Stainless Steel Coil Tube for Fan Coil Unit (FCU) HVAC Systems
1. Product Overview
The stainless steel coil tube (盘管, Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchanger component specifically designed for integration into Fan Coil Unit (FCU) air conditioning systems. This product represents a critical interface between thermal energy transfer media and the conditioned air stream, serving as the primary evaporator or condenser element within commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) installations.
Based on extensive research into demand response quantification and control strategies for fan coil unit air conditioning systems, this coil tube product is engineered to optimize thermal performance under dynamic load conditions, enabling efficient energy management in smart building environments. The coil tube is supplied in coiled form to facilitate on-site bending, shaping, and installation into various FCU configurations including ceiling-mounted, wall-mounted, and concealed ducted units.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, mechanical strength, and long-term durability in humid and chemically aggressive environments typical of HVAC applications.
- Base Material: Austenitic Stainless Steel (奥氏体不锈钢), conforming to ASTM A269 / GB/T 12771 standards
- Grade Options: SUS304 (06Cr19Ni10), SUS316L (022Cr17Ni12Mo2) for enhanced chloride resistance
- Corrosion Resistance: Excellent resistance to condensate water, dehumidification by-products, and ambient humidity
- Thermal Conductivity: 14.2–16.3 W/(m·K) at 20°C, providing efficient heat transfer between refrigerant/water and air streams
- Mechanical Properties: Tensile strength ≥ 520 MPa; elongation ≥ 30%; suitable for cold forming and bending operations
- Operating Temperature Range: -40°C to +250°C, accommodating both heating and cooling cycles
- Surface Finish: Mill finish or electropolished (Ra ≤ 0.4 μm) to minimize fouling and bacterial growth
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管) |
| Catalogue No. | 383 |
| Outer Diameter (OD) | 6.0 mm, 8.0 mm, 9.53 mm, 12.7 mm (customizable) |
| Wall Thickness | 0.3 mm – 1.0 mm (selectable per thermal load requirement) |
| Inner Diameter (ID) | 4.0 mm – 11.0 mm |
| Coil Length | 5 m – 50 m per coil (standard); up to 100 m on request |
| Coil Outer Diameter | 300 mm – 600 mm |
| Tolerance (OD) | ±0.05 mm |
| Tolerance (Wall Thickness) | ±10% of nominal |
| End Condition | Plain cut, beveled, or threaded (per customer specification) |
| Bending Radius | Minimum 3D (three times outer diameter) |
| Maximum Operating Pressure | 1.6 MPa (standard); 2.5 MPa (heavy-wall option) |
| Surface Treatment | Pickled & passivated; optional electropolishing |
| Packaging | Wooden crate with moisture-proof wrapping; coil secured on reel |
| Standards Compliance | ASTM A269, GB/T 12771, EN 10216-5, JIS G3446 |
4. Manufacturing Process
The production of this stainless steel coil tube follows a rigorous multi-stage manufacturing protocol designed to ensure dimensional precision, metallurgical integrity, and surface quality suitable for HVAC heat exchange applications:
- Hot Rolling (热轧): Continuous casting followed by hot rolling to produce seamless or welded stainless steel strip/pipe blank at elevated temperatures (1100–1250°C).
- Intermediate Annealing (中间退火): Solution annealing at 1050–1100°C with rapid water quenching to dissolve carbides, restore austenitic microstructure, and eliminate work-hardening effects.
- Cold Drawing / Cold Forming (冷拔/冷成型): Precision cold working to achieve final dimensions, wall thickness, and surface finish. Multiple passes through calibrated dies ensure dimensional tolerances within ±0.05 mm.
- Pickling & Passivation (酸洗钝化): Immersion in mixed acid solution (HNO₃ + HF) to remove oxide scale, followed by passivation treatment to form a protective chromium oxide layer.
- Coiling (盘绕): The finished tube is wound onto a reel using controlled tension to maintain straightness and prevent permanent deformation or ovality.
- Quality Inspection (质量检测): Each coil undergoes ultrasonic testing (UT) for internal defects, hydrostatic pressure testing at 1.5× working pressure, dimensional measurement, and visual surface inspection.
5. Applications
This stainless steel coil tube is specifically engineered for the following HVAC and related applications:
- Fan Coil Unit (风机盘管) Heat Exchangers: Primary evaporator/condenser coil element in commercial FCU systems for office buildings, hotels, hospitals, and residential complexes.
- Chilled Water Systems (冷冻水系统): Circulation piping and heat exchanger coils in central air conditioning plants.
- Demand Response Systems (需求响应系统): Integrated into smart building HVAC networks where coil performance is optimized through quantified load control algorithms for peak demand reduction and energy cost savings.
- Industrial HVAC: Process cooling/heating in food processing, pharmaceutical manufacturing, and semiconductor clean rooms requiring hygienic-grade piping.
- Marine & Coastal Environments: SUS316L grade coils for HVAC systems in coastal facilities where chloride-induced pitting corrosion is a concern.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and inspection processes
- ISO 14001:2015 — Environmental Management System certification for sustainable production practices
- EN 10204 3.1 — Third-party material inspection certificates provided with each batch
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Pipes and Tubes
- GB/T 12771 — Chinese National Standard for welded stainless steel tubes for general application
- EN 10216-5 — European Standard for welded stainless steel tubes for heat exchangers
- Pressure Vessel Compliance: Product suitable for incorporation into ASME Section VIII and PED 2014/68/EU regulated equipment upon request
7. Unique Selling Points
Research-Driven Optimization: Product development informed by advanced academic research on fan coil unit demand response quantification and control (风机盘管空调系统需求响应量化及控制研究), ensuring the coil tube's thermal characteristics are optimized for dynamic load management and energy-efficient operation in smart building environments.
- Precision Dimensional Control: Tolerances of ±0.05 mm on outer diameter ensure seamless integration into fin-tube heat exchanger assemblies with optimal air-side heat transfer coefficients.
- Superior Corrosion Longevity: Austenitic stainless steel construction provides 2–3× the service life of conventional copper tube alternatives in condensate-rich environments, reducing lifecycle replacement costs.
- Hygienic Surface Quality: Electropolished finish (Ra ≤ 0.4 μm) minimizes biofilm formation and condensate-related microbial growth, critical for hospital and food-grade applications.
- Flexible Coil Supply: Delivered in coiled form enabling on-site fabrication into custom coil geometries, reducing shipping costs and enabling just-in-time installation.
- Thermal Performance Optimization: Wall thickness range of 0.3–1.0 mm allows engineers to balance heat transfer rate against pressure drop, maximizing COP (Coefficient of Performance) in FCU systems.
8. Technical Notes
For optimal performance in fan coil unit demand response applications, the coil tube should be paired with fin configurations (aluminum or stainless steel) having fin spacing of 1.5–2.5 mm and tube pitch of 22–32 mm. The coil assembly's overall thermal efficiency is governed by the NTU (Number of Transfer Units) method, where the stainless steel tube wall thermal resistance should be minimized through appropriate wall thickness selection relative to the expected fluid velocity and heat transfer coefficient.
Wenzhou Jixing Metal Materials Co., Ltd. provides full technical documentation including mill test certificates, material traceability records, and application engineering support for all coil tube orders. Custom specifications are available upon submission of detailed thermal load calculations and system design parameters.