Stainless Steel Coil Tube for Ice Storage Systems (Coiltube)
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for coiled-pipe ice storage tanks and thermal energy storage systems. Drawing upon advanced theoretical research into the ice melting process of coiled-pipe storage configurations, this product is engineered to optimize heat transfer efficiency, minimize thermal stratification losses, and extend operational service life in cryogenic and sub-zero environments. The coil tube serves as the primary heat exchange element in phase-change thermal storage systems, facilitating the controlled freezing and melting cycles essential for energy management applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, cryogenic toughness, and long-term dimensional stability. The material composition and mechanical properties are as follows:
- Base Material: Austenitic stainless steel grades including 304 (UNS S30400), 304L (UNS S30403), 316L (UNS S31603), and 321 (UNS S32100), with selection based on application-specific environmental and thermal requirements.
- Corrosion Resistance: Superior resistance to chloride-induced pitting and stress corrosion cracking (SCC), particularly in 316L grade with molybdenum (Mo) content of 2.0–2.5%.
- Cryogenic Performance: Maintains ductility and impact toughness at temperatures as low as −196°C (liquid nitrogen temperature), with no risk of ductile-to-brittle transition.
- Thermal Conductivity: 14–16 W/(m·K) at ambient temperature, providing adequate heat transfer capability while maintaining structural integrity.
- Non-magnetic Properties: Essential for applications near sensitive instrumentation or electromagnetic environments.
- Hygienic Surface: Electropolished or passivated inner surface with surface roughness (Ra) ≤ 0.4 μm, ensuring fluid cleanliness and reducing fouling.
Specifications
| Parameter | Specification / Range | Standard / Test Method |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ50.8 mm (1/4" – 2") | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / GB/T 21832 |
| Coil Pitch | 10 mm – 50 mm (adjustable per design) | Custom engineering specification |
| Coil Diameter | Φ200 mm – Φ2000 mm | Custom engineering specification |
| Coil Length (Uncoiled) | 5 m – 500 m (continuous) | — |
| Surface Finish | Mirror polished (Ra ≤ 0.2 μm) / Electropolished (Ra ≤ 0.4 μm) / Industrial pickled (Ra ≤ 1.6 μm) | ASTM A269 / GB/T 21832 |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm | ISO 4287 |
| Tolerance (Wall Thickness) | ±10% (minimum ±0.05 mm) | ASTM A213 |
| Operating Temperature | −196°C to +400°C | Material datasheet |
| Maximum Working Pressure | Up to 2.5 MPa (design-dependent) | ASME BPV Code Section VIII |
| Heat Treatment | Solution annealed (1050°C – 1150°C) + water/quench | ASTM A213 |
| Welding Method | TIG (GTAW) / Orbital TIG / Laser welding | ASME Section IX |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical homogeneity, and surface integrity:
- Raw Material Procurement: Cold-rolled stainless steel strip or seamless pipe blanks sourced from certified mills, with full chemical composition analysis (C, Cr, Ni, Mo, Si, Mn) verified against ASTM/GB standards.
- Coil Winding & Forming: Precision CNC-controlled coil winding machines form the straight tube into the designated helical coil geometry. The winding process maintains constant coil pitch and diameter tolerance to prevent stress concentration and ensure uniform heat transfer characteristics.
- Welding (for welded tube configurations): High-purity argon-shielded TIG welding or orbital TIG welding is employed to join tube sections. Weld quality is verified via 100% visual inspection and periodic radiographic testing (RT) or ultrasonic testing (UT).
- Solution Annealing: The formed coil is subjected to solution annealing at 1050°C–1150°C followed by rapid quenching to dissolve carbide precipitates, restore full austenitic microstructure, and maximize corrosion resistance.
- Pickling & Passivation: Post-welding pickling removes oxide scale using a mixed acid solution (HNO₃ + HF or H₂SO₄ + HNO₃), followed by passivation to establish a stable chromium oxide (Cr₂O₃) passive film on the surface.
- Surface Polishing / Electropolishing: Mechanical polishing (orbital or belt) or electrochemical polishing achieves the specified surface roughness, critical for minimizing thermal boundary layer resistance and ensuring hygienic fluid flow.
- Quality Inspection & Testing: Each batch undergoes dimensional measurement, hydrostatic pressure testing (typically 2× working pressure), magnetic particle inspection (MT) for surface defects, and spectroscopic chemical analysis.
- Packaging & Delivery: Coils are individually wrapped in protective film, placed on wooden pallets or steel cradles, and shipped with full material traceability documentation.
Applications
The stainless steel coil tube is a critical component in a diverse range of thermal management and energy storage systems:
- Ice Storage Thermal Energy Systems: Primary heat exchange element in coiled-pipe ice storage tanks (CIIST), where the coil facilitates controlled ice formation on the tube outer surface and subsequent melting during peak demand periods. Theoretical modeling of the ice melting process confirms that optimal coil geometry minimizes thermal stratification and maximizes ice utilization efficiency.
- Cold Chain & Refrigeration: Heat exchange coils in walk-in freezers, blast chillers, and cryogenic storage systems operating at −40°C to −196°C.
- Process Industry Heat Exchangers: Spiral coil heat exchangers in chemical processing, pharmaceutical manufacturing, and food & beverage industries requiring hygienic, corrosion-resistant heat transfer surfaces.
- Geothermal & District Heating Systems: Submerged coil configurations for ground-source heat exchange and thermal energy storage in district energy networks.
- Specialty Applications: Laboratory cryostats, industrial freezing systems, solar thermal energy storage, and HVAC (Heating, Ventilation, and Air Conditioning) energy recovery systems.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance systems and certifications to ensure product reliability and international market acceptance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality control processes.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- ASME Section VIII — Compliance with pressure vessel and heat exchanger design codes for applications subject to regulated pressure.
- CE Marking (EU) — Conformity with European Pressure Equipment Directive (PED 2014/68/EU) and relevant EN standards.
- EN 10204 3.1 / 3.2 — Third-party inspection certificates for material and product conformity.
- GB/T Standards Compliance — Full adherence to Chinese national standards including GB/T 12771 (stainless steel seamless tubes), GB/T 21832 (welded tubes), and GB/T 24511 (pressure vessel materials).
- Material Traceability: Each coil batch is accompanied by a full heat number traceability record, chemical analysis report, mechanical test certificate, and non-destructive testing (NDT) documentation.
Unique Selling Points
The Coiltube product from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through the following value propositions:
- Theoretically Optimized Geometry: Coil dimensions and pitch are derived from rigorous theoretical analysis of ice nucleation, growth, and melting dynamics in coiled-pipe configurations, ensuring maximum thermal storage density and discharge efficiency.
- Cryogenic Reliability: Proven performance at extreme sub-zero temperatures with no risk of brittle fracture, enabling safe operation in the most demanding thermal environments.
- Custom Engineering Capability: Full customization of coil diameter, pitch, tube dimensions, surface finish, and material grade to match specific system design requirements.
- Hygienic & Corrosion-Resistant Construction: Electropolished surfaces and premium austenitic grades provide unmatched longevity in corrosive, humid, or food-grade environments.
- End-to-End Quality Assurance: From raw material certification through final inspection, every production stage is documented and traceable, ensuring zero-defect delivery.
- Cost-Effective Energy Storage Solution: The optimized coil design reduces the required tank volume and refrigerant charge while maintaining high ice utilization rates, lowering total system capital and operating costs.