Abstract Tension wound finned tubes are high-efficiency heat exchange components fabricated by wrapping fin strips tightly around the outer surface of base tubes under controlled tension, followed by shaping and locking processes. Distinguished from welded or brazed finned tubes, this technology eliminates thermal damage to base tubes and fins, ensures tight fin-tube bonding, and exhibits superior adaptability to diverse materials and structural designs. This paper systematically elaborates on the core manufacturing processes and technical control points of tension wound finned tubes, analyzes their inherent performance advantages over conventional finned tube types, outlines typical application scenarios across multiple industrial sectors, and provides practical selection guidelines. The content serves as a technical reference for engineers engaged in heat exchange system design, equipment manufacturing, and energy conservation optimization.
1. Introduction
Heat exchange efficiency is a critical indicator determining the energy utilization rate and compactness of industrial equipment. Finned tubes, as the core components of heat exchangers, achieve enhanced heat transfer by extending the heat exchange surface area of base tubes. Traditional finned tube manufacturing technologies such as high-frequency welding, brazing, and mechanical clamping have limitations: welding processes cause heat-affected zones (HAZ) that degrade material properties, brazing has strict requirements for material compatibility, and mechanical clamping suffers from poor bonding tightness and high contact thermal resistance.
Tension wound finned tube technology overcomes these drawbacks through a cold-working process that relies on mechanical tension to realize tight fin-tube integration. This technology enables flexible matching of base tube and fin materials, supports the production of finned tubes with complex structures, and ensures stable heat transfer performance under long-term thermal cycling and vibration conditions. With the global demand for high-efficiency, low-energy-consumption heat exchange equipment, tension wound finned tubes have gained widespread application in HVAC, chemical engineering, refrigeration, and automotive industries.
2. Core Manufacturing Technologies of Tension Wound Finned Tubes
The manufacturing process of tension wound finned tubes is a precise cold-forming procedure centered on tension control, spiral winding, and shape locking. The key steps and technical control points are as follows:
2.1 Preprocessing of Base Tubes and Fin Strips
1. Base tube preparation
Common base tube materials include carbon steel (Q235B), low-alloy steel (16Mn), stainless steel (304/316L), copper, and aluminum alloys. The base tubes undergo strict surface treatment: derusting via shot blasting or pickling, degreasing with alkaline cleaning agents, and drying to remove surface oxides, oil stains, and impurities. The surface roughness is controlled within Ra 1.6–3.2 μm to enhance the friction force between the base tube and fins. Additionally, the base tubes are straightened to ensure straightness error ≤ 1 mm/m, avoiding winding deviation during the finning process.
2. Fin strip preparation
Fin strips are typically made of materials with high thermal conductivity and good formability, such as aluminum alloy (1060/3003), copper, and stainless steel strips with thickness ranging from 0.2 to 1.0 mm. The fin strips are cut to preset widths (10–50 mm) and undergo edge trimming to remove burrs, preventing scratches to the base tube surface during winding. For corrosion-resistant applications, the fin strips can be pre-coated with galvanized or epoxy layers.
2.2 Tension-Controlled Spiral Winding
This is the core step of the manufacturing process, directly determining the bonding quality and heat transfer performance of the finned tubes:
1. Equipment setup: The preprocessed base tube is clamped on a precision winding machine, with one end connected to a rotary drive system and the other to a tension control unit. The fin strip is fed into the winding head, which is equipped with a tension sensor and a pressing roller.
2. Tension parameter optimization: According to the material and thickness of the base tube and fin strip, the winding tension is precisely adjusted (typically 500–2000 N for aluminum fins and carbon steel base tubes). Sufficient tension ensures the fin strip is tightly wrapped around the base tube, eliminating gaps at the contact interface; excessive tension, however, may cause deformation of the base tube or tearing of the fin strip.
3. Spiral winding execution: The base tube rotates at a constant speed, while the fin strip is fed at a preset rate, forming a spiral fin structure on the base tube surface. The fin pitch (distance between adjacent fins) is adjusted by controlling the ratio of base tube rotation speed to fin strip feeding speed, with adjustable ranges from 3 to 20 mm. The winding head maintains a stable angle (15°–30°) relative to the base tube axis to ensure uniform fin distribution.
2.3 Fin Shaping and Locking
To prevent fin loosening during operation, the wound fins undergo shaping and locking treatment, with two mainstream processes:
1. Mechanical crimping locking: A crimping roller presses the edge of the fin strip radially inward, causing plastic deformation of the fin and base tube contact area to form a mechanical interlock. This process enhances the bonding strength between fins and the base tube, with shear strength ≥ 150 MPa, meeting the requirements of high-vibration working conditions.
2. Heat setting treatment: For finned tubes used in high-temperature environments, the assembled components are heated to 150–300°C (below the recrystallization temperature of the base tube material) and held for a certain period, followed by natural cooling. This process eliminates residual stress from winding, stabilizes the fin structure, and prevents thermal deformation during service.
2.4 Post-Processing and Quality Inspection
1. Surface treatment: Based on application requirements, the finned tubes are subjected to anti-corrosion treatment, such as galvanizing for carbon steel components (coating thickness 8–12 μm) to resist atmospheric corrosion, or passivation for stainless steel components to enhance surface oxidation resistance. For chemical industry applications, epoxy powder coating can be applied to achieve acid and alkali resistance.
2. Dimensional inspection: Key parameters including fin height, pitch, thickness, and base tube outer diameter are measured using precision instruments. The dimensional tolerance of fin height is controlled within ±0.2 mm, and the pitch tolerance within ±0.3 mm to ensure consistent heat transfer performance.
3. Performance testing: Non-destructive testing methods such as ultrasonic testing are used to detect internal gaps between fins and the base tube. Additionally, sample tubes undergo heat transfer performance testing, with the heat transfer coefficient required to be 10–20% higher than that of smooth tubes. Hydraulic pressure testing is also conducted (1.5 times the rated working pressure) to verify the pressure resistance of the base tube.
3. Core Advantages of Tension Wound Finned Tubes
Compared with high-frequency welded, brazed, and mechanically clamped finned tubes, tension wound finned tubes exhibit the following unique technical advantages:
3.1 Minimal Thermal Damage and Excellent Material Compatibility
The tension winding process is a cold-working procedure without high-temperature welding or brazing, thus avoiding HAZ formation on the base tube and fin surfaces. This preserves the original mechanical properties and thermal conductivity of the materials, enabling flexible matching of dissimilar materials (e.g., aluminum fins with copper base tubes, stainless steel fins with carbon steel base tubes). This material compatibility expands the application scope of finned tubes in special working conditions such as high-temperature and corrosive environments.
3.2 Low Contact Thermal Resistance and High Heat Transfer Efficiency
The controlled tension ensures tight bonding between fins and the base tube, with contact gap ≤ 0.01 mm, significantly reducing contact thermal resistance (≤ 0.001 m²·K/W). Combined with the turbulence-promoting effect of spiral fins on fluid flow, the heat transfer coefficient of tension wound finned tubes is 15–30% higher than that of brazed finned tubes. In practical applications, this advantage can reduce the volume of heat exchange equipment by 20–40% while maintaining the same heat transfer capacity.
3.3 High Structural Stability and Long Service Life
The mechanical crimping or heat setting locking process ensures strong bonding between fins and the base tube, capable of withstanding long-term thermal cycling and vibration without fin loosening or detachment. The service life of tension wound finned tubes is 2–3 times that of mechanically clamped finned tubes, reaching 10–15 years in normal working conditions. Additionally, the cold-forming process avoids microcracks caused by thermal stress, improving the fatigue resistance of the components.
3.4 Flexible Design and Cost-Effectiveness
The tension winding process allows for flexible adjustment of fin parameters (height, pitch, thickness) to meet the heat transfer requirements of different working conditions. For example, small-pitch (3–5 mm) fins can be used for high heat load scenarios, while large-pitch (10–20 mm) fins are suitable for dust-laden fluid environments to prevent clogging. Moreover, the automated winding process has high production efficiency, with a single production line capable of manufacturing 5,000–10,000 meters of finned tubes per day, and the production cost is 10–20% lower than that of high-frequency welded finned tubes.
4. Typical Application Scenarios of Tension Wound Finned Tubes
Tension wound finned tubes are widely used in industries requiring efficient heat exchange, compact equipment structure, and stable operation, with typical applications as follows:
4.1 HVAC and Refrigeration Industry
This is the largest application sector for tension wound finned tubes. They are core components of air conditioning units, heat pumps, cooling towers, and cold storage evaporators. Aluminum fins paired with copper base tubes are the mainstream choice, leveraging the high thermal conductivity of copper and aluminum to achieve efficient heat exchange between air and refrigerant. In central air conditioning systems, tension wound finned tube heat exchangers reduce energy consumption by 10–15% compared with traditional exchangers, while their compact structure saves installation space.
4.2 Chemical and Petrochemical Industry
Tension wound finned tubes are used in condensers, reboilers, waste heat recovery exchangers, and other equipment in chemical plants. Stainless steel fins paired with alloy steel base tubes are selected for corrosive media (e.g., acidic flue gas, organic solvents) and high-temperature/pressure conditions (≤ 400°C, ≤ 10 MPa). The tight fin-tube bonding prevents medium leakage, and the corrosion-resistant surface treatment ensures long-term stable operation of the equipment. For example, in petroleum refining processes, they recover waste heat from flue gas to preheat crude oil, improving energy utilization efficiency by 20–25%.
4.3 Automotive and Transportation Industry
In automotive engine cooling systems, tension wound finned tubes are used in radiators and intercoolers. Aluminum alloy fins and base tubes are adopted to reduce the weight of the cooling system by 30–40%, improving vehicle fuel efficiency. The high structural stability of these finned tubes enables them to withstand the vibration and temperature fluctuations of engine operation, extending the service life of the cooling system. Additionally, they are applied in thermal management systems of new energy vehicles, realizing efficient heat exchange between batteries and cooling media.
4.4 Power and Metallurgical Industry
In thermal power plants and biomass power plants, tension wound finned tubes are used in air preheaters and economizers to recover waste heat from flue gas. Carbon steel fins paired with low-alloy steel base tubes are cost-effective options for medium-temperature (200–300°C) flue gas environments. In metallurgical plants, they are used in sintering machine waste heat recovery systems, with their high heat transfer efficiency reducing energy consumption per ton of steel by 50–80 kWh. The dust-resistant large-pitch fin design also reduces cleaning frequency and maintenance costs.
4.5 Renewable Energy Industry
In solar thermal power systems, tension wound finned tubes are used in parabolic trough collectors, with high thermal conductivity copper fins and base tubes absorbing solar radiation to heat the heat transfer fluid. In geothermal energy utilization systems, corrosion-resistant stainless steel tension wound finned tubes are adopted to exchange heat between geothermal fluid and working medium, ensuring efficient and stable power generation.
5. Selection and Optimization Guidelines for Tension Wound Finned Tubes
To maximize the performance of tension wound finned tubes in heat exchange systems, the following selection and optimization principles should be followed:
5.1 Material Matching Based on Working Conditions
- Low-temperature, non-corrosive environments (e.g., HVAC systems): Select copper base tubes with aluminum fins for high thermal conductivity and cost-effectiveness.
- Medium-temperature, mildly corrosive environments (e.g., chemical plant condensers): Use stainless steel (304) base tubes with stainless steel fins, complemented by passivation treatment.
- High-temperature, highly corrosive environments (e.g., marine heat exchangers): Adopt titanium alloy base tubes with titanium fins or 316L stainless steel fins with epoxy coating to enhance corrosion resistance.
5.2 Fin Parameter Optimization According to Heat Transfer Requirements
- High heat load scenarios (e.g., industrial furnaces): Choose fins with large height (30–50 mm) and small pitch (3–5 mm) to maximize the heat exchange area.
- Dust-laden fluid scenarios (e.g., metallurgical flue gas): Select fins with small height (10–20 mm) and large pitch (10–20 mm) to prevent dust accumulation and reduce cleaning workload.
- Low flow resistance requirements (e.g., ventilation systems): Optimize the fin spiral angle (15°–20°) to balance heat transfer efficiency and fluid pressure loss.
5.3 Process Selection Based on Application Scenarios
- High-vibration environments (e.g., automotive engines): Prioritize mechanical crimping locking to ensure fin structural stability.
- High-temperature thermal cycling environments (e.g., power plant boilers): Adopt heat setting treatment to eliminate residual stress and prevent fin deformation.
6. Conclusion
Tension wound finned tube technology, as an advanced cold-forming heat exchange component manufacturing process, exhibits unique advantages in material compatibility, heat transfer efficiency, structural stability, and cost-effectiveness compared with traditional technologies. Its core lies in precise tension control during winding and reliable shaping locking, which ensure tight fin-tube bonding and minimal contact thermal resistance."
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