Introduction to spiral flat tube heat exchangers

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The spiral flat tube is a type of heat exchange tube first proposed by the Swiss company Allares and improved by the American company Brown (Brown in Houston). Due to the unique structure of the tube, the fluid flows in a spiral pattern within it, which increases the level of turbulence. Experimental studies have shown that the heat transfer coefficient on the inner wall of spiral flat tubes is generally much higher than that of ordinary circular tubes, with this difference being most pronounced at low Reynolds numbers, reaching 2–3 times higher ； As the Reynolds number increases, the heat transfer coefficient can usually also be increased by more than 50%. 　　Its manufacturing process involves first flattening the circular tube and then twisting it into a spiral shape. According to the research by Dr. Liu Along from Zhejiang Huanchen Technology, when the tubes are inserted, they are arranged in a uniform pattern to form a tube bundle; this bundle has no supporting elements, and it relies instead on the contact points of the external helical lines on the outer edges of the spiral flat tubes to support itself. In the pipe lining, the spiral flow of the fluid increases its turbulence level, reducing the thickness of the boundary layer that acts as the main thermal resistance for heat transfer, thereby enhancing heat transfer within the pipe. In the shell side, since the flow channels between the spiral flat tubes are also spiral-shaped, the fluid moving through them experiences centrifugal force, which causes its speed and direction to change periodically, thereby enhancing the longitudinal mixing of the fluid. Furthermore, as the fluid passes through the spiral contact points between adjacent tubes, a wake that is detached from the tube wall is formed, which increases the turbulence of the fluid itself and disrupts the heat transfer boundary layer on the tube wall; as a result, the heat transfer in the shell side is also enhanced. As a result of the simultaneous enhancement of heat transfer both inside and outside the tube, its heat transfer efficiency is significantly higher than that of conventional shell-and-tube exchangers, especially in heat exchange processes where the fluid has high viscosity and flow is stagnant on one or both sides. The heat exchangers made using these heat exchange tubes have the following advantages: 1. Low pressure drop, 2. High heat transfer efficiency, 3. Resistance to scaling, 4. No clogging. These advantages overcome the shortcomings of traditional heat exchangers, making them the ideal equipment for recovering low-temperature waste heat. These heat exchangers perform very well when used with slag flushing water, and are thus the most ideal choice for such applications.