Stainless Steel Coil Tube (盘管) — Thermal Transfer Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) produced by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous spiral tube designed for high-efficiency heat exchange applications. Unlike conventional straight or U-bend tubes, the coil tube (盘管) geometry maximizes the surface-area-to-volume ratio, thereby enhancing convective and radiative heat transfer coefficients within compact installation footprints. This product line is manufactured to meet the stringent thermal performance requirements identified in rigorous heat transfer analysis of coil radiators (盘管散热器的传热分析), ensuring optimal thermal conductivity, pressure drop minimization, and long-term structural integrity under cyclic thermal loading conditions.
Material Composition & Mechanical Properties
The coil tubes are fabricated from austenitic stainless steel grades selected for their superior corrosion resistance, thermal stability, and workability during cold-forming operations. The primary alloy grades offered include:
- 304 (UNS S30408): Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, with excellent general corrosion resistance and weldability.
- 316L (UNS S31603): Chromium (Cr) 17–18%, Nickel (Ni) 10–14%, Molybdenum (Mo) 2–3%, offering enhanced resistance to chloride-induced pitting and crevice corrosion.
- 321 (UNS S32100): Chromium (Cr) 17–19%, Titanium (Ti) stabilized, suitable for elevated-temperature service up to 870°C (1600°F).
| Property | 304 Grade | 316L Grade | 321 Grade |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa, 0.2% offset) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 45 | ≥ 40 |
| Thermal Conductivity (W/m·K, 300°C) | ~15.7 | ~14.6 | ~16.0 |
| Thermal Expansion (10⁻⁶/K, 20–600°C) | ~16.5 | ~16.3 | ~16.8 |
| Maximum Service Temperature (°C) | 870 | 870 | 870 |
| Density (kg/m³) | ~8000 | ~8030 | ~8010 |
Detailed Specifications
| Parameter | Specification / Range |
|---|---|
| Tube Outer Diameter (OD) | 6 mm – 50 mm (customizable) |
| Tube Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch (center-to-center spacing) | 10 mm – 80 mm |
| Coil Outer Diameter | 50 mm – 1500 mm |
| Coil Length (developed tube length) | Up to 50 m continuous |
| Surface Finish | Mirror polish (Ra ≤ 0.2 μm), Matte, or Pickled & Passivated |
| End Treatment | Plain cut, Beveled, Flanged, or Threaded (per customer drawing) |
| Tolerance on OD | ±0.1 mm (standard); ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% (standard); ±5% (precision grade) |
| Coil Straightness Deviation | ≤ 1.5 mm/m |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous multi-stage process to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Raw Material Selection: Cold-rolled stainless steel strip (SSR) conforming to ASTM A240 / EN 10088 standards, with certified chemical composition and mechanical property test reports.
- Tube Forming (Rolling): Precision roll-forming or hydraulic press-forming of flat strip into seamless circular tubes, with controlled reduction ratios to avoid micro-cracking in the weld zone.
- Welding (where applicable): Argon-shielded TIG (Tungsten Inert Gas) welding for longitudinal seam closure, achieving weld bead strength ≥ 95% of base metal.
- Coil Winding (盘管成型): The formed tube is wound onto a precision mandrel using CNC-controlled winding equipment. The winding process maintains constant tension to prevent ovality, kinking, or residual stress concentration at coil transitions.
- Heat Treatment / Solution Annealing: For grades requiring stress relief (e.g., 321 stabilization), the coil tube is annealed at 1050°C ± 20°C followed by rapid air cooling to restore full austenitic structure and maximum ductility.
- Pickling & Passivation: Immersion in nitric-hydrofluoric acid mixture to remove oxide scale, followed by passivation treatment to establish a stable chromium oxide film (Cr₂O₃) for corrosion protection.
- Surface Finishing: Electropolishing or mechanical polishing for mirror-finish applications requiring low-friction fluid flow and minimal fouling.
- Quality Inspection: Dimensional verification via coordinate measuring machine (CMM), hydrostatic pressure testing, eddy current testing for wall thickness mapping, and visual inspection per ASME BPV Code Section VIII.
Heat Transfer Performance Characteristics
The coil geometry of this product provides distinct thermodynamic advantages over straight-tube heat exchangers, as validated by computational fluid dynamics (CFD) and experimental heat transfer analysis:
- Enhanced Convective Coefficient: The secondary Dean vortex flow induced by the helical curvature increases the Nusselt number (Nu) by 1.5–2.5× compared to equivalent straight tubes at the same Reynolds number (Re).
- Compact Design: Achieves up to 40% greater heat transfer area per unit volume, reducing overall system footprint.
- Uniform Temperature Distribution: The continuous spiral path promotes turbulent mixing even at lower flow velocities (Re > 2300), minimizing thermal stratification.
- Low Pressure Drop: Optimized coil pitch and diameter ratios are engineered to balance heat transfer enhancement against frictional pressure loss, maintaining system pumping efficiency.
Applications
The Stainless Steel Coil Tube is deployed across a broad spectrum of industrial and commercial thermal systems:
- Automotive & Transportation: Radiator cores, intercooler tubes, and engine oil coolers requiring high thermal cycling endurance.
- Chemical & Petrochemical Processing: Reactor coil heat exchangers, reboilers, and condensers handling aggressive media (acids, halides, high-temperature hydrocarbons).
- Food & Beverage Industry: Pasteurization coils, milk coolers, and hygienic heat exchangers compliant with 3-A Sanitary Standards.
- Pharmaceutical & Biotechnology: Sterilizable-in-place (SIP) coil systems for bioreactors and cleanroom HVAC applications.
- Power Generation: Boiler economizer tubes, condenser coil bundles, and waste heat recovery systems.
- Domestic & Commercial HVAC: Radiator coils, underfloor heating loops, and solar thermal collector tubes.
- Oil & Gas Downstream: Subsea heat exchangers and cryogenic process coils.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains an internationally accredited quality management system ensuring consistent product performance and traceability:
- ISO 9001:2015 — Quality Management Systems certification covering all production facilities.
- ISO 14001:2015 — Environmental Management Systems certification for sustainable manufacturing practices.
- ASME BPV Code Section VIII, Div. 1 — Compliance for pressure vessel and heat exchanger components.
- ASTM A213 / A269 — Conformance for wrought austenitic stainless steel tubing.
- EN 10216-5 / EN 10217-7 — European standard compliance for seamless and welded stainless steel tubes.
- JIS G3446 / G3459 — Japanese Industrial Standard compliance for seamless and welded austenitic stainless steel tubes.
- CE Marking — European Conformity for pressure equipment per PED 2014/68/EU.
- Mill Test Certificates (MTC) — Full EN 10204 3.1 material certification provided with every shipment.
Unique Selling Points
- Customizable Geometry: Coil pitch, diameter, and tube cross-section are tailored to specific heat transfer duty calculations, enabling optimal thermal-hydraulic matching for each application.
- Superior Corrosion Resistance: 316L and duplex-grade options withstand chlorinated, acidic, and marine environments where carbon steel alternatives would suffer rapid degradation.
- Hygienic & Sanitary Grade: Electropolished interior surfaces (Ra ≤ 0.2 μm) prevent microbial adhesion and facilitate automated clean-in-place (CIP) protocols.
- Full Traceability: Every coil tube batch is linked to its mill heat number, chemical analysis, mechanical test results, and heat treatment records.
- Extended Service Life: Engineering analysis confirms >25-year operational lifespan under normal thermal cycling conditions, significantly reducing total cost of ownership (TCO).
- Technical Support: Comprehensive heat transfer analysis, CFD modeling, and application engineering support available for custom system design.
Ordering Information
Customers are advised to provide the following parameters when placing an order for custom coil tube configurations:
- Material grade (304, 316L, 321, or custom alloy)
- Tube outer diameter and wall thickness
- Coil outer diameter and pitch
- Total developed tube length
- Surface finish specification
- Operating temperature and pressure range
- Applicable industry standard or code
- End connection type and orientation
Note: All specifications listed herein represent typical values for standard production configurations. Custom specifications are available upon request and are subject to engineering review and sampling approval prior to mass production. Wenzhou Jixing Metal Materials Co., Ltd reserves the right to refine specifications based on evolving industry standards and process improvements.