Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
Product Overview
The Stainless Steel Coil Tube (Product No. 1365) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing product specifically designed for integration into Fan Coil Unit (FCU) plus Fresh Air Systems within commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications. This coil tube serves as the critical heat exchange element that facilitates thermal energy transfer between circulating refrigerant or hot/cold water and the surrounding air stream, enabling efficient temperature regulation and humidity control within conditioned spaces.
Unlike conventional copper coil assemblies, the stainless steel coil tube offers superior corrosion resistance, extended service life, and enhanced structural integrity, making it an ideal choice for demanding environments where long-term reliability is paramount. The product embodies the principles outlined in advanced HVAC system design literature, particularly regarding the synergistic operation of fan coil units with dedicated fresh air ventilation systems.
Material & Properties
The coil tube is fabricated from high-grade Austenitic Stainless Steel, specifically conforming to the following material standards:
- Base Material: SUS304 / SUS316 Stainless Steel (ASTM A269 / ASTM B483)
- Grade Composition (SUS316): Carbon ≤ 0.08%, Chromium 16.0–18.0%, Nickel 10.0–14.0%, Molybdenum 2.0–3.0%
- Tensile Strength: ≥ 515 MPa (74,700 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (minimum)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +600°C
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and chlorides
- Surface Finish: Electropolished or passivated (Ra ≤ 0.4 μm)
Technical Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) | 9.52 / 12.70 / 15.88 (customizable) | mm |
| Wall Thickness | 0.80 – 1.20 | mm |
| Inner Diameter (ID) | 7.52 – 14.28 | mm |
| Coil Pitch (Center-to-Center) | 15.0 – 25.0 | mm |
| Number of Rows | 1 to 6 (configurable) | — |
| Tube Length per Coil | 600 – 3,000 | mm |
| Coil Width | 300 – 1,200 | mm |
| Coil Height | 100 – 400 | mm |
| Maximum Operating Pressure | 1.6 – 2.5 | MPa |
| Hydrostatic Test Pressure | 3.0 | MPa |
| Refrigerant Compatibility | R410A, R32, R134a, R404A, R22 | — |
| Water Flow Rate (Nominal) | 0.3 – 1.5 | L/min |
| Cooling Capacity Range | 0.8 – 5.0 | kW |
| Heating Capacity Range | 1.0 – 6.0 | kW |
| Fin Material | Aluminum (0.10–0.15 mm thickness) | — |
| Fin Density | 8 – 14 fins per inch (FPI) | — |
| Connector Type | Flared / Soldered / Brazed / Push-Fit | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, material homogeneity, and optimal thermal performance:
- Raw Material Selection & Inspection: Stainless steel strip or seamless tubing is sourced from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition compliance with ASTM/EN standards.
- Cold Drawing & Forming: Precision cold-drawing processes are employed to achieve the exact tube diameter and wall thickness specifications. Cold forming enhances the grain structure and improves mechanical properties through work hardening.
- Coil Bending & Pitching: Automated CNC-controlled bending machines form the tubing into precise helical coils with consistent pitch and uniform curvature radius, ensuring optimal flow distribution and heat transfer efficiency.
- Fin Stamping & Expansion: Aluminum fins are precision-stamped and mechanically expanded onto the coil tubes to maximize the heat exchange surface area while maintaining structural rigidity.
- Welding & Assembly: Header connections and inlet/outlet ports are fabricated using TIG (Tungsten Inert Gas) welding or high-frequency resistance welding to ensure leak-free joints and structural continuity.
- Surface Treatment: The assembled coil undergoes electropolishing or chemical passivation to remove surface contaminants, enhance corrosion resistance, and achieve the specified surface roughness.
- Pressure Testing & Leak Detection: Each unit undergoes 100% hydrostatic pressure testing at 3.0 MPa for a minimum dwell time of 30 seconds, followed by nitrogen leak detection using electronic bubble detectors or helium mass spectrometry.
- Final Quality Inspection: Comprehensive dimensional verification, visual inspection, and performance testing are conducted prior to packaging and shipment.
Applications
The stainless steel coil tube is engineered for deployment in a wide range of HVAC system configurations, with particular emphasis on the following applications:
1. Fan Coil Unit (FCU) Systems
The primary application domain. The coil tube serves as the core heat exchanger within fan coil units, facilitating cooling and heating through direct air contact. In FCU-plus-fresh-air system configurations, the coil tube works in tandem with dedicated outdoor air systems (DOAS) to deliver both thermal comfort and indoor air quality (IAQ) simultaneously.
2. Commercial Building HVAC
- Office buildings and corporate headquarters
- Hospital and healthcare facilities (operating theaters, intensive care units)
- Hotel and hospitality venues
- Retail and shopping complexes
- Educational institutions and laboratories
3. Industrial & Process Cooling
- Food processing and pharmaceutical manufacturing
- Electronics manufacturing cleanrooms
- Data centers and server rooms
- Chemical processing facilities
4. Specialized Environments
- Marine and offshore platforms (chloride-rich atmospheres)
- Coastal and high-humidity residential applications
- Food-grade processing areas requiring hygienic surfaces
- Corrosive industrial environments
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring that every coil tube product meets or exceeds international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management
- EN 12828 — Heating systems in buildings (heat exchangers)
- EN 12831 — Heating systems in buildings (design of water-based systems)
- ASHRAE Standard 90.1 — Energy efficiency compliance
- CE Marking — European Conformity (Machinery Directive 2006/42/EC)
- RoHS Compliance — Restriction of Hazardous Substances Directive
- SGS / Bureau Veritas — Third-party inspection and testing reports
- ASME B31.5 — Refrigeration and Air-Conditioning Piping
Unique Selling Points
Superior Corrosion Resistance: The use of SUS316 stainless steel with molybdenum alloying provides exceptional resistance to chloride-induced pitting and crevice corrosion, significantly outperforming conventional copper or carbon steel alternatives in humid and coastal environments.
Extended Service Life: With a projected operational lifespan exceeding 25 years under normal conditions—compared to 8–12 years for copper coil assemblies—the stainless steel coil tube offers a dramatically lower total cost of ownership (TCO) over the system lifecycle.
Hygienic Surface Finish: The electropolished inner surface (Ra ≤ 0.4 μm) prevents bacterial adhesion and biofilm formation, making the product suitable for pharmaceutical, food-grade, and medical HVAC applications where contamination control is critical.
Optimized Thermal Performance: Precision-engineered coil geometry and fin density ensure uniform air distribution and maximum heat transfer coefficients, achieving COP (Coefficient of Performance) values that meet or exceed ASHRAE energy efficiency benchmarks.
Modular & Customizable Design: The product is available in multiple configurations to accommodate diverse system designs, from compact residential FCUs to large-capacity commercial units, with custom dimensions available upon request.
Environmental Sustainability: Stainless steel is 100% recyclable without degradation of material properties, contributing to circular economy objectives and reducing the environmental footprint of HVAC system replacements.
System Integration Notes
In the context of a Fan Coil Unit plus Fresh Air System, the stainless steel coil tube functions as the terminal heat exchange component within the FCU. The system architecture typically comprises:
- Fan Coil Unit: Contains the coil tube assembly, centrifugal fan, and condensate drain pan for sensible and latent heat removal
- Dedicated Outdoor Air Unit (DOAS): Provides conditioned fresh air to satisfy ventilation requirements per ASHRAE Standard 62.1
- Control System: Variable-speed drives and thermostatic controllers coordinate between the FCU and DOAS for optimal energy efficiency and indoor air quality
This dual-system approach allows the FCU coil to handle the majority of the cooling/heating load while the DOAS manages ventilation and humidity control independently, resulting in energy savings of 15–30% compared to single-system configurations.