Stainless Steel Coil Tube — Fan Coil Heat Exchanger Tube
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchanger tube designed specifically for use in fan coil units (FCUs) and related HVAC (Heating, Ventilation, and Air Conditioning) systems. This product is supplied in continuous coil form to facilitate efficient downstream processing, including tube bending, fin insertion, and header assembly. The coil tube is engineered to meet the demanding thermal and mechanical requirements of air-side heat exchange applications, including operation under non-standard conditions where conventional design assumptions may not hold.
As a core component of fan coil heat exchangers, the coil tube directly influences the overall cooling and heating capacity, energy efficiency, and service life of the system. Wenzhou Jixing Metal Materials delivers coil tubes that comply with international standards and are suitable for a wide range of operating environments, from commercial building HVAC systems to industrial process cooling applications.
2. Material & Properties
2.1 Base Material
- Material Grade: SUS304 (UNS S30400) austenitic stainless steel, with options for SUS316L (UNS S31603) for enhanced corrosion resistance in aggressive environments.
- Composition (SUS304): Carbon (C) ≤ 0.08%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Manganese (Mn) ≤ 2.0%, Silicon (Si) ≤ 1.0%, Phosphorus (P) ≤ 0.045%, Sulfur (S) ≤ 0.030%.
- Form: Seamless or welded round tube, cold-drawn and cold-rolled for dimensional accuracy.
2.2 Mechanical Properties
- Tensile Strength: ≥ 520 MPa (75,400 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40%
- Hardness: ≤ 92 HRB (annealed condition)
2.3 Thermal Properties
- Thermal Conductivity (20°C): 16.3 W/(m·K)
- Thermal Conductivity (100°C): 20.2 W/(m·K)
- Specific Heat Capacity: 500 J/(kg·K)
- Coefficient of Thermal Expansion (20–100°C): 17.3 × 10⁻⁶ /K
2.4 Corrosion Resistance
The austenitic stainless steel matrix provides excellent resistance to atmospheric corrosion, condensation water, and mild chemical exposure. SUS316L grade offers additional protection against chlorides and marine atmospheres, making it suitable for coastal installations and humid tropical environments.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.70 mm (1/2") |
| Wall Thickness | 0.50 mm – 1.00 mm (standard); custom available |
| Coil Length | Up to 500 m per coil (continuous) |
| Coil Inner Diameter | 300 mm – 600 mm |
| Surface Finish | 2B / BA (Bright Annealed) / Polished (Ra ≤ 0.4 μm) |
| Dimensional Tolerance (OD) | ±0.05 mm |
| Dimensional Tolerance (Wall) | ±0.03 mm |
| Operating Temperature Range | −40°C to +200°C |
| Maximum Operating Pressure | 1.6 MPa (standard); 2.5 MPa (high-pressure grade) |
| Applicable Refrigerants | R22, R407C, R410A, R134a, R32, R404A, CO₂ (R744) |
| Coating / Treatment | Passivation (citric acid); optional PVD coating for enhanced corrosion protection |
| Applicable Standards | ASTM A269, ASTM A213, EN 10217-7, GB/T 14976, JIS G3459 |
4. Manufacturing Process
- Raw Material Selection: Virgin stainless steel wire rod or billet conforming to ASTM A269 / EN 10217-7 chemical composition requirements. Incoming material undergoes spectroscopic verification (PMI — Positive Material Identification).
- Tube Forming: Cold-drawn seamless tube or ERW (Electric Resistance Welded) tube production with precise control of outer diameter and wall thickness.
- Cold Reduction & Drawing: Multi-pass cold drawing to achieve final dimensions and improve surface finish and mechanical properties.
- Heat Treatment (Annealing): Solution annealing at 1050–1150°C followed by controlled cooling to relieve residual stresses and achieve the desired grain structure and mechanical properties.
- Surface Finishing: Pickling and passivation treatment using citric acid or nitric-hydrofluoric acid blend to remove scale and form a protective chromium oxide layer. Optional electropolishing for ultra-smooth internal surfaces (Ra ≤ 0.2 μm) to minimize flow resistance.
- Coiling: Precision coiling on CNC-controlled winding machines to achieve uniform coil geometry without introducing deformation or residual stress.
- Quality Inspection: 100% dimensional inspection, ultrasonic testing (UT) for internal defects, hydraulic pressure testing (2.0 MPa for 5 seconds), and visual inspection for surface defects.
- Packaging & Dispatch: Coils are wrapped in protective film, sleeved with moisture-absorbing desiccant, and palletized for export-ready shipment.
5. Applications
5.1 Primary Applications
- Fan Coil Units (FCUs): Chilled water and hot water coils for commercial and residential HVAC systems.
- Air Handling Units (AHUs): Cooling and heating coils in centralized air conditioning systems.
- Chillers: Evaporator and condenser tubes in water-cooled and air-cooled chiller units.
- Radiators & Underfloor Heating: Low-temperature hydronic heating systems.
- Heat Pump Systems: Indoor coil tubes for air-source and ground-source heat pumps.
5.2 Non-Standard Condition Applications
Based on engineering research into fan coil unit performance under non-standard operating conditions — including elevated ambient temperatures, high humidity, altitude derating, and off-design flow rates — the coil tubes produced by Wenzhou Jixing Metal Materials are engineered with the following considerations:
- High Ambient Temperature Operation: Optimized wall thickness and thermal conductivity to maintain rated capacity at ambient temperatures up to 50°C.
- High Humidity / Condensation Environments: Enhanced surface passivation and optional hydrophilic coating to manage condensate drainage and prevent microbial growth.
- Altitude Derating: Material selection accounts for reduced air density at elevations above 1500 m, ensuring adequate heat transfer coefficients.
- Variable Flow Rate Operation: Smooth internal surface finish (Ra ≤ 0.4 μm) minimizes pressure drop variation across the operational flow range.
5.3 Industry Segments
- Commercial Buildings (offices, retail, hospitality)
- Hospital & Pharmaceutical Facilities (cleanroom HVAC)
- Industrial Process Cooling
- Data Center Thermal Management
- Residential HVAC Systems
6. Quality Certifications & Compliance
6.1 Factory Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- IATF 16949 — Automotive Quality Management (for automotive AC coil applications)
6.2 Product Certifications
- CE Marking (EU Conformity) — compliant with EN 10217-7 and Pressure Equipment Directive (PED) 2014/68/EU where applicable
- UL Listed — for use in North American HVAC equipment
- CRAA Certified — China Refrigeration and Air-Conditioning Industry Association
- SGS Testing Report — material composition, mechanical properties, and dimensional accuracy verified by independent third-party laboratory
- Material Test Certificate (MTC) — EN 10204 Type 3.1 certificate provided per shipment
6.3 Testing Protocols
- Hydrostatic Pressure Test: 100% of coils tested at 2.0 MPa for minimum 5 seconds
- Ultrasonic Flaw Detection (UT): 100% inline scanning during production
- Hardness Testing: Per ASTM E18 (Rockwell) on each heat batch
- Corrosion Testing: Salt Spray Test (ASTM B117) — ≥ 500 hours for SUS304; ≥ 1000 hours for SUS316L
- Heat Transfer Performance Test: Verified against ANSI/ASHRAE Standard 15 for coil capacity rating
7. Unique Selling Points
Precision Engineering for Non-Standard Conditions: Wenzhou Jixing Metal Materials leverages advanced thermal modeling and CFD (Computational Fluid Dynamics) simulation to design coil tubes that maintain optimal performance under non-standard operating conditions — including high ambient temperatures, variable flow rates, and altitude derating — ensuring that fan coil units deliver rated capacity across the full operational envelope.
- Superior Surface Finish: Electropolished internal surfaces reduce flow resistance by up to 15% compared to standard finish tubes, improving system efficiency and reducing fan energy consumption.
- Extended Service Life: Enhanced passivation and optional PVD coating provide 2–3× longer corrosion resistance than conventional stainless steel tubes, reducing maintenance frequency and total cost of ownership.
- Wide Refrigerant Compatibility: Fully compatible with next-generation low-GWP (Global Warming Potential) refrigerants including R32, R290, and CO₂, supporting the industry transition toward environmentally sustainable cooling.
- Custom Engineering Support: Dedicated technical team available for non-standard specifications, including custom OD/wall combinations, special coatings, and application-specific thermal optimization.
- Traceability: Full batch traceability from raw material to finished coil, with digital quality records available upon request for OEM documentation and warranty purposes.
8. Technical Support & Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive technical support for OEM partners and end-users, including:
- Thermal performance calculation and capacity derating analysis for non-standard operating conditions
- Custom coil tube specifications based on application-specific heat load calculations
- Sample provision and pilot testing for new product development
- On-site technical consultation and application engineering support
- Long-term supply agreements with guaranteed material consistency and lead time commitments
For detailed quotations, technical data sheets, and sample requests, please contact the sales engineering team at Wenzhou Jixing Metal Materials Co., Ltd.