Stainless Steel Coil Tube for Fan Coil Unit (FCU) Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange tube designed specifically for use in Fan Coil Unit (FCU) systems. These coil tubes serve as the core heat transfer components in hydronic air distribution systems, enabling efficient thermal energy exchange between circulating water and ambient air within commercial, industrial, and residential HVAC (Heating, Ventilation, and Air Conditioning) applications.
Derived from extensive engineering knowledge in FCU selection and system design, this product line addresses critical performance challenges such as pressure drop optimization, heat transfer coefficient maximization, and long-term corrosion resistance under varying fluid conditions.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, primarily conforming to ASTM A213 TP304 and ASTM A213 TP316L specifications. Key material properties include:
- Chemical Composition: Carbon (C) ≤ 0.08%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Molybdenum (Mo) ≤ 2.0% (for 316L grade)
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular corrosion (IGC) due to low carbon content
- Thermal Conductivity: 16.3 W/(m·K) at 20°C, ensuring efficient heat transfer performance
- Tensile Strength: ≥ 515 MPa, providing structural integrity under thermal cycling
- Operating Temperature Range: −196°C to +450°C
- Surface Finish: Electropolished or passivated surface with roughness Ra ≤ 0.4 μm, minimizing fouling and biofilm accumulation
Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | Φ7.94 mm / Φ9.53 mm / Φ12.70 mm / Φ15.88 mm |
| Tube Wall Thickness | 0.50 mm / 0.65 mm / 0.80 mm / 1.00 mm |
| Coil Pitch | 16 mm / 19 mm / 25 mm / 32 mm |
| Row Configuration | 2-row, 3-row, 4-row (configurable) |
| Tube Length per Coil | 300 mm – 1,200 mm |
| Coil Diameter | Φ150 mm – Φ600 mm |
| Operating Pressure | ≤ 1.0 MPa (design pressure) |
| Design Service Life | ≥ 20 years |
| Heat Transfer Coefficient | ≥ 3,200 W/(m²·K) (water-to-air) |
| Pressure Drop (at rated flow) | ≤ 15 kPa |
| Standard Length | Custom (1 m – 6 m coil bundle) |
| Applicable Standards | ASTM A213, GB/T 14976, EN 10216-5 |
Manufacturing Process
The production of these coil tubes follows a rigorously controlled multi-stage manufacturing sequence to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Selection: Certified stainless steel seamless or welded pipe blanks are sourced from accredited mills, with each batch verified via Positive Material Identification (PMI) testing.
- Cutting & Deburring: Precision laser or mechanical cutting to specified lengths, followed by internal and external deburring to eliminate stress concentrators.
- Cold Forming / Coiling: The tubes are cold-bent into helical coil configurations using CNC-controlled coiling machines, maintaining wall thickness uniformity within ±10% of the original wall thickness.
- Heat Treatment: Solution annealing at 1,050–1,150°C followed by rapid water quenching to restore full austenitic microstructure and eliminate residual stresses from cold forming.
- Surface Treatment: Pickling and passivation (or electropolishing) to remove scale, restore chromium oxide passive film, and achieve the required surface finish.
- Quality Inspection: 100% visual inspection, dimensional verification via laser measurement, and periodic ultrasonic testing (UT) for wall thickness confirmation.
Applications
These stainless steel coil tubes are integral components in a wide range of HVAC and thermal management systems:
- Commercial HVAC: Fan coil units in office buildings, hotels, hospitals, and shopping centers for precise temperature and humidity control
- Industrial Process Cooling: Heat rejection coils in process cooling systems where corrosion resistance is paramount
- Cleanroom Systems: Low-fouling coil tubes for pharmaceutical, semiconductor, and food processing facilities requiring ultra-clean air distribution
- Marine & Offshore HVAC: Corrosion-resistant coil tubes for shipboard and offshore platform climate control systems
- Chilled Beam Systems: Indirect evaporative cooling and chilled beam terminal units in high-performance building systems
- Heat Recovery Units (HRU): Energy recovery ventilation systems requiring durable, long-life heat exchange surfaces
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing excellence
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European health, safety, and environmental protection standards
- EN 10204 3.1 — Third-party material certification for each production batch
- ASTM F49 — Compliance with standard specification for seamless and welded austenitic stainless steel tubing
- ASME B31.5 — Adherence to pressure piping and piping components standards
Unique Selling Points
1. Optimized Coil Geometry for Minimal Pressure Drop: Engineered coil pitch and tube diameter ratios that reduce hydraulic resistance while maintaining high heat transfer surface area — critical for energy-efficient FCU operation.
2. Superior Corrosion Durability: Low-carbon austenitic stainless steel construction ensures resistance to condensation water corrosion, eliminating the common failure mode of carbon steel coils in humid environments.
3. Precision Cold-Forming Technology: Advanced CNC coiling ensures uniform tube geometry, preventing localized stress concentrations and ensuring consistent performance across the entire coil bundle.
4. System-Level Engineering Insight: Product design incorporates lessons learned from comprehensive FCU system design studies, addressing real-world issues such as water hammer, uneven air distribution, and coil fouling.
5. Customization Capability: Flexible configuration options (row count, coil diameter, tube OD, pitch) allow tailoring to specific system design parameters for optimal thermal-hydraulic performance.