Technology on Different Finned Tubes

(Elliptical) String type finned tube 

Itis fabricated with a batch of single fins that were processed by the punch press and then manually or mechanically, with a certain distance (wingspan) on the base tube. This is the earliest fin tube fabrication with low cost and simple production process/ technology, easy to maintain. Divides into manual set and mechanical set. Manual set uses a tool that relies on the power of man to press the fins one by one. This method is limited by the pressure of the fin, so it is easy to get loose. The machine - set fin is carried on the wing piece machine. Due to the mechanical impact or liquid pressure, the pressure of the fin is high, so it can be used in a larger volume. The bonding strength between fin and tube is high and not easy to loosen. Mechanical transmission has high productivity, but the noise is large, the safety is poor, and the working conditions of the workers are not good. Although the hydraulic transmission does not have the above problem, but the equipment price is more expensive, the technical requirement to use maintenance personnel is higher, its productivity is also lower.

 Embedded G Type (Crimped) Fin Tube

The inlaid spiral fin tube is a spiral groove that preforms a certain width and depth on the steel tube, and then the steel strip is embedded in the steel pipe. In the process of winding, due to certain pretension force, the steel belt will tighten in the spiral groove, thus ensuring a certain contact area between the steel belt and the steel pipe. In order to prevent the steel belt from falling off, the two ends of the steel belt should be welded to the steel pipe. In order to facilitate inlaying, there should be a certain side gap between the steel belt and the spiral groove. If the side gap is too small, the inlaying process is difficult to proceed smoothly. In addition, the winding steel belt always has a certain rebound, the result of which makes the steel belt and spiral groove bottom not very good joint. Inlaid fin can be carried out on general equipment, but the cost is not high, but the process complex production efficiency is low.

Soldering Spiral Crimped Fin Tube

These types of fins are semi-crimped and wrapped under tension around the outside of the base tube. Fins are either tack welded or brazed to the base tube at each end of the tube. These finned tubes can be further HOT DIPPED GALVANISED for surface protection where as the deposition of Zinc also adds up to the efficiency of finned tubes. Effected by galvanized zinc thickness (when it is too chick, the zinc layer will fall off easily due to poor stability), and the zinc liquid can’t seep into the gap entirely, the binding  between fin and steel tube is still not good. Besides, heat transfer coefficient of zinc is lower than steel (about 78% of steel) and zinc is highly vulnerable to corrosion in acids and sulfides. To sum, hot dip galvanized continuous crimped finned tube is not suitable for air pre-heater in boiler gas waste heat recovery.

HF (High Frequency)Solid Fin Tube

Currently HF Fin Tube is one of the most widely used helical fin tubes, you can see it as waste heat recovery in power, metallurgy, concrete, oil and gas, petrochemical, etc. When winding the steel strip around steel tube, the use of high frequency current skin effect and proximity effect on steel strip and steel pipe surface heating, until the plastic state or melt, the coil steel belt must be under pressure to complete welding. Comparing with embedded type and spot welding spiral crimped type, it is more advanced either on fin tube quality or production efficiency or automation degree.

Three-Roll Extruded Integral Fin Tube

The Extruded Fin is formed from an outer aluminum tube with a large wall thickness (muff), which is aligned over an inner base tube. The two tubes are pushed through three arbors with rotating discs that literally squeeze or extrude the aluminum fins up and out of the muff material in a spiral shape in one operation. Comparing with welding fin tube, DR Extruded Fin has higher production efficiency with low cost on material and high heat transfer. At present, it divides into copper or aluminum single metal fin tube and bi-metal composited fin tube.