The U-tube heat exchanger is characterized by its ability to allow the tube bundle to expand and contract freely, eliminating thermal stress caused by temperature differences between the tube and shell, and offering excellent thermal compensation performance. The tube side is a double-pass configuration with a longer flow path and higher flow velocity, resulting in better heat transfer performance. It has a strong pressure-bearing capacity, and the tube bundle can be withdrawn from the shell for easy maintenance and cleaning. The structure is simple and cost-effective, making it suitable for situations where there is a significant temperature difference between the tube and shell walls, or where the shell-side medium is prone to fouling while the tube-side medium is clean and less prone to fouling, as well as for high-temperature, high-pressure, and highly corrosive environments....