Stainless Steel Coil Tube — Fan Coil & Radiant Cooling System Application
Product Code: No. 291 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Category: Coil Tube (盘管)
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular component formed into helical or serpentine coil configurations, primarily designed for integration into Fan Coil Units (FCUs) and Floor Radiant Cooling Systems operating in hot and humid climatic zones. These coil tubes serve as the primary heat exchange medium, facilitating efficient thermal transfer between the circulating working fluid (typically chilled water or refrigerant) and the surrounding air or radiant surfaces.
Based on experimental research into the cooling characteristics of floor radiation coupled with fan coil air conditioning systems in tropical and subtropical regions, Wenzhou Jixing Metal Materials Co., Ltd. has developed a specialized coil tube product that meets the rigorous demands of high-humidity, high-temperature environments. The coil tube is engineered to maintain structural integrity and thermal performance under continuous cyclic thermal loading, condensation exposure, and corrosive atmospheric conditions.
2. Material Composition & Properties
2.1 Base Material
- Primary Alloy: Austenitic Stainless Steel (奥氏体不锈钢)
- Standard Grades: AISI 304 (UNS S30408), AISI 316L (UNS S31603), AISI 321 (UNS S32108)
- Chromium Content (Cr): 18.0%–20.5% by mass
- Nickel Content (Ni): 8.0%–10.5% by mass
- Molybdenum Content (Mo): 2.0%–3.0% by mass (316L grade)
2.2 Mechanical Properties
- Tensile Strength (抗拉强度): ≥ 520 MPa (304 grade); ≥ 570 MPa (316L grade)
- Yield Strength (屈服强度): ≥ 205 MPa
- Elongation (延伸率): ≥ 40% (indicating superior formability for coil winding)
- Hardness (硬度): ≤ 200 HB
- Thermal Conductivity (导热系数): 14.5–16.3 W/(m·K) at 20°C
2.3 Corrosion Resistance
- Pitting Resistance Equivalent Number (PREN): ≥ 24 (316L grade)
- Acid Rain Resistance: Compliant with GB/T 15386 standards
- Condensation Resistance: Suitable for continuous exposure to high-humidity environments (RH > 85%)
- Chloride Ion Resistance: Effective against chloride-induced pitting corrosion in coastal and industrial settings
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm, Φ8.0 mm, Φ9.5 mm, Φ12.0 mm (customizable) | GB/T 14976, ASTM A213 |
| Wall Thickness | 0.5 mm – 1.5 mm | GB/T 14976 |
| Coil Pitch (螺旋间距) | 10 mm – 50 mm (adjustable per design requirement) | Customer specification |
| Coil Diameter (盘管直径) | Φ150 mm – Φ600 mm | GB/T 14976 |
| Effective Length (有效长度) | 10 m – 200 m per coil assembly | — |
| Surface Finish | No.4 Brushed (2B), Mirror Polish (Ra ≤ 0.4 μm) | ASTM A480 |
| Maximum Operating Temperature | −40°C to +350°C | — |
| Maximum Operating Pressure | 1.6 MPa (standard); 4.0 MPa (reinforced) | GB 150 |
| Winding Method | Continuous helical winding with cold-forming process | Internal process standard |
| End Treatment | Beveled, threaded (NPT/BSP), or flanged connections | ASME B1.20.1 |
| Packaging | Protective wrapping, wooden pallet, moisture-barrier film | ISO 4180 |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Selection & Inspection: Stainless steel seamless tubes sourced from certified mills undergo spectroscopic analysis (OES), hydrostatic testing, and dimensional verification prior to processing.
- Surface Preparation: Tubes are cleaned, degreased, and passivated to remove scale and contaminants, ensuring a clean substrate for subsequent forming operations.
- Cold Coil Winding (冷弯盘管成型): Precision CNC-controlled winding machines form the straight tube into helical coil configurations with controlled pitch, diameter, and tension. The cold-forming process eliminates the need for post-forming annealing, preserving the material's mechanical properties.
- Support Ring Installation: Stainless steel or PTFE-coated support rings are welded or crimped at regular intervals to maintain coil geometry and prevent collapse under operational loads.
- Welding & Connection Fabrication: Inlet and outlet ports are fabricated using TIG (Tungsten Inert Gas) welding or orbital welding, followed by visual and radiographic inspection (RT) of weld seams.
- Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure for a minimum dwell time of 30 minutes, ensuring zero leakage.
- Final Inspection & Passivation: Completed assemblies receive acid pickling and passivation treatment to restore the passive chromium oxide layer, followed by dimensional and surface quality verification.
4.2 Quality Control Measures
- 100% visual inspection of all weld joints
- Random sampling for ultrasonic testing (UT) and eddy current testing (ECT)
- Batch-wise mechanical property verification through tensile testing
- Corrosion resistance verification via salt spray testing (ASTM B117, ≥ 500 hours)
5. Applications
5.1 Primary Application Domains
- Fan Coil Units (风机盘管): Coil tubes serve as the core heat exchanger element in FCUs used for commercial and residential HVAC systems, particularly in hot and humid climates where dehumidification and cooling capacity are critical.
- Floor Radiant Cooling Systems (地板辐射供冷系统): Embedded within floor slabs, coil tubes distribute chilled water for radiant cooling, providing uniform temperature distribution and superior thermal comfort in tropical and subtropical regions.
- Coupled Hybrid Cooling Systems: In floor radiation coupled fan coil configurations, coil tubes operate as part of a dual-zone system where radiant panels handle sensible cooling while fan coils manage latent (moisture) loads — a strategy validated through experimental research for enhanced energy efficiency in hot-humid zones.
- Industrial Heat Exchangers: Condensers, evaporators, and process cooling loops in chemical, pharmaceutical, and food processing industries.
- Refrigeration & Cryogenic Systems: Low-temperature coil assemblies for cold storage facilities and industrial refrigeration circuits.
5.2 Performance Advantages in Hot-Humid Environments
Experimental studies on floor radiation coupled fan coil systems in tropical climates have demonstrated that stainless steel coil tubes maintain stable thermal performance even under sustained high ambient humidity (RH 70%–95%) and elevated temperatures (30°C–40°C). The austenitic stainless steel matrix resists condensation-induced corrosion that commonly degrades carbon steel alternatives, ensuring long-term reliability and reduced maintenance frequency.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| GB/T 14976 | Chinese National Standard — Seamless stainless steel tubes for heat exchangers |
| ASTM A213 / A269 | American standard for austenitic stainless steel seamless tubes (welded & seamless) |
| EN 10216-5 | European standard for austenitic stainless steel tubes for heat exchangers |
| ASME B31.3 | Process piping design and construction compliance |
| CE Marking | Conformity with European Directive requirements for pressure equipment |
| ISO 4180 | International standard for packaging and transport of steel products |
| Material Mill Certificate (MTC) | EN 10204 Type 3.1 material test certificates provided with each batch |
7. Unique Selling Points
- Corrosion-Resistant in Harsh Environments: The 316L grade option provides exceptional resistance to chloride pitting and crevice corrosion, making it ideal for coastal installations and humid tropical climates where carbon steel alternatives would suffer rapid degradation.
- High Thermal Efficiency: Precision coil geometry with optimized pitch and diameter ratios maximizes the heat transfer surface area per unit volume, achieving superior cooling capacity in compact fan coil and radiant floor systems.
- Long Service Life: With proper installation, the stainless steel coil tube offers a service life exceeding 25 years without significant performance degradation, significantly outperforming copper and carbon steel alternatives in corrosive environments.
- Research-Validated Design: The product design incorporates findings from experimental research on floor radiation coupled fan coil cooling systems in hot-humid regions, ensuring that thermal and hydraulic performance is optimized for the most demanding climatic conditions.
- Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers full customization of coil dimensions, pitch, material grade, end connections, and surface finish to meet specific project requirements.
- Hygienic Grade Available: Mirror-polished surface finish (Ra ≤ 0.4 μm) is available for food processing, pharmaceutical, and biomedical applications requiring sanitary-grade heat exchange components.
8. Conclusion
The Stainless Steel Coil Tube (Product No. 291) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. represents a high-performance, corrosion-resistant heat exchange solution purpose-built for fan coil units, floor radiant cooling systems, and hybrid cooling configurations in hot and humid climates. Backed by rigorous material science, validated thermal performance research, and adherence to international quality standards, this product delivers exceptional reliability, efficiency, and longevity for demanding HVAC and industrial applications worldwide.