Stainless Steel Coil Tube (盘管) — Model Series 815
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube), designated under product reference Series 815 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular component formed into helical or serpentine coil configurations. This product is specifically designed for integration into fan coil units (FCUs), including the ECR400-type and other commercial-grade HVAC (Heating, Ventilation, and Air Conditioning) systems. The coil tube serves as the primary heat exchange element, facilitating efficient thermal transfer between circulating refrigerant or hot water and the surrounding air stream.
Extensive experimental research on ECR400-type fan coil unit performance has demonstrated that the geometric and material characteristics of the coil tube are among the most critical factors influencing overall system efficiency, pressure drop, and heat transfer coefficient. This product line incorporates findings from such studies to optimize coil geometry, wall thickness uniformity, and surface finish, ensuring peak thermal-hydraulic performance across a wide range of operating conditions.
2. Material & Properties
The coil tubes are manufactured from high-grade austenitic stainless steel, with the following material options available:
- SUS304 / AISI 304 (UNS S30400) — The standard grade offering excellent corrosion resistance, formability, and weldability. Suitable for general-purpose HVAC and refrigeration applications.
- SUS316 / AISI 316 (UNS S31600) — Enhanced molybdenum content provides superior resistance to chlorides and aggressive environments. Recommended for coastal, marine, and chemical processing installations.
- SUS321 / AISI 321 (UNS S32100) — Titanium-stabilized grade offering improved resistance to intergranular corrosion at elevated temperatures.
Key Mechanical and Physical Properties (SUS304 Grade)
| Property | Value / Specification |
|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa (75,400 psi) |
| Yield Strength (屈服强度) | ≥ 205 MPa (29,730 psi) |
| Elongation (延伸率) | ≥ 40% |
| Thermal Conductivity (热导率) | 16.3 W/(m·K) at 20°C |
| Operating Temperature Range (工作温度范围) | −196°C to +870°C |
| Corrosion Resistance (耐腐蚀性) | Excellent resistance to atmospheric, aqueous, and mild chemical environments |
| Surface Finish (表面光洁度) | Mirror finish (Ra ≤ 0.4 μm) or standard pickled & passivated finish (Ra ≤ 1.6 μm) |
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name (产品名称) | Stainless Steel Coil Tube (盘管) | — |
| Product Reference (序号) | 815 | — |
| Outer Diameter (外径, OD) | 6.35 mm (1/4"), 9.53 mm (3/8"), 12.7 mm (1/2") | ASTM A269 / GB/T 12771 |
| Wall Thickness (壁厚) | 0.50 mm – 1.50 mm (customizable) | ASTM A269 / GB/T 12771 |
| Coil Diameter (盘管直径) | 150 mm – 500 mm (customizable) | — |
| Coil Pitch (盘管间距) | 10 mm – 25 mm | — |
| Number of Turns (圈数) | 8 – 40 turns (application-dependent) | — |
| Tubing Length (管长) | 3 m – 30 m (customizable per coil) | — |
| Material Grade (材质) | SUS304 / SUS316 / SUS321 | ASTM A270 / GB/T 21830 |
| Surface Treatment (表面处理) | Pickled & Passivated (酸洗钝化) / Mirror Polish | — |
| Connection Type (连接方式) | Flared, Welded (TIG), or Threaded fittings | ASME B31.9 |
| Pressure Rating (耐压等级) | Up to 4.0 MPa (580 psi) | ASME B31.9 / GB/T 12771 |
| Applicable Refrigerants (适用制冷剂) | R22, R410A, R134a, R32, R407C, CO₂ (R744) | — |
| Custom Fabrication (定制加工) | Available — dimensions, geometry, and surface finish tailored to OEM requirements | — |
4. Manufacturing Process
The production of Series 815 Stainless Steel Coil Tubes follows a rigorously controlled multi-stage manufacturing workflow:
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Raw Material Procurement & Inspection (原材料采购与检验)
Virgin stainless steel seamless tubes conforming to ASTM A269 or GB/T 12771 are sourced from certified mills. Each batch undergoes spectroscopic composition analysis (OES) and mechanical testing to verify conformance to specified grades.
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Tube Straightening & Cutting (管材矫直与切割)
Seamless tubes are fed through automated straightening machines to achieve straightness tolerances of ≤ 0.5 mm/m. Precision laser or plasma cutting systems segment tubes to required lengths with tolerances of ± 0.5 mm.
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End Finishing (端部加工)
Tube ends are deburred, chamfered, and prepared for subsequent bending and connection operations. Flaring or threading is applied as specified.
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Coil Bending (盘管成型)
Computer-controlled CNC bending machines form the straight tubes into precise helical or serpentine coil geometries. Bend radii are controlled to prevent wall thinning (minimum wall thickness reduction ≤ 15%) and ovality (≤ 8% of nominal OD). The bending process is optimized based on experimental findings regarding coil geometry's influence on fan coil unit thermal performance, ensuring optimal balance between heat transfer surface area and air-side pressure drop.
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Heat Treatment (热处理)
Post-bending annealing at 1050°C – 1100°C in a controlled atmosphere furnace relieves residual stresses introduced during cold forming, restores full austenitic microstructure, and ensures dimensional stability.
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Pickling & Passivation (酸洗钝化)
Tubes are immersed in a citric or nitric acid-based pickling solution to remove scale and oxidation. Subsequent passivation treatment forms a protective chromium oxide layer, enhancing long-term corrosion resistance.
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Hydrostatic & Pneumatic Testing (水压与气密性试验)
Each coil assembly undergoes 100% hydrostatic pressure testing at 1.5× the rated working pressure for a minimum dwell time of 60 seconds, followed by helium leak detection (detection limit ≤ 1×10⁻⁹ mbar·L/s) to ensure absolute integrity.
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Final Inspection & Packaging (终检与包装)
Dimensional verification via laser scanning, visual surface inspection, and material traceability documentation are completed. Coils are packaged with moisture-absorbing desiccants and anti-corrosion wrapping in export-grade wooden crates or palletized containers.
5. Applications
The Series 815 Stainless Steel Coil Tube is engineered for demanding thermal management applications:
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HVAC Fan Coil Units (暖通空调风机盘管)
Primary application domain. The coil tubes serve as the core heat exchange component in commercial and residential fan coil units, including ECR400-type and other centrifugal/blower-driven configurations. Experimental research has confirmed that optimized coil geometry directly correlates with improved COP (Coefficient of Performance) and reduced fan power consumption.
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Industrial Refrigeration (工业制冷)
Used in evaporator and condenser assemblies for cold storage, process cooling, and industrial chiller systems handling refrigerants including R410A, R134a, R32, and CO₂.
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Heat Exchangers (换热器)
Integrated into shell-and-coil heat exchangers for heating and cooling duty in chemical, pharmaceutical, and food processing industries.
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Automotive & Transportation HVAC (汽车与交通暖通)
Employed in refrigeration units for commercial vehicles, rail cars, and marine air conditioning systems where corrosion resistance and durability are paramount.
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Domestic Water Heating (家用热水系统)
Used in indirect water heating coils for solar thermal and condensing boiler systems, leveraging the non-toxic, food-safe properties of austenitic stainless steel.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications:
- ISO 9001:2015 — Quality Management Systems (质量管理体系)
- ISO 14001:2015 — Environmental Management Systems (环境管理体系)
- ISO 45001:2018 — Occupational Health and Safety Management Systems (职业健康安全管理体系)
- CE Marking — Conformity with EU Machinery and Pressure Equipment Directives
- UL Listed — Underwriters Laboratories safety certification for HVAC components
- ASME Stamp — American Society of Mechanical Engineers certification for pressure-containing components
- EN 10204 3.1 — Material test certificates conforming to European standard
All products are manufactured in strict compliance with the following international and national standards:
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severely Corrosive Services
- ASTM A270 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Applications
- ASME B31.9 — Refrigeration Piping and Heat Transfer Components
- GB/T 12771 — Non-alloy and Alloy Steel Tubes for Heat Exchange and General Heat Transfer
- GB/T 21830 — Stainless Steel Tubes for Heat Exchange and General Heat Transfer
- JIS G3459 — Stainless Steel Tubes for Heat Exchangers
7. Unique Selling Points
Research-Driven Design Optimization: The Series 815 coil tube incorporates geometric parameters validated through experimental performance studies of ECR400-type fan coil units. This ensures that coil diameter, pitch, and turn count are optimized for maximum heat transfer efficiency while minimizing air-side pressure drop — a direct advantage over conventionally designed coil products.
- Precision CNC Bending: Automated forming ensures repeatable coil geometry with wall-thinning controlled to ≤ 15%, preserving structural integrity and thermal performance across the full production run.
- Full Material Traceability: Every coil tube is traceable to its mill heat number, enabling complete supply chain accountability and facilitating customer quality audits.
- Custom Fabrication Capability: OEM-specific coil geometries, dimensions, and surface finishes are available, supporting rapid prototyping and volume production for bespoke HVAC system designs.
- 100% Leak Testing: Hydrostatic and helium leak testing at every unit ensures zero-defect delivery and eliminates field failure risk.
- Multi-Grade Material Options: SUS304, SUS316, and SUS321 grades provide flexibility for applications ranging from standard indoor HVAC to aggressive marine and chemical environments.
- Sustainability: Stainless steel coil tubes are 100% recyclable, with the manufacturing process designed to minimize energy consumption and waste in accordance with ISO 14001 environmental management standards.
8. Technical Support & Documentation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:
- Material Test Certificates (MTC) per EN 10204 3.1 for every shipment
- Dimensional inspection reports with laser scanning data
- Thermal performance simulation data (CFD analysis) upon request
- Application engineering consultation for system integration
- Warranty period of 24 months from date of delivery against manufacturing defects