The tube bundle includes finned tubes, tube headers, side beams, and supporting accessories.

The tube bundle is the heat transfer component of the air cooler. Fin tubes are composed of fins and tube bases (bare tube), and are the core components for heat transfer in air coolers. Due to the low heat release coefficient of the air film, it is necessary to add fins on the outer surface of the heat transfer tube (base tube) to enhance its heat transfer (expand the heat transfer area and increase the turbulence of the air). The tube box header combines single finned tubes into a collective and is used to distribute and guide fluids. Each tube bundle should have at least two box headers. According to different structures, it can be divided into plug-type pipe headers, detachable cover plate type pipe headers, collection type pipe headers, disassembly type pipe headers, etc. For multi-pass tube bundles with two or more tube passes, when the temperature difference between the fluid inlet and outlet is large, the temperature difference and thermal expansion difference between the tube walls of each tube pass are also large, which often causes bending deformation of the finned tubes, resulting in fin loosening and affecting heat transfer efficiency. Even due to excessive temperature stress, the expansion joint (or weld) between the heat transfer tube and the tube sheet may be pulled off. Therefore, when the temperature difference between the inlet and outlet of the same pipe box fluid is greater than the specified value, a decomposed pipe box or U-shaped pipe structure should be used. Side beams and connecting accessories are used to support and connect various components of the tube bundle. Side beams are generally made of cold-formed steel plates, which have good rigidity and save materials. They can also be made of large steel sections, but they are not commonly used at present. The connection methods between finned tubes and tube sheets include strength expansion, strength welding, and a combination of expansion welding.