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The shell-and-tube heat exchanger is a common type of tubular heat exchanger; its structure consists of a bundle of U-shaped tubes, and it is suitable for high-temperature, high-pressure conditions or situations with large temperature differences in industries such as petrochemicals, coal chemistry, pharmaceuticals, and power generation. Basic structure and components: Shell: It is a cylindrical enclosure whose function is to house the tube bundle and the shell-side fluid. U-tube bundle: It consists of multiple U-shaped metal tubes; common metal materials include stainless steel, copper, titanium alloys, etc. The two ends of these U-tubes are fixed to the same tube sheet, thereby forming a tube-side flow channel. Tube sheet: Fixes the tube bundle and connects it to the shell, separating the tube side from the shell side. Tube box (head): Located at both ends of the shell; it is used to distribute and collect the fluid in the tube side. Baffles: Plates installed inside the shell that enhance turbulence in the fluid flowing through the tube side, thereby improving heat transfer efficiency. Working principle: The fluid in the tube side enters the U-tubes, flows through them, and then returns to the other end of the tube box. Shell-side fluid: flows in a tortuous path within the shell along the baffle plates, exchanging heat with the tube-side fluid through the tube walls. Thermal compensation feature: One end of the U-tube is fixed, while the other end can expand and contract freely, thereby avoiding thermal stress issues caused by temperature changes. Main advantages: Automatic compensation for thermal expansion deformation; no need to install expansion joints ； It has a relatively simple structure with few sealing points, making it suitable for use under high-pressure conditions. The tube bundle can be withdrawn as a whole for cleaning or replacement ； Compared to floating-head heat exchangers, it has a simpler structure and lower manufacturing costs. Disadvantages and limitations: The curved section on the inner side of the U-tube is prone to scaling, making mechanical cleaning difficult ； Each U-tube operates in a two-flow mode, with a low flow rate that may affect heat transfer efficiency ； The U-tubes are arranged in concentric circles on the tube sheet, making it difficult to install pipes in the central area ； If a single U-tube leaks, it is usually necessary to plug the tube or replace the entire tube bundle. Considerations for selection and design: Fluid distribution – Dirty or high-viscosity fluids are suitable for use in the shell side (to facilitate cleaning), while corrosive or high-pressure fluids are better used in the tube side. Selection of the number of pipes: Usually, the number of pipes is an even value (such as 2 or 4), as it is necessary to balance the relationship between pressure drop and heat transfer coefficient. Material matching: Select the appropriate pipe material based on the corrosivity of the medium; for example, titanium pipes can be used in seawater environments, while Hastelloy can be used for acidic solutions. Vibration protection: Vibration-damping structures must be installed in the shell side at high flow rates to prevent resonance-induced cracking of the U-tubes. Comparison with other heat exchangers: U-tube type, Fixed tube sheet type, Floating head type with thermal compensation. Advantages: (U-tubes can expand and contract freely); Disadvantages: (Expansion joints are required); Advantages: (The floating head end can move). Maintenance ease: Medium (the tube bundle can be removed); Disadvantages: (It cannot be removed); Advantages: (Easy to disassemble). Applicable temperature difference: Large (no thermal stress); Small (ΔT)