Stainless Steel Coil Tube (Coiltube) for HVAC Fan Coil Units
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered heat exchanger component designed specifically for use in Fan Coil Units (FCU) and related HVAC (Heating, Ventilation, and Air Conditioning) systems. This product represents a critical element in the thermal management architecture of modern building climate control systems, where efficient heat transfer between the refrigerant and air stream is paramount.
The coil tube is engineered with a focus on optimizing the Cold Air Ratio and Dehumidification Coefficient (析湿系数), two coupled parameters that govern the thermodynamic performance of fan coil units. The design ensures superior latent and sensible heat exchange capabilities, enabling precise temperature and humidity control in commercial and industrial environments.
Material & Properties
Base Material
- Material Grade: Stainless Steel (typically SUS304 / AISI 304, with optional SUS316 / AISI 316L for enhanced corrosion resistance)
- Chemical Composition: Fe balance, Cr 18–20%, Ni 8–10.5%, Mn ≤2%, Si ≤0.75%, C ≤0.08%
- Corrosion Resistance: Excellent resistance to condensation water, chlorides, and atmospheric corrosion, ensuring long-term durability in humid operating environments
- Thermal Conductivity: ~16 W/(m·K) for SUS304 grade
- Operating Temperature Range: −40°C to +150°C
- Surface Treatment: Passivated finish (acid pickling and passivation) to enhance surface oxide layer integrity
Key Performance Characteristics
- High thermal efficiency with optimized fin-to-tube contact resistance
- Minimal fouling tendency due to smooth, passivated inner surface
- Resistance to galvanic corrosion when paired with aluminum fins
- Long service life exceeding 20 years under normal operating conditions
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Tube Outer Diameter (OD) | 7.0 / 8.0 / 9.52 | mm |
| Tube Wall Thickness | 0.35 / 0.40 / 0.50 | mm |
| Tube Pitch (Horizontal) | 12.7 / 15.9 / 19.05 | mm |
| Tube Pitch (Vertical) | 12.7 / 15.9 / 19.05 | mm |
| Fin Material | Aluminum (Al-Mg-Si alloy) / Copper | — |
| Fin Thickness | 0.10 / 0.12 / 0.15 | mm |
| Fin Density | 10–14 | fins/inch (FPI) |
| Rows | 2 / 3 / 4 | — |
| Working Pressure (Water Side) | ≤ 1.0 (tested at 1.5) | MPa |
| Refrigerant Type | R22 / R410A / R32 / Water-Glycol | — |
| Heat Transfer Efficiency (E) | ≥ 0.85 | — |
| Dehumidification Coefficient (ε) | 0.6–0.85 (optimized range) | — |
| Cold Air Ratio (CAR) | Optimized for coupled heat-mass transfer | — |
| Standard Length | 400 / 500 / 600 / 800 / 1000 | mm |
| Custom Length | Available upon request | mm |
Manufacturing Process
Production Workflow
- Raw Material Inspection: Incoming stainless steel tubes undergo spectroscopic analysis (OES) to verify chemical composition compliance with ASTM A269 / ASME SA-269 standards.
- Tube Straightening & Cutting: Precision straightening followed by CNC cutting to specified lengths with ±0.5 mm tolerance.
- Fin Insertion (Fin Coiling): Aluminum fins are inserted into the tube using automated fin-insertion machinery, ensuring uniform fin engagement and minimal tube distortion.
- U-Bend Forming: Hydraulic U-bending equipment forms return bends with consistent bend radii (typically 2× tube OD) to minimize flow resistance and stress concentration.
- Header Assembly: Tubes are assembled into header blocks (end caps) using brazing or welding, with precise alignment to ensure uniform flow distribution.
- Brazing: Vacuum brazing or flux brazing is performed at 600–650°C to create hermetic, leak-tight joints between tubes and headers.
- Surface Cleaning & Passivation: Post-brazing cleaning removes residual flux; passivation treatment restores and enhances the protective chromium oxide layer.
- Pressure Testing: Each coil tube undergoes 100% pressure testing at 1.5× working pressure for minimum 30 seconds to verify integrity.
- Final Inspection & Packaging: Dimensional verification, visual inspection, and protective packaging (VCI wrap + wooden crate) prior to shipment.
Process Quality Controls
- Inline optical inspection of fin engagement and bend geometry
- Helium leak detection for critical applications (sensitivity ≤ 1×10⁻⁹ mbar·L/s)
- Ultrasonic wall thickness measurement at random intervals
- Thermal performance testing on sampled units per ASHRAE Standard 34
Applications
Primary Application Domains
- Commercial HVAC Systems: Fan coil units for office buildings, shopping malls, hotels, and hospitals requiring precise temperature and humidity control
- Industrial Climate Control: Process cooling in pharmaceutical manufacturing, food processing, and electronics assembly facilities
- Residential HVAC: High-end residential ventilation and air conditioning systems
- Specialized Environments: Cleanrooms, laboratories, data centers, and cold storage facilities where corrosion resistance and thermal precision are critical
- Marine & Coastal Applications: HVAC systems in coastal regions where chloride-induced corrosion is a primary concern
Performance in Fan Coil Unit Systems
The coupled analysis of Cold Air Ratio (CAR) and Dehumidification Coefficient (ε) demonstrates that this stainless steel coil tube achieves optimal performance when:
- The surface temperature of the coil is maintained below the dew point of incoming air for effective latent heat removal
- The fin density and tube arrangement are calibrated to balance sensible and latent heat transfer ratios according to the specific psychrometric requirements of the application
- Flow maldistribution is minimized through optimized header design and tube layout
Quality Certifications & Standards Compliance
Applicable Standards
| Standard | Description |
|---|---|
| ASTM A269 / ASME SA-269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport |
| EN 10217-7 | European Standard for Heat-Exchanger Tubes and Heat-Treatment Tubes |
| ASHRAE Standard 34 | Methods of Testing Air-Cooled and Water-Cooled Heat Exchangers |
| ISO 9001:2015 | Quality Management Systems — Requirements |
| ISO 14001:2015 | Environmental Management Systems — Requirements |
Certifications Held
- ISO 9001:2015 Quality Management System Certification
- ISO 14001:2015 Environmental Management System Certification
- CE Marking (European Conformity) for HVAC components
- UL Listing (where applicable for North American markets)
- RoHS Compliance (Restriction of Hazardous Substances)
Unique Selling Points
- Superior Corrosion Resistance: Stainless steel construction eliminates the risk of internal corrosion and scaling common in copper tube alternatives, extending service life and reducing maintenance costs
- Optimized Coupled Heat-Mass Transfer: Design parameters are calibrated for optimal Cold Air Ratio and Dehumidification Coefficient performance, ensuring efficient simultaneous temperature and humidity control
- Low Flow Resistance: Smooth inner surface finish (Ra ≤ 0.8 μm) minimizes pressure drop, reducing pumping energy consumption
- Hygienic Design: Passivated stainless steel surface is non-toxic, non-porous, and resistant to microbial growth — ideal for food-grade and pharmaceutical applications
- Customization Capability: Full customization of tube OD, wall thickness, fin density, row count, and coil dimensions to meet specific OEM requirements
- Manufacturing Scale: Annual production capacity exceeding 50,000 units with consistent quality assurance through automated manufacturing and 100% pressure testing
Technical Notes
Note: The performance of the coil tube in fan coil unit systems is highly dependent on the coupling between the Cold Air Ratio and Dehumidification Coefficient. Proper selection requires a comprehensive psychrometric analysis of the operating conditions, including supply air temperature, return air temperature, and desired indoor humidity setpoint. Wenzhou Jixing Metal Materials Co., Ltd provides technical consultation and selection support for optimal system design.
Ordering Information
- Product Catalog Number: 245
- Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd
- Minimum Order Quantity: 50 sets
- Lead Time: 15–30 working days (standard configurations); 45–60 working days (custom configurations)
- Warranty: 24 months from date of shipment