Stainless Steel Spiral Coil Tube for Heat Exchanger Applications
Product Overview
The Stainless Steel Spiral Coil Tube is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed specifically for integration into advanced spiral coil heat exchanger systems. These coil tubes are formed from high-grade austenitic stainless steel wire through a multi-stage cold-forming and coiling process, resulting in a continuous helical geometry that maximizes the heat transfer surface area per unit volume. The spiral configuration promotes turbulent flow within the tube bore, significantly enhancing convective heat transfer coefficients compared to conventional straight-tube designs.
Building upon the research findings presented in the study "Investigation of Flow and Heat Transfer Performance of Novel Spiral Coil Heat Exchangers," these coil tubes are engineered to optimize the interplay between fluid dynamics and thermal exchange. The helical curvature induces secondary Dean-type vortices within the flowing fluid, which continuously disrupt the thermal boundary layer, thereby reducing the overall thermal resistance and improving the overall heat transfer effectiveness of the system.
Material & Properties
The coil tubes are fabricated from premium-grade austenitic stainless steels, selected for their exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The following material grades are available:
- SAE 304 (UNS S30400): General-purpose austenitic stainless steel with excellent corrosion resistance and formability. Chromium content of 18–20% and nickel content of 8–10.5% provide robust passive film protection in most aqueous and mildly aggressive environments.
- SAE 316L (UNS S31603): Low-carbon variant with added molybdenum (2–3%) for superior resistance to pitting and crevice corrosion, particularly in chlorinated environments and marine applications.
- SAE 321 (UNS S32100): Titanium-stabilized grade offering enhanced resistance to intergranular corrosion at elevated temperatures (up to 870°C), suitable for high-temperature heat exchange duty.
- SAE 310S (UNS S31008): High-temperature austenitic grade with elevated chromium (25–27%) and nickel (19–22%) content, capable of sustained service in oxidizing atmospheres up to 1100°C.
Mechanical Properties (Annealed Condition):
- Tensile Strength: 515–720 MPa (depending on grade and wall thickness)
- Yield Strength: 205–310 MPa (0.2% offset)
- Elongation: ≥40% (minimum, 50 mm gauge length)
- Hardness: 120–200 HV (Vickers)
- Thermal Conductivity: 14.6–16.3 W/(m·K) at 25°C
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C (20–100°C)
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") |
| Wall Thickness | 0.25 mm – 3.0 mm |
| Coil Diameter | 50 mm – 500 mm (adjustable per application) |
| Pitch (Helix Spacing) | 5 mm – 40 mm |
| Coil Length | 1 m – 500 m (continuous or custom-cut) |
| OD Tolerance | ±0.1 mm (for OD ≤ 10 mm); ±0.2 mm (for OD > 10 mm) |
| Wall Thickness Tolerance | ±10% of nominal |
| Coil Diameter Tolerance | ±2% |
| Pitch Tolerance | ±0.5 mm |
| Surface Finish | Bright annealed / Pickled and passivated / Electropolished (Ra ≤ 0.4 μm) |
| Maximum Operating Temperature | Up to 870°C (Grade 321); Up to 1100°C (Grade 310S) |
| Maximum Operating Pressure | Up to 40 MPa (6,000 PSI), depending on geometry |
| End Condition | Flat cut / Beveled / Threaded / Flanged (custom) |
| Applicable Standards | ASTM A269, ASTM A270, EN 10217, GB/T 12771 |
Manufacturing Process
The production of high-precision stainless steel spiral coil tubes involves a rigorous multi-stage manufacturing sequence, each step carefully controlled to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Wire Selection & Inspection: Cold-drawn stainless steel wire is sourced from certified mills and subjected to incoming quality control, including chemical composition verification (via optical emission spectrometry), tensile testing, and surface defect inspection.
- Wire Annealing: Wire is annealed at controlled temperatures (typically 1050–1150°C) followed by rapid quenching to achieve a fully austenitic microstructure with optimal formability and minimum residual stress.
- Tube Forming: The annealed wire is drawn through precision-die tooling to form seamless tubes with controlled wall thickness. Multi-pass drawing ensures uniformity and minimizes microstructural distortion.
- Intermediate Annealing: Periodic annealing between drawing passes relieves accumulated work-hardening and prevents cracking during subsequent forming operations.
- Spiral Coiling: The formed tube is fed through a CNC-controlled coiling machine that imparts the helical geometry with precise control over coil diameter and pitch. The coiling rate and feed speed are synchronized to prevent kinking, ovality, or localized plastic deformation.
- Post-Coil Annealing (if required): For applications requiring stress relief or specific mechanical properties, the coiled product may undergo solution annealing followed by controlled cooling.
- Pickling & Passivation: The coil is subjected to acid pickling (typically using a mixture of nitric and hydrofluoric acid) to remove surface oxide scale, followed by passivation treatment to restore and enhance the protective chromium oxide passive film.
- Final Quality Inspection: Each batch undergoes comprehensive dimensional verification (laser micrometry for OD, ultrasonic wall thickness gauging), visual inspection for surface defects, and hydrostatic pressure testing to confirm structural integrity.
Applications
The spiral coil tube geometry offers distinct advantages in heat transfer applications, as demonstrated in the referenced research on novel spiral coil heat exchangers. Key application domains include:
- Shell-and-Tube Heat Exchangers: Spiral coil tubes serve as the tube bundle element in process heat exchangers, providing up to 40–60% higher heat transfer coefficients compared to equivalent straight tubes due to enhanced turbulence from Dean vortex effects.
- Plate-and-Shell Compact Heat Exchangers: Utilized in compact exchanger designs where high surface-area-to-volume ratios are critical for space-constrained installations.
- Process Cooling & Heating Systems: Integrated into chemical processing plants, refineries, and pharmaceutical manufacturing facilities for precise thermal control of process streams.
- Refrigeration & HVAC Systems: Employed as evaporator and condenser coils in industrial refrigeration units, leveraging the enhanced heat transfer performance for improved energy efficiency.
- Food & Beverage Processing: Used in pasteurization, sterilization, and heat recovery systems where sanitary-grade surface finish and corrosion resistance are paramount.
- Power Generation: Applied in feedwater heaters, economizers, and waste heat recovery systems within thermal power plants.
- Oil & Gas Industry: Deployed in offshore heat exchanger systems and subsea processing units where resistance to chloride-induced corrosion is essential.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications to assure product quality and regulatory compliance:
- ISO 9001:2015 — Quality Management Systems certification, demonstrating systematic control of all manufacturing processes.
- ISO 14001:2015 — Environmental Management Systems certification, ensuring environmentally responsible production practices.
- CE Marking (EU) — Conformity with European Union directives for pressure equipment and mechanical components.
- ASME Stamp (U Stamp) — Authorization for fabrication of pressure-containing components per ASME Boiler and Pressure Vessel Code.
- NACE MR0175 / ISO 15156 — Compliance with requirements for materials used in H₂S-containing environments in the oil and gas industry.
- NSF/ANSI 61 — Certification for materials in contact with potable water (where applicable).
- 3-A Sanitary Standards — Compliance with food-grade manufacturing requirements for dairy, beverage, and pharmaceutical applications.
Each production lot is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 3.1 or 3.2, documenting chemical composition, mechanical properties, and traceability to the heat number of the source material. Third-party inspection by organizations such as SGS, Bureau Veritas, or TÜV is available upon customer request.
Unique Selling Points
- Enhanced Heat Transfer Performance: The helical geometry generates secondary flow patterns (Dean vortices) that intensify turbulent mixing, yielding heat transfer coefficients 40–60% higher than conventional straight tubes at equivalent Reynolds numbers.
- Compact Design: Achieves high thermal duty in significantly reduced footprint, enabling space-optimized equipment design and reduced installation costs.
- Low Fouling Tendency: The induced turbulence continuously scours the inner tube surface, reducing the rate of fouling accumulation and extending maintenance intervals.
- Full Traceability: Every coil tube is traceable to its source material heat number, with complete documentation of all processing parameters.
- Custom Engineering: Flexible capability to produce coil tubes to customer-specific geometries, tolerances, and material specifications, supported by engineering consultation and CFD-based thermal performance analysis.