Stainless Steel Coil Tube for Ice Storage Thermal Energy Systems
Product No.: 1674 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Spiral Tubing) is a precision-engineered tubular component specifically designed for thermal energy storage and recovery applications, particularly in ice storage (ice-slurry) systems. This product represents a critical heat exchange element within ice storage devices, where its geometric configuration and material properties directly influence the overall thermodynamic efficiency of the system.
Unlike conventional straight piping, the coil tube geometry provides a significantly increased surface-area-to-volume ratio, enabling superior heat transfer rates between the refrigerant and the ice-storage medium. The continuous spiral or helical winding pattern ensures uniform distribution of thermal load across the entire device, minimizing localized hot or cold spots that could compromise ice formation efficiency or accelerate thermal degradation.
Based on extensive research into the thermal performance characteristics of ice storage devices, this coil tube product has been optimized to achieve maximum heat exchange effectiveness while maintaining structural integrity under repeated freeze-thaw cycles and cyclic thermal stress.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical durability in cryogenic and sub-zero operating environments.
- Primary Material Grades: AISI 304 (UNS S30400), AISI 316L (UNS S31603), and AISI 321 (UNS S32100)
- Corrosion Resistance: Excellent resistance to chloride-induced pitting and crevice corrosion, essential for brine-based ice storage systems
- Cryogenic Performance: Maintains ductility and mechanical strength at temperatures as low as −196°C (liquid nitrogen temperature range)
- Thermal Conductivity: Approximately 16.3 W/(m·K) for 304 grade at 20°C; 14.6 W/(m·K) for 316L grade
- Coefficient of Thermal Expansion: 17.3 × 10⁻⁶ /K (304 grade), ensuring dimensional stability during thermal cycling
- Non-Magnetic Properties: Inherently non-magnetic in annealed condition, suitable for environments requiring electromagnetic compatibility
- Hygienic Surface Finish: Interior surface roughness ≤ 0.4 μm Ra (Ra = Root Mean Square Average Roughness), facilitating efficient heat transfer and preventing biofilm accumulation
Specifications
| Parameter | Specification | Standard / Tolerance |
|---|---|---|
| Outer Diameter (OD) | 12 mm – 108 mm (customizable) | ASME B36.19M / EN 10217-7 |
| Wall Thickness | 1.0 mm – 6.0 mm | ±0.1 mm (±10%) |
| Coil Diameter (CD) | 200 mm – 3000 mm | ±5 mm |
| Coil Length | 1 m – 50 m (continuous) | ±2% |
| Number of Turns | 10 – 500 turns | As per design requirement |
| Pitch (Helical Spacing) | OD + 2 mm to OD + 20 mm | ±0.5 mm |
| Operating Temperature Range | −196°C to +400°C | AISI 304/316L specification |
| Maximum Working Pressure | Up to 4.0 MPa (580 psi) | ASME B31.3 / EN 13480 |
| Hydrostatic Test Pressure | 1.5× Working Pressure | 30-minute hold |
| Surface Finish (Interior) | Electropolished / Passivated | ≤ 0.4 μm Ra |
| Surface Finish (Exterior) | No. 4 Brushed / No. 1 Mill Finish | Per customer specification |
| End Treatment | Plain / Threaded / Flanged / Weld Prep | ASME B1.20.1 (threads) |
| Delivery Form | Coiled on spool / Bundled / Palletized | Export-grade packaging |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical quality, and consistent thermal performance:
- Raw Material Selection & Inspection: Cold-rolled stainless steel tubing is sourced from certified mills and subjected to incoming quality inspection, including chemical composition analysis (Spectroscopy), mechanical property verification (Tensile Strength, Yield Strength, Elongation), and visual surface examination.
- Dimensional Trimming & End Preparation: The straight tubing is cut to the required length with precision shearing or plasma cutting, followed by end deburring, chamfering, and preparation for subsequent forming operations.
- Coil Forming (Cold Bending): Using computer-controlled (CNC) tube coiling machines, the straight tubing is helically wound around a mandrel to achieve the specified coil diameter and pitch. The bending process is carefully controlled to avoid work-hardening, surface distortion, or ovalization of the tube cross-section. A maximum bend radius-to-diameter ratio (R/D) of ≥ 5 is maintained to prevent material thinning and micro-cracking.
- Stress Relief Annealing: Following coiling, the formed coil tubes are subjected to a controlled heat treatment cycle (typically 850°C – 1050°C, depending on grade) to relieve residual stresses introduced during cold forming. This step restores full ductility and ensures dimensional stability during subsequent service.
- Surface Treatment & Passivation: The annealed coil tubes undergo pickling and passivation treatment (using nitric acid/hydrofluoric acid solution) to remove oxide scale and form a protective chromium oxide layer. For applications requiring ultra-clean surfaces, additional electropolishing may be applied.
- Quality Control & Testing: Each batch undergoes comprehensive inspection, including dimensional verification (OD, wall thickness, coil diameter, pitch), hydrostatic pressure testing, leak testing (helium or air), and visual/magnifier inspection for surface defects. Non-destructive testing (NDT) methods such as eddy current testing or magnetic particle inspection may be employed for critical applications.
- Packaging & Dispatch: The finished coil tubes are protected against mechanical damage and corrosion during transit, wrapped in moisture-proof material, and secured on export-grade wooden pallets or steel spools.
Applications
The Stainless Steel Coil Tube is a versatile component with broad applicability across multiple industries, with particular emphasis on thermal management and energy storage systems:
- Ice Storage Thermal Energy Systems: The primary application domain. Coil tubes serve as the heat exchange medium within ice storage tanks, facilitating efficient ice formation during off-peak electrical hours and subsequent heat absorption during peak demand periods. This enables load-shifting strategies that reduce peak electricity consumption and associated costs.
- Commercial Refrigeration & Cold Chain: Used in walk-in coolers, freezers, cold storage warehouses, and refrigerated transport systems where reliable, corrosion-resistant heat exchange tubing is required.
- Building HVAC Systems: Integrated into air handling units, heat recovery ventilators, and radiant cooling panels for energy-efficient climate control in commercial and industrial facilities.
- Industrial Process Cooling: Employed in chemical processing, pharmaceutical manufacturing, food and beverage production, and semiconductor fabrication facilities where precise temperature control and material compatibility are critical.
- Geothermal & Renewable Energy Systems: Utilized as heat exchanger elements in ground-source heat pump systems and solar thermal energy collection arrays.
- Food & Beverage Industry: Suitable for pasteurization, brewing, dairy processing, and other applications requiring sanitary-grade stainless steel heat exchange components.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and standards compliance for this product line:
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health & Safety Management
- EN 10204-3.1 — Test Reports with Specific Statement of Compliance
- ASME Section IX — Welding Qualification (for welded coil tube assemblies)
- ASTM A269 / ASTM A312 — Seamless and welded austenitic stainless steel tubing
- EN 10217-7 — Stainless steel tubes for heat exchangers
- GB/T 12771 — Chinese national standard for stainless steel tubes for general purposes
- CE Marking — European Conformity for applicable pressure equipment directives
Each shipment is accompanied by a Mill Test Certificate (MTC) and a Heat Number Traceability Record, ensuring full material provenance from raw steel production through to final delivery. Batch-specific quality documentation is available upon request for regulatory audit or project-specific compliance verification.
Unique Selling Points
- Optimized Thermal Performance: The coil geometry, informed by thermal performance research on ice storage devices, maximizes heat transfer coefficient (U-value) while minimizing pressure drop, resulting in energy savings of up to 30% compared to conventional straight-tube configurations in ice storage applications.
- Superior Cryogenic Durability: The austenitic stainless steel matrix retains full mechanical integrity through thousands of freeze-thaw cycles, with no risk of brittle fracture — a critical advantage over carbon steel alternatives in sub-zero environments.
- Customization Capability: Full range of dimensional customization (OD, wall thickness, coil diameter, pitch, length) to meet specific thermal design requirements, from small-scale commercial ice storage to large-scale district energy systems.
- Hygienic & Corrosion-Resistant: Electropolished interior surfaces and passivated exterior finish ensure long service life in aggressive brine solutions (NaCl, CaCl₂) and compliance with food-grade hygiene standards (FDA, 3-A Sanitary Standards).
- Complete Traceability: Every coil tube is heat-number traceable with full material certification, providing unmatched quality assurance for critical infrastructure and regulated industry applications.
Note: The thermal performance of ice storage devices utilizing this coil tube product has been validated through systematic experimental research, demonstrating consistent and reliable heat exchange behavior across a wide range of operating conditions. For detailed thermal performance data, system integration guidance, or custom engineering consultation, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.