Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Precision Stainless Steel Coil Tube (盘管)
Reference Document: Simulation Study on Dynamic Demand Response Mechanism and Characteristics of Fan Coil Unit Air Conditioning Systems
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular product specifically designed for integration into fan coil unit (FCU) air conditioning systems. These coil tubes serve as the core heat exchange elements within HVAC (Heating, Ventilation, and Air Conditioning) terminal units, facilitating efficient thermal transfer between circulating fluids and ambient air. The coil geometry—characterized by continuous helical winding—maximizes the heat transfer surface area within a compact spatial envelope, making it indispensable for demand-responsive air conditioning architectures where rapid thermal load modulation is required.
Wenzhou Jixing Metal Materials Co., Ltd. produces these coil tubes to meet the stringent thermal performance and structural integrity requirements imposed by modern dynamic demand response (DDR) air conditioning systems. The product is engineered to withstand repeated thermal cycling, corrosion exposure, and mechanical stress inherent in commercial and industrial HVAC installations.
2. Material Composition and Properties
2.1 Base Material Grades
The coil tubes are manufactured from high-grade austenitic stainless steel, selected for optimal combinations of corrosion resistance, thermal conductivity, and mechanical ductility:
- 304 (UNS S30408): Standard austenitic grade with 18% Cr, 8% Ni; excellent general corrosion resistance and formability.
- 316 (UNS S31608): Enhanced austenitic grade with 2–3% Mo addition; superior resistance to chlorides and aggressive environments.
- 316L (UNS S31603): Low-carbon variant of 316; reduced intergranular corrosion susceptibility after welding.
- 321 (UNS S32100): Ti-stabilized austenitic grade; enhanced resistance to intergranular corrosion at elevated temperatures.
2.2 Key Mechanical Properties
| Property | Unit | Typical Value (304 Grade) | Typical Value (316 Grade) |
|---|---|---|---|
| Tensile Strength (抗拉强度) | MPa | ≥ 515 | ≥ 515 |
| Yield Strength (屈服强度) | MPa | ≥ 205 | ≥ 170 |
| Elongation (延伸率) | % | ≥ 40 | ≥ 40 |
| Thermal Conductivity (导热系数) | W/(m·K) | 16.3 | 14.6 |
| Density (密度) | g/cm³ | 7.93 | 8.00 |
| Maximum Operating Temperature (最高工作温度) | °C | 870 | 870 |
| Minimum Operating Temperature (最低工作温度) | °C | -196 | -196 |
2.3 Corrosion Resistance Characteristics
The austenitic microstructure provides inherent resistance to pitting (点蚀), crevice corrosion (缝隙腐蚀), and general atmospheric degradation. The 316 and 316L grades offer additional protection against chloride-induced stress corrosion cracking (Cl-SCC), making them suitable for coastal installations and environments with high humidity or chemical exposure. The chromium oxide passive film (Cr₂O₃) self-heals under aerobic conditions, ensuring long-term surface integrity.
3. Technical Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD, 外径) | 3.0 mm – 25.4 mm | ASTM A213 / EN 10216-5 |
| Wall Thickness (壁厚) | 0.3 mm – 1.5 mm | ASTM A269 / GB/T 14976 |
| Coil Pitch (盘管螺距) | 8 mm – 50 mm (customizable) | Manufacturer Specification |
| Coil Diameter (盘管直径) | 100 mm – 1500 mm | Application-specific |
| Coil Length (盘管长度) | 500 mm – 12,000 mm | Custom order |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (polished) | ASTM A269 / EN 10217-7 |
| Roundness Tolerance (圆度公差) | ≤ ±0.05 mm | ISO 8035 |
| Dimensional Tolerance (尺寸公差) | ±0.03 mm (OD); ±0.02 mm (wall) | ASTM A213 |
| Pressure Rating (压力等级) | Up to 1.6 MPa (standard); 4.0 MPa (reinforced) | ASME B31.5 |
| Welding Quality (焊接质量) | 100% helium leak-tested; leak rate ≤ 1×10⁻⁹ Pa·m³/s | ISO 15497 |
4. Manufacturing Process
The production of stainless steel coil tubes follows a multi-stage precision manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection (原材料选择): Certified stainless steel strip or seamless tube stock from approved mills, verified through spectroscopic analysis (光谱分析) for chemical composition compliance.
- Cold Forming / Seamless Drawing (冷成型/无缝拉拔): Tube blanks are cold-drawn through precision dies to achieve exact outer diameter and wall thickness specifications. This process enhances grain structure and mechanical properties through strain hardening.
- Heat Treatment (热处理): Solution annealing at 1050–1150 °C followed by rapid water quenching to restore full austenitic structure, eliminate residual stresses from cold working, and achieve maximum ductility.
- Precision Coiling (精密盘绕): Computer-controlled CNC coiling machines wind the tube into the specified helical geometry with controlled pitch and diameter tolerances. Real-time monitoring ensures geometric fidelity throughout the winding process.
- Welding (焊接): Orbital TIG (Tungsten Inert Gas) welding is employed for end-connection fabrication. Argon shielding gas prevents oxidation of the weld zone. Weld parameters are optimized to minimize distortion and maintain metallurgical continuity.
- Surface Finishing (表面精整): Electropolishing (电解抛光) or mechanical polishing achieves the required surface roughness. This step removes any residual surface contamination and enhances the passive film stability.
- Quality Inspection (质量检测): Multi-stage inspection including dimensional measurement (CMM), visual surface examination, hydrostatic pressure testing, and helium leak detection.
- Packaging and Storage (包装与储存): Protective packaging prevents mechanical damage and atmospheric exposure during transit and storage.
5. Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. finds extensive application across multiple industrial and commercial domains:
5.1 HVAC Fan Coil Unit Systems (风机盘管空调系统)
Primary application domain. The coil tube serves as the heat exchange core within fan coil units, enabling precise thermal regulation in commercial buildings, hospitals, hotels, and data centers. In dynamic demand response systems, the coil tube's thermal mass and heat transfer characteristics directly influence the system's ability to respond to variable load demands.
5.2 Process Cooling and Heating (工艺冷却与加热)
Industrial process coils for chemical processing, pharmaceutical manufacturing, and food and beverage production where sanitary-grade surfaces and corrosion resistance are mandatory.
5.3 Refrigeration Systems (制冷系统)
Evaporator and condenser coils in commercial refrigeration equipment, cold storage facilities, and industrial chiller systems.
5.4 Power Generation (发电)
Steam coils, economizer tubes, and air preheater elements in boiler systems and waste heat recovery units.
5.5 Marine and Offshore (海洋与海上平台)
Heat exchanger coils in marine HVAC systems, ballast water treatment, and offshore platform utility systems where 316/316L grades provide essential chloride resistance.
5.6 Medical and Laboratory Equipment (医疗与实验室设备)
Precision thermal management coils in medical imaging equipment, laboratory incubators, and controlled environment chambers.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and ensures compliance with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for consistent product quality |
| ISO 14001:2015 | Environmental Management System for sustainable manufacturing practices |
| ASTM A213 | Standard specification for austenitic stainless steel seamless tubes |
| ASTM A269 | Standard specification for austenitic stainless steel seamless and welded tubes |
| EN 10216-5 | European standard for austenitic stainless steel heat exchanger tubes |
| GB/T 14976 | Chinese national standard for seamless stainless steel tubes for general application |
| ASME B31.5 | Process piping code compliance for pressure-rated applications |
| Mill Test Reports (MTR) | Full chemical and mechanical property certification for each heat/batch |
7. Unique Selling Points
- Dynamic Demand Response Compatibility: Coil geometry and material selection optimized for rapid thermal response, supporting smart building energy management systems that modulate heating and cooling loads in real time.
- Precision CNC Coiling: Computer-numeric-control winding ensures geometric accuracy within ±0.05 mm, guaranteeing uniform heat transfer performance across the entire coil surface.
- Multi-Grade Material Availability: Full range from 304 to 316L and 321 grades, enabling customers to match material properties to specific environmental and performance requirements.
- Custom Engineering Capability: Tailored coil pitch, diameter, length, and configuration to meet application-specific thermal and spatial constraints.
- End-to-End Quality Traceability: From raw material certification through final inspection, each coil tube carries full traceability documentation supporting compliance audits and warranty claims.
- Extended Service Life: Superior corrosion resistance eliminates the need for protective coatings or replacement cycles, reducing total cost of ownership over the system lifetime.
8. Conclusion
The Stainless Steel Coil Tube produced by Wenzhou Jixing Metal Materials Co., Ltd. represents a precision-engineered solution for demanding thermal management applications, particularly within fan coil unit air conditioning systems operating under dynamic demand response protocols. The combination of metallurgical excellence, dimensional precision, and comprehensive quality assurance positions this product as a reliable component for next-generation HVAC infrastructure.