Use of U-tube heat exchangers?
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What are the advantages and disadvantages of U-tube heat exchangers? What are the differences in investment costs between U-tube heat exchangers and other types of heat exchangers? Our plant uses U-tube heat exchangers for methanol distillation; circulating water flows through the tube side, while methanol flows through the shell side. The circulating water is not very clean and tends to get clogged. What methods can be used for cleaning it? What measures should be taken in case of leaks?
The heat exchange tubes of a U-tube heat exchanger are shaped like U’s, with both ends fixed to the same tube sheet. The tube bundle can expand and contract freely, so no thermal stress is generated due to temperature differences in the fluid. Since this type of heat exchanger has only one tube sheet, it is relatively inexpensive and has a simple structure. Additionally, the tube bundle can be removed for cleaning between the tubes, which are the advantages of this type of heat exchanger. Its drawback is that the heat transfer performance is poor due to the large spacing between the tubes, especially the larger gaps in the middle section. Due to the varying curvatures of the pipes in each row and their different lengths, the distribution of the pipes is not as uniform as that of straight pipes. The tubes in the middle section of the tube bundle cannot be inspected or replaced; after blockage, the failure rate of these tubes is twice that of straight tubes, as the entire supporting load is borne by a single tube sheet, and the thickness of such a tube sheet, for a given shell inner diameter, is greater than that of other types of tube sheets. When the heat exchanger has a large diameter, it is difficult to support the U-shaped section, and the tube bundle has poor vibration resistance.