Stainless Steel Finned Coil Tube for Heat Exchanger Applications
Product Overview
The Stainless Steel Finned Coil Tube (Coiltube) is a high-performance tubular component engineered specifically for use in finned coil heat exchanger systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product represents an advanced integration of precision coil-forming technology with metallurgical excellence in austenitic stainless steel alloys. The product is designed to maximize heat transfer efficiency while maintaining structural integrity under prolonged thermal cycling, pressure differentials, and corrosive media exposure.
Based on extensive research and experimental validation documented in the study "Design Improvement and Experimental Research of Finned Coil Heat Exchangers", this coil tube product incorporates design refinements that address common performance bottlenecks found in conventional finned coil configurations. The optimization focuses on enhanced thermal conductivity, reduced flow resistance, improved fin-to-tube bonding integrity, and extended service life under demanding industrial conditions.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior combination of corrosion resistance, thermal stability, and mechanical ductility required for repeated coil forming operations.
- Base Material: Austenitic stainless steel conforming to AISI 304, AISI 316, or equivalent grades (UNS S30400 / UNS S31600)
- Chromium Content: 18–20% minimum, providing robust passive film formation for oxidation resistance
- Nickel Content: 8–12%, ensuring austenitic microstructure stability across operating temperature ranges
- Molybdenum Content: 2–3% (in 316 grade), enhancing resistance to pitting and crevice corrosion in chloride-rich environments
- Carbon Content: ≤ 0.08% (standard) or ≤ 0.03% (304L/316L low-carbon variants), minimizing intergranular sensitization during welding or heat treatment
- Surface Finish: Mill finish, pickled, or electrolytic polishing (Ra ≤ 0.8 μm for high-purity applications)
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and food-grade chemical environments; resistant to stress corrosion cracking (SCC) in dilute chloride solutions
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, adequate for heat exchanger duty with fin augmentation
- Operating Temperature Range: −196°C to +870°C (continuous service)
- Maximum Operating Pressure: Up to 2.5 MPa (dependent on wall thickness and coil geometry)
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Finned Coil Tube (Coiltube) |
| Product Code | 1014 |
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Inner Diameter | 50 mm – 500 mm (configurable) |
| Coil Length (Developed) | 3 m – 50 m per coil (standard); longer upon request |
| Number of Turns | 10 – 200 turns per coil |
| Fin Type | Integral fin, attached fin (lanced, spiral wound, or welded) |
| Fin Material | Aluminum (Al 1100/3003) or Stainless Steel (matching tube grade) |
| Fin Height | 2 mm – 12 mm |
| Fin Density | 8 – 25 fins per inch (FPI) |
| Fin-to-Tube Bonding | Mechanical interlock, brazed, or TIG welded |
| End Treatment | Plain ends, flared, threaded, or fitted with couplings |
| Surface Treatment | Pickled & passivated; optional passivation treatment per ASTM A967 |
| Standards Compliance | ASTM A269, ASTM A270, ASME B31.3, EN 10217-7, GB/T 12771 |
| Pressure Test | Hydrostatic test at 1.5× working pressure; pneumatic test available |
| Packaging | Coiled on wooden reels or steel drums; moisture-proof wrapping |
Manufacturing Process
The production of the stainless steel finned coil tube follows a rigorous multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and optimal heat transfer performance:
- Material Selection & Incoming Inspection: Cold-rolled stainless steel strip is sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES), mechanical property verification, and visual surface inspection to confirm compliance with specified chemical composition and grade requirements.
- Strip Cutting & Edge Preparation: The stainless steel strip is precision-cut to the required width and edge quality. Edges are deburred and straightened to ensure uniform wall thickness after forming.
- Tube Forming (Cold Forming): The strip is formed into tubular shape via cold-rolling or roll-forming technology. Seams are closed through either:
- Continuous TIG (Tungsten Inert Gas) welding with argon shielding, or
- Mechanical locking/seamless forming for thin-wall configurations
- Coil Forming (Coiling): The formed tube is precisely coiled onto mandrels using CNC-controlled coiling machines. The coiling process maintains uniform curvature without inducing residual stress concentrations or work hardening beyond acceptable limits. Springback compensation algorithms ensure dimensional accuracy of the finished coil geometry.
- Fin Application: Fins are applied to the coil tube using one of the following methods:
- Integral Fin (Slit Tube): The tube wall is slit longitudinally and expanded to form integral fins, eliminating thermal contact resistance at the fin-tube interface.
- Attached Fin (Lanced/Pressed): Fins are pressed or lanced into pre-drilled holes in the tube surface, providing mechanical interlock.
- Spiral Wound Fin: A continuous fin strip is helically wound and soldered/brazed onto the tube surface.
- Heat Treatment (if applicable): Post-forming annealing may be performed to relieve residual stresses introduced during cold forming. Solution annealing at 1050–1150°C followed by rapid quenching restores full austenitic structure and corrosion resistance.
- Pickling & Passivation: The finished coil tube undergoes acid pickling (hydrofluoric/nitric acid blend) to remove oxidation scale, followed by passivation treatment to restore the chromium oxide passive film. This step is critical for ensuring long-term corrosion resistance, particularly at welded joints.
- Non-Destructive Testing (NDT): Finished products undergo:
- Helium or nitrogen leak testing to verify weld integrity
- Hydrostatic pressure testing at 1.5× design pressure for minimum 30 seconds
- Visual inspection of fin alignment, tube surface quality, and dimensional conformity
- Optional eddy current testing for subsurface defect detection
- Final Inspection & Packaging: Each coil is dimensionally verified, tagged with a material traceability certificate, and packaged on protective reels with moisture-barrier wrapping for shipment.
Applications
The stainless steel finned coil tube is engineered for demanding thermal management applications where corrosion resistance, hygiene, and long-term reliability are paramount:
- Air Conditioning & Refrigeration (HVAC/R): Evaporators and condensers in commercial and industrial HVAC systems, particularly in environments requiring non-toxic, non-corrosive materials (food processing facilities, pharmaceutical clean rooms)
- Food & Beverage Industry: Heat exchangers for pasteurization, sterilization, and thermal processing systems where product contact requires FDA-compliant sanitary materials
- Pharmaceutical Manufacturing: Process heat exchangers in GMP-regulated facilities requiring cleanable, non-reactive surfaces
- Chemical Processing: Heat recovery and temperature control systems handling corrosive fluids, acids, and solvents
- Marine & Offshore Applications: Seawater-cooled heat exchangers where chloride-induced corrosion resistance is critical
- Automotive & Transportation: Battery thermal management systems for electric vehicles, HVAC coils for commercial vehicles
- Power Generation: Waste heat recovery systems, economizers, and air preheaters
- Oil & Gas: Process cooling and heat exchange in upstream and downstream operations
- Electronics Cooling: High-power electronics thermal management in data centers and industrial equipment
Quality Certifications & Standards
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing processes
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management
- CE Marking — Conformity with European Union safety, health, and environmental protection requirements (Directive 2014/68/EU — Pressure Equipment Directive)
- ASME Stamp — Pressure vessel and piping component certification (where applicable)
- NSF/ANSI 61 — Drinking water system components certification (for potable water applications)
- 3-A Sanitary Standards — Dairy and food processing equipment certification
- Mill Test Certificates (MTC) — EN 10204 Type 3.1 certificates provided for every batch, documenting chemical composition, mechanical properties, and heat number traceability
- Material Compliance: Full compliance with ASTM A269, ASTM A270, EN 10217-7, and GB/T 12771 specifications
- Traceability: Each product batch is linked to raw material mill certificates, enabling full supply chain traceability from raw steel mill to end user
Unique Selling Points
Research-Validated Design Optimization: This product incorporates findings from peer-reviewed experimental research on finned coil heat exchanger design improvements. Key optimizations include enhanced fin geometry for superior heat transfer coefficient (U-value improvement of 15–30% over conventional designs), optimized coil pitch for balanced flow distribution, and improved fin-to-tube thermal contact resistance through advanced bonding techniques.
- Superior Corrosion Resistance: The austenitic stainless steel construction provides unmatched resistance to atmospheric, aqueous, and chemical corrosion, eliminating the need for protective coatings and extending service life significantly compared to carbon steel alternatives.
- Hygienic & Food-Grade Compliance: Smooth internal surfaces with low roughness values prevent microbial harborage, making these coils suitable for food, beverage, and pharmaceutical applications without secondary treatment.
- Thermal Efficiency Enhancement: The finned coil configuration dramatically increases the external heat transfer area, achieving compact heat exchanger designs with reduced footprint and weight compared to bare tube alternatives.
- Full Traceability & Certification: Every coil tube is accompanied by comprehensive mill test certificates and conforms to international standards, facilitating regulatory compliance and quality assurance in critical applications.
- Customization Capability: Flexible manufacturing parameters allow customization of tube diameter, wall thickness, coil geometry, fin configuration, and end treatments to meet specific application requirements.
- Long Service Life: Combined resistance to corrosion, thermal fatigue, and mechanical wear ensures reliable operation for 15–25+ years in most industrial environments with minimal maintenance.