Stainless Steel Coil Tube (Coiltube) — Organic Heat Carrier Furnace Application
Product Overview
The stainless steel coil tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tubular product designed for high-temperature heat transfer applications, particularly in organic heat carrier (OHC) furnace systems. Unlike conventional straight pipes, coil tubes are produced in a continuous coiled configuration, which eliminates the need for field welding joints, significantly reducing the risk of leakage and failure points in thermal systems. This product is specifically engineered to meet the demanding requirements of organic heat carrier systems, where fluid dynamics governed by the Reynolds number (Re) play a critical role in ensuring safe and efficient heat transfer operation.
The coil tube integrates metallurgical excellence with geometric precision, enabling optimal turbulent flow characteristics within organic heat carrier media such as synthetic oils and molten salts. The continuous coil geometry ensures uniform heat absorption along the entire tube length, contributing to stable thermal performance and extended service life.
Material & Properties
Base Material
- Grade Options: Austenitic stainless steel grades including SUS304, SUS310S, SUS321, and TP310H, selected based on maximum operating temperature and corrosive environment.
- Composition: High chromium (Cr ≥ 18%) and nickel (Ni ≥ 8%) content ensuring excellent oxidation resistance, thermal fatigue resistance, and mechanical stability at elevated temperatures.
- Corrosion Resistance: Superior resistance to oxidation, carburization, and scaling in organic heat carrier media up to 600°C (1112°F).
Key Physical and Mechanical Properties
- Thermal Conductivity: 14–16 W/(m·K) at operating temperature, enabling efficient radiant and convective heat transfer.
- Thermal Expansion Coefficient: 16–17 × 10⁻⁶ /K, compatible with expansion joint design in furnace systems.
- Yield Strength: ≥ 205 MPa (at room temperature); retains ≥ 60% strength at 600°C.
- Surface Finish: Mirror polish (Ra ≤ 0.4 μm) or industrial finish (Ra ≤ 1.6 μm), depending on application requirements.
- Reynolds Number Design Target: Engineered to maintain turbulent flow (Re ≥ 4000) in organic heat carrier media, ensuring adequate heat transfer coefficients and preventing localized overheating (hot spots).
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ14 mm – Φ60 mm (customizable) |
| Wall Thickness | 0.8 mm – 4.0 mm |
| Coil Diameter | Φ500 mm – Φ3000 mm |
| Coil Length (Continuous) | Up to 500 m per coil (seamless) |
| Material Grade | SUS304 / SUS310S / SUS321 / TP310H |
| Maximum Operating Temperature | ≤ 600°C (1112°F) |
| Maximum Operating Pressure | ≤ 2.5 MPa (362.6 psi) |
| Heat Carrier Medium | Synthetic organic oil / Molten salt / Thermal fluid |
| Surface Treatment | Pickled & passivated / Mirror polished |
| Standards Compliance | ASTM A213 / ASTM A269 / GB/T 12771 / JIS G3459 |
| Reynolds Number (Design) | Re ≥ 4000 (turbulent flow regime) |
| Wall Thickness Tolerance | ± 10% of nominal |
| Coil Straightness | ≤ 1.5 mm/m |
Manufacturing Process
- Raw Material Selection: High-purity stainless steel wire rod sourced from certified mills, undergoing incoming inspection for chemical composition (spectrometric analysis) and mechanical properties.
- Wire Drawing: Multi-stage cold drawing through tungsten carbide (WC) dies to achieve precise dimensional tolerances and enhanced mechanical strength through work hardening.
- Intermediate Annealing: Solution annealing at 1050–1150°C in controlled atmosphere (N₂ or H₂) followed by controlled cooling to restore ductility and eliminate residual stresses.
- Coil Forming: Precision coiling on CNC-controlled winding machines with constant tension control to ensure uniform coil geometry and prevent work hardening at bend regions.
- Pickling & Passivation: Immersion in mixed acid bath (HNO₃ + H₂SO₄) to remove surface scale, followed by passivation treatment to establish a protective chromium oxide film.
- Hydrostatic Testing: 100% pressure testing at 1.5× working pressure to verify weld integrity and dimensional conformance.
- Final Inspection: Dimensional verification, surface quality assessment, and material certification documentation.
Applications
- Organic Heat Carrier Furnace Systems: Primary application for heating medium circulation in industrial thermal processing lines, where Reynolds number-based safety assessment ensures reliable heat transfer performance.
- Chemical Processing Industry: Heat exchanger tubes for chemical reactors, distillation columns, and process heating loops.
- Food & Pharmaceutical Industry: Sanitary-grade heat transfer coils for sterilization, pasteurization, and process heating requiring hygienic surface finishes.
- Petrochemical & Refining: Reboiler tubes, vaporizers, and process heating elements in refinery operations.
- Pulp & Paper Industry: Heat transfer coils in digesters and bleaching processes.
- Textile Dyeing: Circulation heating elements in dyeing and finishing equipment.
- Plastic Processing: Heating coils for injection molding machines and extruders.
Quality Certifications & Standards
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- ASTM A213 — Standard Specification for Seamless Austenitic Stainless Steel Tubes for High-temperature Service
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes
- JIS G3459 — Japanese Industrial Standard for Stainless Steel Tubes
- EN 10216-5 — European Standard for Welded Stainless Steel Tubes
- Material Test Reports (MTR): Provided with each batch, including chemical analysis, mechanical test results, and hydrostatic test records.
Unique Selling Points
- Reynolds Number–Based Safety Design: The coil tube is specifically engineered with geometric parameters (OD, wall thickness, coil diameter) calibrated to maintain turbulent flow conditions (Re ≥ 4000) in organic heat carrier media, ensuring uniform heat distribution and preventing dangerous hot spots that could lead to thermal runaway or material degradation.
- Seamless Continuous Coil Configuration: Eliminates field joints and welding points, providing a monolithic, leak-free thermal circuit with superior long-term reliability.
- Extended Service Life: Superior oxidation resistance and thermal fatigue performance of austenitic stainless steel grades ensure 10–15+ years of reliable service in high-temperature organic heat carrier environments.
- Customizable Geometry: Flexible coil diameter and length options allow seamless integration into various furnace configurations and heat exchanger designs.
- Reduced Maintenance: The absence of joints and the corrosion-resistant surface finish minimize inspection frequency and unplanned shutdowns.
- Energy Efficiency: Optimized turbulent flow characteristics maximize the heat transfer coefficient, reducing fuel consumption and improving overall system thermal efficiency.
Technical Notes on Reynolds Number Safety Assessment
The safety of coil-type organic heat carrier furnace tubes is fundamentally dependent on maintaining adequate flow velocity within the tube to ensure turbulent flow conditions. The Reynolds number is calculated as:
Re = (ρ × v × D) / μ
Where ρ is the fluid density (kg/m³), v is the flow velocity (m/s), D is the inner diameter (m), and μ is the dynamic viscosity (Pa·s). When Re falls below the critical value of approximately 2300 (laminar flow regime), heat transfer efficiency degrades significantly, leading to localized overheating of the tube wall. This can cause rapid oxidation, scaling, and ultimately tube rupture. Wenzhou Jixing Metal Materials Co., Ltd. designs each coil tube product with dimensional parameters that guarantee Re ≥ 4000 under minimum design flow conditions, providing a safety margin of approximately 74% above the laminar-turbulent transition threshold.
By integrating rigorous metallurgical selection, precision manufacturing, and fluid dynamics-based design principles, the stainless steel coil tube product from Wenzhou Jixing Metal Materials Co., Ltd. represents a state-of-the-art solution for safe, efficient, and reliable organic heat carrier furnace systems.