Stainless Steel Coil Tube for Internal-Melting Ice Storage Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product specifically designed for application in Internal-Melting Coil Tube Ice Storage Systems (Internal-Melting Coil Tube Ice Storage System). This product represents a critical heat-exchange component within advanced thermal energy storage (TES) infrastructure, where stainless steel coil tubes are embedded within ice slurry or ice blocks to facilitate controlled freezing and melting cycles for peak-load shifting and energy management. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube product is engineered to withstand repeated thermal cycling, corrosive brine environments, and high mechanical stress while maintaining structural integrity over extended service life.
The coil tube design enables efficient heat transfer between the refrigerant fluid circulating within the tube and the surrounding phase-change material (PCM), typically water or saltwater brine, thereby achieving high-density thermal storage with minimal footprint. This product is classified under the literature and research category, reflecting its development and optimization based on rigorous experimental research into internal-melting coil tube ice storage system performance.
Material & Properties
Material Composition
The coil tube is fabricated from high-grade austenitic stainless steel, with the primary grade being SAE/AISI 304 (UNS S30400), supplemented by SAE/AISI 316L (UNS S31603) for applications requiring enhanced chloride resistance. The material composition is as follows:
- AISI 304 Grade: Carbon (C) ≤ 0.08%, Manganese (Mn) ≤ 2.0%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Silicon (Si) ≤ 1.0%, Phosphorus (P) ≤ 0.045%, Sulfur (S) ≤ 0.030%
- AISI 316L Grade: Carbon (C) ≤ 0.03%, Manganese (Mn) ≤ 2.0%, Chromium (Cr) 16.0–18.0%, Nickel (Ni) 10.0–14.0%, Molybdenum (Mo) 2.0–3.0%, Silicon (Si) ≤ 1.0%, Phosphorus (P) ≤ 0.030%, Sulfur (S) ≤ 0.030%
Mechanical Properties
- Tensile Strength: ≥ 520 MPa (AISI 304); ≥ 485 MPa (AISI 316L)
- Yield Strength: ≥ 205 MPa (AISI 304); ≥ 170 MPa (AISI 316L)
- Elongation at Break: ≥ 40% (AISI 304); ≥ 35% (AISI 316L)
- Hardness: ≤ 217 HB (AISI 304); ≤ 210 HB (AISI 316L)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (AISI 304); 14.6 W/(m·K) at 20°C (AISI 316L)
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion in brine and refrigerant environments
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | Φ 8 mm – Φ 50 mm (customizable) | ASTM A213 / GB/T 12771 |
| Tube Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / EN 10217-7 |
| Coil Bending Diameter | ≥ 4× OD (minimum bend radius) | ISO 4427 |
| Coil Length per Spool | Up to 500 m (standard); customizable | — |
| Surface Finish | Pickled & Passivated (2B finish); Ra ≤ 0.8 μm | ASTM A967 |
| End Forming | Plain cut, beveled, or threaded (per customer specification) | ASME B1.20.1 |
| Pressure Rating | Up to 1.6 MPa (standard); up to 4.0 MPa (reinforced) | ASME B31.3 |
| Tolerance on OD | ±0.05 mm (precision grade); ±0.1 mm (standard grade) | GB/T 14976 |
| Tolerance on Wall Thickness | ±10% (standard); ±5% (precision grade) | ASTM A213 |
| Heat Treatment | Solution Annealed (1050–1150°C), Water Quenched | ASTM A967 |
| Storage Medium Compatibility | Water, Ethylene Glycol Solutions, Calcium Chloride Brine (up to 25%) | — |
| Design Life | ≥ 25 years under normal operating conditions | — |
Manufacturing Process
The production of stainless steel coil tubes for ice storage applications follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and corrosion resistance:
- Raw Material Selection: Cold-rolled stainless steel strip is sourced from certified mills, with incoming inspection verifying chemical composition (via Optical Emission Spectroscopy, OES) and mechanical properties.
- Coil Winding & Forming: The stainless steel strip is precision-wound into a coil tube configuration using CNC-controlled coiling machinery. The winding process maintains consistent inter-coil spacing and uniform bend radius to prevent stress concentration points.
- Resistance Welding (Furnace Welding): The tube seam is formed using automated resistance welding or induction furnace welding. Weld bead height is controlled to ≤ 0.1 mm to minimize internal flow resistance and prevent fouling in heat-exchange applications.
- Solution Annealing: The formed coil tube undergoes solution annealing at 1050–1150°C followed by rapid water quenching. This process dissolves carbide precipitates, relieves residual stresses, and restores full austenitic microstructure for optimal corrosion resistance and ductility.
- Pickling & Passivation: The annealed tube is subjected to acid pickling (nitric/hydrofluoric acid blend) to remove mill scale and oxide layers, followed by passivation treatment to form a stable chromium oxide (Cr₂O₃) protective film.
- Hydrostatic Testing: Each coil tube undergoes 100% hydrostatic pressure testing at 1.5× the design pressure to verify weld integrity and absence of leaks or defects.
- Dimensional Inspection: Final product dimensions are verified using ultrasonic thickness gauging, laser diameter measurement, and visual inspection for surface defects.
- Coiling & Packaging: The finished coil tube is wound onto steel spools with protective end caps and packaged with moisture-absorbing desiccants for shipment.
Applications
The stainless steel coil tube is primarily engineered for the following applications within the thermal energy storage and HVAC (Heating, Ventilation, and Air Conditioning) industry:
- Internal-Melting Ice Storage Systems: The coil tube serves as the heat-transfer conduit embedded within ice blocks or ice slurry tanks, enabling efficient refrigerant-to-ice heat exchange during the charging (freezing) cycle and ice-to-refrigerant heat exchange during the discharging (melting) cycle.
- Commercial & Industrial Peak-Load Shifting: Utilized in commercial buildings, hospitals, and industrial facilities to shift cooling loads from peak to off-peak hours, reducing energy costs and grid stress.
- Cold Chain Logistics: Applied in refrigerated warehouses and cold storage facilities where high-density thermal storage is required for temperature-controlled environments.
- Process Cooling Systems: Used in chemical processing, food and beverage manufacturing, and pharmaceutical facilities requiring reliable, corrosion-resistant heat exchange components.
- Geothermal Heat Exchange: Deployed in ground-source heat pump systems where stainless steel coil tubes are installed in boreholes for efficient ground thermal energy extraction.
- Marine & Offshore Cooling: Suitable for shipboard and offshore platform cooling systems where resistance to seawater corrosion and mechanical vibration is critical.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and certifications ensuring product compliance with international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System Certification
- CE Marking — European Conformity for pressure equipment and components
- EN 10204 3.1 — Material Test Certificate (Third-Party Inspection Available)
- ASTM / ASME — Product conformance to applicable American standards
- GB/T — Compliance with Chinese National Standards for stainless steel tubes
- PED (Pressure Equipment Directive 2014/68/EU) — For pressure-containing applications
Each production batch is accompanied by a Mill Test Certificate (MTC) documenting chemical composition, mechanical test results, heat treatment records, and dimensional inspection data. Third-party inspection by agencies such as SGS, BV (Bureau Veritas), or TÜV is available upon customer request.
Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel composition provides exceptional resistance to brine corrosion, ensuring long service life even in aggressive chemical environments common in ice storage systems.
- Thermal Cycling Durability: Engineered to withstand thousands of freeze-thaw cycles without degradation of mechanical properties or development of fatigue cracks.
- Precision Manufacturing: Tight dimensional tolerances and consistent wall thickness ensure uniform heat transfer performance across the entire coil tube length.
- Customizable Design: Flexible customization of tube diameter, wall thickness, coil length, and end forming to meet specific system design requirements.
- Research-Backed Performance: Product specifications are informed by experimental research on internal-melting coil tube ice storage systems, ensuring optimal thermal efficiency and system compatibility.
- Cost-Effective Lifecycle: The combination of long design life, low maintenance requirements, and high thermal efficiency delivers superior total cost of ownership compared to alternative materials.
Note: All specifications are subject to continuous improvement based on ongoing experimental research and customer feedback. For project-specific requirements, consult with Wenzhou Jixing Metal Materials Co., Ltd. engineering team for tailored product configuration and technical support.