Stainless Steel Flat Coil Tube (Coiltube) — Product No. 1327
Product Overview
The Stainless Steel Flat Coil Tube (hereinafter referred to as "Coiltube") manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a high-performance, precision-engineered tubular product designed for demanding fluid transfer and heat exchange applications. Unlike conventional round-section stainless steel tubing, the flat coil tube features an elliptical or flattened cross-sectional geometry that is wound into a compact coil configuration. This unique design maximizes the surface-area-to-volume ratio, thereby significantly enhancing heat transfer efficiency while minimizing the footprint of the installed assembly.
The product is particularly distinguished by its superior hydraulic characteristics, as demonstrated through rigorous experimental research on the fluid dynamics of flat coil tubes. The optimized cross-sectional profile reduces flow resistance and pressure drop under turbulent flow conditions, making it an ideal choice for applications requiring efficient fluid conveyance within constrained spatial envelopes.
Material & Properties
The Coiltube is fabricated from high-grade austenitic stainless steel alloys, selected for their exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The following material specifications are available:
- AISI 304 (UNS S30400) — General-purpose alloy with excellent corrosion resistance in oxidizing environments; chromium content ≥ 18%, nickel content ≥ 8%.
- AISI 316 (UNS S31600) — Enhanced corrosion resistance due to molybdenum addition (2–3% Mo); suitable for chemical processing and marine environments.
- AISI 316L (UNS S31603) — Low-carbon variant of 316L for superior weldability and resistance to intergranular corrosion.
- AISI 321 (UNS S32100) — Stabilized with titanium; resistant to sensitization in high-temperature service up to 870°C (1600°F).
- AISI 310S (UNS S31008) — High-temperature alloy with enhanced oxidation resistance for service temperatures up to 1150°C (2100°F).
Key material properties for the standard AISI 304 grade include:
- Tensile Strength: ≥ 515 MPa (75 ksi)
- Yield Strength (0.2% offset): ≥ 205 MPa (30 ksi)
- Elongation: ≥ 40% (in 50 mm gauge length)
- Hardness (annealed): ≤ 92 HRB
- Thermal Conductivity (20°C): 16.3 W/(m·K)
- Specific Heat Capacity: 500 J/(kg·K)
- Linear Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /K
- Maximum Service Temperature: 870°C (1600°F) for 304; 1150°C (2100°F) for 310S
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Flat Coil Tube (Coiltube) | — |
| Product No. | 1327 | — |
| Tube Cross-Section Shape | Flat / Elliptical / Rectangular (customizable) | ASTM A269, GB/T 12771 |
| Outer Width (a) | 6.0 mm – 50.0 mm | — |
| Outer Height (b) | 3.0 mm – 25.0 mm | — |
| Wall Thickness (t) | 0.5 mm – 3.0 mm | — |
| Coil Diameter (OD) | 150 mm – 1200 mm | — |
| Coil Length (per roll) | Up to 100 m (continuous) | — |
| Surface Finish | 2B (cold-rolled), BA (bright annealed), No. 4 Brushed, Mirror (8K) | ASTM A480 |
| Tolerance on Dimensions | ±0.05 mm (width & height); ±0.02 mm (wall thickness) | GB/T 12771, ASTM A213 |
| End Condition | Plain, Beveled, or Threaded (upon request) | — |
| Coil Pitch | Customizable; standard 10 mm – 50 mm | — |
| Maximum Operating Pressure | Up to 4.0 MPa (600 psi) depending on geometry | ASME B31.3 |
| Heat Treatment | Solution Annealed and Pickled (SAP) | ASTM A269 |
| Testing | Hydrostatic, Eddy Current, Spectroscopic (PMI) | ASTM E2785, GB/T 247 |
Manufacturing Process
The production of the Stainless Steel Flat Coil Tube follows a multi-stage precision manufacturing sequence to ensure dimensional accuracy, surface integrity, and metallurgical quality:
- Hot-Rolled Strip Production: Stainless steel slabs are hot-rolled into strip of the required base alloy grade, followed by descaling and coiling.
- Cold Reduction (Cold Rolling): The hot-rolled strip is cold-rolled to the target thickness with tight tolerance control, reducing grain size and improving surface finish.
- Intermediate Annealing: Periodic annealing in a controlled-atmosphere furnace (reducing atmosphere: N₂ + H₂ or vacuum) relieves cold-work hardening and restores ductility for subsequent forming operations.
- Precision Forming to Flat/Elliptical Cross-Section: The round tube blank is passed through a series of progressive die sets (roll-forming or mandrel-drawing process) to achieve the desired flat or elliptical cross-sectional profile with uniform wall thickness.
- Solution Annealing and Pickling: The formed tube is heat-treated at 1050°C–1150°C (depending on alloy) in a high-purity hydrogen or vacuum atmosphere, followed by acid pickling to remove oxide scale and restore full corrosion resistance.
- Coil Winding: The flat tube is wound into a helical coil of the specified outer diameter and pitch using a computerized winding machine to ensure consistent coil geometry.
- Final Surface Treatment: Optional polishing, passivation, or passivation-etching processes are applied to achieve the required surface finish grade (2B, BA, No. 4, or Mirror).
- Quality Inspection & Testing: Each coil undergoes 100% eddy current testing for wall thickness and flaw detection, hydrostatic pressure testing, and positive material identification (PMI) via optical emission spectroscopy.
- Packaging & Dispatch: Coils are wrapped in protective moisture-barrier film, secured on wooden pallets or steel frames, and labeled with full traceability documentation.
Hydraulic Performance Characteristics
Based on experimental research into the hydraulic behavior of flat coil tubes, the following performance characteristics have been established:
- Enhanced Heat Transfer Coefficient: The flat cross-section increases the wetted perimeter relative to the cross-sectional area, resulting in a Nusselt number (Nu) 30–50% higher than equivalent round tubes under turbulent flow conditions (Re > 10,000).
- Reduced Pressure Drop: The streamlined elliptical profile minimizes flow separation and secondary vortex formation, yielding a Darcy friction factor (f) reduction of approximately 15–25% compared to round tubes of equivalent flow area.
- Optimal Aspect Ratio: Experimental data indicates that an aspect ratio (a/b) of 1.5–2.5 provides the best balance between heat transfer enhancement and acceptable pressure drop, where a is the major axis and b is the minor axis of the elliptical cross-section.
- Flow Regime Transition: The critical Reynolds number for transition from laminar to turbulent flow in flat coil tubes is approximately 2,100–2,400, marginally higher than the classical value of 2,300 for circular tubes, attributed to the stabilizing effect of the flattened geometry on near-wall velocity profiles.
Applications
The Stainless Steel Flat Coil Tube is engineered for a broad spectrum of industrial and commercial applications:
- Heat Exchangers: Shell-and-tube heat exchangers, plate-fin heat exchangers, and compact heat recovery units where high surface-area density is critical.
- Refrigeration & Air Conditioning: Evaporators, condensers, and liquid separators in HVAC systems, refrigerated transport, and cold storage facilities.
- Automotive Industry: Intercoolers, oil coolers, and charge air cooling systems for diesel and gasoline engines; EV battery thermal management modules.
- Chemical Processing: Reactor cooling jackets, distillation column internals, and heat recovery systems in petrochemical and pharmaceutical plants.
- Food & Beverage Industry: Pasteurizers, pasteurization coils, CIP (Clean-In-Place) systems, and heat exchangers for dairy, brewery, and beverage processing (FDA-compliant 304/316L grades).
- Power Generation: Feedwater heaters, economizers, and superheater elements in thermal power plants.
- Oil & Gas: Subsea heat exchangers, gas cooler bundles, and cryogenic process piping (316L/310S grades).
- Medical & Laboratory Equipment: Dialysis machines, autoclaves, and process tubing in medical device manufacturing.
- Marine & Offshore: Seawater coolers, ballast water heat exchangers, and marine HVAC systems (316/316L grades with Mo resistance).
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and complies with the following international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- ISO/TS 22163 — Automotive Quality Management System (IATF 16949 alignment)
- ASME — American Society of Mechanical Engineers (material certification for pressure vessels)
- EN 10204 3.1 — Material Test Reports per European Standard
- GB/T 12771 — Chinese National Standard for Welded Stainless Steel Tubes
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Similar Services
- ASTM A213 — Standard Specification for Seamless Austenitic Chromium-Nickel Stainless Steel Tubes for Heat-Transfer Applications
- EN 10216-5 — European Standard for Heat Exchangers and Similar Heat Transfer Equipment
- NSF/ANSI 61 — Drinking Water System Components (for food-grade 304/316L applications)
- CE Marking — European Conformity for Pressure Equipment Directive (PED 2014/68/EU)
Unique Selling Points
- Superior Heat Transfer Efficiency: The flat cross-sectional geometry delivers 30–50% higher heat transfer coefficients compared to equivalent round tubes, enabling more compact and cost-effective heat exchanger designs.
- Reduced Pressure Drop: Optimized elliptical profile minimizes flow resistance, lowering pumping energy requirements and improving system efficiency.
- Compact Installation Footprint: The coil configuration maximizes heat exchange surface area per unit volume, ideal for space-constrained installations.
- Full Material Traceability: Every coil is accompanied by a mill test certificate (MTC) with heat number, chemical analysis, mechanical properties, and PMI verification.
- Custom Engineering: Wenzhou Jixing offers fully customizable cross-sectional dimensions, coil geometry, surface finish, and end conditions to meet specific project requirements.
- Rigorous Testing Protocol: 100% inline eddy current inspection, hydrostatic testing, and dimensional verification ensure zero-defect delivery.
- Multi-Grade Availability: Wide selection of stainless steel grades from standard 304/316 to specialized high-temperature and high-corrosion-resistance alloys.
Note: All specifications are subject to change without prior notice. For project-specific requirements, contact Wenzhou Jixing Metal Materials Co., Ltd directly to obtain a tailored engineering quotation and material certification package.