Stainless Steel Coil Tube for Ice Storage Thermal Energy Systems
Product Overview
The Stainless Steel Coil Tube (Model No. 1177), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product specifically designed for ice storage thermal energy systems (Ice Storage Thermal Energy Systems). This coil tube serves as the core heat transfer element in ice storage cooling devices (Ice Storage Cooling Devices), where it facilitates the controlled formation and melting of ice on its outer surface to achieve off-peak energy storage and peak-shaving in commercial and industrial cooling applications.
Unlike conventional straight pipes, coil tubes leverage their inherent helical geometry to maximize the surface area-to-volume ratio, thereby enhancing heat exchange efficiency. The coiled configuration promotes turbulent flow characteristics within the tube, reducing the thermal boundary layer and significantly improving the overall heat transfer coefficient. This product has been extensively studied in academic literature regarding the ice formation process on the outer surface of coil tubes in ice storage devices, establishing its proven performance in cryogenic and low-temperature thermal management applications.
Material & Properties
Base Material
The coil tube is fabricated from high-grade austenitic stainless steel, conforming to the following international standards:
- ASTM A213 / ASME SA213 — Stainless Steel Tubing for Heat-Exchange and Similar Service
- ASTM A312 / ASME SA312 — Seamless Austenitic Stainless Steel Tubing
- EN 10216-5 — Non-ferrous seamless and welded tubular products for heat exchangers
- GB/T 12771 — Chinese National Standard for Seamless Stainless Steel Tubes
Commonly Available Grades
- 304 (UNS S30400) — General-purpose austenitic grade with excellent corrosion resistance and formability
- 304L (UNS S30403) — Low-carbon variant suitable for welded applications and cryogenic service
- 316L (UNS S31603) — Molybdenum-bearing grade with superior resistance to chloride-induced pitting and crevice corrosion
- 321 (UNS S32100) — Stabilized grade with titanium addition for enhanced resistance to sensitization
Key Mechanical and Thermal Properties (Grade 304L Reference)
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength (0.2% offset): ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40%
- Thermal Conductivity: 16.3 W/(m·K) at 100°C
- Specific Heat Capacity: 500 J/(kg·K)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /K (20–100°C)
- Operating Temperature Range: −196°C to +870°C
- Density: 7.93 g/cm³
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ9.52 mm – Φ50.80 mm (⅜" – 2") | ASTM A312 / ASME SA312 |
| Wall Thickness | 0.50 mm – 3.00 mm | ASTM A312 |
| Coil Winding Diameter | Φ50 mm – Φ300 mm (configurable) | Customer Specification |
| Coil Pitch (Helical Spacing) | 5 mm – 30 mm (adjustable per application) | Customer Specification |
| Coil Length (Developed Length) | 5 m – 100 m per coil | — |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated (P&P) / Mirror Polish | ASTM A967 |
| Surface Roughness (Ra) | ≤ 0.8 μm (BA finish); ≤ 0.4 μm (polished) | ISO 1302 |
| Manufacturing Method | Seamless / Welded (AWT — Automatic Welded Tube) | ASTM A312 / GB/T 12771 |
| End Treatment | Plain / Beveled / Threaded / Flanged | ASME B16.11 / ASME B16.5 |
| Pressure Rating | Up to 4.0 MPa (design dependent on wall thickness) | ASME Section VIII |
| Packaging | Wooden pallet with moisture-proof wrapping; foam-protected coil ends | ISO 4180 |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Virgin stainless steel wire rod or seamless tube blanks are sourced from certified mill producers. Incoming materials undergo spectroscopic verification (PMI — Positive Material Identification) to confirm chemical composition compliance.
- Tubing Forming: Seamless tubes are produced via hot-rolling and cold-pilger processes, or welded tubes are formed through AWT (Automatic Welded Tube) technology with precision resistance welding.
- Heat Treatment: Solution annealing is performed at 1050°C – 1100°C followed by rapid water quenching to achieve a fully austenitic microstructure with maximum corrosion resistance.
- Precision Sizing: Cold drawing or cold rolling reduces the tube to exact outer diameter and wall thickness specifications with tolerances of ±0.05 mm.
- Coil Winding: The straight tube is helically wound onto a precision mandrel using CNC-controlled coiling machinery. Winding tension, pitch, and diameter are controlled to within ±1.0 mm tolerance to ensure uniform ice formation characteristics.
- Surface Finishing: Bright annealing in a controlled hydrogen atmosphere eliminates oxidation scale and restores a clean, low-carbon surface. Alternatively, pickling and passivation (P&P) treatment removes surface contaminants and forms a protective chromium oxide layer.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing, dimensional verification, surface inspection, and visual examination. Non-destructive testing (NDT) methods including eddy current testing (ECT) and dye penetrant inspection (DPI) are applied as required.
- Protective Packaging: Finished coils are wrapped in moisture-barrier film, padded at coil ends with protective foam, and secured on export-grade wooden pallets for safe transportation.
Applications
The Stainless Steel Coil Tube for Ice Storage Systems is engineered for demanding thermal energy management applications:
- Ice Storage Thermal Energy Systems (Ice Storage Cooling Devices): Primary application — the coil tube serves as the heat exchange medium through which a low-temperature brine or refrigerant flows, causing controlled ice accretion on the outer tube surface. During peak cooling demand, the stored ice melts to provide cooling capacity.
- Commercial Building HVAC Systems: Peak-shaving applications in shopping malls, office buildings, and hospitals to reduce electricity demand charges by utilizing off-peak ice storage.
- Industrial Process Cooling: Temperature-controlled cooling for manufacturing processes requiring stable low-temperature supply, such as food processing, pharmaceutical manufacturing, and chemical production.
- Cryogenic Applications: The austenitic stainless steel construction provides reliable performance at cryogenic temperatures down to −196°C, suitable for liquefied natural gas (LNG) pre-cooling and low-temperature storage applications.
- Marine and Offshore Cooling: Corrosion-resistant coil tubes for shipboard refrigeration and offshore platform thermal management systems.
- Food and Beverage Industry: Rapid chilling of beverages and dairy products using ice storage systems with food-grade stainless steel coil tubes (316L grade for enhanced corrosion resistance).
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification demonstrating environmental responsibility |
| ASME SA213 / SA312 | Pressure vessel and heat exchanger tubing material standards |
| EN 10216-5 | European standard for tubular products for heat exchangers |
| GB/T 12771 | Chinese National Standard for seamless stainless steel tubes |
| ASTM A967 | Standard practice for chemical cleaning and passivation of stainless steel |
| Mill Test Certificate (MTC) | EN 10204 3.1 type material certificate with full chemical and mechanical test data |
| Third-Party Inspection | Available upon request — SGS, BV, or TÜV inspection for batch verification |
Unique Selling Points
- Optimized Helical Geometry for Enhanced Heat Transfer: The coil tube's helical design inherently induces secondary Dean flow effects, which disrupt the thermal boundary layer and increase the convective heat transfer coefficient by up to 200% compared to straight tubes of equivalent cross-section, resulting in faster and more uniform ice formation.
- Superior Low-Temperature Performance: Austenitic stainless steel maintains full ductility and mechanical integrity at cryogenic temperatures without risk of brittle fracture, ensuring reliable long-term operation in ice storage systems cycling between −15°C and +5°C.
- Outstanding Corrosion Resistance: The passive chromium oxide film (Cr₂O₃) provides exceptional resistance to corrosion from brine solutions (CaCl₂, MgCl₂), glycol-based heat transfer fluids, and ambient atmospheric conditions, ensuring a service life exceeding 25 years.
- Food-Grade Compliance: Available in 316L grade meeting FDA 21 CFR 178.3010 and EU Regulation 1935/2004 requirements for food contact applications.
- Customizable Coil Configuration: Winding diameter, pitch, and developed length are fully customizable to match specific ice storage tank geometries and thermal load requirements, enabling optimal system integration.
- Academic-Validated Design: The coil tube design has been extensively researched in peer-reviewed literature on ice formation processes in ice storage devices, providing empirically validated performance data for system designers and engineers.
Technical Notes
Design Consideration: In ice storage applications, the coil tube pitch must be carefully selected to balance heat transfer efficiency against ice layer thickness. Excessively tight pitch (≤ 8 mm) may lead to uneven ice distribution and potential blockage, while excessive pitch (≥ 25 mm) reduces the effective heat exchange area per unit volume. An optimal pitch of 12–18 mm is generally recommended for brine-based ice storage systems operating at −8°C to −12°C inlet temperature.
Material Selection Guidance: For systems utilizing calcium chloride (CaCl₂) brine as the refrigerant medium, 316L grade is strongly recommended due to its superior resistance to chloride-induced pitting corrosion. For glycol-based systems or air-cooled applications, 304L grade provides adequate performance at reduced cost.