Stainless Steel Coil Tube for Fan Coil Unit (FCU) Systems
Product Catalog No. 1062 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered heat exchange component designed for integration into Fan Coil Unit (FCU) air conditioning systems. This product represents the core thermal transfer element within hydronic cooling and heating loops, facilitating efficient heat dissipation between circulating refrigerant water and ambient air streams. The coil tube geometry—characterized by continuous helical winding with uniform pitch and consistent wall thickness—enables maximized surface-area-to-volume ratios, which are critical for achieving optimal thermal performance in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) installations.
Grounded in advanced thermodynamic simulation research, particularly the Summer Energy Saving Simulation and Control Research of Fan Coil Unit Air Conditioning Systems, this product line has been optimized to minimize seasonal energy consumption during peak cooling loads. The design incorporates insights from computational fluid dynamics (CFD) modeling and experimental validation of heat exchanger performance under varying operating conditions, ensuring that each coil tube meets stringent energy efficiency benchmarks.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term structural integrity in aqueous environments.
- Primary Material: SUS304 / AISI 304 (18/8 Stainless Steel) — containing a minimum of 18% Chromium (Cr) and 8% Nickel (Ni), providing superior resistance to general atmospheric and waterborne corrosion.
- Alternative Grade: SUS316L / AISI 316L — with added Molybdenum (Mo, 2–3%) for enhanced resistance to chloride-induced pitting and crevice corrosion, suitable for coastal or chemically aggressive environments.
- Surface Finish: Passivated mirror or matte finish (Ra ≤ 0.4 μm for mirror; Ra ≤ 0.8 μm for matte), ensuring minimal fouling resistance and prolonged thermal efficiency.
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, providing reliable heat transfer performance across the operating temperature range of −20°C to +150°C.
- Mechanical Properties: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40% (ASTM A270 compliant).
- Corrosion Resistance: Passivation potential ≥ +300 mV (Fe/Cr ratio), with excellent resistance to deionized water, glycol-based heat transfer fluids, and condensate.
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | 9.52 mm (⅜"), 12.70 mm (½"), 15.88 mm (⅝") | ASTM A269 / EN 10217-7 |
| Wall Thickness | 0.80 mm – 1.20 mm (tolerance ±0.05 mm) | ASTM A270 |
| Coil Pitch (Center-to-Center Spacing) | 12.70 mm – 25.40 mm (customizable) | ASHRAE 15 / ISO 22197 |
| Number of Rows | 1 to 6 rows (configurable) | — |
| Fin Material | Aluminum (Al 1100/1100-H14) or Copper (Cu C1100) | ASTM B209 / ASTM B152 |
| Fin Thickness | 0.10 mm – 0.20 mm | — |
| Fin Density | 10 FPI – 14 FPI (Fins Per Inch) | — |
| Operating Pressure | Up to 1.6 MPa (16 bar) design; 2.4 MPa hydrostatic test | ISO 5149 |
| Operating Temperature Range | −20°C to +150°C | — |
| Cooling Capacity (Typical) | 1.2 kW – 12.5 kW per unit (dependent on configuration) | ASHRAE 40 / ISO 13373-1 |
| Heat Transfer Efficiency (EER) | ≥ 2.8 (Seasonal Energy Efficiency Ratio, optimized) | EN 14511 |
| Available Lengths | 600 mm, 800 mm, 1000 mm, 1200 mm, or custom | — |
| End Connections | Flared, threaded (G1/2, G3/4, G1), brazed, or welded | ISO 7-1 / ISO 228-1 |
4. Manufacturing Process
The production of these coil tubes follows a rigorous multi-stage manufacturing sequence designed to ensure dimensional accuracy, material homogeneity, and long-term reliability:
- Material Selection & Incoming Inspection: Raw stainless steel strip or seamless tube is procured from certified mills. Each batch undergoes spectroscopic analysis (Optical Emission Spectroscopy, OES) to verify chemical composition compliance with ASTM A270/A269 specifications.
- Forming & Coil Winding: Precision tube-bending machines with servo-controlled tooling form the helical coil geometry. The winding process is executed at controlled speeds to prevent work-hardening, micro-cracking, or ovality exceeding 3% of nominal OD.
- Fin Attachment: Aluminum or copper fins are slitted, pressed, and crimped onto the formed tubes using automated fin-stamping and insertion equipment. Fin-to-tube bonding integrity is verified through pull-force testing (minimum 20 N per fin).
- Heat Treatment & Stress Relief: Post-forming annealing at 1050°C in a protective atmosphere (argon or vacuum) restores full austenitic microstructure, eliminating residual stresses and ensuring maximum ductility and corrosion resistance.
- Passivation & Surface Treatment: Chemical passivation using citric acid or nitric acid solutions establishes a stable chromium oxide film (Cr₂O₃), enhancing passive film integrity and preventing free iron contamination.
- Hydrostatic Pressure Testing: Each coil assembly is pressure-tested at 1.5× working pressure (minimum 2.4 MPa) with a hold time of ≥ 5 minutes to verify weld integrity and structural soundness.
- Performance Verification: Sample units are tested in accordance with ISO 13373-1 in a calibrated environmental chamber to confirm cooling capacity, air-side pressure drop, and water-side heat transfer coefficients under standardized conditions.
5. Applications
The Stainless Steel Coil Tube for FCU systems is deployed across a broad spectrum of commercial, industrial, and institutional HVAC applications:
- Commercial Buildings: Office towers, retail complexes, hotels, and hospitality venues requiring distributed cooling with high energy efficiency during summer peak loads.
- Healthcare Facilities: Hospitals, clinics, and pharmaceutical cleanrooms where corrosion resistance, hygienic surface finish, and reliable condensate management are paramount.
- Residential HVAC: High-end residential installations, apartments, and villas utilizing VRF (Variable Refrigerant Flow) or hydronic fan coil systems for zoned temperature control.
- Industrial Processes: Precision temperature control in electronics manufacturing, data centers, and laboratory environments where stable thermal performance is critical.
- Energy-Efficient Retrofit Projects: Upgrading existing FCU installations to improve Seasonal Energy Efficiency Ratio (SEER) and reduce peak cooling demand, as validated by summer energy-saving simulation studies.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes.
- ISO 14001:2015 — Environmental Management System certification, reflecting commitment to sustainable manufacturing practices and reduced environmental impact.
- EN 10204 3.1 — Material certification providing full traceability of raw material mill test reports.
- CE Marking — Conformity with European directives for mechanical and thermal safety requirements.
- ASHRAE Standards Compliance: Products designed and tested in accordance with ASHRAE Standard 40 (Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment) and ASHRAE 15 (Safety Standard for Refrigeration Systems).
- ISO 13373-1 — Performance testing conducted per international heat exchanger rating standards.
- RoHS & REACH Compliance — Restricted Substances compliance ensuring environmental and occupational safety.
7. Unique Selling Points
- Research-Validated Energy Optimization: Product design informed by peer-reviewed summer energy-saving simulation research, incorporating CFD-derived geometry optimization to reduce cooling energy consumption by up to 15% compared to conventional coil configurations.
- Superior Corrosion Durability: Austenitic stainless steel construction with passivated surface finish ensures service life exceeding 20 years in aggressive condensate and glycol environments, eliminating the need for replacement due to tube-side corrosion.
- Modular Configurability: Multi-row, multi-diameter, and custom-length options enable system designers to tailor thermal performance precisely to load profiles, reducing oversizing and improving part-load efficiency.
- Low Fouling Resistance: Mirror-finish surface treatment minimizes biofilm and mineral deposit accumulation, maintaining thermal performance over extended operating cycles and reducing maintenance frequency.
- Full Traceability: Each production batch is documented with mill certificates, dimensional inspection reports, and pressure test records, supporting OEM warranty claims and regulatory audits.
Note: All specifications are subject to final confirmation based on specific project requirements. Custom engineering support is available for non-standard configurations. Contact Wenzhou Jixing Metal Materials Co., Ltd. for detailed technical consultation and quotation.