Stainless Steel Coil Tube for Heat Recovery Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Coil Tube (盘管) — Precision Formed Stainless Steel Tubular Products
Product Reference No.: 745
1. Product Overview
The stainless steel coil tube is a precision-engineered tubular product designed primarily for use in modular air conditioning units, particularly in heat recovery systems (Heat Recovery Units, HRUs). These coil tubes serve as the core heat exchange elements within combined air handling units (组合式空调箱), facilitating efficient thermal energy transfer between supply and exhaust air streams. The coil configuration maximizes the surface-area-to-volume ratio, enabling superior heat transfer coefficients while maintaining compact spatial footprints within HVAC (Heating, Ventilation, and Air Conditioning) assemblies.
Wenzhou Jixing Metal Materials Co., Ltd. manufactures these coil tubes to meet the demanding performance requirements of commercial and industrial air conditioning systems. The products are engineered to deliver consistent thermal efficiency, long service life, and resistance to corrosion under continuous operating conditions involving moisture, chemical exposure, and thermal cycling.
2. Material & Properties
2.1 Base Material
- Primary Alloy: Austenitic stainless steel (奥氏体不锈钢), typically Grade 304 (UNS S30408) or Grade 316L (UNS S31603)
- Alternative Grades: 304L, 321, 316Ti depending on application-specific corrosion and temperature requirements
- Standards Compliance: ASTM A213/A213M, GB/T 12771, EN 10217-7
2.2 Mechanical Properties
| Property | 304/304L Grade | 316/316L Grade |
|---|---|---|
| Tensile Strength (抗拉强度), MPa | ≥ 515 | ≥ 515 |
| Yield Strength (屈服强度), MPa | ≥ 205 | ≥ 205 |
| Elongation (延伸率), % | ≥ 40 | ≥ 40 |
| Hardness (硬度), HRB | ≤ 92 | ≤ 92 |
| Density (密度), g/cm³ | 8.00 | 8.03 |
| Thermal Conductivity (热导率), W/(m·K) @ 100°C | 16.3 | 14.6 |
| Operating Temperature Range (工作温度范围) | −196°C to +870°C | −196°C to +870°C |
2.3 Corrosion Resistance
- Excellent resistance to atmospheric corrosion, fresh water, and dilute organic acids
- Grade 316L offers superior resistance to chlorides (氯化物) and marine environments due to molybdenum (Mo) addition (2–3% by weight)
- Passive film (钝化膜) self-healing capability ensures long-term protection in humid HVAC environments
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (外径, OD) | Ø 6.0 mm – Ø 25.4 mm (customizable) |
| Wall Thickness (壁厚) | 0.3 mm – 1.2 mm |
| Coil Pitch (盘管螺距) | 8 mm – 30 mm (adjustable per design) |
| Coil Diameter (盘管外径) | Ø 100 mm – Ø 500 mm |
| Effective Length (有效长度) | 500 mm – 6000 mm per assembly |
| Surface Finish (表面光洁度) | 2B (mill finish) or BA (Bright Annealed), Ra ≤ 0.4 μm |
| End Treatment (端部处理) | Flanged, threaded, grooved, or plain-cut per customer drawing |
| Tolerance on OD (外径公差) | ± 0.05 mm (standard); ± 0.02 mm (precision grade) |
| Tolerance on Wall Thickness (壁厚公差) | ± 10% |
| Material Certification (材质证明) | EN 10204 3.1 / 3.2 test certificates available |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection (原材料选择): Cold-rolled stainless steel strip or seamless tube stock conforming to ASTM/GB standards, with full mill certification.
- Coil Winding (盘管成型): Precision CNC-guided forming on dedicated coil winding machines to achieve consistent pitch, concentricity, and dimensional accuracy. The winding process is controlled to prevent work-hardening (加工硬化) that could impair thermal fatigue resistance.
- Welding (焊接): Inert gas tungsten arc welding (IGTAW / TIG) or orbital automatic welding for end joints, ensuring full-penetration welds with minimal heat-affected zone (热影响区, HAZ).
- Heat Treatment (热处理): Solution annealing (固溶处理) at 1010–1150°C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation (酸洗钝化): Removal of weld scale and oxide layers using nitric-hydrofluoric acid blend, followed by passivation treatment to establish a stable chromium oxide protective film.
- Surface Cleaning & Inspection (表面清洁与检验): Ultrasonic testing (超声检测, UT) for wall thickness verification, hydrostatic pressure testing (水压试验) for leak integrity, and visual inspection per ASTM E165.
- Packaging (包装): Protective end caps, moisture-absorbing desiccant, and export-grade wooden or metal crates for international shipment.
4.2 Quality Control Measures
- In-process dimensional verification at every winding station using laser micrometers
- 100% hydrostatic testing at 1.5× maximum operating pressure for 30 seconds
- Spectroscopic analysis (光谱分析) for chemical composition verification on every heat lot
- Dimensional reporting with as-built coil geometry data for OEM integration
5. Applications
5.1 Primary Application: Modular Air Conditioning Units (组合式空调箱)
Stainless steel coil tubes are the primary heat transfer elements in heat recovery modules of modular air handling units. In these systems, the coil tube array facilitates total energy heat recovery (全热回收), recovering both sensible and latent heat from the exhaust air stream and transferring it to the incoming fresh air stream. This significantly reduces the energy consumption of the HVAC system by up to 60–70% compared to conventional ventilation without heat recovery.
5.2 Additional Applications
- Industrial Air Handling: Cooling coils and heating coils in process air systems for pharmaceutical, semiconductor, and food processing facilities
- Chilled Water Systems: Fan coil units (FCUs) and air-water heat exchangers in commercial buildings
- Refrigeration Systems: Evaporator and condenser coils in commercial refrigeration equipment
- Process Heat Exchangers: Plate-and-tube heat exchangers in chemical and petrochemical industries
- Marine HVAC: Corrosion-resistant coil assemblies for shipboard ventilation and air conditioning systems
6. Performance Analysis: Heat Recovery Efficiency
Based on thermodynamic analysis of coil-based heat recovery systems in modular air conditioning units, the following performance characteristics have been established:
- Sensible Heat Recovery Efficiency (显热回收效率): 65% – 85%, depending on coil geometry, airflow velocity, and temperature differential
- Total Heat Recovery Efficiency (全热回收效率): 70% – 90%, incorporating latent heat transfer through moisture exchange
- Pressure Drop (压降): Typically 50 – 200 Pa across the coil assembly at design airflow rates
- Heat Transfer Coefficient (传热系数): Enhanced by the high surface-area-to-volume ratio of the coil configuration, achieving U-values of 30 – 60 W/(m²·K) for air-to-air configurations
The stainless steel material contributes to long-term efficiency retention by preventing fouling, scaling, and corrosion-induced degradation of the heat transfer surface, unlike carbon steel alternatives which may experience efficiency losses of 15–25% over a 5-year service period.
7. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| EN 10204 3.1 | Material test certificates conforming to European standards |
| EN 10217-7 | Standard for austenitic stainless steel tubes for heat exchangers |
| ASTM A213/A213M | American standard for seamless austenitic stainless steel tubes for heat exchangers and similar services |
| GB/T 12771 | Chinese national standard for stainless steel seamless tubes for general purposes |
| CE Marking | European Conformity marking for products intended for the European Economic Area |
| TÜV / SGS Inspection | Third-party inspection and testing available upon request |
8. Unique Selling Points
- Superior Corrosion Resistance (卓越的耐腐蚀性): Austenitic stainless steel construction ensures decades of reliable service in humid, chemically aggressive HVAC environments without degradation of thermal performance or structural integrity.
- Precision Coil Geometry (精密盘管几何): CNC-controlled winding ensures uniform pitch and concentricity, maximizing heat transfer surface utilization and minimizing airflow maldistribution.
- Thermal Fatigue Durability (热疲劳耐久性): Solution-annealed microstructure provides excellent resistance to thermal cycling fatigue, critical for systems experiencing daily temperature fluctuations.
- Customizable Design (可定制设计): Flexible manufacturing capability accommodates custom dimensions, end treatments, and material grades to meet specific OEM requirements.
- Hygienic Surface Quality (卫生级表面质量): Bright annealed (BA) surface finish with Ra ≤ 0.4 μm ensures minimal fouling and easy cleanability, essential for food-grade and pharmaceutical applications.
- Full Traceability (完整可追溯性): Every coil tube assembly is traceable to its mill heat number, with complete documentation of chemical composition, mechanical testing, and dimensional verification.
9. Technical Data Summary
For detailed engineering drawings, material certifications, and custom specification inquiries, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. The company maintains an in-house technical engineering team capable of providing thermal performance modeling, CFD (Computational Fluid Dynamics) analysis, and application-specific design support for coil tube integration into modular air conditioning and heat recovery systems.