Stainless Steel Coil Tube for HVAC Radiation & Fan Coil Unit Applications
Supplier: Wenzhou Jixing Metal Materials Co., Ltd.
Product Catalog No.: 416
1. Product Overview
The Stainless Steel Coil Tube (SS Coil Tube) is a precision-engineered tubular product specifically designed for use in Radiation Coil Tubes (辐射盘管) and Fan Coil Units (FCU, 风机盘管) within commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. These coil tubes serve as the primary heat exchange elements in cooling and heating applications, transferring thermal energy between refrigerant or chilled water and the surrounding air medium.
Based on comparative experimental research conducted on cooling conditions for radiation coil tubes and fan coil units, the performance of the coil tube geometry, material composition, and surface treatment directly influences the overall thermal efficiency, pressure drop characteristics, and long-term durability of the HVAC system. Wenzhou Jixing Metal Materials Co., Ltd. manufactures coil tubes that meet rigorous engineering standards to ensure optimal heat transfer performance and extended service life under demanding cooling and heating cycles.
2. Material & Properties
The coil tubes are fabricated from high-quality austenitic stainless steel grades, selected for their superior corrosion resistance, thermal conductivity, and mechanical strength under cyclic thermal loading conditions.
- Primary Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), and SUS321 (UNS S32100)
- Corrosion Resistance: Excellent resistance to waterborne corrosion, dehumidification condensate attack, and mild chemical environments typical in HVAC applications
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, ensuring efficient heat exchange performance
- Operating Temperature Range: −196°C to +870°C (SUS304), accommodating extreme cooling and heating scenarios
- Mechanical Strength: Tensile strength ≥ 515 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
- Surface Finish: Electropolished or passivated inner surface to minimize flow resistance and prevent biofilm accumulation
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm, 9.53 mm, 12.70 mm (1/4", 3/8", 1/2") | ASTM A213 / ASTM A269 |
| Wall Thickness | 0.50 mm – 1.50 mm | ASME B36.19M |
| Bend Radius | 1.5D – 5D (minimum 1.5 × OD) | EN 10217-7 |
| Coil Diameter | 50 mm – 300 mm (configurable) | Custom per project requirements |
| Pitch / Spacing | 3.0 mm – 10.0 mm (adjustable) | ASHRAE Handbook – HVAC Systems and Equipment |
| Tolerance (OD) | ±0.05 mm | ISO 4628 |
| Tolerance (Wall Thickness) | ±10% of nominal | ASTM A269 |
| Surface Roughness (Ra) | ≤ 0.4 μm (electropolished) | ISO 1302 |
| Pressure Test | 2.5 × working pressure, 30-second hold | ISO 11114-1 |
| Maximum Working Pressure | ≤ 1.6 MPa (configurable up to 4.0 MPa) | EN 10217-7 |
| Refrigerant Compatibility | R-134a, R-410A, R-407C, R-32, Water/Glycol mixtures | ASHRAE Standard 34 |
4. Manufacturing Process
The production of precision stainless steel coil tubes follows a multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Material Selection & Inspection: Certified stainless steel strip or seamless tube stock is procured and subjected to spectroscopic analysis (PMI – Positive Material Identification) to verify chemical composition compliance with ASTM specifications.
- Cold Forming / Coiling: Precision CNC-controlled coiling machinery bends the tube stock into the required helical geometry with controlled springback compensation to achieve exact pitch and diameter tolerances.
- Welding (if applicable): For welded coil configurations, TIG (Tungsten Inert Gas) welding or orbital welding is employed with argon shielding to produce leak-tight joints with minimal heat-affected zone (HAZ) distortion.
- Heat Treatment: Solution annealing at 1050–1150°C followed by controlled cooling to restore full austenitic microstructure and relieve residual stresses introduced during forming.
- Pickling & Passivation: Immersion in a mixed acid bath (HNO₃ + HF) to remove surface oxides, followed by passivation to establish a chromium-rich passive film for enhanced corrosion resistance.
- Surface Finishing: Optional electropolishing to achieve Ra ≤ 0.4 μm inner surface finish, reducing flow friction and preventing fouling.
- Quality Inspection: 100% visual inspection, dimensional verification using coordinate measuring machines (CMM), dye penetrant testing (DPT) for surface defects, and hydrostatic pressure testing.
5. Applications
The SS Coil Tube is engineered for a wide range of thermal management applications, with particular emphasis on cooling performance as validated by comparative experimental studies:
- Fan Coil Units (FCU): Primary heat exchange coils in chilled water or DX (Direct Expansion) fan coil units for commercial buildings, hotels, hospitals, and cleanroom environments.
- Radiation Coil Tubes: Indirect radiation cooling systems where coil tubes are embedded in ceilings, walls, or floors to provide radiant cooling with minimal air movement.
- Air Handling Units (AHU): Chilled water coils within large-scale air handling systems for process cooling and space conditioning.
- Chillers & Heat Exchangers: Tubular heat exchanger elements in industrial chiller units and process cooling loops.
- Cold Storage Systems: Evaporator coils in low-temperature refrigeration and cold storage facilities.
- Process Cooling: Precision cooling coils for food and beverage processing, pharmaceutical manufacturing, and electronics thermal management.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the listed international standards:
- ISO 9001:2015 – Quality Management System Certification
- ISO 14001:2015 – Environmental Management System Certification
- CE Marking – European Conformity for construction and machinery directives
- EN 10217-7 – Cold-drawn stainless steel tubes for technical purposes
- ASTM A213 / A269 – Standard specifications for stainless steel tubes
- ASME B36.19M – Welded and seamless wrought stainless steel pipe and tube
- EN 10204 3.1 – Material test certificates (Mill Test Reports)
- RoHS & REACH Compliance – Restriction of hazardous substances and chemical regulation compliance
7. Unique Selling Points
Performance-Validated Design: Coil tube geometries are informed by comparative experimental research on cooling conditions between radiation coil tubes and fan coil units, ensuring empirically optimized thermal performance.
- Precision Engineering: CNC-controlled coiling with ±0.05 mm OD tolerance ensures uniform heat transfer surface area and consistent hydraulic performance across the entire coil assembly.
- Enhanced Corrosion Resistance: Electropolished and passivated surfaces provide superior resistance to condensate-induced corrosion, a critical failure mode in HVAC coil applications.
- Low Flow Resistance: Smooth inner surface finish (Ra ≤ 0.4 μm) minimizes pressure drop, reducing pumping energy consumption and improving system COP (Coefficient of Performance).
- Custom Configurations: Flexible design capabilities accommodate project-specific requirements for coil diameter, pitch, tube length, and bend radius.
- Full Traceability: Each production batch is accompanied by complete material traceability documentation, including mill test reports, heat numbers, and process records.
- Extended Service Life: Austenitic stainless steel construction provides corrosion-free operation exceeding 25 years under normal HVAC conditions, significantly reducing lifecycle maintenance costs.
8. Technical Reference
Comparative Experimental Study on Cooling Conditions of Radiation Coil Tubes and Fan Coil Units (《辐射盘管和风机盘管供冷工况实验对比研究》) — This research provides the experimental basis for understanding the thermal-hydraulic performance differences between radiation coil tube systems and conventional fan coil unit systems under cooling loads. The findings inform the geometric and material design parameters of the SS Coil Tube product line, ensuring that each coil configuration delivers optimal cooling capacity, sensible heat ratio (SHR), and latent heat removal performance tailored to the intended application environment.