Stainless Steel Coil Tube (Coiltube) — Model No. 1430
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Precision Stainless Steel Coil Tube for Thermal Energy Storage Systems
Reference Document: Experimental Study on the Cold Storage Mechanism of Coiltube-Type Ice Storage Tanks
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous spiral tubing manufactured to exacting dimensional tolerances, designed for integration into ice thermal energy storage (TES) systems and other high-performance heat exchange applications. Unlike discrete pipe segments joined by welding or fittings, the coil tube is formed as a single uninterrupted length of helically wound tubing, eliminating interstitial weld points and thereby minimizing leakage risk while maximizing thermal transfer efficiency across the entire active surface area.
This product is specifically optimized for coiltube-type ice storage tank configurations, where the spiral geometry is embedded within a phase-change medium (typically ice) to facilitate rapid cold charge and discharge cycles. The coiltube configuration ensures uniform flow distribution, reduced pressure drop compared to serpentine alternatives of equivalent length, and superior structural integrity under repeated thermal cycling.
2. Material and Properties
The coil tube is fabricated from austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term dimensional stability under cryogenic and thermal cycling conditions.
- Base Material: Austenitic Stainless Steel (typically Grade 304 / UNS S30408 or Grade 316L / UNS S31603)
- Key Alloying Elements: Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, Manganese (Mn) <2%, Carbon (C) <0.08%
- Corrosion Resistance: Superior resistance to chlorides, deionized water, brine solutions, and ambient atmospheric corrosion
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C (Grade 304), ensuring efficient heat transfer between the working fluid and the phase-change medium
- Operating Temperature Range: −196°C to +450°C, accommodating cryogenic ice storage applications without embrittlement
- Mechanical Properties: Yield strength ≥205 MPa, tensile strength ≥515 MPa, elongation ≥40%
- Surface Finish: Pickled and passivated (2B finish) or polished (BA finish, Ra ≤ 0.8 μm) to minimize fouling and reduce hydraulic resistance
- Non-Magnetic: Fully austenitic microstructure confirmed by magnetic permeability testing (≤ 3 μ)
3. Specifications
| Parameter | Specification |
|---|---|
| Product Model | 1430 Series Coiltube |
| Outer Diameter (OD) | 6 mm – 32 mm (customizable per engineering requirement) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Helical Pitch | 10 mm – 50 mm (configurable for optimal heat transfer density) |
| Coil Diameter (CD) | 100 mm – 500 mm |
| Continuous Length | Up to 200 m per coil (seamless, no intermediate joints) |
| Dimensional Tolerance (OD) | ±0.05 mm |
| Dimensional Tolerance (Wall) | ±10% of nominal |
| Helical Roundness | ≤ 0.5% of coil diameter |
| Material Grade | 304 / 316L / 321 (selectable) |
| Surface Treatment | Pickled & Passivated (2B) or Electropolished (Ra ≤ 0.4 μm) |
| Maximum Working Pressure | 1.6 MPa (standard); 4.0 MPa (reinforced wall option) |
| Design Life | ≥ 25 years under continuous thermal cycling |
| Packaging | Wooden drum with moisture-proof wrapping and VCI (Vapor Corrosion Inhibitor) coating |
4. Manufacturing Process
The production of the 1430 Series Coiltube follows a rigorously controlled multi-stage manufacturing sequence:
- Material Receiving and Inspection: Stainless steel strip or seamless tube stock is verified against mill certificates (EN 10204 Type 3.1), with chemical composition confirmed by XRF (X-ray Fluorescence) spectroscopy and mechanical properties validated through tensile testing.
- Coil Forming (Helical Winding): The tube blank is fed through precision-guided forming dies on a CNC-controlled coil winding machine. The helical pitch and coil diameter are maintained within tight tolerances through real-time laser measurement feedback loops.
- Stress Relief Annealing: The formed coil undergoes controlled annealing at 1050°C – 1150°C in a protective nitrogen atmosphere to eliminate residual forming stresses, restore full austenitic ductility, and prevent cold-work hardening effects that could compromise fatigue life.
- Pickling and Passivation: Immersion in a mixed acid bath (HNO₃/HF) removes oxide scale and impurities, followed by passivation to establish a protective chromium oxide film (≥ 10 nm thickness), verified by copper sulfate spot testing per ASTM A967.
- End Finishing: Coil ends are deburred, chamfered, and sealed with protective caps to prevent internal contamination during storage and transportation.
- Quality Inspection: Each coil undergoes 100% dimensional verification (OD, wall thickness, coil diameter, pitch), visual inspection for surface defects, and hydrostatic pressure testing at 1.5× the maximum working pressure for a minimum of 30 seconds.
5. Applications
The 1430 Series Coiltube is engineered for demanding thermal energy management applications:
- Ice Thermal Energy Storage (TES) Systems: Primary application — the coiltube serves as the working fluid conduit within ice storage tanks, enabling off-peak cold generation (charging) and peak-load cold delivery (discharging). The helical geometry maximizes the heat transfer area per unit volume while maintaining low hydraulic resistance.
- Commercial District Cooling: Integrated into large-scale cooling distribution networks for office complexes, shopping malls, and data centers, providing peak-shaving and load-balancing capabilities.
- Process Cooling in Industrial Facilities: Application in chemical processing, pharmaceutical manufacturing, and food processing where precise temperature control and hygienic materials are mandatory.
- Cryogenic Heat Exchangers: Suitable for liquefied natural gas (LNG) terminal heat exchangers and cryogenic storage systems owing to the material's resistance to low-temperature embrittlement.
- Refrigeration and Air Conditioning Systems: Evaporator and condenser coil applications in commercial refrigeration units and high-capacity HVAC systems.
6. Quality Certifications and Standards Compliance
| Standard / Certification | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Manufacturing and supply chain controls |
| ISO 14001:2015 | Environmental Management System — Sustainable production practices |
| ASTM A778 | Standard Specification for Seamless Austenitic Stainless Steel Welding Pipe and Tubing |
| ASTM A967 | Standard Practice for Chemical Cleaning and Passivation of Stainless Steel Parts |
| EN 10217-7 | Technical Delivery Conditions for Stainless Steel Tubes for Mechanical and Technical Purposes |
| GB/T 12771 | Chinese National Standard for Stainless Steel Tubes for General Purposes |
| EN 10204 Type 3.1 | Test Reports — Material certification with verified test data |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (optional, for potable water applications) |
7. Unique Selling Points
- Seamless Continuous Helical Geometry: Eliminates intermediate weld joints, reducing potential leak points by 100% compared to segmented serpentine alternatives and enabling superior fatigue performance under repeated thermal cycling (≥ 10,000 cycles validated).
- Optimized for Phase-Change Heat Transfer: Coil geometry and pitch are engineered specifically for ice thermal storage applications, achieving a heat transfer coefficient improvement of 25–40% over conventional straight-tube designs due to enhanced turbulence and reduced boundary layer thickness at the tube surface.
- Low Hydraulic Resistance: The helical configuration provides a more uniform flow distribution with a pressure drop approximately 15–30% lower than equivalent-length serpentine coils, reducing pumping energy consumption in TES systems.
- Full Material Traceability: Every coil is traceable to the original steel mill heat number with complete chemical and mechanical test data, ensuring compliance with stringent regulatory and client audit requirements.
- Customizable Engineering: Coil diameter, pitch, tube OD, and wall thickness are configurable to match specific system design parameters, enabling optimal integration into bespoke thermal energy storage architectures.
- Long Service Life: Designed for a minimum 25-year operational lifespan under continuous thermal cycling conditions, with corrosion allowance incorporated into wall thickness specifications.
8. Technical Notes
Based on experimental research into the cold storage mechanism of coiltube-type ice storage tanks, the helical coil configuration demonstrates superior thermal performance characteristics compared to alternative geometries. The continuous spiral path ensures that the working fluid (typically chilled water or brine solution) traverses the phase-change interface uniformly, minimizing temperature stratification within the storage medium and maximizing the effective utilization of the stored cold energy. Wenzhou Jixing Metal Materials Co., Ltd. applies these validated design principles to produce coil tubes that deliver predictable, repeatable thermal performance in real-world TES installations.
Document Reference: Product Technical Specification No. 1430 | Wenzhou Jixing Metal Materials Co., Ltd.