Stainless Steel Coiled Tube (Coiltube) — Heat Transfer Application Series
Product Overview
The Stainless Steel Coiled Tube (hereinafter referred to as "Coiltube") is a precision-engineered coiled piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for heat transfer applications within enclosed sandwich spaces, where efficient thermal exchange is critical. The Coiltube is formed by continuously coiling a seamless or welded stainless steel pipe into a helical configuration, providing an exceptionally high surface-area-to-volume ratio that maximizes heat dissipation or absorption within confined geometries.
This product line draws upon advanced research findings in the field of convective and conductive heat transfer within enclosed sandwich configurations. The coiled geometry enables turbulent flow promotion, boundary layer disruption, and enhanced Nusselt number performance compared to straight-tube alternatives of equivalent diameter and length. The Coiltube is suitable for deployment in industrial heat exchangers, thermal storage systems, refrigeration coils, and specialized HVAC components where spatial constraints demand compact yet high-efficiency thermal solutions.
Material & Properties
Available Grades
- 304 (UNS S30400 / 1.4301) — Austenitic stainless steel with excellent general corrosion resistance, formability, and weldability. Suitable for most industrial and food-grade applications.
- 316 (UNS S31600 / 1.4401) — Molybdenum-enhanced austenitic grade offering superior resistance to pitting and crevice corrosion in chloride-containing environments.
- 316L (UNS S31603 / 1.4404) — Low-carbon variant of 316 for improved weldability and resistance to sensitization in high-temperature service.
- 321 (UNS S32100 / 1.4541) — Titanium-stabilized austenitic grade for elevated-temperature applications up to 870 °C.
- 304L (UNS S30403 / 1.4307) — Low-carbon version of 304 for applications requiring extensive welding without risk of intergranular corrosion.
- Custom Alloys — Including 904L, 2205 Duplex, and 6Mo grades available upon request for extreme environments.
Key Mechanical & Thermal Properties (Typical — Grade 304)
- Density: 7.93 g/cm³
- Thermal Conductivity (25 °C): 16.3 W/(m·K)
- Specific Heat Capacity (25 °C): 500 J/(kg·K)
- Coefficient of Thermal Expansion (20–100 °C): 17.3 × 10⁻⁶ /K
- Tensile Strength (Annealed): ≥ 515 MPa
- Yield Strength (0.2% Offset): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Operating Temperature Range: −196 °C to +870 °C (grade-dependent)
Surface Finish Options
- 2B Cold-Rolled Finish (Ra ≤ 0.5 μm)
- Ba & Be Polished Finish (Ra ≤ 0.1 μm)
- Electropolished Finish (Ra ≤ 0.05 μm, for pharmaceutical and food-grade service)
- Pickled & Passivated Finish (for enhanced corrosion resistance)
- Custom Matte or Mirror Polish upon request
Specifications
| Parameter | Specification Range | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6 mm – 114.3 mm (¼" – 4½") | ASTM A213 / EN 10216-5 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm | ASTM A213 / GB/T 12771 |
| Coil Pitch (Helix Spacing) | Customizable, typically 5 mm – 50 mm | Per customer drawing |
| Coil Diameter (Helix Mean Diameter) | 50 mm – 500 mm | Per customer drawing |
| Number of Coils / Turns | 1 – 500+ turns (custom) | Per customer drawing |
| Overall Coil Length | 100 mm – 5,000 mm | Per customer drawing |
| End Preparation | Plain, Beveled, Threaded (NPT/BSP/Metric), or Flanged | ASME B1.20.1 / ISO 7-1 |
| Dimensional Tolerance | OD: ±0.05 mm; WT: ±0.02 mm; Pitch: ±0.5 mm | ISO 2852 / GB/T 12771 |
| Surface Roughness | Ra 0.05 μm – 0.5 μm (depending on finish) | ISO 1302 |
| Pressure Rating | Up to 30 MPa (depending on grade, OD, and WT) | ASME B31.3 / EN 13480 |
| Testing | Hydrostatic Test, Eddy Current, Ultrasonic (UT), Dye Penetrant (PT) | ASTM A213 / ASME Sec. VIII |
| Packaging | Wooden crate, plywood box, or export-grade pallet with moisture barrier | ISO 4180 |
Manufacturing Process
The production of the Coiltube follows a rigorously controlled multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and consistent thermal performance:
- Raw Material Selection & Inspection: Certified stainless steel seamless tubes or ERW (Electric Resistance Welded) tubes are sourced from approved mills. Incoming material undergoes chemical composition analysis (via Optical Emission Spectroscopy — OES), mechanical property verification, and visual inspection per ASTM A213 and EN 10216-5 requirements.
- End Preparation & Cleaning: Tube ends are cut to length using precision sawing or laser cutting to eliminate burrs and deformation. Interior surfaces are cleaned using chemical pickling or mechanical brush methods to remove scale and contaminants.
- Coiling / Helix Forming: The straight tube is fed into a computer-controlled coiling machine (CNC coil winding system) that applies controlled bending force to form the helical geometry. The coiling process is performed at ambient temperature (cold coiling) to preserve the material's original mechanical properties and avoid work-hardening effects that could compromise fatigue life. Tooling is precisely calibrated to achieve the specified coil diameter, pitch, and turn count with tolerances within ±0.5 mm.
- Solution Annealing (if required): For applications requiring full stress relief or enhanced corrosion resistance, the coiled assembly may undergo solution annealing at 1010–1150 °C followed by controlled cooling, then pickling and passivation in nitric or citric acid.
- Non-Destructive Testing (NDT): Each coil undergoes comprehensive NDT including eddy current testing (per ASTM E309) for wall thickness verification, ultrasonic testing for internal defects, and dye penetrant testing for surface discontinuities. Hydrostatic pressure testing is performed at 1.5× the maximum operating pressure.
- Final Dimensional Verification: Coordinate Measuring Machine (CMM) or laser scanning is employed to verify coil diameter, pitch uniformity, overall length, and straightness of end extensions.
- Packaging & Dispatch: Finished Coiltubes are individually wrapped in protective film, placed in export-grade wooden crates or plywood boxes with desiccant packs, and labeled with traceability documentation.
Applications
The Coiltube finds extensive application across multiple industries where compact, high-efficiency heat transfer is required within spatially constrained environments:
- Industrial Heat Exchangers: Coil bundles used in shell-and-coil heat exchangers for process fluid heating and cooling in chemical, petrochemical, and pharmaceutical plants. The helical geometry promotes turbulent flow, increasing the convective heat transfer coefficient by up to 2–4× compared to straight tubes.
- Enclosed Sandwich Space Thermal Management: As demonstrated in advanced research on heat transfer in enclosed sandwich configurations, the Coiltube is deployed within double-walled or multi-layered enclosures to manage thermal gradients, reduce hot spots, and maintain uniform temperature distribution across sandwich panels.
- Refrigeration & Air Conditioning (HVAC): Evaporator and condenser coils for commercial refrigeration units, chillers, and heat pump systems where compact coil assemblies maximize heat exchange in limited installation spaces.
- Thermal Energy Storage (TES): Coiltube arrays embedded within phase-change material (PCM) containers for latent heat thermal storage systems, enabling efficient charging and discharging of thermal energy.
- Food & Beverage Processing: Pasteurization coils, cooling coils for milk and juice processing, and CIP (Clean-In-Place) compatible heat transfer elements meeting FDA and 3-A sanitary standards.
- Power Generation: Condenser tubes and heat recovery coils in cogeneration and waste heat recovery systems.
- Marine & Offshore: Heat exchange coils for ballast water treatment, engine cooling, and HVAC systems on vessels operating in corrosive marine environments (316L or duplex grades).
- Automotive & Aerospace: Compact heat exchanger coils for thermal management in electric vehicle battery cooling systems and aircraft environmental control units.
Unique Selling Points
- Enhanced Heat Transfer Performance: The helical coil geometry inherently induces secondary Dean vortices within the tube flow, disrupting the thermal boundary layer and significantly elevating the Nusselt number (Nu). This results in heat transfer rates up to 4× higher than equivalent straight-tube configurations at the same mass flow rate.
- Compact Footprint: Achieves maximum heat exchange surface area within minimum installation volume, making it ideal for space-constrained sandwich enclosures and modular heat exchanger designs.
- Custom Engineering Capability: Wenzhou Jixing Metal Materials offers fully customizable coil geometries — including variable-pitch coils, multi-layer helical assemblies, and integrated manifold configurations — tailored to specific thermal performance targets via CFD (Computational Fluid Dynamics) simulation and thermal modeling.
- Full Material Traceability: Each Coiltube is accompanied by a Mill Test Certificate (MTC) per EN 10204 Type 3.1, with complete traceability from raw material heat number through to final inspection.
- Corrosion Resistance: Available in multiple stainless steel grades to withstand aggressive chemical, marine, and high-temperature environments with minimal maintenance lifecycle costs.
Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Certified for manufacturing of stainless steel tubes and coils |
| ISO 14001:2015 | Environmental Management System — Sustainable manufacturing practices |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| ASTM A213 / A269 | Standard Specification for Seamless and Wrought Stainless Steel Tube for High-Temperature Service |
| EN 10216-5 | Non-alloy and Alloy Steel Tubes for Pressure Purposes — Technical Delivery Conditions for Stainless Steel Tubes |
| ASME BPV Code / Sec. VIII Div. 1 | Boiler and Pressure Vessel Code compliance for pressure-containing applications |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes |
| EN 10204 Type 3.1 | Inspection Document — Test Report with material-specific testing data |
| PED 2014/68/EU | European Pressure Equipment Directive compliance (where applicable) |
| CE Marking | Conformity with applicable European directives for market access |
Technical Note on Heat Transfer in Enclosed Sandwich Configurations
Research published in the field of enclosed sandwich space thermal management has demonstrated that the integration of stainless steel coiltubes within confined double-wall enclosures significantly improves the overall thermal performance of the system. The coiled geometry facilitates natural and forced convection patterns that are difficult to achieve with straight-tube arrangements in the same spatial envelope. Key performance indicators include:
- Up to 60–80% reduction in thermal resistance compared to bare sandwich panels of equivalent thickness
- Effective reduction of temperature gradients across the enclosure face, minimizing thermal stress and improving structural uniformity
- Scalable design approach where coil density and pitch can be optimized via numerical simulation (ANSYS Fluent / CFD) to match specific heat flux requirements
This research-informed design philosophy is integral to the engineering approach adopted by Wenzhou Jixing Metal Materials in the development and supply of Coiltube products for high-performance thermal management applications.
Contact & Ordering Information
For custom Coiltube