Stainless Steel Coil Tube — Model No. 274 (Liquid Circulation Heat Recovery System)
Product Overview
The Stainless Steel Coil Tube (Model No. 274) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing product designed specifically for liquid circulation heat recovery systems. This product represents an advanced solution in thermal energy management, integrating high-performance austenitic stainless steel with optimized helical geometry to maximize heat transfer efficiency while maintaining structural integrity under continuous cyclic thermal loading.
The coil tube is the core heat exchange element in a three-coil tube liquid circulation system, where it facilitates convective heat transfer between working fluids of differing temperatures. Its helical configuration provides a significantly larger surface-area-to-volume ratio compared to straight-tube alternatives, enabling compact installation with superior thermal performance.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, with the following key material specifications:
- Base Alloy: AISI 304 / 316L Stainless Steel (UNS S30408 / S31603)
- Chromium (Cr) Content: 18.0–20.0% (provides primary corrosion resistance)
- Nickel (Ni) Content: 8.0–12.0% (stabilizes austenitic microstructure)
- Molybdenum (Mo) Content: Up to 2.5% (in 316L variant, enhances pitting resistance)
- Carbon (C) Content: ≤ 0.030% (low-carbon grade for weldability and sensitization resistance)
- Operating Temperature Range: −196°C to +870°C (−321°F to +1,600°F)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 16–17 × 10⁻⁶ /°C (100–500°C)
- Corrosion Resistance: Excellent resistance to oxidation, acid media, and chloride environments
- Mechanical Strength: Tensile strength ≥ 515 MPa; Yield strength ≥ 205 MPa (annealed condition)
Specifications
| Parameter | Specification |
|---|---|
| Product Model | No. 274 — Coil Tube (Coiltube) |
| Tube Outer Diameter (OD) | 6 mm / 8 mm / 10 mm / 12 mm (customizable) |
| Tube Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Diameter | 50 mm – 300 mm (configurable per system design) |
| Coil Length | Up to 100 m per continuous coil |
| Material Grade | AISI 304 / 316L Stainless Steel |
| Surface Finish | 2B / BA (Bright Annealed) / Custom polish (Ra ≤ 0.4 μm) |
| Maximum Operating Pressure | Up to 1.6 MPa (232 psi) |
| Heat Transfer Efficiency | Enhanced by 30–50% over straight-tube configurations due to secondary flow effects |
| End Connections | Welded / Flanged / Threaded / Brazed (as required) |
| Applicable Standards | ASTM A269 / ASME B36.19M / GB/T 12771 |
| Working Fluid Compatibility | Water, glycol solutions, light hydrocarbons, refrigerants |
Manufacturing Process
The production of the Model No. 274 Coil Tube follows a rigorous, multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical homogeneity, and surface integrity:
- Raw Material Selection: Certified cold-rolled stainless steel strip conforming to ASTM A240/A269 specifications, with full mill test certificates (MTC) and spectroscopic verification.
- Coil Winding: Precision helical coiling on CNC-controlled winding machines with controlled tension to prevent ovalization and maintain uniform curvature radius.
- Tube Forming: Continuous roll-forming or extrusion of the coiled strip into seamless tubular geometry, ensuring consistent wall thickness throughout the coil length.
- Solution Annealing: Heat treatment at 1050–1100°C followed by rapid quenching to restore full solution-hardened microstructure and eliminate residual stresses from forming.
- Pickling & Passivation: Chemical cleaning (HNO₃/HF blend) to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide layer (Cr₂O₃).
- Non-Destructive Testing (NDT): 100% eddy current inspection for wall thickness uniformity; hydrostatic pressure testing at 1.5× maximum operating pressure; visual and dimensional inspection per GB/T 12771.
- Coating & Protection: Optional internal passivation film application for enhanced fluid compatibility; external protective coating for transport and installation phases.
- Final Packaging: Individually wrapped in moisture-barrier film, packed in protective wooden crates with desiccants, and labeled with full traceability documentation.
Applications
The Model No. 274 Stainless Steel Coil Tube is engineered for demanding thermal management applications where corrosion resistance, thermal efficiency, and long service life are critical:
- Industrial Heat Recovery Systems: Primary heat exchange element in three-coil tube liquid circulation heat recovery configurations, recovering waste thermal energy from exhaust streams, process cooling loops, and condenser circuits.
- Boiler & Steam Generation: Water-tube boiler components, economizers, and superheaters in power generation and industrial process plants.
- Refrigeration & HVAC: Condenser and evaporator coil assemblies in commercial and industrial refrigeration systems handling ammonia, R-134a, and other refrigerants.
- Chemical & Petrochemical Processing: Heat exchangers for corrosive process fluids, distillation columns, and reactor cooling circuits.
- Food & Pharmaceutical Industry: Sanitary-grade heat exchange loops requiring hygienic design and resistance to aggressive cleaning agents (CIP/SIP compatible).
- Marine & Offshore: Seawater cooling circuits and desalination plant heat recovery units.
- Renewable Energy Systems: Concentrated solar thermal collectors and geothermal fluid circulation loops.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality assurance protocols and holds the following certifications and complies with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- CE Marking — Conformity with European Union directives for pressure equipment (PED 2014/68/EU)
- Material Compliance: ASTM A269 (Austenitic Stainless Steel Tubing for General Service); ASME B36.19M; EN 10216-5
- Testing Standards: ASTM A999 (Hydrostatic Testing); ASTM E165 (Eddy Current Testing); GB/T 24511 (Non-Destructive Testing of Welds)
- Full Traceability: Each coil tube batch is accompanied by a Mill Test Certificate (MTC/EN 10204 Type 3.1), including chemical composition analysis, mechanical property data, and heat treatment records.
Unique Selling Points
1. Optimized Helical Geometry for Maximum Heat Transfer: The coiled configuration induces Dean vortices within the tube flow, disrupting the thermal boundary layer and enhancing convective heat transfer coefficients by 30–50% compared to equivalent straight-tube designs — validated through experimental and numerical (CFD) studies of three-coil tube liquid circulation systems.
2. Superior Corrosion & Oxidation Resistance: Low-carbon austenitic stainless steel (304/316L) provides exceptional resistance to intergranular corrosion, pitting, and high-temperature oxidation, ensuring decades of reliable service in aggressive chemical environments.
3. Compact & Scalable Design: The coil form factor enables significantly reduced installation footprint while maintaining or exceeding the heat exchange capacity of conventional straight-tube bundles — ideal for retrofit applications and space-constrained installations.
4. Proven Performance in Liquid Circulation Systems: Extensively validated through experimental and numerical research on three-coil tube heat recovery configurations, demonstrating stable thermal performance under cyclic operating conditions with minimal thermal fatigue degradation.
5. Full Quality Traceability & International Compliance: Every product unit is fully traceable to raw material origin, with complete test documentation conforming to international standards (ASTM, ASME, EN, GB), ensuring seamless integration into global supply chains and regulatory frameworks.
Technical Notes
The thermal performance of the coil tube in liquid circulation heat recovery systems is governed by the interplay of geometric parameters (coil diameter, tube diameter, pitch) and fluid dynamic conditions (Reynolds number, Prandtl number). Numerical simulations (using ANSYS Fluent / CFD modeling) and experimental validation confirm that the helical coil geometry generates secondary Dean flow, which significantly enhances radial temperature uniformity and reduces local thermal gradients — a critical advantage in preventing material degradation from thermal stress concentration.
For system-level integration, the Model No. 274 coil tube is designed to be compatible with standard flanged, threaded, and welded connection interfaces, facilitating modular assembly and maintenance access. Custom configurations (coil diameter, length, tube dimensions, end connections) are available upon request to meet specific system design requirements.