Stainless Steel Coil Tube (盘管 / Coiltube) — Model Series 694
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (Wenzhou, Zhejiang Province, China)
Product Category: Literature-Learning Series — Double Helical Coil Tube for Thermal Energy Storage Systems
1. Product Overview
The Stainless Steel Coil Tube (Model Series 694) is a precision-engineered coiled tubing product designed primarily for thermal energy storage and heat exchange applications. Drawing upon advanced research findings from the experimental study "Cascaded Air Source Heat Pump Double Helical Coil Tank Thermal Storage and Discharge Characteristics", this product incorporates optimized helical geometry to maximize heat transfer efficiency within compact volumetric constraints.
Wenzhou Jixing Metal Materials Co., Ltd. manufactures these coil tubes using high-grade austenitic stainless steel, delivering superior corrosion resistance, mechanical durability, and thermal conductivity. The double helical configuration enables enhanced surface-area-to-volume ratios, making these coil tubes particularly suitable for cascaded air source heat pump (CAHP) systems, industrial heat recovery units, and renewable energy storage applications.
2. Material & Properties
2.1 Base Material
- Primary Grades: SUS304 (UNS S30400), SUS316L (UNS S31603), SUS321 (UNS S32100)
- Composition (SUS304): Cr 18.0–20.0%, Ni 8.0–10.5%, Mn ≤2.0%, Si ≤0.75%, C ≤0.08%
- Composition (SUS316L): Cr 16.5–18.5%, Ni 10.0–14.0%, Mo 2.0–3.0%, C ≤0.03%
2.2 Mechanical Properties
- Tensile Strength: ≥520 MPa (SUS304), ≥515 MPa (SUS316L)
- Yield Strength: ≥205 MPa (SUS304), ≥170 MPa (SUS316L)
- Elongation: ≥40% (SUS304), ≥35% (SUS316L)
- Hardenability: Non-magnetic in annealed condition; work-hardening capable
2.3 Thermal Properties
- Thermal Conductivity (25°C): 16.3 W/(m·K) (SUS304), 14.6 W/(m·K) (SUS316L)
- Operating Temperature Range: −196°C to +870°C (continuous service)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C
- Specific Heat Capacity: 500 J/(kg·K)
2.4 Corrosion Resistance
- Excellent resistance to atmospheric, fresh water, and mild chemical environments
- SUS316L grade offers superior pitting and crevice corrosion resistance in chloride-containing media
- SUS321 grade provides enhanced resistance to intergranular corrosion and high-temperature oxidation
- Passive film (Cr₂O₃) self-healing capability in oxidizing environments
3. Technical Specifications
| Parameter | Specification | Unit | Standard Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 – 108.0 (customizable) | mm | GB/T 14976, ASTM A269 |
| Wall Thickness (WT) | 0.5 – 6.0 | mm | GB/T 14976, ASTM A269 |
| Coil Diameter (CD) | 50 – 500 | mm | Custom per application |
| Coil Length (per spool) | 10 – 200 | m | Custom per application |
| Helical Pitch | 15 – 150 | mm | Custom per application |
| Number of Helices | 1 – 4 (double helix configuration available) | — | Per experimental optimization |
| Surface Finish | 2B / BA (Bright Annealed) / Electropolished (Ra ≤ 0.4 μm) | — | GB/T 12771 |
| End Condition | Plain / Beveled / Threaded / Flanged | — | Custom per application |
| Tolerance (OD) | ±0.1 mm (precision grade) | mm | ISO 4287 |
| Tolerance (WT) | ±10% | — | ISO 4287 |
| Delivery Condition | Annealed / Solution Treated | — | ASTM A269 |
| Maximum Operating Pressure | Up to 4.0 MPa (depending on OD and WT) | MPa | ASME B31.3 |
| Maximum Flow Velocity | Up to 15 m/s | m/s | ASME B31.3 |
4. Manufacturing Process
4.1 Process Flow
- Material Selection & Incoming Inspection: Raw stainless steel strip or seamless tube stock is selected per grade specification. Incoming materials undergo spectroscopic analysis (OES), dimensional verification, and surface quality inspection.
- Coil Forming (Cold Bending): Precision cold-bending machines with CNC control form the straight tube stock into the desired helical coil geometry. The double helix configuration is achieved through synchronized dual-axis bending mechanisms, ensuring consistent pitch and radius tolerances.
- Heat Treatment (Annealing): Formed coils undergo solution annealing at 1010–1150°C followed by rapid air or water quenching to restore full austenitic structure, relieve residual stresses, and ensure non-magnetic properties.
- Surface Treatment: Optional electropolishing (EP) removes up to 5–25 μm of surface layer, achieving a mirror-like finish (Ra ≤ 0.4 μm) and enhancing passive film integrity. Pickling and passivation are performed to remove scale and restore corrosion resistance.
- End Processing: Tube ends are cut to length, deburred, and optionally beveled, threaded, or fitted with flanges per customer requirements.
- Final Inspection & Testing: Each coil undergoes hydrostatic pressure testing (1.5× maximum operating pressure), dimensional measurement, visual inspection, and optional eddy current testing for wall thickness verification.
- Coiling & Packaging: Finished coil tubes are wound onto protective spools with anti-condensation packaging and labeled with traceability documentation.
4.2 Double Helix Optimization
Based on experimental research into cascaded air source heat pump double helical coil tank thermal storage and discharge characteristics, the double helix configuration provides the following engineering advantages:
- Increased Heat Transfer Area: The dual helix arrangement increases effective heat exchange surface area by 60–80% compared to single-helix configurations of equivalent coil diameter.
- Improved Thermal Uniformity: The staggered helix arrangement promotes more uniform temperature distribution within the storage tank, reducing thermal stratification losses.
- Enhanced Flow Distribution: Dual inlet/outlet configurations allow balanced fluid distribution, minimizing dead zones and improving heat recovery efficiency.
- Compact Design: Achieves higher thermal storage density in reduced spatial footprint, critical for modular and space-constrained installations.
5. Applications
5.1 Primary Applications
- Cascaded Air Source Heat Pump Systems: Thermal energy storage and heat recovery in multi-stage heat pump configurations
- Industrial Heat Recovery: Waste heat capture and redistribution in manufacturing processes
- Geothermal Systems: Heat exchange coils for ground-source and water-source heat pumps
- Refrigeration & Air Conditioning: Evaporator and condenser coils for commercial HVAC systems
- Food & Beverage Processing: Sanitary heat exchangers for pasteurization, sterilization, and thermal processing
- Pharmaceutical Manufacturing: GMP-compliant heat transfer systems requiring high purity and corrosion resistance
- Marine & Offshore: Seawater heat exchange and desalination systems
- Renewable Energy Storage: Solar thermal energy storage tanks and buffer vessels
5.2 System Integration
These coil tubes are designed for seamless integration into shell-and-coil heat exchangers, vertical storage tanks, and modular heat pump units. The standardized connection interfaces and customizable end conditions facilitate rapid system assembly and commissioning.
6. Quality Certifications & Standards Compliance
6.1 Quality Management
- ISO 9001:2015: Quality Management System certification for consistent product quality and process control
- ISO 14001:2015: Environmental Management System for sustainable manufacturing practices
- ISO 45001:2018: Occupational Health and Safety Management System
6.2 Product Standards
- GB/T 14976: Chinese national standard for cold-rolled stainless steel seamless tubes
- GB/T 12771: Chinese national standard for welded stainless steel tubes
- ASTM A269/A269M: American standard for seamless austenitic stainless steel tubes for chemical and similar severe service
- ASTM A270/A270M: American standard for welded austenitic stainless steel tubes for chemical and similar severe service
- EN 10217-7: European standard for austenitic stainless steel seamless tubes for technical purposes
- JIS G3446: Japanese industrial standard for austenitic stainless steel tubes
6.3 Testing & Verification
- Hydrostatic pressure testing per ASME B31.3
- Chemical composition verification via Optical Emission Spectroscopy (OES)
- Mechanical property testing (tensile, hardness) per ASTM E8/E10
- Corrosion testing (pitting resistance number, PREN) per ASTM G48
- Non-destructive testing (eddy current, ultrasonic) for wall integrity
- Full traceability from raw material mill certificates to finished product documentation
7. Unique Selling Points
- Research-Driven Design: Product geometry optimized based on published experimental research into double helical coil thermal storage characteristics, ensuring performance validated by academic investigation.
- Double Helix Configuration: Proprietary dual-helix forming capability delivers superior heat transfer efficiency and thermal uniformity over conventional single-coil designs.
- Full Customization: Flexible manufacturing capability accommodates custom dimensions, coil configurations, surface finishes, and end conditions to meet specific application requirements.
- Multi-Grade Availability: Selection across SUS304, SUS316L, and SUS321 grades ensures optimal material matching for diverse operating environments and corrosion challenges.
- End-to-End Traceability: Complete material traceability from mill to finished product, with comprehensive documentation supporting regulatory compliance and quality assurance.
- Integrated System Support: Technical consulting services for system integration, thermal performance modeling, and installation guidance to maximize operational efficiency.
8. Technical Support & Documentation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical documentation including material test certificates (MTC), dimensional inspection reports, heat treatment records, and application-specific performance data. Engineering support is available for system design consultation, thermal performance simulation, and installation guidance.
Note: All specifications are subject to change based on evolving material availability and manufacturing process improvements. Customers are advised to confirm final specifications with the manufacturer prior to procurement. Custom orders require minimum order quantity (MOQ) negotiation and lead time confirmation.