Stainless Steel Coil Tube for Fan Coil Unit Air Conditioning Systems
Product Overview
The Stainless Steel Coil Tube (Product No. 1561) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange tube product designed specifically for use in fan coil unit (FCU) air conditioning systems. This coil tube is formed into multi-row serpentine configurations that serve as the core heat transfer element within air-side heat exchangers, enabling efficient thermal exchange between refrigerant and ambient air.
The product represents the culmination of extensive experimental research into optimal coil row configurations for fan coil unit performance. Based on systematic studies regarding the number of coil rows (排数) in FCU air conditioners, this coil tube is engineered to maximize heat transfer efficiency while minimizing pressure drop and airflow resistance across varying row counts — typically ranging from 2-row to 8-row configurations.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical strength, and thermal conductivity characteristics essential for HVAC heat exchange applications.
- Base Material: Austenitic Stainless Steel (grades 304 / 316L per ASTM A269 / GB/T 12771)
- Corrosion Resistance: Excellent resistance to condensation water, chlorides, and atmospheric oxidation — critical for long-term operation in humid indoor environments
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, ensuring efficient heat transfer between refrigerant and air
- Mechanical Strength: Yield strength ≥ 205 MPa (304), ≥ 170 MPa (316L); tensile strength ≥ 515 MPa
- Temperature Range: Continuous operation from −196°C to +400°C
- Surface Finish: Electropolished interior (Ra ≤ 0.4 μm) for reduced fouling and enhanced heat transfer
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) |
| Product No. | 1561 |
| Outer Diameter (OD) | φ6.35 mm / φ7.94 mm / φ9.53 mm (1/4" / 5/16" / 3/8") |
| Wall Thickness | 0.40 mm / 0.50 mm / 0.65 mm |
| Coil Row Configuration | 2-row / 4-row / 6-row / 8-row (experimentally optimized) |
| Tube Length (per row) | 300 mm – 1,200 mm (customizable) |
| Fin Pitch | 10 FPI – 14 FPI (Fins Per Inch) |
| Tube Pitch (Lateral) | 19 mm – 25 mm |
| Row Pitch (Longitudinal) | 25 mm – 32 mm |
| Bend Radius | ≥ 1.5 × OD (cold-formed) |
| Refrigerant Compatibility | R-410A, R-32, R-134a, R-407C, CO₂ (R-744) |
| Maximum Working Pressure | 3.5 MPa (508 psi) |
| Hydrostatic Test Pressure | 5.25 MPa (762 psi) |
| Operating Air Velocity | 1.5 – 4.0 m/s |
| Heat Transfer Efficiency (EER) | ≥ 3.2 (4-row configuration, standard conditions) |
| Service Life | ≥ 20 years (indoor installation) |
Manufacturing Process
The production of this stainless steel coil tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, structural integrity, and optimal thermal performance:
- Material Selection & Inspection: Cold-rolled stainless steel strip (ASTM A240) undergoes incoming inspection for chemical composition (spectroscopic analysis), mechanical properties, and surface quality.
- Precision Forming: The strip is fed through a series of cold-rolling dies to form seamless tube blanks with tight dimensional tolerances (±0.05 mm on wall thickness).
- Welding & Seaming: High-frequency induction welding (HF welding) is employed for longitudinal seam closure, followed by internal and external weld bead grinding to ensure a smooth, uniform interior surface.
- Coil Bending & Forming: Tubes are cold-bent into serpentine coil configurations using CNC-controlled bending machines. Bend radii are maintained at ≥1.5×OD to prevent ovalization and stress concentration.
- Fin Application: Aluminum or copper fins are mechanically applied to the coil tube using hydraulic fin-bonding or orbital welding techniques, ensuring strong thermal contact and leak-tight joints.
- Row Assembly: Individual coil rows are assembled with header tubes (集管) using orbital TIG welding, creating the complete multi-row coil assembly.
- Heat Treatment: Solution annealing at 1050°C followed by rapid water quenching restores full austenitic microstructure and eliminates residual stresses from cold forming.
- Surface Treatment: Electropolishing and passivation treatment are applied to achieve a corrosion-resistant surface with low roughness.
- Quality Testing: Each unit undergoes hydrostatic pressure testing, helium leak detection (sensitivity ≤ 1×10⁻⁹ Pa·m³/s), dimensional verification, and visual inspection.
Applications
This stainless steel coil tube is engineered for demanding HVAC heat exchange applications where reliability, longevity, and thermal efficiency are paramount:
- Fan Coil Units (FCUs): Primary application — providing cooling and heating capacity in commercial and residential HVAC systems. The experimentally optimized row configurations deliver superior performance across design load ranges.
- Chilled Water Heat Exchangers: Used in central air conditioning systems for space conditioning in office buildings, hospitals, hotels, and retail facilities.
- Indoor Unit Evaporators: Integrated into ducted and ductless mini-split air conditioning systems.
- Heat Recovery Systems: Employed in energy recovery ventilators (ERV) and heat recovery ventilators (HRV) for energy-efficient air exchange.
- Industrial Process Cooling: Applicable in food processing, pharmaceutical manufacturing, and electronics cooling where hygienic, corrosion-resistant heat exchange is required.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that every coil tube product meets international standards:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management
- CE Marking — Conformity with European Machinery Directive (2006/42/EC)
- UL Listed — Underwriters Laboratories safety certification for HVAC components
- GB/T 19774 — Chinese National Standard for air-cooled heat exchangers
- ASHRAE 15 — Compliance with safety standards for refrigeration systems
- EN 12830 — European standard for air-cooled heat exchangers for air conditioning
Unique Selling Points
Experimentally Optimized Row Configuration: Unlike conventional coil tubes designed with fixed row arrangements, this product incorporates findings from systematic experimental research on the relationship between coil row count and thermal performance in fan coil units. This enables selection of the optimal row configuration (2 to 8 rows) for specific design conditions — balancing heat transfer capacity against pressure drop, airflow resistance, and condensation management.
- Superior Corrosion Resistance: Stainless steel construction eliminates the risk of galvanic corrosion and condensation-induced degradation common in copper coil alternatives, extending service life beyond 20 years.
- Hygienic Surface: Electropolished interior prevents biofilm formation and refrigerant fouling, maintaining heat transfer efficiency over the entire product lifecycle.
- Low Pressure Drop: Optimized tube geometry and smooth internal surfaces minimize refrigerant-side pressure drop, reducing compressor energy consumption by up to 15%.
- Refrigerant Flexibility: Compatible with all major HFC and natural refrigerants, including next-generation low-GWP options (R-32, R-290, CO₂).
- Customizable Configuration: Available in multiple OD, wall thickness, row count, and coil length combinations to meet specific OEM requirements.
Technical Reference
This product specification is informed by experimental research documented in the study "Experimental Study on the Number of Coil Rows in Fan Coil Unit Air Conditioners" (《关于风机盘管空调器盘管排数的实验研究》), which systematically investigated the thermal-hydraulic performance of multi-row coil configurations under various operating conditions, providing the empirical basis for the optimized row arrangements offered in this product line.