The U-tube heat exchanger bends the heat exchange tubes into a U-shape, with both ends fixed on the same tube plate. As the shell and heat exchange tubes are separate, the tube bundle can expand and contract freely without experiencing thermal stress due to temperature differences in the medium. The U-tube heat exchanger has only one tube plate and no floating head, making its structure relatively simple. The tube bundle can be easily removed and inserted, facilitating cleaning, and it shares the advantages of a floating head heat exchanger. However, since the heat exchange tubes are bent into U-shapes with unequal radii, if the outer tube is damaged, it can be replaced, but other tubes that are damaged can only be plugged. Additionally, compared to the fixed tube plate heat exchanger, the tube bundle in the U-tube design has gaps in the middle due to the restriction of the bending radius of the heat exchange tubes, which allows fluid to take short-cuts easily, affecting the heat transfer efficiency.