Stainless Steel Coil Tube for Ice Storage Systems
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product specifically designed for integration into Ice Storage System Construction Technology (盘管式冰蓄冷系统施工技术). This product serves as the core heat exchange element in thermal energy storage systems, where it is coiled and immersed in ice-slurry or encapsulated ice storage tanks to facilitate the charging (freezing) and discharging (melting) cycles of ice as a phase-change material for thermal energy storage.
Unlike conventional straight-pipe configurations, the coil tube design maximizes the heat transfer surface area within a compact volume, enabling high-efficiency thermal exchange between the refrigerant or chilled water circulating through the tube and the surrounding ice medium. This technology is particularly advantageous in Cooling Load Shifting (CLS) applications, where peak electrical demand is reduced by shifting cooling production to off-peak hours.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term durability in aggressive aqueous environments.
- Base Material: Austenitic Stainless Steel conforming to ASTM A213 / ASTM A269 standards
- Common Grades: 304 (UNS S30408), 316 (UNS S31608), 316L (UNS S31603)
- Corrosion Resistance: Superior resistance to chloride-induced pitting and crevice corrosion, critical for ice-slurry environments containing antifreeze additives (ethylene glycol or propylene glycol)
- Thermal Conductivity: 14–16 W/(m·K) for Grade 304, providing efficient heat transfer performance
- Operating Temperature Range: −196°C to +870°C (vacuum), with practical ice storage application range of −25°C to +5°C
- Mechanical Properties: Tensile strength ≥ 515 MPa (Grade 304), elongation ≥ 40%, ensuring resistance to thermal cycling fatigue
- Surface Finish: Electropolished or passivated interior surface (Ra ≤ 0.4 μm) to minimize flow resistance and prevent biofilm formation
Specifications
| Parameter | Specification | Standard / Tolerance |
|---|---|---|
| Outer Diameter (OD) | 12 mm, 16 mm, 19 mm, 22 mm, 25 mm, 32 mm, 38 mm (custom available) | ASTM A213 ±0.5 mm |
| Wall Thickness | 1.0 mm – 3.0 mm | ASTM A213 ±10% nominal |
| Coil Diameter | 200 mm – 2000 mm (custom configurable) | ±1% of nominal |
| Coil Length | Up to 500 m per continuous coil | Seamless or welded per ASTM A269 |
| Coil Pitch / Spacing | 25 mm – 80 mm (adjustable per design) | ±0.5 mm uniformity |
| Number of Turns | 10 – 500+ turns per coil assembly | — |
| Material Grade | 304 / 316 / 316L / 321 | ASTM A213, ASTM A269, EN 10217 |
| End Connection | Threaded, flanged, welded, or U-bend return | ASME B16.11 / B16.5 |
| Surface Treatment | Pickled & passivated; optional electropolishing | AMS 2700 / ASTM A967 |
| Pressure Rating | Up to 2.5 MPa (design pressure) | Hydrostatic test at 1.5× design pressure |
| Maximum Operating Pressure | 1.6 MPa (typical ice storage application) | ASME Section VIII |
| Thermal Cycling Endurance | ≥ 50,000 freeze-thaw cycles | Internal fatigue testing protocol |
| Weight (Typical) | 0.4 – 2.8 kg/m (depending on OD and wall) | — |
Manufacturing Process
The production of stainless steel coil tubes for ice storage systems follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip or seamless tube stock is procured from certified mills with full mill test certificates (MTC) per EN 10204 3.1.
- Coil Forming: The tube is wound onto precision mandrels using CNC-controlled coil winding machines to achieve uniform coil diameter, pitch, and turn count. For large-diameter coils, multi-axis robotic winding systems ensure geometric consistency.
- Welding (if applicable):strong> Helical or longitudinal welds are performed via TIG (Tungsten Inert Gas) welding with argon back-purging to maintain internal oxide-free surfaces. Weld parameters are optimized per AWS D17.9 for stainless steel.
- Heat Treatment: Solution annealing at 1050–1150°C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation: Immersion in mixed acid solutions (HNO₃ + HF) to remove scale and form a protective chromium oxide passive layer (≥ 2000 mV open circuit potential).
- Electropolishing (Optional):strong> Electrochemical polishing reduces surface roughness to Ra ≤ 0.2 μm, critical for hygienic and low-flow-resistance applications.
- Hydrostatic Testing: Each coil assembly is pressure-tested at 1.5× the design pressure for a minimum dwell time of 30 seconds to verify leak-tightness and structural integrity.
- Dimensional Inspection: Coordinate Measuring Machine (CMM) verification of coil geometry, plus ultrasonic thickness measurement (UT) per ASTM E797.
- Non-Destructive Testing (NDT):strong> Dye Penetrant Inspection (DPI) per ASTM E709 and/or Magnetic Particle Inspection (MPI) for surface defect detection.
Applications
The Stainless Steel Coil Tube is engineered for the following primary application domains:
- Ice Storage Thermal Energy Systems (盘管式冰蓄冷系统):strong> Core heat exchange element in encapsulated ice storage tanks (ICE-type) and internal coil ice storage systems. Facilitates off-peak ice production and on-peak cooling discharge, achieving peak demand reduction of 30–50%.
- Commercial Building HVAC: Shopping malls, office towers, hospitals, and convention centers requiring large-capacity cooling with electrical demand management.
- Industrial Process Cooling: Food and beverage processing, pharmaceutical manufacturing, and chemical plants requiring reliable thermal buffering.
- District Cooling Networks: Centralized ice storage facilities serving multiple end-users through secondary chilled water loops.
- Marine & Offshore Applications: Shipboard cooling systems where space constraints and corrosion resistance are paramount.
- Data Center Thermal Management: High-density server cooling with thermal load shifting to manage power consumption peaks.
Unique Selling Points
- Superior Freeze-Thaw Durability: Engineered to withstand ≥ 50,000 thermal cycling events without cracking, deformation, or loss of mechanical properties—significantly exceeding industry benchmarks of 20,000 cycles.
- High Surface Area-to-Volume Ratio: The coiled geometry provides up to 40% greater heat transfer area per unit volume compared to straight-tube designs, enabling faster ice charging/discharging rates.
- Seamless Corrosion Performance: Grade 316L option offers outstanding resistance to chloride-containing ice slurries, eliminating the need for chemical inhibitors and reducing maintenance costs.
- Customizable Coil Geometry: Modular design allows adaptation to any tank configuration—from cylindrical to rectangular enclosures—with precise pitch control for optimal fluid distribution.
- Full Traceability: Each coil assembly is serialized with laser-marked identification, linked to complete material and manufacturing documentation for lifecycle traceability.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains the following certifications and complies with international standards governing the design, manufacture, and testing of stainless steel coil tubes:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance |
| ASTM A213 / A269 | Seamless & welded austenitic stainless steel tubing |
| EN 10217-7 | Technical delivery conditions for stainless steel tubes |
| ASME Section VIII Div. 1 | Pressure vessel and piping construction |
| NB (National Supervision Bureau) Certification | Chinese pressure equipment manufacturing license |
| TÜV / DNV Third-Party Inspection | Independent quality verification for export orders |
Design Considerations for Ice Storage System Integration
When incorporating the Stainless Steel Coil Tube into a 盘管式冰蓄冷系统 (Coil-Type Ice Storage System), the following engineering parameters must be addressed:
Heat Transfer Coefficient: The design heat transfer coefficient (U-value) for coil tubes in ice-slurry media typically ranges from 150–350 W/(m²·K), dependent on flow velocity, tube geometry, and ice formation dynamics. Computational Fluid Dynamics (CFD) simulation is recommended for system-level optimization.
- Flow Distribution: Multi-port manifold design ensures uniform refrigerant distribution across all coil turns, preventing localized ice bridging or dry-out zones.
- Thermal Expansion Accommodation: Expansion loops or flexible connections must be incorporated to absorb differential thermal expansion between the coil and tank shell (ΔT up to 30°C).
- Anti-Ice-Bridge Geometry: Coil pitch spacing must exceed the maximum ice crystal growth dimension (typically ≥ 3× tube OD) to maintain fluid flow channels during the charging phase.
- Anti-Fouling Design: Electropolished interiors combined with adequate flow velocity (> 1.0 m/s) prevent particulate accumulation and biofilm development over the system lifecycle.
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including coil layout design, system integration guidance, and post-installation performance monitoring to ensure optimal operation of ice storage systems throughout their design life of 20–25 years.