Stainless Steel Coil Tube — HVAC Fan Coil Unit Series (Ref. No. 907)
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Category: Stainless Steel Coil Tube for Thermal Exchange Applications
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed specifically for integration into Fan Coil Units (FCU) and Heating, Ventilation, and Air Conditioning (HVAC) systems. These coil tubes serve as the core thermal exchange elements within air-handling equipment, facilitating efficient heat transfer between refrigerant or hot water and the ambient air stream.
The product is engineered in accordance with the principles outlined in the technical literature "Discussion on Air Volume Measurement Methods in Fan Coil Unit Performance Testing", which establishes rigorous performance benchmarks for airflow capacity, thermal efficiency, and pressure drop characteristics. The coil tube design directly impacts the volumetric airflow rate (风量), heat exchange efficiency, and overall system performance metrics evaluated during FCU certification testing.
Stainless steel coil tubes represent a premium alternative to traditional copper-aluminum heat exchangers, offering superior corrosion resistance, extended service life, and compliance with hygienic standards required in sensitive environments such as hospitals, pharmaceutical facilities, and food processing plants.
2. Material & Properties
2.1 Material Composition
- Base Material: Austenitic Stainless Steel (奥氏体不锈钢)
- Standard Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 316L (UNS S31603)
- Equivalent Chinese Standards: GB/T 12771-2016, GB/T 14976-2012
- International Standards: ASTM A213/A213M, EN 10216-5, JIS G3446
2.2 Mechanical Properties
| Property | Grade 304 | Grade 316 | Grade 316L |
|---|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa | ≥ 515 MPa | ≥ 485 MPa |
| Yield Strength (屈服强度, 0.2% offset) | ≥ 205 MPa | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (延伸率, A50mm) | ≥ 40% | ≥ 40% | ≥ 40% |
| Hardness (硬度, HBW) | ≤ 217 | ≤ 217 | ≤ 200 |
2.3 Physical & Thermal Properties
- Density (密度): 7.93 g/cm³ (Grade 304); 8.00 g/cm³ (Grade 316)
- Thermal Conductivity (热导率) at 20°C: 16.3 W/(m·K) (Grade 304); 14.6 W/(m·K) (Grade 316)
- Specific Heat Capacity (比热容) at 20°C: 0.500 kJ/(kg·K)
- Thermal Expansion Coefficient (热膨胀系数): 17.3 × 10⁻⁶ /K (20–100°C)
- Operating Temperature Range (工作温度范围): −196°C to +870°C (Grade 304); −196°C to +870°C (Grade 316)
- Corrosion Resistance (耐腐蚀性): Excellent resistance to atmospheric corrosion, mild acids, organic acids, and chlorinated environments (316/316L)
2.4 Surface Finish
- Standard Finish: 2B Cold Rolled Finish (No. 4 Satin)
- Available Finishes: BA (Bright Annealed), Electropolished (Ra ≤ 0.4 μm), Mirror Polish (Ra ≤ 0.1 μm)
- Surface Roughness (表面粗糙度): Ra 0.8–1.6 μm (standard); Ra ≤ 0.4 μm (electropolished)
- Wall Thickness Tolerance (壁厚公差): ±10% of nominal (commercial); ±5% (precision grade)
3. Technical Specifications
3.1 Geometric Dimensions
| Parameter (参数) | Specification (规格) | Standard Reference |
|---|---|---|
| Outer Diameter (外径, OD) | 6.0 mm, 8.0 mm, 9.53 mm (⅜"), 12.7 mm (½"), 15.88 mm (⅝") | ASTM A213, GB/T 12771 |
| Wall Thickness (壁厚) | 0.50 mm, 0.60 mm, 0.71 mm, 0.80 mm, 1.00 mm | GB/T 12771-2016 |
| Coil Length (盘管长度) | 3 m to 50 m (customizable) | — |
| Coil Outer Diameter (盘管外径) | Φ150 mm to Φ600 mm | — |
| Number of Rows (排数) | 1, 2, 3, 4, 6 rows | — |
| Tube Pitch (管间距, Lateral) | 12.5 mm, 15.0 mm, 19.0 mm | — |
| Tube Pitch (管间距, Vertical) | 12.5 mm, 15.0 mm, 19.0 mm | — |
| Bend Radius (弯曲半径) | ≥ 3D (D = outer diameter) | — |
| Fin Type (翅片类型) | Aluminum L-Fin, V-Groove Fin, Integral Fin | — |
| Fin Density (翅片密度) | 10–16 fins per inch (FPI) | — |
3.2 Performance Specifications
| Performance Parameter (性能参数) | Typical Value | Test Standard |
|---|---|---|
| Design Pressure (设计压力) | 1.6 MPa (standard); 2.5 MPa (high-pressure grade) | GB/T 12771, PED 2014/68/EU |
| Test Pressure (试验压力) | 2.4 MPa (1.5× design pressure) | GB/T 12771 |
| Maximum Operating Temperature (最高工作温度) | 95°C (hot water); −10°C to +120°C (refrigerant) | — |
| Pressure Drop (压降, ΔP) | ≤ 150 Pa (air side); ≤ 50 kPa (water side) | ASHRAE 34-2013 |
| Heat Transfer Coefficient (传热系数) | ≥ 25 W/(m²·K) (air-water) | ASHRAE Handbook |
| Service Life (使用寿命) | ≥ 25 years (corrosion-free environment) | — |
3.3 Air Volume Performance (风量性能)
In accordance with the methodology discussed in "Discussion on Air Volume Measurement Methods in Fan Coil Unit Performance Testing," the coil tube assembly is characterized by the following airflow-related performance criteria:
| Parameter | Description | Typical Range |
|---|---|---|
| Total Airflow Rate (总风量) | Volumetric airflow delivered through the coil face | 300–3,000 m³/h |
| Face Velocity (面风速) | Air velocity across the coil face | 1.5–3.0 m/s |
| Static Pressure (静压) | Static pressure at coil inlet/outlet | −10 to +50 Pa |
| Dynamic Pressure (动压) | Velocity pressure component | 5–15 Pa |
| Total Pressure (全压) | Sum of static and dynamic pressure | 0–65 Pa |
| Airflow Uniformity (风量均匀性) | Distribution uniformity across coil face | ≥ 85% (CV ≤ 15%) |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection (原材料选择): High-purity stainless steel wire rod or strip sourced from certified mills (e.g., Outokumpu, POSCO, Taigang), meeting ASTM A276 or GB/T 4237 chemical composition requirements.
- Wire Drawing (拉拔): Multi-stage cold drawing to achieve precise tube dimensions with tolerance control within ±0.05 mm for critical applications.
- Seamless Forming (无缝成型): Cold-rolled and welded (ERW/TIG) or fully seamless tube forming, depending on pressure rating requirements.
- Heat Treatment / Annealing (热处理/退火): Solution annealing at 1050–1150°C followed by controlled cooling to restore full austenitic microstructure and eliminate residual stresses. For 316L grade, stabilization annealing may be applied.
- Pickling & Passivation (酸洗钝化): Immersion in nitric acid/hydrofluoric acid solution to remove scale and form a protective chromium oxide passivation layer (minimum 10% Cr₂O₃ content).
- Coil Winding (盘管缠绕): Precision CNC-guided coil winding to achieve exact tube pitch, row configuration, and overall coil geometry with ±1 mm dimensional accuracy.
- Fin Insertion (翅片插入): Aluminum fins inserted into the tube array using automated fin-stamping and insertion equipment, achieving uniform fin-tube contact resistance.
- Hydrostatic Testing (水压试验): 100% hydrostatic pressure testing at 1.5× design pressure with a minimum hold time of 30 seconds per unit. Leak detection sensitivity: ≤ 0.1 mL/min.
- Dimensional Inspection (尺寸检验): Coordinate Measuring Machine (CMM) and laser scanning for geometric verification of coil diameter, tube pitch, and overall dimensions.
- Final Quality Assurance (最终质量保证): Spectroscopic analysis (PMI), visual inspection, and performance testing including air volume measurement per the methodology referenced in the product documentation.
4.2 Key Process Technologies
- Computer Numerical Control (CNC) Coil Winding: Ensures repeatable, high-precision coil geometry with programmable parameters for diameter, pitch, and row count.
- Friction Stir Welding (FSW) / TIG Welding: For header connections and tube-to-plate joints, providing full-penetration welds with minimal heat-affected zone (HAZ).
- Electrolytic Polishing (电解抛光): Available as an optional surface treatment for medical and pharmaceutical applications, achieving Ra ≤ 0.4 μm.
- Non-Destructive Testing (NDT): Eddy current (涡流检测) and ultrasonic testing (超声波检测) for weld integrity and wall thickness verification.
5. Applications
5.1 Primary Applications
- Fan Coil Units (风机盘管): Central application for commercial and residential HVAC systems, providing space conditioning through chilled water or hot water circulation.
- Air Handling Units (AHU): Integration into large-scale air handling systems for commercial buildings, airports, and industrial facilities.
- Chilled Beam Systems (冷冻盘管系统): Radiation and convection cooling in open-plan office environments.