Stainless Steel Coil Tube (Coiltube) — Heat Transfer Radiator Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous tube product specifically designed for high-efficiency heat transfer applications. Unlike conventional straight pipes, coil tubes are formed into a continuous helical or spiral configuration, maximizing the surface-area-to-volume ratio and thereby enhancing convective and conductive heat exchange performance. This product line represents the company's expertise in coil tube fabrication, integrating metallurgical quality with geometric precision to deliver superior thermal management solutions across industrial, HVAC, and energy sectors.
The coil tube design fundamentally differs from straight-pipe heat exchangers by introducing secondary flow patterns (Dean vortices) within the curved geometry, which significantly improves turbulence and heat transfer coefficients. This makes the product particularly suitable for compact heat exchanger cores, radiator assemblies, and thermal energy transfer systems where space efficiency and thermal performance are critical.
Material & Properties
The coil tubes are fabricated from high-grade stainless steel grades selected for their exceptional corrosion resistance, mechanical strength, and thermal conductivity. The primary material grades include:
- SUS 304 (ASTM A213 TP304) — A general-purpose austenitic stainless steel with excellent corrosion resistance, weldability, and formability. Ideal for food-grade, chemical, and general industrial heat transfer applications.
- SUS 316L (ASTM A213 TP316L) — An enhanced austenitic grade with molybdenum addition providing superior resistance to pitting and crevice corrosion in aggressive environments.
- SUS 321 (ASTM A213 TP321) — Titanium-stabilized austenitic stainless steel offering excellent resistance to intergranular corrosion at elevated temperatures.
Key Material Properties
- Thermal Conductivity: 14–16 W/(m·K) (at 20°C)
- Specific Heat Capacity: 500 J/(kg·K)
- Maximum Operating Temperature: Up to 870°C (SUS 304), 870°C (SUS 316L), 900°C (SUS 321)
- Yield Strength: ≥ 205 MPa (SUS 304), ≥ 170 MPa (SUS 316L)
- Tensile Strength: 515–720 MPa (SUS 304)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and marine environments
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code | 807 |
| Material Grade | SUS 304 / SUS 316L / SUS 321 |
| Outer Diameter (OD) | 3.0 mm – 25.0 mm (customizable) |
| Wall Thickness | 0.3 mm – 2.0 mm |
| Coil Diameter | 50 mm – 500 mm (adjustable) |
| Coil Pitch | 3 mm – 20 mm |
| Tube Length | Up to 100 m continuous (custom lengths available) |
| Surface Finish | Bright Annealed / Passivated / Electropolished |
| Manufacturing Standard | ASTM A213 / ASTM A269 / GB/T 12771 |
| Heat Transfer Efficiency | Up to 30% improvement over straight-pipe equivalents |
| Pressure Rating | Up to 6.0 MPa (dependent on diameter and wall thickness) |
| Operating Temperature Range | -196°C to +870°C |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a multi-stage manufacturing process ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Material Selection & Inspection: Raw stainless steel wire rod or seamless tube stock is sourced from certified mills and subjected to spectrographic analysis, mechanical testing, and visual inspection to verify grade compliance and absence of defects.
- Hot/Forged Forming (if applicable): For seamless tube production, the raw billet is heated and pierced through a mandrel to form a hollow tube blank.
- Cold Drawing & Sizing: The tube blank is cold-drawn through precision dies to achieve exact outer diameter and wall thickness tolerances (typically ±0.05 mm).
- Coil Forming: The straight tube is fed through a precision forming die set that bends the tube into the desired helical or spiral configuration. CNC-controlled forming equipment ensures uniform coil diameter and pitch throughout the entire length.
- Heat Treatment (Solution Annealing): The formed coil tube is heat-treated at 1050–1150°C followed by controlled cooling to relieve residual stresses introduced during cold forming and to restore full austenitic microstructure.
- Pickling & Passivation: The surface is treated with acid pickling to remove oxide scale, followed by passivation to form a protective chromium oxide layer, ensuring long-term corrosion resistance.
- Quality Inspection: Each batch undergoes dimensional verification (OD, wall thickness, coil diameter, pitch), pressure testing (hydrostatic or pneumatic), surface inspection, and chemical composition analysis.
Applications
The stainless steel coil tube is employed across a wide range of thermal management and industrial applications:
- Heat Exchanger Cores: Primary component in shell-and-coil, plate-and-coil, and air-to-water heat exchangers for HVAC and refrigeration systems.
- Radiator Assemblies: High-efficiency coil radiators for automotive, industrial, and domestic heating systems, leveraging enhanced convective heat transfer.
- Industrial Process Cooling/Heating: Used in chemical processing, pharmaceutical manufacturing, and food processing for precise temperature control.
- Automotive Thermal Management: Intercoolers, oil coolers, and condenser units in automotive and heavy machinery applications.
- Energy Systems: Solar thermal collectors, geothermal heat exchangers, and waste heat recovery systems.
- Marine & Offshore: Corrosion-resistant heat transfer components in marine engineering and offshore platforms.
- Cryogenic Applications: Low-temperature service in LNG (Liquefied Natural Gas) processing and cryogenic storage systems (SUS 304 grade).
Quality Certifications & Standards
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System
- ASTM A213 — Standard Specification for Ferritic, Austenitic, and Ferritic-Austenitic Stainless Steel Seamless, Cold-Drawn or Cold-Reduced Boilers, Heat Exchangers, and Similar Applications for High-Temperature Service
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Similar Severely Corrosive Services
- GB/T 12771 — Chinese National Standard for Stainless Steel Tubes for Fluid Transport
- EN 10216-5 — European Standard for Non-Alloy and Alloy Steel Tubes for Mechanical, Thermal, and Technical Uses
- PED (Pressure Equipment Directive) 2014/68/EU — Compliance for pressure equipment applications (where applicable)
Unique Selling Points
- Enhanced Heat Transfer Performance: The helical geometry generates Dean secondary flows, increasing the Nusselt number by up to 30% compared to equivalent straight pipes, enabling more compact heat exchanger designs.
- Superior Corrosion Resistance: Austenitic stainless steel grades provide exceptional resistance to oxidation, acid attack, and pitting corrosion, ensuring long service life in aggressive environments.
- Wide Temperature Range: Operational capability from cryogenic (-196°C) to high-temperature (+870°C) conditions makes this product versatile across diverse thermal applications.
- Customizable Geometry: Coil diameter, pitch, tube OD, and wall thickness can be tailored to specific thermal performance requirements and installation constraints.
- Continuous Production Capability: Ability to produce coil tubes up to 100 meters in continuous length eliminates welding joints, reducing leak points and improving system reliability.
- Comprehensive Quality Assurance: Full traceability from raw material to finished product, with certified test reports for chemical composition, mechanical properties, and dimensional accuracy.
Technical Note: The heat transfer enhancement in coil tubes is governed by the Dean number (De = Re × √(d/D)), where Re is the Reynolds number, d is the tube inner diameter, and D is the coil diameter. Optimizing the Dean number is critical to balancing heat transfer performance against pressure drop penalties. Wenzhou Jixing provides engineering consultation to determine the optimal coil geometry for each specific application.