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