Stainless Steel Coil Tube — Fan Coil Unit (FCU) Heat Exchanger Application
Product Overview
The Stainless Steel Coil Tube is a precision-engineered coiled tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into Fan Coil Units with Fresh Air Systems (FCU + Fresh Air System). As a critical heat transfer component, the coil tube facilitates efficient thermal exchange between circulating water and indoor air, directly influencing indoor air quality (IAQ) and pollutant concentration distribution within occupied spaces.
This product is classified under the Documentary Learning category, referencing the technical study titled "Indoor Pollutant Concentration Distribution in Fan Coil Unit with Fresh Air System", which provides the theoretical and empirical foundation for optimizing coil tube geometry, material selection, and system performance in HVAC applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, and long-term structural integrity in HVAC environments.
- Material Grade: SUS304 / SUS316L (ASTM A213 TP304 / TP316L)
- Corrosion Resistance: Excellent resistance to condensation water corrosion, chloride-induced pitting, and general atmospheric oxidation — critical for maintaining air quality over extended service life.
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, ensuring efficient heat transfer between the refrigerant/circulating water and the surrounding air stream.
- Mechanical Properties: Yield strength ≥ 205 MPa; tensile strength ≥ 515 MPa; elongation ≥ 40% — providing dimensional stability under cyclic thermal loading.
- Hygienic Surface Finish: Ra ≤ 0.8 μm inner surface roughness to minimize particulate accumulation and biofilm formation, contributing to reduced indoor pollutant concentration.
- Temperature Range: Operational range of −40°C to +250°C, accommodating both cooling and heating modes.
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 8.0 mm / 9.52 mm / 12.0 mm (±0.1 mm) | ASTM A213 |
| Wall Thickness | 0.50 mm – 1.00 mm (±10%) | GB/T 14976 |
| Coil Pitch (Center-to-Center) | 16 mm – 25 mm (configurable) | Manufacturer Specification |
| Coil Bend Radius | ≥ 3D (minimum 24 mm for OD 8 mm) | ASME B31.9 |
| Tube Length (Uncoiled) | 6 m – 12 m per coil assembly | Custom Order |
| Surface Treatment | Electropolished / Pickled & Passivated | ASTM A967 |
| Pressure Rating | Up to 1.6 MPa (16 bar) working pressure | GB/T 12459 |
| Fins (Optional) | Aluminum or stainless steel plate fins, 10–14 FPI | ASHRAE 90.1 |
| End Forming | Flared / Grooved / Threaded connections | ASME B31.9 |
| Packaging | Protective wrapping with desiccant, wooden crate or export carton | ISO 4180 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage process to ensure dimensional accuracy, material homogeneity, and surface integrity:
- Wire Drawing: Cold-drawn stainless steel wire rod is reduced to precise OD and wall thickness tolerances using multi-stage die sets, ensuring consistent cross-sectional geometry.
- Annealing & Pickling: Intermediate annealing relieves cold-work stresses; subsequent acid pickling removes oxide scale, restoring the passive chromium oxide layer.
- Coil Forming (Spiral Winding): Computer-controlled (CNC) coiling machines wind the tube into precise spiral configurations with controlled pitch and bend radius, preventing ovality and work-hardening at bend points.
- Hydrostatic Testing: Each coil assembly undergoes 100% hydrostatic pressure testing at 1.5× working pressure (2.4 MPa) for a minimum of 30 seconds to verify leak-tightness.
- Fin Application (if applicable): Aluminum or stainless steel fins are mechanically slitted and expanded onto the coil tube using precision fin-insertion equipment.
- Surface Finishing: Final electropolishing or passivation treatment ensures hygienic surface quality with minimal roughness, reducing particulate retention.
- Final Inspection & Packaging: Dimensional verification, visual inspection, and material certification documentation precede protective packaging for shipment.
Applications
The stainless steel coil tube serves as the core heat exchange element in a wide range of HVAC systems, with particular relevance to the indoor air quality optimization studied in the referenced literature:
- Fan Coil Units (FCU) with Fresh Air Systems: Primary application — the coil tube enables precise temperature and humidity control while the fresh air component dilutes indoor pollutants (CO₂, VOCs, particulate matter), resulting in uniform pollutant concentration distribution as analyzed in the referenced study.
- Commercial & Institutional Buildings: Offices, hospitals, schools, and laboratories requiring strict IAQ standards.
- Residential HVAC: High-end residential installations where stainless steel construction eliminates corrosion-related indoor air contamination.
- Cleanroom & Pharmaceutical Facilities: Hygienic surface finish meets GMP requirements for controlled environments.
- Food Processing & Beverage Industry: Resistance to chemical cleaning agents and sanitization cycles.
- Marine & Coastal Environments: SUS316L grade provides enhanced chloride resistance for humid coastal installations.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity to international and national standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing processes.
- ISO 14001:2015 — Environmental Management System for sustainable production practices.
- CE Marking — Conformity with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU).
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes.
- ASTM A213 / A269 — American standards for wrought austenitic stainless steel tubing.
- ASME B31.9 — Pressure Piping, Fuel Gas (building services) design and installation standards.
- RoHS Compliance — Restriction of Hazardous Substances directive compliance.
- Material Test Reports (MTR): Mill certificates and chemical composition analysis provided for every batch.
Unique Selling Points
1. Optimized for Indoor Air Quality: The product design and material selection are informed by peer-reviewed research on pollutant concentration distribution in FCU + Fresh Air systems, ensuring that the coil tube contributes to — rather than degrades — indoor environmental quality.
2. Corrosion-Free Longevity: Unlike carbon steel alternatives, the austenitic stainless steel construction eliminates rust-related particulate release, maintaining air purity throughout the service life (estimated 20+ years).
3. Precision Engineering: CNC-controlled coil forming ensures consistent geometry, maximizing heat transfer surface area and airflow uniformity — directly correlating to the pollutant distribution uniformity discussed in the referenced study.
4. Hygienic Surface: Electropolished interior surfaces with Ra ≤ 0.8 μm prevent microbial growth and particulate adhesion, critical for healthcare and pharmaceutical applications.
5. Customizability: Flexible OD, wall thickness, coil pitch, and fin configuration options allow OEM integration into diverse FCU designs and system architectures.