Stainless Steel Coil Tube — Dish Concentrating Solar Heat Absorption Application
Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing product specifically designed for high-temperature heat absorption applications, including dish concentrating solar (Dish Concentrating Solar Collector, DCSC) systems, industrial heat exchangers, and process piping. The coil tube geometry provides an extended heat transfer surface area within a compact volume, making it an optimal solution for thermal energy capture and fluid circulation in concentrated solar thermal (Concentrated Solar Power, CSP) installations.
This product leverages the superior corrosion resistance, thermal stability, and mechanical integrity of austenitic stainless steel grades, ensuring long service life under cyclic thermal loading conditions encountered in solar thermal systems. The coil tube undergoes rigorous dimensional control and heat treatment to meet exacting performance requirements for high-temperature fluid absorption and distribution.
Material & Properties
Base Material Grades
- 304 (UNS S30408) — General-purpose austenitic stainless steel offering excellent corrosion resistance and formability; suitable for moderate-temperature applications up to approximately 870°C.
- 316L (UNS S31603) — Low-carbon austenitic grade with added molybdenum (2–3%) providing enhanced resistance to pitting and crevice corrosion; recommended for chloride-containing environments and higher-temperature service.
- 321 (UNS S32100) — Titanium-stabilized austenitic grade with superior resistance to intergranular corrosion and thermal cycling fatigue; preferred for sustained high-temperature applications exceeding 600°C.
- 310S (UNS S31008) — High-nickel austenitic grade with exceptional oxidation resistance; suitable for extreme-temperature environments up to 1150°C in oxidizing atmospheres.
Key Physical and Mechanical Properties (Typical for Grade 304)
- Density: 8.0 g/cm³
- Thermal Conductivity (at 20°C): 16.3 W/(m·K)
- Specific Heat Capacity (at 20°C): 500 J/(kg·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /K
- Yield Strength (Annealed): ≥ 205 MPa
- Tensile Strength (Annealed): 515–730 MPa
- Maximum Service Temperature: 870°C (304); 1150°C (310S)
Specifications
| Parameter | Specification / Range |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.5 mm – 3.0 mm | Coil Mean Diameter | 50 mm – 500 mm |
| Coil Pitch (Turn Spacing) | 10 mm – 80 mm (adjustable per design) |
| Coil Length (Developed) | 3 m – 100 m (customizable) |
| Surface Finish | Ba&F (2B), No. 4 Brushed, Polished, or Pickled & Passivated |
| Surface Roughness (Ra) | ≤ 0.8 μm (polished); ≤ 1.6 μm (2B finish) |
| Dimensional Tolerance (OD) | ±0.05 mm – ±0.15 mm (per ISO 6508) |
| Dimensional Tolerance (Wall) | ±10% of nominal |
| Maximum Operating Pressure | Up to 4.0 MPa (design-dependent) |
| Maximum Operating Temperature | Up to 870°C (304); 1150°C (310S) |
| Heat Treatment Condition | Solution Annealed (1050–1150°C, water quench) |
| End Connections | Plain end, Threaded, Flanged, or Soldered (per customer requirement) |
| Standard References | ASTM A269, ASTM A213, EN 10216-5, GB/T 12771 |
Manufacturing Process
- Raw Material Procurement and Inspection: High-purity stainless steel seamless tubes or welded tubes are sourced from certified mills. Incoming material undergoes spectroscopic analysis (Optical Emission Spectroscopy, OES) and mechanical property verification to confirm grade compliance.
- Tube Straightening and Cutting: The straight tube is precisely straightened to eliminate residual curvature, then cut to the required developed length using high-precision sawing or laser cutting equipment.
- Coiling Forming: The straight tube is fed into a multi-roller coiling machine or CNC-controlled bending system. The forming process employs progressive die sets to achieve the target coil mean diameter and pitch with controlled springback compensation. Critical process parameters include:
- Bending die radius (typically ≥ 3× tube OD to prevent ovalization)
- Forming speed (controlled to avoid work hardening)
- Intermittent annealing (if required to relieve accumulated strain)
- Heat Treatment (Solution Annealing): After coiling, the assembly is solution annealed at 1050–1150°C followed by rapid quenching to restore full austenitic microstructure, relieve residual stresses, and ensure uniform mechanical properties throughout the coil.
- Pickling and Passivation: The coil tube is treated with a mixed acid solution (nitric acid/hydrofluoric acid blend) to remove oxide scale and surface contaminants. Subsequent passivation treatment forms a protective chromium oxide film, enhancing corrosion resistance.
- End Processing: Tube ends are deburred, beveled, and finished according to the specified connection type (threading, flanging, or plain end preparation).
- Quality Inspection: Final inspection includes:
- Dimensional measurement (OD, wall thickness, coil diameter, pitch) per ISO 6508
- Surface quality visual and magnification inspection
- Hydrostatic pressure testing (per ASTM A269, minimum 5.0 MPa for 10 seconds)
- Eddy current testing (for detection of internal/external discontinuities)
- Chemical composition verification (OES or wet chemical analysis)
Applications
Primary Application: Dish Concentrating Solar Collector (DCSC) Systems
Based on thermal absorption test and simulation studies (碟式聚光太阳能盘管吸热试验与模拟), the stainless steel coil tube serves as the primary heat receiver in dish-concentrating solar systems. The coiled geometry maximizes the heat transfer surface area exposed to concentrated solar flux while maintaining structural integrity under intense radiative and convective heat loads. Key performance characteristics in this application include:
- Effective absorption of concentrated solar radiation (concentration ratios of 500–2000×)
- Uniform temperature distribution along the coil length
- Compatibility with heat transfer fluids including synthetic thermal oils, molten salts, and pressurized water
- Resistance to thermal fatigue from daily start-stop cycling
Additional Industrial Applications
- Industrial Heat Exchangers: Spiral and coil heat exchangers for process heating, cooling, and condensation services in chemical, petrochemical, and pharmaceutical industries.
- Steam Generators and Boilers: Coiled heating elements for compact boiler designs and waste heat recovery systems.
- Refrigeration and HVAC: Condenser and evaporator coil tubes for commercial refrigeration and air conditioning systems.
- Food Processing Equipment: Sanitary-grade coil tubes for pasteurization, sterilization, and CIP (Clean-in-Place) systems.
- Geothermal Energy Systems: Heat exchange coils for geothermal fluid extraction and utilization.
Quality Certifications and Standards Compliance
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health and Safety Management |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance (where applicable) |
| ASTM A269 / A213 | Material and product specification compliance |
| EN 10216-5 | European standard for stainless steel tubes |
| GB/T 12771 | Chinese national standard for seamless stainless steel tubes |
Unique Selling Points
- Specialized Solar Thermal Design: Coil tube geometry engineered specifically for concentrated solar heat absorption, validated through experimental testing and computational fluid dynamics (CFD) simulation studies.
- Precision Dimensional Control: CNC-driven coiling ensures consistent coil pitch, diameter, and tube integrity with minimal ovalization (typically < 5% of nominal OD).
- Multi-Grade Material Availability: Full range of austenitic stainless steel grades (304, 316L, 321, 310S) to match specific temperature, corrosion, and mechanical requirements.
- Custom Configuration Capability: Tailored coil dimensions, lengths, end treatments, and surface finishes to meet individual project specifications.
- Comprehensive Quality Assurance: Multi-stage inspection protocol including hydrostatic testing, eddy current testing, and dimensional verification at every production stage.
- Proven Thermal Cycling Durability: Material selection and heat treatment optimized for resistance to thermal fatigue under repeated heating and cooling cycles inherent in solar thermal operation.
Supplier Note: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司) maintains an extensive inventory of stainless steel coil tubes across multiple grades and specifications. Custom manufacturing and engineering consultation services are available for specialized solar thermal and industrial heat transfer applications. Technical data sheets, material test certificates (MTC), and third-party inspection reports are provided upon request.