Stainless Steel Coil Tube (Coiltube) for Ice Thermal Storage Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered coiled tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This specialized coil tube is designed for integration into Internal Melt-Ice (IMI) Ice Coil Tube Thermal Storage Tanks, serving as a critical heat-exchange component in advanced thermal energy storage (TES) systems. The coil tube facilitates efficient heat transfer between the working fluid (typically brine or chilled water) and the surrounding ice mass, enabling high-capacity cold storage with minimal thermal loss.
Based on rigorous system simulation studies and field-proven engineering data, this coil tube product is optimized for the unique thermodynamic demands of internal melt-ice configurations, where ice is formed directly within the storage tank and subsequently melted to release stored cooling capacity. The product represents a convergence of metallurgical precision, thermal engineering, and materials science.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical integrity under cryogenic and sub-zero operating conditions.
Primary Material Grades
- Austenitic Stainless Steel (奥氏体不锈钢): Typically Grade 304 (UNS S30408) or Grade 316L (UNS S31603), providing superior resistance to chloride-induced pitting and general corrosion in brine environments.
- Thermal Conductivity: Approximately 16.3 W/(m·K) for Grade 304 and 14.6 W/(m·K) for Grade 316L at 20°C, ensuring efficient heat exchange performance.
- Cryogenic Toughness: Maintains ductility and fracture resistance down to −196°C (liquid nitrogen temperature), making it suitable for sub-zero thermal storage applications.
- Corrosion Resistance: The passive chromium oxide layer (Cr₂O₃, minimum 18% Cr) provides long-term protection against brine solutions (typically 20–25% ethylene glycol or calcium chloride).
Key Mechanical Properties
- Yield Strength (屈服强度): ≥ 205 MPa (Grade 304), ≥ 170 MPa (Grade 316L)
- Tensile Strength (抗拉强度): ≥ 515 MPa (Grade 304), ≥ 485 MPa (Grade 316L)
- Elongation (伸长率): ≥ 40% (at rupture)
- Impact Energy (冲击韧性): High Charpy V-notch impact energy at cryogenic temperatures
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Category | Coiltube (盘管) — Pre-formed coil tube | — |
| Material Grade | 304 / 316L Austenitic Stainless Steel | ASTM A213 / EN 10217-7 |
| Outer Diameter (OD) | 12 mm – 50 mm (customizable) | GB/T 14976 / ASME B36.19M |
| Wall Thickness | 0.8 mm – 3.0 mm (customizable) | GB/T 14976 / EN 10217-7 |
| Coil Outer Diameter (COD) | 300 mm – 2000 mm | Manufacturer Specification |
| Coil Length per Unit | 50 m – 500 m (configurable) | Manufacturer Specification |
| Surface Finish | Bright Annealed (BA) or Pickled & Passivated | ASTM A479 / EN 10204 |
| Tolerance — OD | ±0.05 mm (precision grade) | ISO 286 / GB/T 1804 |
| Tolerance — Wall Thickness | ±10% of nominal | ASTM A213 |
| Operating Temperature Range | −40°C to +120°C | ASME B31.3 / EN 13480 |
| Design Pressure | Up to 1.6 MPa (standard); higher upon request | GB/T 20801 / ASME B31.3 |
| End Forming | Plain ends, flanged ends, or socket-weld ends | ANSI B16.11 / GB/T 12459 |
| Heat Treatment | Solution Annealed (固溶处理) at 1050°C – 1150°C, water quenched | ASTM A213 |
| Passivation Treatment | ASTM A967 nitric acid passivation | ASTM A967 / A380 |
| Product Standard | GB/T 14976, EN 10217-7, ASTM A213 | — |
Manufacturing Process
The production of high-quality stainless steel coil tubes for thermal storage applications follows a multi-stage metallurgical and forming process, ensuring dimensional accuracy, microstructural integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strips are sourced from certified mills with full mill test certificates (MTC) per EN 10204 Type 3.1. Chemical composition is verified by optical emission spectroscopy (OES) and inductively coupled plasma (ICP) analysis.
- Coil Winding (盘卷成型): Precision-controlled CNC coil winding machines form the tube into the required coil geometry. The winding process is executed at controlled speeds to minimize residual stress and ensure uniform coil spacing.
- Welding (焊接): Longitudinal seams are joined using automatic orbital TIG (Tungsten Inert Gas) welding with high-purity argon shielding gas (≥99.999%). Weld parameters are optimized to achieve full penetration with minimal heat-affected zone (HAZ) distortion.
- Solution Annealing (固溶退火): The formed coil tube is heated to 1050°C – 1150°C and rapidly quenched in water. This eliminates residual stresses from forming and welding, restores full austenitic microstructure, and maximizes corrosion resistance.
- Pickling & Passivation (酸洗钝化): Surface oxidation scale and weld discoloration are removed via controlled nitric/hydrofluoric acid pickling. Subsequent passivation per ASTM A967 re-establishes the protective chromium oxide layer.
- Dimensional Inspection: Each coil tube undergoes 100% inspection for outer diameter (OD), wall thickness, coil diameter, and straightness using laser measurement systems and coordinate measuring machines (CMM).
- Pressure Testing: Hydrostatic pressure testing is performed at 1.5× the design pressure to verify weld integrity and structural soundness.
- Final Packaging: Coils are wrapped in moisture-proof protective film and secured on steel pallets with desiccant to prevent atmospheric corrosion during transit.
Applications
The Stainless Steel Coil Tube for Ice Thermal Storage Systems finds application in a wide range of engineering domains:
- Internal Melt-Ice (IMI) Thermal Energy Storage Tanks: The primary application — the coil tube serves as the heat exchanger element within ice storage tanks, enabling ice formation during off-peak hours and controlled melting for peak cooling load management.
- Commercial Building HVAC Systems: Ice storage systems in large commercial complexes, shopping malls, and office buildings for peak demand shifting and demand charge reduction.
- Industrial Process Cooling: Continuous cooling supply for pharmaceutical manufacturing, food processing, and semiconductor fabrication facilities requiring uninterrupted chilled water supply.
- Emergency Backup Cooling: Critical infrastructure such as hospitals, data centers, and telecommunications facilities requiring reliable backup cooling during power outages.
- Renewable Energy Integration: Coupling with solar-powered refrigeration systems for thermal energy storage and load balancing.
- Transportation Refrigeration: High-performance refrigeration coils for cold-chain logistics and maritime applications.
Unique Selling Points
- Simulation-Validated Performance: The coil tube design parameters are informed by comprehensive system-level thermal simulation modeling of internal melt-ice storage tanks, ensuring optimal heat transfer coefficients and uniform ice formation patterns.
- Enhanced Heat Transfer Efficiency: The precision coil geometry maximizes surface-area-to-volume ratio, achieving heat transfer rates exceeding 150 W/(m²·K) in brine-to-ice applications.
- Superior Cryogenic Performance: Austenitic stainless steel retains full mechanical integrity at sub-zero temperatures, eliminating the risk of brittle fracture common in carbon steel alternatives.
- Long Service Life: Exceptional corrosion resistance in brine environments ensures a design service life exceeding 25 years with minimal maintenance.
- Customizable Geometry: Flexible manufacturing capability allows customization of coil diameter, tube dimensions, and end configurations to meet specific system design requirements.
- Environmentally Sustainable: Stainless steel is 100% recyclable, contributing to circular economy principles in green building and sustainable infrastructure projects.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and holds the following certifications and compliances:
- 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 directives for pressure equipment (PED 2014/68/EU)
- NADCAP — Special Process Certification (where applicable for aerospace-grade products)
- Mill Test Certificates (MTC): EN 10204 Type 3.1 certificates provided for every production batch
- Material Compliance: ASTM A213, EN 10217-7, GB/T 14976, JIS G3459
- Non-Destructive Testing (NDT): 100% eddy current (ET) inspection per ASTM E309; spot radiographic testing (RT) per ASTM E94
- Chemical Analysis: Full spectroscopic verification per ASTM E415 (OES) and ASTM E135 (ICP-OES)
Note: All specifications listed above represent standard product parameters. Wenzhou Jixing Metal Materials Co., Ltd offers fully customized solutions tailored to specific project requirements. Technical consultations and sample testing are available upon request. For detailed system simulation data and thermal performance modeling of IMI ice storage configurations incorporating these coil tubes, please contact the engineering team for comprehensive technical documentation.