Stainless Steel Coil Tube (Coiltube) — Fan Coil Unit Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Catalog No. 1668) is a precision-engineered tubular product specifically designed for use in Fan Coil Units (FCUs) and hydronic air handling systems. This coil tube is supplied in a continuous coiled configuration, enabling seamless integration into heat exchanger assemblies where uniform fluid distribution and thermal efficiency are critical performance parameters.
Derived from rigorous research in fan coil unit simulation and incoming flow uniformization (as documented in the study "Simulation Calculation of Fan Coil Units and Experimental Research on Uniformization of Coil Incoming Flow"), this product addresses the engineering challenges of non-uniform flow distribution across coil bundles, which is a primary cause of reduced heat transfer efficiency and uneven temperature profiles in commercial HVAC systems.
Material & Properties
The coil tube is fabricated from high-grade Stainless Steel (Stainless Steel), offering superior corrosion resistance, mechanical strength, and long-term service life in hydronic and HVAC environments.
- Base Material: Austenitic Stainless Steel — Grade 304 (UNS S30408) or Grade 316 (UNS S31603) upon specification
- Carbon Content (C): ≤ 0.08% (304) / ≤ 0.08% (316)
- Chromium (Cr): 18.0–20.0%
- Nickel (Ni): 8.0–11.0% (304) / 10.0–14.0% (316)
- Molybdenum (Mo): — (304) / 2.0–3.0% (316)
- Tensile Strength (Rm): ≥ 520 MPa
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A): ≥ 40%
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +450°C
- Surface Finish: 2B / BA (Bright Annealed) / No. 4 Brushed — selectable
Technical Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) — Cat. No. 1668 | — |
| Outer Diameter (OD) | φ6.0 mm / φ8.0 mm / φ9.52 mm / φ12.0 mm (customizable) | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 1.5 mm (tolerance ±0.05 mm) | ASTM A213 / GB/T 12771 |
| Coil Length (per spool) | 50 m – 200 m (adjustable per customer requirement) | — |
| Coil Inner Diameter | 200 mm – 500 mm | — |
| Roundness Tolerance | ≤ 1% of nominal OD | ISO 1307 |
| Surface Roughness (Ra) | ≤ 0.8 μm (internal) / ≤ 0.4 μm (external) | GB/T 1031 |
| End Condition | Plain / Beveled / Flared / Threaded (custom) | — |
| Hydrostatic Test Pressure | 2.5 × Working Pressure (minimum 10 MPa) | ASTM A213 |
| Packing | Wooden pallet with moisture-proof wrapping | — |
Manufacturing Process
The production of this coil tube follows a tightly controlled multi-stage manufacturing workflow to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Hot Rolling & Annealing: Stainless steel strip is hot-rolled to approximate dimensions and then annealed to relieve internal stresses and achieve the desired austenitic microstructure.
- Cold Forming & Seamless Tube Drawing: The strip is precisely formed into tubular geometry via cold-drawn seamless processes, ensuring uniform wall thickness and absence of weld seams that could act as corrosion initiation sites.
- Precision Sizing & Straightening: Multi-roller sizing stations refine the outer diameter and wall thickness to within tight tolerances (±0.05 mm).
- Intermediate Annealing: Periodic annealing cycles are applied during cold working to prevent work hardening and maintain formability.
- Surface Treatment: Pickling and passivation (酸洗钝化) processes remove scale and oxide layers, restoring the full chromium-rich passive film essential for corrosion resistance.
- Coiling & Spooling: The finished tube is wound onto precision-mandrel spools at controlled tension to prevent deformation and kinking.
- Quality Inspection: Each coil undergoes 100% hydrostatic pressure testing, dimensional measurement (OD, wall thickness, roundness), and surface visual inspection under magnification.
Applications
This stainless steel coil tube is engineered primarily for the following high-performance applications:
- Fan Coil Units (FCUs): Serves as the core heat transfer element in commercial and residential fan coil units, where uniform incoming flow distribution is critical for optimal thermal performance. The seamless construction and smooth internal surface minimize flow resistance and promote even fluid distribution across the coil bundle.
- Air Handling Units (AHUs): Used in chilled water and hot water coil assemblies within centralized air handling systems.
- Chilled Beam Systems: Integrated into active and passive chilled beam terminal units for displacement ventilation.
- Process Cooling & Heating: Applicable in food and beverage processing, pharmaceutical manufacturing, and chemical processing where sanitary-grade stainless steel is mandated.
- Marine & Coastal HVAC: Grade 316 variants provide enhanced resistance to chloride-induced pitting corrosion in high-humidity coastal environments.
- Refrigeration & Heat Pump Systems: Suitable for evaporator and condenser coil assemblies in commercial refrigeration.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- GB/T 12771 — Chinese National Standard for Welded and Seamless Stainless Steel Tubes for General Fluid Conveyance
- ASTM A213 / A269 — American Society for Testing and Materials Standards for Seamless Austenitic Stainless Steel Tubes
- EN 10216-5 — European Standard for Heat Exchanger and Boiler Tubes
- CE Marking — Conformity with European safety and performance directives
- Mill Test Certification (MTC): Full chemical composition analysis and mechanical property verification provided per EN 10204 Type 3.1
Unique Selling Points
Flow Uniformization Engineering: This coil tube is developed with direct reference to advanced research in fan coil unit simulation and incoming flow uniformization. The precision-controlled internal geometry and surface finish are specifically optimized to minimize flow maldistribution — a well-documented root cause of degraded heat transfer efficiency in conventional coil assemblies. By reducing turbulence-induced pressure drops and promoting laminar-to-transitional flow uniformity, this product delivers measurable improvements in coefficient of performance (COP) for downstream HVAC systems.
- Seamless Construction: Eliminates weld seams that serve as preferential corrosion sites and flow disruption points, ensuring long-term hydraulic reliability.
- Precision Dimensional Control: Tight tolerances on OD (±0.05 mm) and wall thickness ensure consistent fin-to-tube bonding during downstream heat exchanger assembly, maximizing thermal contact conductance.
- Material Grade Flexibility: Available in both 304 and 316 grades, providing customers with the option to balance cost-efficiency (304) against superior chloride corrosion resistance (316) based on application-specific environmental conditions.
- Customizable Configuration: OD, wall thickness, coil length, and end conditions are all configurable to meet specific OEM and project requirements.
- Full Traceability: Every coil is accompanied by a complete Mill Test Certificate (MTC) with chemical analysis, mechanical test data, and heat number traceability for full supply chain accountability.