Stainless Steel Coil Tube — Coiltube for Ice Thermal Storage Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed into continuous spiral or helical coils. These coil tubes are specifically designed for high-efficiency heat exchange applications, with particular emphasis on ice thermal storage systems (Ice Thermal Energy Storage Systems), including configurations that integrate both internal ice melting (Internal Ice Melting) and external ice melting (External Ice Melting) methodologies. The coil geometry maximizes heat transfer surface area within a compact volume, making these products ideal for district cooling, building energy management, and industrial process cooling applications.
The product is manufactured in accordance with international and national standards governing stainless steel tubing, ensuring dimensional accuracy, metallurgical integrity, and long-term corrosion resistance in demanding thermal cycling environments.
Material & Properties
Coil tubes are produced from austenitic stainless steel grades selected for their superior combination of corrosion resistance, thermal conductivity, mechanical strength, and low-temperature performance — critical attributes for ice thermal storage and cryogenic applications.
- Primary Grades: AISI 304 (UNS S30408), AISI 316L (UNS S31603), and 316Ti (UNS S31675)
- Alternative Grades: AISI 321 (UNS S32108), AISI 347H (UNS S34725), and duplex grades (2205 / UNS S31803) for elevated pressure or chloride-rich environments
- Surface Finish: Bright annealed, pickled & passivated (P&P), or custom finishes per client specification
- Thermal Conductivity: 14–16 W/(m·K) at 20°C (grade-dependent)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and cryogenic environments; pitting resistance equivalent number (PREN) ≥ 24 for 316L
- Mechanical Properties: Tensile strength 515–720 MPa; elongation ≥ 40% (annealed condition)
- Operating Temperature Range: −196°C to +870°C (grade-dependent)
- Hygienic Compliance: Optional electropolished finish with Ra ≤ 0.4 μm for pharmaceutical and food-grade applications
Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6 mm – 108 mm | ASTM A269 / EN 10217-7 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm | ASTM A269 / EN 10217-7 |
| Coil Outer Diameter (COD) | 500 mm – 2,000 mm | Manufacturer's Specification |
| Coil Pitch / Layer Spacing | 1.2 × OD – 2.5 × OD (customizable) | Manufacturer's Specification |
| Coil Length per Spool | 10 m – 300 m (continuous) | — |
| Minimum Bend Radius | 3 × OD (without deformation) | ASTM A213 |
| Pressure Rating | Up to 15 MPa (PN150) at 20°C | EN 12379 / ASME B31.3 |
| End Preparation | Plain end, beveled, threaded, or flanged | ASME B16.11 / B16.18 |
| Tolerance — OD | ±0.05 mm to ±0.5 mm (depending on size) | ASTM A269 |
| Tolerance — Wall Thickness | ±10% of nominal | ASTM A269 |
| Heat Transfer Coefficient (U-value) | 800 – 2,500 W/(m²·K) (system-dependent) | ASHRAE Handbook |
| Surface Roughness (Ra) | 0.8 – 1.6 μm (standard); ≤ 0.4 μm (electropolished) | ASTM A967 |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing workflow to ensure consistent quality, dimensional accuracy, and metallurgical performance:
- Raw Material Procurement: High-purity stainless steel strip or wire is sourced from certified mills, with each batch accompanied by a mill test certificate (MTC) verifying chemical composition and mechanical properties.
- Coil Winding / Helical Forming: The stainless steel tube stock is fed through a CNC-controlled coil winding machine that forms the tube into a precise helical or spiral coil geometry. The winding parameters — including coil diameter, pitch, and layer count — are programmatically controlled to meet design specifications for target heat transfer performance.
- Seam Welding (for welded tubes): Where applicable, the tube is formed and seam-welded using Transverse Magnetic Pulse Welding (TMPW) or Continuous Welding (CW) processes, followed by internal and external grinding to achieve a smooth weld seam.
- Heat Treatment / Solution Annealing: Coiled tubes undergo solution annealing at 1010–1150°C followed by controlled cooling to restore full austenitic structure, relieve residual stresses, and ensure optimal corrosion resistance and ductility.
- Pickling & Passivation (P&P): A chemical treatment removes surface oxides, scale, and contaminants, followed by passivation to establish a protective chromium oxide layer that enhances corrosion resistance.
- Quality Inspection: Each coil is subjected to dimensional inspection (OD, wall thickness, coil diameter, pitch), hydrostatic pressure testing (per ASTM A269), and surface inspection. Non-destructive testing (NDT) methods including eddy current (EC) and ultrasonic testing (UT) are employed to detect internal and surface defects.
- End Preparation & Packaging: Tube ends are prepared per specification (beveled, threaded, or flanged). Coils are wrapped in protective film, shrink-wrapped, and palletized for shipping to prevent mechanical damage and surface contamination.
Applications
The stainless steel coil tube is a versatile heat exchange component with broad application across multiple industries:
- Ice Thermal Storage Systems: The primary design application — coil tubes are embedded in ice storage tanks to facilitate controlled ice formation and melting. In internal ice melting (Internal Ice Melting) configurations, refrigerant or chilled water flows through the coil tube while ice forms on the exterior surface. In external ice melting (External Ice Melting) configurations, ice is formed around the coil tube and then melted by warm fluid passing through the tube. Hybrid systems combining both approaches leverage the advantages of each to optimize system efficiency and discharge rates.
- District Cooling & Building Energy Management: Coil tubes serve as heat exchangers in centralized cooling plants, enabling peak-load shifting and energy cost reduction.
- Industrial Process Cooling: Used in chemical processing, pharmaceutical manufacturing, food and beverage production, and semiconductor fabrication where precise temperature control and corrosion resistance are critical.
- Refrigeration & HVAC Systems: Employed as evaporators, condensers, and air-cooled heat exchangers in commercial and industrial refrigeration systems.
- Automotive & Aerospace: Lightweight coil tube assemblies used in engine cooling, fuel systems, and hydraulic circuits.
- Geothermal & Solar Thermal Systems: Coil tubes deployed in ground-source heat exchangers and solar thermal collectors for renewable energy applications.
- Medical & Laboratory Equipment: Electropolished coil tubes used in cryogenic equipment, laboratory reactors, and medical device manufacturing.
Quality Certifications & Compliance
All stainless steel coil tube products are manufactured under a certified quality management system and conform to the following international and national standards:
- Quality Management: ISO 9001:2015 (Quality Management Systems)
- Material Standards: ASTM A269 (Seamless, Welded, and Heavy-Walled Austenitic Stainless Steel Tubing), ASTM A213 (Welded Austenitic Stainless Steel Tubing for Heat-Transfer Equipment), EN 10217-7 (Heat-Exchanger and Heat-Sink Tubes), EN 10216-5 (Heat-Exchanger Tubes)
- Pressure Vessel & Piping Codes: ASME Section VIII Division 1, ASME B31.3 (Process Piping), PED 2014/68/EU (Pressure Equipment Directive)
- Hygienic Standards: 3-A Sanitary Standards, EHEDG Guidelines (for food and pharmaceutical applications)
- Environmental Compliance: RoHS 2011/65/EU, REACH (EC) No. 1907/2006
- Testing & Inspection: Hydrostatic testing per ASTM A269, eddy current inspection per ASTM E309, ultrasonic inspection per ASTM E1316
- Documentation: Mill Test Certificate (MTC / EN 10204 3.1), Certificate of Conformance (CoC), and full traceability documentation for each batch
Unique Selling Points
- Optimized for Ice Thermal Storage: Coil geometry and material selection are specifically engineered for ice thermal storage applications, enabling high heat transfer rates during both ice formation and melting phases. The design supports hybrid internal-external ice melting configurations for maximum system flexibility and efficiency.
- Customizable Coil Geometry: Coil diameter, pitch, layer configuration, and tube dimensions are fully customizable to meet specific system design requirements, enabling tailored thermal performance optimization.
- Exceptional Cryogenic Performance: Maintains full mechanical integrity and corrosion resistance at temperatures as low as −196°C, making it ideal for liquid nitrogen and deep-cooling applications.
- End-to-End Traceability: Every coil tube product is traceable from raw material mill certificate through final inspection, ensuring full supply chain transparency and compliance with stringent industry requirements.
- Extended Service Life: The combination of high-grade austenitic stainless steel, proper heat treatment, and passivation treatment ensures a service life exceeding 25 years in typical thermal cycling environments, significantly reducing lifecycle costs.
- Sustainable Manufacturing: Energy-efficient coil winding processes and fully recyclable stainless steel materials contribute to a reduced carbon footprint and alignment with global sustainability goals.
Wenzhou Jixing Metal Materials Co., Ltd. — Specializing in precision stainless steel coil tubes for high-performance heat exchange and thermal storage applications. Custom engineering solutions available upon request.