Stainless Steel Coil Tube (Coiltube) — Thermal Energy Storage & Ice-Melting Cooling System
Wenzhou Jixing Metal Materials Co., Ltd. presents its premium-grade Stainless Steel Coil Tube (Coiltube), engineered for high-performance thermal energy storage applications, particularly in ice-storage cooling systems utilizing external ice-melting heat extraction methodologies. This product series is designed to meet the rigorous demands of modern HVAC, refrigeration, and thermal management industries, offering superior thermal conductivity, corrosion resistance, and mechanical durability.
Product Overview
The Stainless Steel Coil Tube is a precision-wound tubular component manufactured from high-grade austenitic stainless steel alloys. It serves as a critical heat exchange element within ice-storage tanks, where it facilitates the transfer of thermal energy between the stored ice mass and the circulating refrigerant or secondary coolant fluid. The coil tube geometry maximizes the surface-area-to-volume ratio, enabling efficient heat absorption during the ice-melting phase and rapid heat rejection during the freezing phase.
In applications involving Thermal Conductive Plastic Coil Tube Ice Storage Tanks with External Ice Melting Cooling Extraction, the stainless steel coil tube operates in a dynamic thermal cycle, absorbing latent heat from the melting ice while delivering chilled fluid to the load. The dynamic characteristics of such systems—including startup transients, steady-state operation, and shutdown recovery—are critically dependent on the material properties and geometric configuration of the coil tube.
Material & Properties
Base Alloy Composition
The coil tube is fabricated from Austenitic Stainless Steel, predominantly grades 304 (UNS S30408) and 316 (UNS S31603), selected for their exceptional combination of thermal conductivity, corrosion resistance, and formability at both ambient and sub-zero temperatures.
- Grade 304 (UNS S30408): Standard austenitic grade with approximately 18% Chromium (Cr) and 8% Nickel (Ni). Suitable for general-purpose thermal applications in non-aggressive environments.
- Grade 316 (UNS S31603): Enhanced austenitic grade containing 2–3% Molybdenum (Mo), providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- Grade 321 (UNS S32103): Titanium-stabilized austenitic grade for applications requiring resistance to intergranular corrosion at elevated temperatures.
Key Physical & Thermal Properties
- Thermal Conductivity: 14–16 W/(m·K) at 20°C (typical for austenitic stainless steel)
- Specific Heat Capacity: 450–500 J/(kg·K)
- Coefficient of Thermal Expansion: 16–17.5 × 10⁻⁶ /K
- Density: 7,900–8,000 kg/m³
- Operating Temperature Range: −196°C to +870°C (Grade 304); −196°C to +870°C (Grade 316)
- Corrosion Resistance: Excellent resistance to atmospheric, acidic, and alkaline media; superior chloride resistance with Mo-bearing grades
- Mechanical Strength: Tensile strength ≥ 515 MPa (annealed condition); Yield strength ≥ 205 MPa
- Magnetic Property: Non-magnetic in annealed condition (permeability < 1.05)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm (customizable) | ASTM A213 / GB/T 14976 |
| Wall Thickness | 0.5 mm – 2.0 mm (tolerance ±10%) | ASTM A213 / GB/T 14976 |
| Coil Winding Diameter | 100 mm – 600 mm (customizable per tank geometry) | Customer-specific / ISO 286 |
| Coil Length | Up to 50 m continuous length per coil assembly | — |
| Surface Finish | Bright annealed (BA), 2B finish, or electropolished (Ra ≤ 0.4 μm) | ASTM A240 / GB/T 3280 |
| Material Grade | SUS304, SUS316, SUS321, SUS316L (UNS S31603) | ASTM A213 / JIS G4305 |
| Welding Method | TIG (GTAW) seamless welding; orbital welding for end connections | ASME BPVC Section VIII / ISO 3959 |
| Hydrostatic Test Pressure | 3.0 – 6.0 MPa (depending on OD and wall thickness) | ASTM A213 / EN 10216 |
| Maximum Design Pressure | 2.5 MPa (typical for thermal storage applications) | ASME BPVC Section VIII Div. 1 |
| Heat Exchanger Efficiency | ≥ 92% (NTU-effectiveness method, ice-melting cycle) | ASHRAE Handbook — Heat Transfer |
| Ice Storage Density | 150 – 250 kWh/m³ (latent heat storage capacity) | ASHRAE Handbook — HVAC Systems |
| Service Life | ≥ 25 years (design life under normal operating conditions) | — |
Manufacturing Process
1. Raw Material Selection & Incoming Inspection
Hot-rolled stainless steel coils conforming to ASTM A213/A213M or GB/T 14976 are procured from certified mills. Each incoming lot undergoes spectroscopic analysis (OES) for chemical composition verification, tensile testing, and hardness measurement to ensure compliance with the specified grade requirements.
2. Cold Drawing & Sizing
The raw coil is cold-drawn through a series of dies to achieve the target outer diameter and wall thickness. This process work-hardens the material, improving mechanical strength and dimensional precision. Intermediate annealing cycles are performed to relieve residual stresses and restore ductility when required.
3. Surface Treatment
Depending on the application, tubes undergo one of the following surface treatments:
- Bright Annealing (BA): Heating in a reducing atmosphere to produce a clean, reflective surface with minimal oxide scale.
- 2B Finish: Cold-rolled and annealed for a uniform matte appearance.
- Electropolishing: Electrochemical dissolution to achieve Ra ≤ 0.4 μm surface roughness, critical for hygienic and high-efficiency heat transfer applications.
- Pickling & Passivation: Removal of mill scale and formation of a protective chromium oxide layer (Cr₂O₃) for enhanced corrosion resistance.
4. Precision Coiling & Winding
Using CNC-controlled coiling machinery, the straight tube is wound into a helical coil geometry with precise pitch, diameter, and number of turns. The winding parameters are optimized based on the thermal performance requirements of the target ice-storage tank, including:
- Coil pitch (spacing between adjacent turns) to balance heat transfer area against flow resistance.
- Winding diameter to ensure uniform ice formation and melting throughout the tank cross-section.
- Number of turns and total coil length to achieve the desired thermal storage capacity.
5. End Preparation & Welding
Tube ends are beveled and prepared for orbital TIG (Tungsten Inert Gas) welding. End connections are fabricated using either:
- Socket Welding: For high-pressure connections with ferrule-type fittings.
- Butt Welding: For seamless integration into manifold headers.
- Threaded Connections: For modular installation and maintenance access.
6. Quality Inspection & Testing
Each coil tube assembly undergoes comprehensive quality verification:
- Dimensional Inspection: CMM (Coordinate Measuring Machine) verification of OD, wall thickness, coil diameter, and pitch.
- Hydrostatic Pressure Testing: Full-length testing at 1.5× design pressure with hold time ≥ 30 seconds.
- Non-Destructive Testing (NDT): Eddy current (ET) inspection for surface and near-surface defects; ultrasonic testing (UT) for volumetric integrity.
- Corrosion Testing: Salt spray testing (ASTM B117) for ≥ 500 hours without pitting or red rust formation.
- Thermal Cycling Test: 1,000+ freeze-thaw cycles to verify fatigue resistance and dimensional stability.
7. Packaging & Dispatch
Completed coil assemblies are packaged in moisture-proof wrapping with desiccant inserts, secured on wooden pallets or custom crating. Each shipment includes a Certificate of Conformity (CoC), Material Test Report (MTR), and dimensional inspection report.
Applications
1. Ice-Storage Cooling Systems (Thermal Energy Storage)
The primary application domain for this coil tube product is in Ice Storage Air Conditioning Systems, where the coil tube is installed within insulated ice-storage tanks. During off-peak hours, the system freezes water around the coil to store latent heat. During peak demand periods, the coil tube extracts cooling energy from the melting ice, shifting peak electrical load and reducing operational costs by 30–50%.
2. Dynamic External Ice-Melting Cooling Extraction
As studied in the referenced experimental work on Dynamic Characteristics of External Ice Melting Cooling Extraction from Thermal Conductive Plastic Coil Tube Ice Storage Tanks, the stainless steel coil tube serves as the heat exchange interface in systems where ice is formed externally on the coil surface. The dynamic thermal response—including startup lag, steady-state cooling capacity, and recovery time after load interruption—is characterized by the thermal mass, geometry, and material conductivity of the coil tube.
3. District Cooling Networks
Stainless steel coil tubes are deployed in district cooling infrastructure to provide centralized thermal storage, enabling load leveling and demand response across multiple connected buildings.
4. Industrial Process Cooling
Applications include pharmaceutical cold-chain storage, food processing refrigeration, chemical process cooling, and semiconductor manufacturing temperature control.
5. Building Energy Management Systems (BEMS)
Integration with smart building control systems enables automated scheduling of ice-making and ice-melting cycles, optimizing energy consumption based on real-time electricity pricing and building load profiles.
Quality Certifications & Standards Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- CE Marking — Conformity with European Machinery Directive (2006/42/EC)
- ASME Stamp — Pressure Vessel and Piping Components (where applicable)
- GB/T Standards Compliance — Chinese National Standards for stainless steel tubes (GB/T 14976, GB/T 3280, GB/T 13296)
- ASTM Standards Compliance — ASTM A213/A213M, ASTM A269/A269M, ASTM A240/A240M
- JIS Standards Compliance — JIS G4305 (for Japanese market exports)
- EN Standards Compliance — EN 10216-5 (welded austenitic stainless steel tubes)
- NSF/ANSI 61 — Drinking Water System Components (for potable water applications)
Unique Selling Points
- Superior Thermal Performance: Optimized coil geometry and high-conductivity austenitic stainless steel deliver heat exchange efficiency exceeding 92% in ice-melting cooling cycles, outperforming conventional copper coil alternatives by 15–20% in latent heat extraction rate.
- Exceptional Corrosion Resistance: Unlike copper or carbon steel coils, the austenitic stainless steel construction resists degradation in glycol-based brine solutions, chloride-containing water, and humid industrial atmospheres, eliminating the risk of galvanic corrosion in mixed-material systems.
- Long Service Life: Designed for ≥ 25 years of continuous operation with minimal maintenance, significantly reducing total cost of ownership (TCO) compared to conventional coil materials.
- Customizable Geometry: CNC-controlled coiling allows precise customization of coil diameter, pitch, and length to match specific tank configurations and thermal performance requirements.
- Food-Grade & Hygienic Options: Electropolished surface finish (Ra ≤ 0.4 μm) available for pharmaceutical, food & beverage, and semiconductor applications requiring strict hygiene standards.
- Full Traceability: Each coil tube is accompanied by a complete Material Test Report (MTR) with heat-number traceability, ensuring full supply chain transparency and regulatory compliance.
- Dynamic Thermal Characterization: Performance data validated through experimental studies on ice-melting cooling extraction dynamics, providing engineering confidence in system design and operational forecasting.
Conclusion
Wenzhou Jixing Metal Materials Co., Ltd. delivers a world-class Stainless Steel Coil Tube product line that combines metallurgical excellence, precision manufacturing, and application-specific thermal engineering. Whether deployed in commercial ice-storage air conditioning systems, district cooling networks, or specialized industrial thermal management applications, this product series represents the state-of-the-art in latent heat energy storage technology, offering unmatched reliability, efficiency, and longevity.