U-tube heat exchangers bend the heat exchange tubes into a U-shape, with both ends fixed on the same tube sheet. Since the shell and tubes are separate, the tube bundle can expand and contract freely without generating temperature difference stress due to medium temperature differences. U-tube heat exchangers have only one tube sheet, no floating head, and a relatively simple structure. The tube bundle can be freely pulled out and inserted for easy cleaning, offering the advantages of floating head heat exchangers. However, because the heat exchange tubes are bent into U-shapes with varying radii, only the outermost tubes can be replaced if damaged; other damaged tubes must be plugged. Additionally, compared to fixed tube sheet heat exchangers, the bending radius constraints create gaps in the center of the tube bundle, allowing fluid to easily short-circuit, which affects heat transfer efficiency.
Basic Introduction:
In a shell-and-tube heat exchanger, two fluids exchange heat: one flows inside the tubes (tube side), and the other flows outside the tubes (shell side). The tube wall serves as the heat transfer surface. To enhance the heat transfer coefficient of the shell-side fluid, a certain number of transverse baffles are typically installed inside the shell. These baffles not only prevent fluid short-circuiting and increase fluid velocity but also force the fluid to flow across the tube bundle multiple times along a specified path, significantly increasing turbulence. Common baffle types include segmental and disc-and-doughnut, with the former being more widely used. Each time the fluid passes through the tube bundle inside the tubes is called one tube pass, and each time it passes through the shell is called one shell pass. To increase the fluid velocity inside the tubes, appropriate partitions can be installed inside the end caps to evenly divide all tubes into several groups. Thus, the fluid can pass through only part of the tubes each time and travel back and forth through the tube bundle multiple times, known as multi-tube pass. Similarly, to increase the shell-side velocity, longitudinal baffles can be installed inside the shell to allow the fluid to pass through the shell space multiple times, known as multi-shell pass. In a shell-and-tube heat exchanger, due to the temperature difference between the fluids inside and outside the tubes, the temperatures of the shell and tube bundle also differ.
Note: The above information and technical parameters are compiled and released by Yangzhou Dare Electric Co., Ltd.
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