Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Catalog No.: 580
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) is a precision-engineered tubing product specifically designed for integration into HVAC (Heating, Ventilation, and Air Conditioning) fan coil unit systems. This product series represents a critical heat-exchange component within indoor air distribution networks, where it serves as the primary medium for thermal energy transfer between refrigerant or hot water circuits and ambient air.
Developed with advanced metallurgical engineering principles, these coil tubes are manufactured to meet the stringent requirements of modern climate control systems. The product is particularly suited for environments demanding high corrosion resistance, thermal efficiency, and long-term operational reliability. The coil tube design incorporates a continuous helical winding configuration that maximizes surface-area-to-volume ratio, thereby enhancing heat dissipation and absorption performance under controlled PI-λD-μ (Proportional-Integral-Fractional Derivative-Fractional Integral) control algorithms used in automated temperature regulation systems.
2. Material Composition and Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, corrosion resistance, and thermal conductivity. The following table summarizes the key material properties:
| Property | Specification | Test Standard |
|---|---|---|
| Base Material | SUS304 / 06Cr19Ni10 (AISI 304) | GB/T 20878-2007 |
| Chromium (Cr) | 18.0 – 20.0% | — |
| Nickel (Ni) | 8.0 – 10.5% | — |
| Manganese (Mn) | ≤ 2.0% | — |
| Carbon (C) | ≤ 0.08% | — |
| Sulfur (S) | ≤ 0.030% | — |
| Tensile Strength | ≥ 520 MPa | GB/T 228.1-2021 |
| Yield Strength (0.2% offset) | ≥ 205 MPa | GB/T 228.1-2021 |
| Elongation (A₅₀) | ≥ 40% | GB/T 228.1-2021 |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) | ASTM E1461 |
| Density | 7.93 g/cm³ | — |
| Corrosion Resistance | Passivated surface, 96h NSS test, no pitting | GB/T 10125-2012 |
| Operating Temperature Range | −196°C to +870°C | — |
3. Geometric Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | Φ9.52 mm / Φ12.70 mm / Φ15.88 mm | ±0.05 mm |
| Wall Thickness | 0.40 mm – 0.80 mm | ±0.03 mm |
| Coil Winding Diameter | Φ150 mm – Φ600 mm (configurable) | ±1.0 mm |
| Tube Length (per coil) | 2 m – 15 m | ±50 mm |
| Coil Pitch | 12 mm – 25 mm | ±0.5 mm |
| Number of Turns | 15 – 80 turns | ±1 turn |
| End Form | Flat cut / Beveled / Flared (as specified) | — |
| Surface Finish | Mirror polished (Ra ≤ 0.4 μm) / Brushed | — |
| Maximum Working Pressure | 1.6 MPa (design); 2.4 MPa (burst) | — |
| Hydrostatic Test Pressure | 2.5 MPa for 30 seconds, no leakage | — |
4. Manufacturing Process
The production of these stainless steel coil tubes follows a rigorous multi-stage manufacturing protocol:
- Raw Material Selection and Verification: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectrographic analysis (OES) to confirm chemical composition compliance with GB/T 20878 and ASTM A240 standards.
- Coil Forming (螺旋成型): The flat strip is fed through precision CNC-controlled coiling machinery equipped with hydraulic tension control systems to form the helical coil geometry. Laser-guided tooling ensures dimensional accuracy within specified tolerances.
- Welding (对接焊/氩弧焊): Longitudinal seams are sealed using TIG (Tungsten Inert Gas) welding with high-purity argon shielding. Post-weld heat treatment eliminates residual stresses and restores the austenitic microstructure. Weld bead geometry is controlled to minimize flow resistance and ensure uniform wall thickness at the seam.
- Surface Treatment and Passivation: The coil tube undergoes acid pickling and passivation treatment to remove surface oxides and establish a stable chromium oxide protective layer, enhancing long-term corrosion resistance.
- Quality Inspection: Each coil is subjected to 100% hydrostatic pressure testing, dimensional measurement via ultrasonic wall thickness gauging, and visual inspection of weld integrity. Random samples undergo radiographic testing (RT) and hardness testing per ASTM E10.
- Packaging: Qualified products are wound onto protective cores, wrapped in moisture-barrier film, and shipped in export-grade wooden cases.
5. Applications
The stainless steel coil tube is designed for the following primary application domains:
- HVAC Fan Coil Units (风机盘管): Primary heat exchanger medium in commercial and residential air conditioning systems, where the coil tube transfers thermal energy between water/refrigerant and ambient air.
- Commercial Building Climate Control: Integration into chilled water and hot water distribution systems in office buildings, hotels, hospitals, and shopping centers.
- Food Processing and Pharmaceutical Industries: Sanitary-grade coil tubes for temperature-controlled processing equipment requiring hygienic, corrosion-resistant components.
- Marine and Coastal Environments: HVAC systems in ships, offshore platforms, and coastal facilities where chloride-induced corrosion is a concern.
- Automated Temperature Control Systems: Compatibility with advanced PID and fractional-order (PI-λD-μ) controller implementations for precise room temperature regulation in smart building systems.
6. Quality Certifications and Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| GB/T 14976-2017 | Chinese national standard for cold-rolled stainless steel seamless tubes |
| ASTM A269/A269M | American standard for austenitic stainless steel welded tubing |
| EN 10217-7 | European standard for austenitic stainless steel tubes for pressure purposes |
| NSF/ANSI 61 | Drinking water system components certification (where applicable) |
| CE Marking | Conformity with European health, safety, and environmental protection standards |
7. Unique Selling Points
Superior Corrosion Resistance: The high chromium-nickel austenitic composition provides outstanding resistance to atmospheric corrosion, acidic condensate, and chlorinated environments—critical for HVAC applications where moisture and refrigerant condensate are constant exposure factors.
Enhanced Thermal Performance: The precision-coiled geometry with optimized pitch and diameter ratios delivers up to 18% greater heat transfer efficiency compared to conventional finned tube configurations, reducing system energy consumption.
Control-System Compatibility: Designed with uniform thermal response characteristics that facilitate stable operation under advanced fractional-order PI-λD-μ control algorithms, enabling precise room temperature regulation with minimal overshoot and fast settling time.
Long Service Life: With a design service life exceeding 25 years under normal operating conditions, the coil tube eliminates the need for frequent replacement, reducing total cost of ownership (TCO) in commercial HVAC installations.
Hygienic Surface: Mirror-polished internal surface (Ra ≤ 0.4 μm) prevents biofilm accumulation and mineral scale adhesion, maintaining consistent thermal performance throughout the operational lifespan.
8. Technical Notes
Wenzhou Jixing Metal Materials Co., Ltd. provides custom configuration services for coil tube dimensions, winding parameters, and end-form geometries tailored to specific OEM requirements. Technical support is available for integration with automated control systems utilizing improved optimization algorithms (including IACOA-based parameter tuning) for optimal thermal regulation performance.
Note: All specifications are subject to revision based on continuous product development. Customers are advised to consult the latest technical data sheet for current specifications before procurement.