U-shaped heating tubes are also known as non-uniform heating tubes. They feature evenly distributed high-temperature resistance wires within a high-temperature resistant stainless steel seamless tube, with a dense filling of crystalline magnesium oxide powder that has good thermal conductivity and insulation properties in the gaps. This structure is not only advanced and highly efficient but also ensures even heat distribution. When an electric current passes through the high-temperature resistance wires, the heat generated diffuses through the crystalline magnesium oxide powder to the surface of the metal tube, then transfers to the heated object or water, achieving the heating objective.