Stainless Steel Coil Tube for Brushless DC Fan Coil Units
Product Overview
The stainless steel coil tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component designed primarily for integration into Brushless Direct Current (BLDC) Fan Coil Units (FCUs) and other HVAC (Heating, Ventilation, and Air Conditioning) thermal exchange systems. This product represents a high-performance coil configuration that optimizes heat transfer efficiency while maintaining structural integrity under prolonged thermal cycling conditions.
As a core component within the thermal management architecture of modern commercial and residential climate control systems, the stainless steel coil tube serves as the primary medium for heat exchange between the circulating refrigerant or hot water circuit and the ambient air stream. The product is engineered to meet the demanding operational requirements of BLDC-driven fan coil units, which offer superior energy efficiency, precise speed control, and reduced acoustic emissions compared to traditional AC motor-driven systems.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term durability in humid and chemically aggressive environments typical of HVAC applications.
- Base Material: AISI 304 (UNS S30400) or AISI 316L (UNS S31603) austenitic stainless steel, depending on the specific corrosion resistance requirements of the application environment.
- Chromium (Cr) Content: 18.0–20.0 wt% — provides primary corrosion resistance through passive oxide film formation.
- Nickel (Ni) Content: 8.0–11.0 wt% — stabilizes the austenitic crystal structure and enhances ductility.
- Molybdenum (Mo) Content: Up to 2.5 wt% (316L grade) — improves resistance to pitting and crevice corrosion in chloride-containing environments.
- Carbon (C) Content: ≤ 0.03 wt% (L-grade) — minimizes intergranular corrosion susceptibility during welding and heat treatment operations.
- Operating Temperature Range: −40 °C to +250 °C (continuous service).
- Thermal Conductivity: Approximately 14.5–16.3 W/(m·K) at 20 °C.
- Corrosion Resistance: Superior resistance to atmospheric corrosion, condensation water, and mild chemical exposure inherent to HVAC condensate and refrigerant circuits.
- Mechanical Properties: Tensile strength ≥ 520 MPa; yield strength ≥ 205 MPa; elongation ≥ 40%.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | 6.35 mm (1/4") / 9.53 mm (3/8") / 12.7 mm (1/2") | ASTM A213 / GB/T 12771 |
| Tube Wall Thickness | 0.4 mm – 1.0 mm (precision controlled) | ASME B31.5 |
| Coil Diameter (Mean) | 50 mm – 200 mm (configurable per design) | Custom / Project-Specific |
| Number of Rows | 1 – 4 rows (standard configurations) | HVAC Industry Practice |
| Fin Density | 10 – 16 fins per inch (FPI) | ASHRAE Standards | Fin Material | Aluminum (Al 1100/1200) or Stainless Steel | ASTM B209 |
| Surface Finish | Mirror polish (Ra ≤ 0.2 μm) or matte finish (Ra ≤ 0.8 μm) | ASTM A478 |
| Working Pressure | Up to 1.6 MPa (hot water circuit) / 2.5 MPa (refrigerant circuit) | EN 12828 / ISO 5149 |
| Cooling Capacity Range | 2.0 kW – 15.0 kW (per coil unit, depending on configuration) | ASHRAE Standard 17 |
| Heating Capacity Range | 2.5 kW – 18.0 kW (per coil unit, depending on configuration) | ASHRAE Standard 17 |
| Refrigerant Compatibility | R410A, R32, R134a, R407C, CO₂ (R744) | EN 378 / ASHRAE 34 |
| Service Life | ≥ 25 years (continuous operation) | Industry Benchmark |
| Weight (Typical, 4-Row Configuration) | 1.2 kg – 3.5 kg | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorously controlled multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and consistent performance across all production batches.
- Raw Material Selection & Inspection: Cold-rolled stainless steel coil stock is procured from certified mills and subjected to spectroscopic analysis (OES) and mechanical testing to verify chemical composition and mechanical properties conform to specified grades.
- Precision Slitting & Leveling: The master coil is slit to the required tube strip width using high-precision slitting lines with ±0.05 mm tolerance control. The strip is then leveled to ensure uniform flatness prior to forming.
- Tube Forming (Seamless or Welded): The strip is formed into tubular cross-sections through either cold-rolled seamless forming (for small diameters) or high-frequency induction welding (HFW) with full-penetration weld seam verification. The welding process employs inert gas (Argon) shielding to prevent oxidation.
- Hydroforming & Coil Bending: The formed tubes are hydroformed to achieve precise internal and external dimensions, then bent into the designated coil configuration using CNC-controlled bending equipment. The bending radius is optimized to prevent wall thinning and ovality beyond acceptable limits (≤ 10% ovality).
- Fin Application: Aluminum or stainless steel fins are applied to the coil tubes using either a fin-tube pressing method or brazed construction. Fin thickness, density, and alignment are controlled to within ±0.02 mm to ensure uniform airflow distribution and maximum heat transfer surface area.
- Surface Treatment & Passivation: The completed coil assembly undergoes acid pickling and passivation treatment to remove scale, restore the protective chromium oxide passive layer, and enhance long-term corrosion resistance.
- Quality Inspection & Pressure Testing: Each coil tube unit undergoes 100% leak testing (helium leak detection or pressure decay method) and dimensional inspection. Random samples are subjected to hydrostatic pressure testing at 1.5× the maximum working pressure for a minimum of 30 minutes.
- Packaging & Dispatch: Verified products are packaged with protective wrapping and desiccant materials to prevent moisture exposure during transit and storage.
Applications
The stainless steel coil tube is engineered for versatile deployment across multiple sectors requiring efficient, reliable, and durable heat exchange solutions:
- Commercial HVAC Systems: Primary heat exchange component in BLDC Fan Coil Units for office buildings, shopping malls, hotels, and hospitals, where low-noise operation and energy efficiency are paramount.
- Residential Climate Control: Integration into ducted and ductless mini-split air conditioning systems, providing superior condensate resistance compared to copper alternatives.
- Industrial Process Cooling: Application in precision temperature control systems for pharmaceutical manufacturing, food processing, and semiconductor fabrication facilities.
- Marine & Offshore Environments: Utilization in HVAC systems aboard vessels and offshore platforms, leveraging the corrosion resistance of 316L stainless steel in high-chloride environments.
- Medical & Cleanroom Applications: Deployment in hospital operating theaters, laboratories, and cleanrooms where non-corrosive, easily sanitized, and hygienic heat exchange surfaces are required.
- Automotive Thermal Management: Application in electric vehicle (EV) battery thermal management systems and cabin climate control units.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity with international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification, demonstrating systematic commitment to consistent product quality and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification, reflecting responsible environmental practices throughout the manufacturing lifecycle.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking (EU) — Conformity with European health, safety, and environmental protection standards under applicable directives.
- ASME BPV Code Compliance — Where applicable, pressure-containing components are manufactured in accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code.
- Material Certifications: Mill Test Reports (MTR) and EN 10204 Type 3.1 Certificates supplied with each shipment, providing full traceability of chemical composition and mechanical properties.
- Third-Party Testing: Products undergo independent verification by accredited laboratories (SGS, TÜV, Bureau Veritas) for dimensional accuracy, pressure integrity, and corrosion performance.
Unique Selling Points
1. BLDC-Compatible Thermal Design: The coil tube geometry is specifically optimized for integration with Brushless DC motor-driven fan systems, ensuring balanced airflow distribution, minimal pressure drop, and acoustic performance aligned with the low-noise characteristics of BLDC technology.
2. Extended Service Life: The use of premium austenitic stainless steel provides a service life exceeding 25 years — significantly outperforming copper-aluminum alternatives in corrosive or high-condensate environments.
3. Precision Manufacturing Tolerances: CNC-controlled bending and forming processes deliver dimensional accuracy of ±0.1 mm, ensuring seamless integration into pre-engineered fan coil unit assemblies.
4. Environmental Sustainability: The stainless steel coil tube is 100% recyclable, contains no harmful heavy metals, and contributes to the energy efficiency of HVAC systems through optimized heat transfer performance, reducing overall carbon footprint.
5. Full Traceability: Each production batch is accompanied by complete material documentation and testing records, providing end-to-end traceability from raw material to finished product.