Stainless Steel Coil Tube — Thermal Energy Storage Grade (Coiltube)
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tube product formed into a helical coil configuration, designed primarily for thermal energy storage applications including ice storage tanks (Ice Storage Accumulation Systems), district heating networks, heat exchangers, and refrigeration systems. The coil tube leverages the inherent thermal conductivity of austenitic stainless steel combined with the geometric advantages of a helical arrangement to maximize heat transfer surface area within a compact volume. This product is particularly suited for latent heat thermal energy storage (LHTES) systems where phase-change materials (PCM), such as water-ice systems, are employed for peak-load shifting and energy efficiency optimization.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, conforming to international material standards. The primary grades utilized include:
- SUS304 / AISI 304 / ASTM A213 TP304 — General-purpose grade with excellent corrosion resistance and formability
- SUS316L / AISI 316L / ASTM A213 TP316L — Enhanced molybdenum content for superior resistance to pitting and crevice corrosion in aggressive environments
- SUS321 / AISI 321 / ASTM A213 TP321 — Titanium-stabilized grade for elevated-temperature service
Key material properties include:
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, ensuring efficient heat dissipation during cooling and heating cycles
- Corrosion Resistance: High resistance to oxidation, chlorides, and acidic/alkaline media
- Mechanical Strength: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa (minimum)
- Operating Temperature Range: −196°C to +870°C, accommodating cryogenic ice storage to high-temperature district heating applications
- Surface Finish: Ra ≤ 0.8 μm (electropolished or passivated) to minimize fouling and biofilm formation
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ19.05 mm, Φ25.4 mm, Φ31.75 mm, Φ38.1 mm, Φ44.45 mm, Φ50.8 mm (customizable) |
| Wall Thickness | 0.8 mm – 3.0 mm (tolerance ±0.1 mm) |
| Coil Pitch | 25 mm – 150 mm (adjustable per design requirements) |
| Coil Diameter | Φ300 mm – Φ3000 mm (custom coil diameters available) |
| Tube Length per Coil | Up to 2000 m continuous (seamless configuration) |
| Material Grade | SUS304, SUS316L, SUS321, SUS310S |
| Applicable Standards | ASTM A213, ASTM A269, GB/T 12771, EN 10216-5, JIS G3459 |
| Surface Treatment | Passivated, Electropolished (Ra ≤ 0.4 μm), or Mill Finish |
| Pressure Rating | Up to 2.5 MPa (design dependent) |
| Packaging | Wooden crate or steel frame with moisture-proof wrapping |
| Minimum Order Quantity (MOQ) | 100 meters per coil assembly |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence:
- Hot Rolling / Cold Drawing: Billet steel is hot-rolled into seamless tubes, followed by cold drawing or cold rolling to achieve precise dimensional tolerances and enhanced mechanical properties.
- Solution Annealing: Tubes are solution-annealed at 1050°C – 1150°C in a protective atmosphere (nitrogen or argon) to restore full austenitic microstructure and relieve residual stresses.
- Coil Forming (Coiling): The straight tube is cold-formed into a helical coil using CNC-controlled coiling machinery. The forming process is optimized to prevent ovalization, wall thinning, and work hardening at the bend radii. A minimum bend radius of 3× OD is maintained.
- Welding & End Preparation: Inlet and outlet ends are prepared with precision-cut flat faces or fitted with threaded/flanged connections (ASME B16.5, EN 1092-2).
- Surface Treatment: Passivation (citric acid or nitric acid treatment) or electropolishing is performed to remove surface iron contamination and enhance the passive chromium oxide layer.
- Non-Destructive Testing (NDT): Each coil tube undergoes 100% eddy current testing (ECT) for internal and external defects, and hydrostatic pressure testing at 1.5× working pressure.
- Final Inspection & Packaging: Dimensional verification (OD, wall thickness, coil pitch, straightness) is performed per ISO 3951 sampling plans before protective packaging.
Applications
Primary Application: Ice Storage Thermal Energy Systems
Based on extensive research into coil-type ice storage tank thermal performance, the coil tube configuration offers significant advantages in latent heat energy storage systems. The helical coil arrangement provides:
- High heat transfer surface-to-volume ratio, enabling rapid ice formation (charging) and efficient heat release (discharging)
- Uniform temperature distribution within the storage tank, reducing thermal stratification losses
- Structural integrity under repeated freeze-thaw cycling (over 10,000 cycles demonstrated)
Additional Applications
- Industrial heat exchangers (shell-and-tube, plate-fin configurations)
- Refrigeration and air conditioning systems
- District heating and cooling distribution networks
- Chemical processing and pharmaceutical equipment (hygienic-grade 316L)
- Solar thermal energy collection and storage systems
- Food and beverage processing (dairy, brewing, beverage pasteurization)
- Marine and offshore heat exchange systems (316L grade for seawater service)
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- EN 10204 Type 3.1 — Material Test Certificate (independent third-party inspection)
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU)
- NSF/ANSI 61 — Drinking Water System Components (for potable water applications)
- GB/T 19001 — Chinese National Quality Management Standard
Each production batch is accompanied by a full material traceability record, including mill test certificates (MTC), chemical composition analysis, mechanical test reports, and dimensional inspection data. The company supports third-party inspection by agencies such as SGS, Bureau Veritas, and TÜV upon customer request.
Unique Selling Points
- Research-Driven Design: Product development informed by peer-reviewed studies on coil-type ice storage tank thermal performance, ensuring optimal geometry for heat transfer efficiency.
- Custom Coil Configuration: Flexible customization of coil diameter, pitch, tube length, and material grade to match specific system design parameters.
- Full-Length Seamless Construction: Eliminates longitudinal weld seams within the coil, reducing leak risk and enhancing fatigue resistance in cyclic thermal applications.
- Wide Temperature Envelope: Single material solution covering cryogenic (−196°C) to high-temperature (870°C) service, simplifying procurement and maintenance.
- Extended Service Life: Stainless steel coil tubes designed for 25+ years of service in aggressive thermal cycling environments without degradation of mechanical or thermal properties.