Stainless Steel Coil Tube for Fan Coil Unit (FCU) HVAC Systems
Product Overview
The stainless steel coil tube is a precision-engineered heat exchange component designed specifically for Fan Coil Unit (FCU) air conditioning systems. As a critical element within the HVAC (Heating, Ventilation, and Air Conditioning) industry, these coil tubes facilitate efficient thermal transfer between circulating refrigerant or hot water and ambient air. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product combines superior corrosion resistance, thermal conductivity, and mechanical integrity to meet the demanding performance requirements of modern building climate control systems.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, ensuring long-term durability and resistance to degradation under continuous thermal cycling and exposure to moisture-laden air streams.
Material Composition
- Base Material: Austenitic Stainless Steel (Grade 304 / 316L)
- Chromium (Cr): 18–20% (primary corrosion resistance element)
- Nickel (Ni): 8–10% (stabilizes austenitic microstructure)
- Molybdenum (Mo): 2–3% (enhanced pitting resistance in 316L variant)
- Carbon (C): ≤ 0.08% (prevents intergranular corrosion during welding)
Mechanical & Thermal Properties
- Tensile Strength: 520–720 MPa (depending on grade and cold-work condition)
- Yield Strength: 205–310 MPa
- Elongation at Break: 35–55%
- Thermal Conductivity: 14–16 W/(m·K) at 25°C
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /°C
- Operating Temperature Range: −40°C to +200°C
- Corrosion Resistance: Excellent resistance to condensation water, chlorides, and atmospheric pollutants
Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 6.35 mm / 8.0 mm / 9.53 mm / 12.7 mm (customizable) |
| Wall Thickness | 0.3 mm – 0.6 mm (precision rolled) |
| Fins Per Inch (FPI) | 8 – 14 fins per inch |
| Fin Material | Aluminum (Al-Mg-Si alloy) or Stainless Steel |
| Fin Thickness | 0.10 mm – 0.15 mm |
| Row Configuration | 1-row / 2-row / 3-row / 4-row (configurable) |
| Tube Pitch (TPT) | 19.05 mm – 25.4 mm |
| Fin Spacing | 1.8 mm – 3.0 mm |
| Overall Coil Length | 300 mm – 1500 mm (application-dependent) |
| Surface Treatment | Pickled & Passivated (P&P) / Electropolished |
| Pressure Rating | Up to 1.6 MPa (working pressure) |
| Refrigerant Compatibility | R-410A, R-32, R-22, Water/Glycol Solutions |
Manufacturing Process
- Coil Slitting & Leveling: The parent stainless steel coil is slit to precise width and leveled to eliminate residual stresses, ensuring uniform tube geometry.
- Cold Forming (Tube Making): Flat strip is passed through a series of progressive dies to form seamless circular tubes with tight dimensional tolerances (±0.05 mm).
- Hydroforming / Expansion: Tubes are expanded into the aluminum or steel fins using a hydroforming process, creating a tight metal-to-metal bond that maximizes thermal contact without soldering.
- U-Bend Formation: Pre-formed tubes are bent into U-shaped serpentine configurations using CNC-controlled bending machines to achieve consistent bend radii and prevent wall thinning.
- Header Assembly: U-bends are welded to inlet and outlet headers using TIG (Tungsten Inert Gas) welding with argon shielding to maintain metallurgical purity.
- Pressure Testing: Each coil assembly undergoes 100% pneumatic or hydraulic pressure testing at 1.5× working pressure to verify leak-tightness.
- Cleaning & Passivation: Interior surfaces are cleaned of weld oxides and contaminants, followed by passivation treatment to restore the passive chromium oxide film.
- Final Inspection: Dimensional verification, visual inspection, and performance testing are conducted prior to packaging.
Applications
- Commercial HVAC Systems: Primary heat exchange element in fan coil units for office buildings, shopping malls, and hospitality facilities.
- Residential Air Conditioning: Indoor unit coil for ducted and ductless mini-split systems.
- Industrial Process Cooling: Precision temperature control in manufacturing environments requiring corrosion-resistant heat exchangers.
- Chilled Water Systems: Hot water heating coils for low-temperature radiant heating applications.
- Energy-Efficient Demand Response Systems: Optimized for integration with smart building control systems utilizing piecewise linear regression algorithms for load modulation and energy management.
Quality Certifications & Standards Compliance
- Material Certification: ASTM A213 / ASTM A269 / EN 10216-5 / GB/T 14976
- Manufacturing Standard: ISO 9001:2015 Quality Management System
- Product Testing: EN 12828 (radiant heating components) / ASHRAE 34 (refrigerating systems)
- Environmental Compliance: RoHS Directive 2011/65/EU / REACH Regulation (EC) No 1907/2006
- Mill Certification: 3.1 Certificate per EN 10204
- Welding Procedure: AWS D10.9 (stainless steel welding) / ISO 15614
Unique Selling Points
Exceptional Corrosion Durability: The austenitic stainless steel construction provides outstanding resistance to condensate-induced corrosion, a common failure mode in aluminum coil tubes, extending service life beyond 15 years in aggressive indoor environments.
Hydroformed Fin-to-Tube Bond: The mechanical interlock achieved through hydroforming eliminates the need for brazing flux, ensuring zero thermal contact resistance and preventing solder-related contamination in the refrigerant circuit.
Smart Building Integration: Designed with uniform thermal response characteristics that facilitate accurate modeling using piecewise linear regression methods, enabling precise demand response quantification and energy optimization in Building Energy Management Systems (BEMS).
Full Customization Capability: Flexible geometry, row count, and fin density configurations allow OEMs to optimize coil performance for specific capacity requirements, noise levels, and pressure drop constraints.