Stainless Steel Coil Tube for Solar Cavity High-Temperature Heat Collection (Product No. 842)
Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube), designated as Product No. 842 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product specifically designed for cavity-type high-temperature solar heat collectors (Solar Cavity High-Temperature Heat Collection Systems). This coil tube serves as the critical heat exchange and energy transfer component within concentrated solar thermal systems, where it absorbs, transports, and distributes high-temperature thermal energy generated by concentrated solar radiation.
Through rigorous numerical simulation and optimization of cavity-type high-temperature heat collection characteristics, Wenzhou Jixing has developed a coil tube geometry and material configuration that maximizes thermal absorption efficiency while minimizing radiative and convective heat losses. The product represents the culmination of advanced computational fluid dynamics (CFD) analysis, thermal radiation modeling, and metallurgical engineering expertise tailored specifically for extreme thermal environments.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of thermal stability, oxidation resistance, and mechanical integrity at elevated operating temperatures.
- Primary Material Grade: AISI 321 (UNS S32100) / AISI 310S (UNS S31008) — Chromium-Nickel-Titanium stabilized austenitic stainless steels
- Alternative Grades Available: AISI 316L (UNS S31603), AISI 304L (UNS S30403)
- Chromium Content (Cr): 19%–27% (provides superior oxidation and corrosion resistance)
- Nickel Content (Ni): 9%–35% (ensures austenitic microstructure stability at high temperatures)
- Maximum Continuous Operating Temperature: Up to 1150°C (2092°F) for Grade 310S; up to 870°C (1598°F) for Grade 321
- Thermal Conductivity: 15–30 W/(m·K) at operating temperatures
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C
- Surface Finish: Electropolished or passivated (Ra ≤ 0.4 μm) to minimize radiative heat loss and enhance absorptance when coated
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion (IGC) under high-temperature solar thermal conditions
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Product Designation | No. 842 — Coil Tube for Solar Cavity Collector | — |
| Outer Diameter (OD) | 8 – 108 (customizable) | mm |
| Wall Thickness (WT) | 0.5 – 5.0 (customizable) | mm |
| Coil Inner Diameter (CID) | 50 – 600 (customizable) | mm |
| Coil Length / Total Uncoiled Length | Up to 10,000 (continuous) | m |
| Coil Pitch / Spacing | 1.2 × OD – 2.5 × OD (optimized for heat transfer) | — |
| Material Grade | AISI 321 / 310S / 316L / 304L | — |
| Manufacturing Standard | ASTM A213 / ASTM A269 / GB/T 12771 | — |
| End Treatment | Plain end, beveled end, threaded, or flanged | — |
| Tolerance (OD) | ±0.05 – ±0.10 | mm |
| Tolerance (WT) | ±10% | — |
| Surface Coating (Optional) | Selective absorber coating (e.g., Al₂O₃, CrN, TiN) for enhanced solar absorptance (α ≥ 0.95) and low emittance (ε ≤ 0.10) | — |
| Maximum Operating Pressure | Up to 16 MPa (design-dependent) | MPa |
| Heat Collection Efficiency (System-Level) | ≥ 65% (optimized cavity configuration) | % |
| Operating Temperature Range | 200°C – 1100°C (depending on grade) | °C |
Manufacturing Process
The production of the No. 842 stainless steel coil tube follows a rigorously controlled multi-stage manufacturing process designed to ensure dimensional precision, microstructural homogeneity, and optimal thermal performance:
- Raw Material Selection and Inspection: Virgin stainless steel strip or seamless tube stock is sourced from certified mills (e.g., Outokumpu, POSCO, Tsingshan). Each batch undergoes spectroscopic analysis (OES) and mechanical property verification to confirm compliance with the specified chemical composition and tensile strength requirements.
- Pipe Forming / Strip Rolling: For welded coil tubes, precision cold-rolled stainless steel strip is formed into a tubular shape via roll-forming or induction-welded seam joining. For seamless variants, hot-rolled or cold-drawn seamless tube is used.
- Coil Winding / Spooling: The formed tube is precisely wound into the required coil geometry using CNC-controlled coiling equipment. The coil pitch, inner diameter, and total length are calibrated to match the optimized thermal hydraulic configuration derived from CFD simulation studies of the cavity-type heat collector.
- Heat Treatment (Solution Annealing): The coil tube undergoes solution annealing at 1050°C–1150°C followed by rapid water quenching to dissolve carbides, restore full austenitic microstructure, and eliminate residual stresses introduced during cold forming.
- Pickling and Passivation: The surface is treated with a mixed acid solution (HNO₃/HF) to remove oxide scale, followed by passivation to form a protective chromium oxide layer, ensuring long-term corrosion resistance.
- Surface Finishing / Coating: For solar absorber applications, a selective absorber coating (e.g., TiN, CrN, or Al₂O₃-based thin-film coating) may be applied via Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD) to achieve solar absorptance (α) ≥ 0.95 and thermal emittance (ε) ≤ 0.10 at operating temperatures.
- Non-Destructive Testing (NDT): Each coil tube undergoes 100% inspection using helical eddy current testing (ECT) and/or ultrasonic testing (UT) to detect subsurface defects, seam weld imperfections, and wall thickness variations.
- Dimensional Verification and Final Inspection: Final product dimensions (OD, WT, coil geometry) are verified using laser measurement systems and CMM (Coordinate Measuring Machine) gauging. Material certificates (Mill Test Reports / MTR) are compiled for each shipment.
Applications
The No. 842 stainless steel coil tube is engineered for demanding high-temperature thermal applications, with primary deployment in the following sectors:
- Cavity-Type High-Temperature Solar Heat Collectors: Serves as the primary heat absorption and transfer element within cavity concentrator systems, where concentrated solar radiation heats the coil tube surface to temperatures exceeding 800°C, driving thermodynamic cycles or process heat generation.
- Solar Thermal Power Generation (CSP): Integrated into solar power towers and linear Fresnel systems as a heat exchange medium for superheated steam generation and thermal energy storage.
- Industrial Process Heating: Used in solar-powered industrial drying, calcination, smelting, and chemical processing where high-temperature heat sources are required.
- Solar Desalination and Water Treatment: Employed in high-temperature solar distillation systems for seawater desalination and wastewater treatment in arid regions.
- Research and Development: Utilized in experimental solar thermal research facilities and national laboratories for studying high-temperature heat transfer phenomena, cavity radiation characteristics, and novel absorber coating technologies.
- Hybrid Solar-Nuclear and Solar-Fuel Systems: Applied in hybrid energy systems where solar heat supplements nuclear or fossil fuel thermal inputs for improved overall system efficiency.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification systems to ensure global compliance and customer confidence:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes
- ISO 14001 — Environmental Management System certification
- ASTM A213 / A269 — Compliance with American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tube
- GB/T 12771 — Chinese National Standard for welded stainless steel tube for general use
- GB/T 14976 — Chinese National Standard for seamless stainless steel tube
- EN 10216-5 — European Standard for welded stainless steel tubes
- JIS G3447 — Japanese Industrial Standard for seamless austenitic stainless steel tube
- Mill Test Reports (MTR): Provided with every shipment, including chemical composition analysis, mechanical property data, and heat treatment records
- Third-Party Inspection: Available upon request (SGS, BV, TUV, Intertek)
Unique Selling Points
- Simulation-Optimized Design: The coil tube geometry is derived from comprehensive numerical simulation of cavity-type high-temperature heat collection characteristics, including radiative heat transfer modeling, CFD analysis of fluid flow within the coil, and parametric optimization of coil pitch and diameter for maximum thermal efficiency.
- Extreme Temperature Capability: Capable of sustained operation at temperatures up to 1100°C, far exceeding conventional stainless steel tubing limits, enabling use in the most demanding concentrated solar thermal applications.
- Selective Absorber Coating Integration: In-house PVD/CVD coating capability enables application of high-performance selective absorber coatings directly on the coil tube, achieving solar absorptance ≥ 0.95 with thermal emittance ≤ 0.10 — a critical performance parameter for high-temperature solar collectors.
- Customization Flexibility: Full customization of coil geometry (OD, WT, coil diameter, pitch, total length) to match specific cavity collector designs, enabling seamless integration into proprietary or turnkey solar thermal systems.
- End-to-End Quality Assurance: From raw material spectroscopic verification through final NDT and dimensional inspection, every production stage is documented and traceable, with complete MTR packages provided for each order.
- Integrated Research and Manufacturing: Wenzhou Jixing combines academic-level thermal simulation expertise with precision manufacturing capabilities, ensuring that each coil tube is not only dimensionally accurate but also thermally optimized for its intended application.
Note: The No. 842 Stainless Steel Coil Tube represents a specialized product developed through systematic study of cavity-type high-temperature solar heat collection characteristics (《太阳能盘管腔式高温集热特性模拟与优化》). All specifications are subject to the final engineering design agreement and applicable project-specific requirements. For detailed technical consultation, custom design, or quotation, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.