U-tube exchangers

Kettle-type reboilers, evaporators, etc., are often U-tube exchangers with enlarged shell sec tions for vapor-liquid separation. The U-tube bundle replaces the floating-heat bundle of Fig. 11-36. ... 

The U-tube exchanger with copper tubes, cast-iron header, and other parts of carbon steel is used for water and steam services in office buildings, schools, hospitals, hotels, etc. Nonferrous tube sheets and admiralty or 90-10 copper-nickel tubes are the most frequently used substitute materials. These standard exchangers are available from a number of manufacturers at costs far below those of custom-built process-industry equipment. 

Kettle-type-reboiler costs are 15 to 25 percent greater than for equivalent internal-floatiug-head or U-tube exchangers. The higher extra is applicable with relatively large kettle-to-port-diameter ratios... 

Figure 10-1K. U-tube exchanger. (Used by permission Yuba Heat Transfer Division of Connell Limited Partnership.)...

Figure 10-25A. Tubesheet layout for U-tube exchanger. Tube passes two or four. Tube sizes and pitch % in. on in.A. Radius of bend 2Vj X tube diameter.

Exchangers with an internal floating head, Figures 12.5 and 12.6, are more versatile than fixed head and U-tube exchangers. They are suitable for high-temperature differentials... 

An estimate of the number of tubes in a U-tube exchanger (twice the actual number of U-tubes), can be made by reducing the number given by equation 12.3a by one centre row of tubes. 

The U-tube exchanger (Fig. 4) is the best solution to the thermal stress problem, because each tube is free to expand or contract independently of the others or of the shell. However, there are disadvantages to the U-tube exchanger the tubes cannot be mechanically cleaned around the bend, the inner tubes cannot be individually replaced, the long-radius U-tubes are particularly subject to vibration, and single-pass tube-side flow is not possible. 

B) U-tube exchanger with bonnet-type stationary head, split-flow shell, 483-mm (19-in) inside diameter with tubes 21-m (7-ft) straight length. SIZE 19-84 TYPE GBU. 

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