Stainless Steel Coil Tube (Coiltube) — Thermal Energy Storage Grade
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered continuous-wound tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed primarily for thermal energy storage applications — particularly external ice-melting (ice-slurry) thermal storage systems — the Coiltube delivers superior heat transfer performance, exceptional corrosion resistance, and mechanical durability under cyclic thermal loading conditions. The product is supplied in a continuous coiled configuration, enabling seamless integration into large-scale heat exchanger assemblies, cold storage tanks, and district cooling distribution networks.
Based on extensive research into the dynamic characteristics of external ice-melting coil tube thermal storage systems, this Coiltube product line has been specifically optimized to withstand the repeated freezing and thawing cycles inherent in ice-based thermal storage operations. The coil geometry maximizes surface-area-to-volume ratio, facilitating rapid heat exchange during both charging (cooling) and discharging (heating) phases of the thermal cycle.
Material & Properties
The Coiltube is fabricated from high-grade austenitic stainless steel, selected for its outstanding combination of thermal conductivity, corrosion resistance, and cryogenic toughness. The material complies with international standards including ASTM A269, ASTM A312, EN 10217-7, and GB/T 12771.
- Primary Alloy Grades: 304 (UNS S30408), 316L (UNS S31603), 321 (UNS S32108), and duplex 2205 (UNS S32205) available upon request
- Corrosion Resistance: Excellent resistance to chlorides, sulfates, and de-icing salts commonly encountered in thermal storage fluid loops
- Cryogenic Performance: Retains full ductility and tensile strength at temperatures as low as −196 °C (liquid nitrogen temperature), making it suitable for ice-based thermal storage
- Thermal Conductivity: 14.9–16.3 W/(m·K) for 304 grade; up to 29 W/(m·K) for 316L at elevated temperatures
- Maximum Operating Temperature: 870 °C (304), 870 °C (316L), 300 °C (2205 duplex)
- Minimum Operating Temperature: −196 °C without embrittlement
- Surface Finish: 2B (cold-rolled and annealed), BA (Bright Annealed), or No. 4 brushed finish; surface roughness Ra ≤ 0.8 μm
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Product Code | 1426 | Internal Catalog |
| Material Grade | 304 / 316L / 321 / 2205 (Duplex) | ASTM A269 / A312 |
| Outer Diameter (OD) | 6 mm – 50.8 mm (¼" – 2") | ASTM A751 |
| Wall Thickness | 0.5 mm – 3.0 mm | ±10% tolerance |
| Coil Inner Diameter (CID) | 300 mm – 1500 mm | Custom configurable |
| Coil Length per Spool | Up to 1,200 m (continuous) | — |
| Surface Treatment | Pickled & Passivated (P&P) | ASTM A967 |
| End Condition | Plain end, beveled, or cap-closed | Per customer drawing |
| Forming Method | Continuous cold-drawn & coil-wound | — |
| Maximum Working Pressure | Up to 15.0 MPa (2,175 psi) | ASME B31.3 |
| Thermal Cycle Endurance | >≥ 100,000 freeze-thaw cyclesInternal test protocol | |
| Applicable Fluids | Water, glycol solutions, brine, ethylene glycol, ammonia | — |
| Operating Temperature Range | −196 °C to +870 °C | — |
| Packaging | Wooden crate with moisture-proof wrapping, coil secured with steel bands | ISO 11607 |
Manufacturing Process
The production of the Coiltube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Virgin stainless steel wire rod is sourced from certified mills, with chemical composition verified via Optical Emission Spectrometry (OES) and confirmed to meet ASTM A269/A312 specifications.
- Wire Drawing: The rod is drawn through a series of tungsten carbide (WC) dies to achieve the target OD and wall thickness. A multi-stage drawing process ensures uniform cross-sectional geometry.
- Intermediate Annealing: Periodic solution annealing at 1050–1150 °C followed by controlled water quenching relieves cold-work hardening, restores full austenitic microstructure, and prevents cracking during subsequent forming operations.
- Coil Forming (Coiling): The drawn tube is wound onto precision mandrels using a CNC-controlled coil-winding machine. The winding tension is carefully controlled to prevent ovality, distortion, or inter-coil contact damage.
- Final Annealing & Pickling: The completed coil undergoes a final solution heat treatment, followed by acid pickling (HNO₃/HF blend) and passivation to remove scale, restore chromium oxide passive film, and ensure corrosion resistance.
- Quality Inspection: Every coil is subjected to hydrostatic pressure testing (per ASTM A269, at 1.5× the maximum working pressure for a minimum of 30 seconds), dimensional verification (OD, wall thickness via ultrasonic gauge), and visual surface inspection.
- Coil Stabilization & Packaging: Coils are stabilized on rotating drums to prevent relaxation, wrapped in moisture-barrier film, and secured in export-grade wooden crates.
Applications
The Coiltube finds extensive application across multiple high-performance engineering domains:
- Ice-Based Thermal Energy Storage (TES): Primary application in external ice-melting thermal storage systems where the Coiltube serves as the heat exchange element within ice slurry or ice-on-coil (OIC) storage tanks. The coil's high surface-area-to-volume ratio enables rapid heat absorption and release during charging and discharging cycles.
- District Cooling Systems: Used in large-scale district cooling networks for commercial complexes, airports, and data centers to manage peak load and improve energy efficiency.
- Cold Storage & Refrigeration: Integrated into evaporator assemblies for industrial cold storage facilities, food processing plants, and pharmaceutical cold chains.
- Process Heat Exchangers: Employed in chemical processing, petrochemical, and pharmaceutical industries where corrosion-resistant heat exchange tubes are required.
- Building Services (HVAC): Utilized in chiller coils, cooling towers, and condenser units for commercial and industrial HVAC systems.
- Cryogenic Systems: Suitable for cryogenic applications including LNG (Liquefied Natural Gas) handling, medical gas systems, and laboratory cryostats due to exceptional low-temperature toughness.
- Marine & Offshore: Deployed in marine cooling systems and offshore platform heat exchange assemblies where resistance to saltwater corrosion is critical.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Union directives (Pressure Equipment Directive 2014/68/EU where applicable)
- EN 10204 3.1 Certificate — Material test certificates provided with each shipment
- ASME "S" Stamp — Available for pressure-containing applications per ASME B31.3
- NACE MR0175 / ISO 15156 — Compliance for sour service environments (upon request)
- RoHS & REACH Compliance — Free of hazardous substances per EU regulations
- Third-Party Inspection: Available from SGS, Bureau Veritas, or TÜV upon customer request
Unique Selling Points
1. Cryogenic-Grade Thermal Storage Optimization: Unlike conventional coil tubes, this product is specifically engineered for the dynamic thermal cycling demands of ice-melting storage systems. Research-backed design ensures reliable performance over ≥100,000 freeze-thaw cycles without degradation of heat transfer efficiency or structural integrity.
2. Continuous-Coil Supply Advantage: Supplied as continuous coils up to 1,200 meters per spool, eliminating field welding joints and reducing installation time, leak risk, and labor costs compared to straight-length tubing.
3. Precision Dimensional Control: Tight tolerances on OD (±0.05 mm) and wall thickness (±10%) ensure optimal fit within heat exchanger headers and storage tank manifolds, minimizing pressure drop and maximizing flow uniformity.
4. Full Traceability: Every coil is accompanied by a complete quality dossier including mill test certificates, chemical analysis reports, mechanical property data, and hydrostatic test records — enabling full material traceability from raw steel to finished product.
5. Custom Configuration: Flexible customization of OD, wall thickness, coil diameter, surface finish, and end preparation to meet project-specific engineering requirements, supported by in-house R&D and technical design services.
Wenzhou Jixing Metal Materials Co., Ltd is committed to delivering premium-quality stainless steel Coiltube solutions that meet the most demanding thermal energy storage and heat exchange applications worldwide. For detailed technical data sheets, sample requests, or custom quotation inquiries, please contact our engineering team directly.