Xinxiang Songjin Machinery Co., Ltd. holds a national invention for the spiral flat tube forming machine. The tube forming process ensures that the wall thickness remains unchanged and does not exceed the material's yield point, maintaining the mechanical integrity of the tube. Both ends of the tube remain circular, facilitating connection with the tube sheet. The range of tube materials is extensive, including carbon steel, stainless steel, Cr-Mo alloys, duplex and super duplex alloys, as well as titanium, zirconium, and tantalum, with tube diameters ranging from φ12 to φ40.
The heat transfer rate of spiral flat tubes is significantly better than that of ordinary smooth tubes, with lower pressure drop and reduced susceptibility to fouling and blockage.
A simulation study was conducted with fluids having a Reynolds number less than 1000 to compare the differences between spiral flat tubes and spiral elliptical flat tubes, while analyzing the field synergy angle of the two tube cross-sections and comparing them with straight flat tubes and straight elliptical flat tubes. The results indicate that the Nusselt number on the wall of both spiral tubes increases with the Reynolds number, with the rate of increase gradually slowing; the comprehensive performance evaluation factor of both spiral tubes increases with the Reynolds number, and that of the spiral flat tube is higher than that of the spiral elliptical flat tube, making it the preferred choice under these conditions. For self-supporting spiral tubes, at the same Reynolds number, the pressure loss of the spiral elliptical flat tube is lower than that of the spiral flat tube, but its heat transfer performance is inferior to that of the spiral flat tube.

The spiral flat tube (Twisted tube) was proposed by Sweden's Alards company and improved by the American Koch Heat Transfer Company, LP, as an enhanced heat transfer tube.

The structural feature of the spiral flat tube is that any cross-section of the heat exchange section is elliptical. When assembled into a heat exchanger, it can be a mixed tube bundle (i.e., a combination of spiral flat tubes and smooth tubes) or a pure spiral flat tube bundle.

Its manufacturing process involves two forming steps: "flattening" and "twisting." The tube cross-section resembles an ellipse, with the aspect ratio of the ellipse designed based on the flow velocities of the tube side and shell side. When the tube side flow rate is low, the aspect ratio can be increased to reduce the flow area and increase the velocity. The unique structure of the spiral flat tube allows both the tube side and shell side fluids to undergo spiral motion simultaneously, enhancing turbulence. The overall heat transfer coefficient of a spiral flat tube heat exchanger is 40% higher than that of a conventional heat exchanger, while the pressure drop remains almost the same.

In recent years, spiral flat tube heat exchangers have been further refined and developed. They are more reliable and efficient than other types of heat exchangers and can be used in almost any system where shell-and-tube heat exchangers are specified. Since 1984, thousands of spiral flat tube heat exchangers have been manufactured and sold worldwide, applicable to gas-gas, liquid-liquid, and liquid-gas heat exchange processes across various industries, including chemical, petroleum, food, papermaking, power, metallurgy, mining, and urban heating.

Spiral flat tubes can simultaneously improve the heat transfer coefficients on both the inner and outer sides of the heat exchange tube, thereby significantly enhancing the overall heat transfer coefficient and total heat exchange efficiency.