Stainless Steel Coil Tube for Fan Coil Unit (FCU) Applications
Product Overview
The Stainless Steel Coil Tube (Catalog No. 565) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into Fan Coil Unit (FCU) Air Conditioning Systems. This coil tube serves as the critical heat exchange element within FCU assemblies, facilitating efficient thermal transfer between circulating refrigerant or hot water and the surrounding airstream.
Addressing one of the most persistent engineering challenges in HVAC (Heating, Ventilation, and Air Conditioning) systems — condensation formation and water leakage — this product incorporates advanced metallurgical treatments and geometric optimizations to mitigate moisture accumulation on the coil surface, thereby enhancing system reliability, reducing maintenance frequency, and extending operational service life.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and structural integrity under cyclic thermal loading conditions.
- Primary Alloy Grades: Austenitic stainless steel conforming to AISI 304 (UNS S30400) and AISI 316L (UNS S31603), providing superior resistance to chloride-induced pitting corrosion.
- Surface Finish: Electropolished and passivated to achieve a surface roughness of ≤ 0.4 μm Ra, minimizing condensate adhesion and facilitating self-draining characteristics.
- Corrosion Resistance: Demonstrates a pitting resistance equivalent number (PREN) of ≥ 19 for 316L grade, ensuring long-term durability in humid indoor environments with elevated relative humidity (RH) levels.
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, providing reliable heat transfer performance across a wide operating temperature range of −20°C to +80°C.
- Mechanical Properties: Tensile strength ≥ 520 MPa; yield strength ≥ 205 MPa; elongation ≥ 40% (AISI 304); excellent formability for coil winding operations.
Specifications
| Parameter | Specification |
|---|---|
| Product Catalog Number | 565 |
| Product Designation | Coil Tube (盘管) |
| Material Grade | AISI 304 / AISI 316L Stainless Steel |
| Outer Diameter (OD) | Φ6.0 mm / Φ8.0 mm / Φ9.52 mm (customizable) |
| Wall Thickness | 0.3 mm – 0.8 mm |
| Coil Inner Diameter (ID) | 50 mm – 300 mm (configurable per FCU model) |
| Tube Length per Coil | Up to 15,000 mm (continuous seamless) |
| Coil Row Configuration | 1-Row / 2-Row / 4-Row / 6-Row |
| Tube Pitch (Center-to-Center) | 12.7 mm – 25.4 mm |
| Operating Temperature Range | −20°C to +80°C |
| Maximum Operating Pressure | 1.6 MPa (16 bar) |
| Hydrostatic Test Pressure | 2.4 MPa (24 bar) |
| Surface Treatment | Electropolished / Passivated / Anti-Condensate Coating (optional) |
| Compliance Standards | ASTM A269 / ASTM A270 / EN 10217-7 / GB/T 12771 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
Manufacturing Process
The production of this coil tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical homogeneity, and functional performance:
- Raw Material Selection: Certified stainless steel wire rod sourced from accredited mills, subjected to spectroscopic analysis for chemical composition verification (Fe, Cr, Ni, Mo, C, Si, Mn, P, S).
- Tube Forming: Cold-drawn seamless tubing produced via rotary piercing or capillary drawing processes to achieve precise wall thickness tolerances (±0.05 mm).
- Coil Winding: Computerized CNC winding machines form the tube into the specified helical geometry, with automated tension control to prevent ovality and distortion. Winding tolerances maintained at ±0.5 mm for coil diameter and ±1.0 mm for tube pitch.
- Welding: Inlet and outlet headers welded using TIG (Tungsten Inert Gas) welding under argon shielding, ensuring leak-tight joints with penetration integrity verified by 100% visual inspection and spot ultrasonic testing (UT).
- Surface Treatment: Electrochemical passivation removes free iron and forms a stable chromium oxide layer (Cr₂O₃), enhancing passive film stability and reducing condensate surface tension.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing, dimensional measurement, and visual surface inspection prior to packaging.
Applications
This stainless steel coil tube is engineered for deployment in a broad spectrum of HVAC and thermal management systems:
- Commercial FCU Systems: Central air conditioning units in office buildings, hotels, hospitals, and educational facilities.
- Residential HVAC: Ducted split-system air conditioners and cassette fan coil units.
- Industrial Process Cooling: Precision temperature control in semiconductor fabrication, pharmaceutical cleanrooms, and data centers.
- Heat Recovery Systems: Energy recovery ventilators (ERV) and heat exchangers where corrosion resistance is paramount.
- Chilled Water Distribution: Terminal units in hydronic cooling systems operating with treated water circuits.
Condensation Mitigation — Unique Selling Points
Based on extensive study of condensation phenomena in fan coil unit air conditioning systems, Wenzhou Jixing Metal Materials Co., Ltd has integrated several proprietary design and manufacturing strategies to address the persistent challenge of condensate formation, drip leakage, and associated operational inefficiencies:
- Optimized Surface Roughness: Electropolished finish with Ra ≤ 0.4 μm significantly reduces the surface energy of the tube, promoting condensate sheet-flow drainage rather than discrete droplet formation, thereby minimizing drip-related water leakage.
- Anti-Condensate Coating Option: An optional hydrophobic nanocoating (fluoropolymer-based) can be applied to the tube exterior, increasing the contact angle of water droplets to ≥ 110°, enabling self-shedding behavior even at low airflow velocities.
- Geometric Optimization: Tube pitch and coil geometry are engineered to promote uniform airflow distribution across the coil face, reducing localized cold spots that accelerate condensation beyond the drain pan capacity.
- Hydrophilic Fin Compatibility: The coil tube is designed for seamless integration with hydrophilic aluminum fins, which further enhance condensate drainage efficiency through capillary action along fin surfaces.
- Thermal Performance Enhancement: Enhanced heat transfer coefficients reduce the surface temperature differential between the coil and ambient air, directly limiting the rate of condensation nucleation.
- Corrosion-Free Longevity: Unlike carbon steel alternatives, the 304/316L stainless steel construction eliminates internal rust formation, preventing clogging of the tube bore and maintaining consistent hydraulic performance over the system's entire service life.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that all coil tube products meet or exceed international standards:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing excellence.
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices.
- ASTM A269 / A270 — Conformance to American Society for Testing and Materials standards for stainless steel tubing.
- EN 10217-7 — European standard for stainless steel tubes for heat exchangers and similar applications.
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes for general use.
- Mill Test Reports (MTR): Each batch is accompanied by a full chemical composition and mechanical property test report.
- Third-Party Inspection: Available upon request through SGS, Bureau Veritas, or TÜV Rheinland for independent verification.
Technical Summary
The Wenzhou Jixing Catalog No. 565 Stainless Steel Coil Tube represents a convergence of advanced materials science, precision manufacturing, and applied HVAC engineering. By directly addressing the condensation challenges inherent in fan coil unit systems through optimized surface engineering, geometric design, and optional functional coatings, this product delivers superior thermal efficiency, extended service intervals, and reduced total cost of ownership (TCO) for building operators. The product is available in standard configurations and fully supports OEM customization for specific system requirements.