Stainless Steel Coil Tube for Fan Coil Unit (FCU) Applications
Product Overview
The Stainless Steel Coil Tube (Product Code: 1068) is a precision-engineered coil product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed specifically for integration into non-standard Fan Coil Unit (FCU) assemblies. As a critical heat exchanger component, this coil tube facilitates efficient thermal transfer between refrigerant and air streams, serving as the core performance element in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. The product is engineered to meet stringent performance evaluation criteria, including comprehensive power consumption cooling/heating capacity coefficient assessments, ensuring optimal energy efficiency and thermal output in diverse operating conditions.
Unlike conventional coil tubes, this product is tailored for non-standard FCU configurations where customized dimensional tolerances, enhanced corrosion resistance, and superior thermal conductivity are paramount. The coil tube is manufactured to comply with industry benchmarks for comprehensive power consumption evaluation, enabling accurate performance coefficient determination across varying load conditions.
Material and Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel (UNS S30408 / AISI 304) or UNS S31603 (AISI 316) depending on application requirements
- Alternative Grades: 201 Stainless Steel (UNS S30100) for cost-sensitive applications; 321 Stainless Steel (UNS S32100) for elevated-temperature service
- Surface Treatment: Passivated finish with chromium oxide protective layer; optional electropolished surface for enhanced hygiene in pharmaceutical and food-grade applications
Mechanical Properties
- Tensile Strength: ≥ 520 MPa (minimum yield strength ≥ 205 MPa)
- Elongation at Break: ≥ 40% (ensuring formability during coil winding operations)
- Hardness: HV 150–200 (annealed condition)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (AISI 304)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion in humid HVAC environments
- Operating Temperature Range: −196°C to +870°C (continuous service)
Key Performance Characteristics
- Thermal Efficiency Coefficient: Optimized for high COP (Coefficient of Performance) in FCU thermal cycling
- Anti-scaling Performance: Smooth internal surface minimizes fouling factor accumulation, maintaining heat transfer efficiency over extended service life
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (linear, 20–300°C range), compatible with standard expansion loop designs
Technical Specifications
| Parameter | Specification | Standard / Tolerance |
|---|---|---|
| Product Code | 1068 – Coiltube | Wenzhou Jixing Internal Specification |
| Outer Diameter (OD) | 7.94 mm / 9.53 mm / 12.7 mm (customizable) | ±0.1 mm |
| Wall Thickness | 0.30 mm – 1.00 mm | ±0.05 mm |
| Coil Diameter | 150 mm – 1200 mm (configurable) | ±2 mm |
| Coil Length | Custom (up to 3000 m per coil) | ±50 mm |
| Roundness Tolerance | ≤ 0.05 mm | ASTM A580 |
| Surface Roughness (Ra) | ≤ 0.8 μm (internal); ≤ 0.4 μm (external, electropolished) | ISO 1302 |
| Refrigerant Compatibility | R22, R410A, R32, R134a, R407C, Ammonia (NH₃) | ASHRAE 34 |
| Maximum Working Pressure | 4.0 MPa (gauge) | ASME B31.5 |
| Hydrostatic Test Pressure | 6.0 MPa | — |
| Corrosion Test (Salt Spray) | ≥ 1000 hours (ASTM B117, 5% NaCl, 35°C) | ASTM B117 |
| Standards Compliance | ASTM A580, EN 10216-5, GB/T 14976, ISO 13473 | Multi-standard certified |
| Delivery Condition | Annealed and Pickled (AP) | — |
Manufacturing Process
Process Flow
- Raw Material Procurement: Selection of certified stainless steel strip from approved mills with full mill test certificates (MTC) conforming to EN 10204 Type 3.1 or equivalent.
- Slitting and Leveling: Precision slitting to specified width with edge burr removal; cross-roller leveling to achieve flatness within 0.1% of strip length.
- Coil Winding (Coiling): Computer-controlled CNC coiling machine winds the strip into the specified coil diameter with uniform layer tension, ensuring consistent pitch and concentricity. Tension control systems maintain layer-to-layer stability within ±5% deviation.
- Heat Treatment (Annealing): Continuous annealing in protective atmosphere (95% N₂ + 5% H₂) at 1050°C – 1100°C, followed by controlled cooling to relieve residual stresses and restore full ductility.
- Pickling and Passivation: Immersion in mixed acid solution (HNO₃ + H₂SO₄) to remove oxide scale, followed by passivation treatment to form a stable chromium oxide protective film (minimum 1000 Å thickness).
- Quality Inspection: 100% dimensional verification, optical surface inspection, and sampling-based hydrostatic pressure testing. Random samples undergo spectrometric analysis (PMI gun) for chemical composition verification.
- Packaging and Dispatch: Moisture-proof wrapping with desiccant, wooden pallet loading, and export-grade container preparation with clear product identification labels.
Quality Control Measures
- In-process monitoring at each manufacturing stage with documented traceability
- Non-Destructive Testing (NDT) including dye penetrant inspection (DPI) for surface defect detection
- Thermal conductivity verification per ASTM E1530 on sampled coils
- Full traceability from raw material heat number to finished coil batch code
Applications
Primary Application: Fan Coil Units (FCU)
The coil tube is the fundamental heat exchange element in non-standard Fan Coil Unit assemblies, where it interfaces with:
- Air Handling Systems: Commercial HVAC ductwork in office buildings, hospitals, hotels, and retail facilities
- Refrigerant Circuits: Vapor-compression systems utilizing HFC, HFO, or NH₃-based refrigerants
- Chilled Water Loops: Central chilled water distribution systems operating at 6°C – 18°C supply temperature
Performance Evaluation Context
This product is specifically designed to support comprehensive power consumption cooling/heating capacity coefficient evaluation protocols. In non-standard FCU configurations, the coil tube's geometry and material properties directly influence:
- SCOP (Seasonal Coefficient of Performance): Optimized coil design contributes to higher seasonal energy efficiency ratios
- EER (Energy Efficiency Ratio): Enhanced heat transfer surface area-to-volume ratio improves cooling EER by 8–15% compared to standard coils
- SEER (Seasonal Energy Efficiency Ratio): Consistent thermal performance across variable load conditions
- Comprehensive Power Consumption Assessment: Accurate thermal output enables reliable determination of unit-level energy consumption metrics for building energy management system (BEMS) integration
Additional Application Domains
- Industrial Process Cooling: Precision temperature control in electronics manufacturing, chemical processing, and food processing
- Pharmaceutical Cleanroom HVAC: Electropolished coils meeting GMP (Good Manufacturing Practice) requirements for aseptic environments
- Marine HVAC Systems: 316-grade coil tubes providing superior resistance to salt-laden air in shipboard ventilation
- Custom OEM Assemblies: Non-standard dimensional configurations for specialized equipment manufacturers
Quality Certifications and Compliance
| Certification / Standard | Scope | Validity |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Active |
| ISO 14001:2015 | Environmental Management System | Active |
| ASTM A580 | Standard Specification for Stainless Steel Bars and Shapes | Compliant |
| EN 10216-5 | Seamless Heat Exchanger Tubes — Non-ferrous and their Alloys | Compliant |
| GB/T 14976 | Chinese National Standard — Cold-rolled Seamless Stainless Steel Tubes | Compliant |
| ISO 13473 | Welded Tubes and Pipes — Technical Delivery Conditions | Compliant |
| CE Marking | EU Market Conformity (Pressure Equipment Directive 2014/68/EU where applicable) | Active |
| RoHS 2.0 (2011/65/EU) | Restriction of Hazardous Substances | Compliant |
| REACH (EC 1907/2006) | Chemical Substance Registration | Compliant |
Unique Selling Points
- Non-Standard Customization Capability: Full dimensional customization to meet non-standard FCU design requirements, enabling OEM partners to differentiate their products in the market
- Superior Thermal Performance: Optimized coil geometry and high-conductivity austenitic stainless steel deliver measurable improvements in comprehensive power consumption cooling/heating capacity coefficients
- Extended Service Life: Exceptional corrosion resistance eliminates the need for chemical treatment or replacement in aggressive HVAC environments, reducing total cost of ownership (TCO)
- Food and Pharma Grade Option: Electropolished internal surface (Ra ≤ 0.25 μm) suitable for hygienic applications without additional passivation
- Full Traceability: Each coil batch is traceable to raw material mill heat number, providing complete quality documentation for regulatory compliance
- Environmental Sustainability: Stainless steel is 100% recyclable; manufacturing process incorporates energy-efficient continuous annealing with nitrogen atmosphere, minimizing carbon footprint
Technical Notes
Design Consideration: When selecting coil tube specifications for non-standard FCU assemblies, the thermal resistance of the coil wall should be calculated using the formula: R_wall = ln(OD/ID) / (2π × k × L), where k is thermal conductivity and L is coil length. Wenzhou Jixing provides engineering support for thermal performance modeling to ensure optimal coil tube selection for specific application parameters.
Installation Note: All coil tube installations should incorporate expansion loops or flexible connections to accommodate differential thermal expansion between the stainless steel coil and the FCU housing material. Maximum unsupported span should not exceed 1.5 meters to prevent vibration-induced fatigue.
Storage Recommendation: Store in a dry, well-ventilated area at ambient temperature (5°C – 35°C). Protect from direct contact with carbon steel to prevent galvanic corrosion. Maintain original packaging until point of installation.