Stainless Steel Coil Tube (Fan Coil Tube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Product No. 308) is a precision-engineered coiled heat exchanger tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for integration into central air conditioning (CAC) fan coil unit (FCU) systems. This product represents a critical component in hydronic cooling and heating applications, where refrigerant or water-based heat transfer media circulate through tightly wound coil configurations to achieve efficient thermal exchange. The coil tube architecture enables compact volumetric packaging while maximizing surface-area-to-volume ratio, thereby optimizing heat transfer coefficients within constrained installation envelopes.
This product has been extensively studied in the context of Fault Monitoring and Diagnosis Systems for Central Air Conditioning Fan Coil Units, where its operational parameters—including flow rate, inlet/outlet temperature differentials, and pressure drop—are continuously monitored to ensure system reliability and energy efficiency.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical durability, and thermal conductivity characteristics.
- Primary Material: AISI 304 / 316L Stainless Steel (UNS S30400 / S31603)
- Chemical Composition (304): Cr 18–20%, Ni 8–10.5%, Mn ≤2%, Si ≤1%, C ≤0.08%, S ≤0.03%
- Chemical Composition (316L): Cr 16–18%, Ni 10–14%, Mo 2–3%, C ≤0.03%
- Thermal Conductivity: 16.3 W/(m·K) at 300 K (AISI 304)
- Specific Heat Capacity: 500 J/(kg·K)
- Operating Temperature Range: −196°C to +870°C
- Maximum Working Pressure: 1.6 MPa (standard); up to 2.5 MPa (reinforced variants)
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical corrosion; enhanced chloride pitting resistance in 316L grade
- Surface Finish: Electropolished (Ra ≤ 0.4 μm) or passivated interior to prevent scale formation and maintain flow efficiency
3. Specifications
| Parameter | Specification |
|---|---|
| Product Category | Coil Tube (盘管) for Fan Coil Units |
| Material Grade | AISI 304 / 316L Stainless Steel |
| Outer Diameter (OD) | 9.52 mm / 12.7 mm / 15.88 mm (3/8", 1/2", 5/8") |
| Wall Thickness | 0.5 mm / 0.8 mm / 1.0 mm (selectable) |
| Coil Diameter (CD) | 100 mm – 350 mm (configurable) |
| Number of Rows | 1 to 6 rows (multi-row configurations available) |
| Fin Spacing (if finned) | 2.0 mm – 3.5 mm |
| Tube Pitch (Lateral) | 1.5× OD to 2.0× OD |
| Maximum Flow Rate | 0.5 – 4.0 m³/h (dependent on configuration) |
| Heat Transfer Capacity | Up to 8.5 kW per unit (standard 4-row configuration) |
| Pressure Drop (Water Side) | ≤ 15 kPa at rated flow |
| Connection Type | Flared, threaded (G1/2", G3/4"), or brazed joints |
| Standard Length | Custom per order (standard: 600 mm – 1200 mm) |
| Applicable Standards | GB/T 14976, ASTM A213, EN 10216-5 |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing sequence:
- Material Selection & Inspection: Cold-rolled stainless steel strips are procured from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition compliance with the specified grade.
- Slitting & Leveling: Coils are slit to precise widths and pass through a leveling mill to ensure flatness and dimensional accuracy prior to forming.
- Tube Forming (Seamless or Welded): The flat strip is rolled into a tubular shape using a roll-forming die set. For welded variants, a TIG (Tungsten Inert Gas) or laser welding process is employed to create a hermetic longitudinal seam.
- Coil Winding: The formed tube is wound around precision mandrels to achieve the designated coil diameter and pitch. CNC-controlled winding ensures uniform spacing and concentricity.
- Heat Treatment: Solution annealing at 1050°C–1150°C followed by rapid water quenching restores full austenitic microstructure, eliminates residual stresses, and maximizes corrosion resistance.
- Surface Treatment: Passivation via citric acid or nitric acid treatment removes free iron and forms a stable chromium oxide passive film. Electropolishing is available for enhanced interior smoothness.
- Quality Inspection: Hydrostatic pressure testing (1.5× working pressure, held for ≥30 seconds), dimensional verification via CMM (Coordinate Measuring Machine), and visual/eddy-current flaw detection are performed on 100% of production lots.
5. Applications
The stainless steel coil tube serves as a core heat exchange element across multiple HVAC (Heating, Ventilation, and Air Conditioning) and industrial thermal management domains:
- Central Air Conditioning Fan Coil Units (FCUs): Primary application in commercial and residential HVAC systems for both cooling and heating cycles, where the coil tube interfaces with chilled water or hot water loops.
- VRF/VAV Systems: Variable Refrigerant Flow and Variable Air Volume systems require high-performance coil tubes with consistent thermal response characteristics.
- Chiller & Condenser Units: Integration into air-cooled and water-cooled chiller packages for industrial process cooling.
- Heat Pump Systems: Utilization in ground-source and air-source heat pump configurations for bidirectional thermal transfer.
- Food & Pharmaceutical Processing: Sanitary-grade applications where hygienic heat exchange is mandated under GMP (Good Manufacturing Practice) guidelines.
- Marine & Offshore Platforms: Corrosion-resistant coil tubes for HVAC systems in harsh salt-spray environments.
- Data Center Cooling: Precision temperature control in high-density computing environments requiring reliable, low-maintenance heat exchangers.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure adherence to international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- CE Marking — European Conformity for HVAC components
- ASME — American Society of Mechanical Engineers stamp (where applicable)
- GB/T 14976 — Chinese National Standard for seamless stainless steel tubes
- EN 10216-5 — European Standard for stainless steel welded tubes
- ASTM A213 / A269 — American material and product standards
- SGS / BV / TUV — Third-party inspection and material verification reports available per lot
7. Unique Selling Points
Engineering Excellence in Thermal Performance:
- Superior Corrosion Resistance: 316L-grade options provide exceptional resistance to chloride-induced pitting and stress corrosion cracking, significantly extending service life in aggressive environments compared to standard carbon steel alternatives.
- Precision Coil Geometry: CNC-controlled winding ensures uniform tube spacing and concentricity, resulting in balanced airflow distribution and optimal heat transfer efficiency with minimal pressure drop.
- Electropolished Interior Surface: The Ra ≤ 0.4 μm interior finish reduces fouling accumulation, maintains consistent flow characteristics over time, and facilitates easy cleaning—critical for systems monitored by automated fault diagnosis protocols.
- Thermal Stability & Durability: Full austenitic microstructure ensures dimensional stability across wide temperature excursions, preventing micro-cracking and fatigue failure during repeated thermal cycling.
- Modular Configurability: Multiple OD, wall thickness, row count, and coil diameter options allow OEM (Original Equipment Manufacturer) customers to tailor thermal performance to specific load profiles.
- Traceability & Reliability: Each production lot undergoes full hydrostatic testing with documented results, ensuring zero-leak integrity upon delivery. Material traceability is maintained through heat-number tracking from mill to finished product.
- Compatibility with Fault Diagnosis Systems: The predictable hydraulic and thermal behavior of these coil tubes facilitates accurate sensor integration and algorithm-based fault detection in smart HVAC monitoring systems, enabling predictive maintenance strategies.
8. Conclusion
The Wenzhou Jixing Metal Materials Co., Ltd. Stainless Steel Coil Tube (Product No. 308) represents a state-of-the-art solution for heat exchange applications in modern HVAC systems. Its combination of premium material selection, precision manufacturing, and rigorous quality assurance positions it as a reliable, high-performance component capable of meeting the demanding requirements of both conventional and smart building management systems. The product's proven compatibility with fault monitoring and diagnosis frameworks further underscores its suitability for next-generation energy-efficient building infrastructure.