Stainless Steel Coil Tube — Low-Temperature Fan Coil Unit Application
Product Overview
The Stainless Steel Coil Tube (产品编号: 619) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange coil designed specifically for demanding low-temperature operating environments. This product represents a specialized segment within the coil tube (盘管) family, engineered to deliver superior thermal performance and structural integrity under conditions where conventional carbon steel or copper coil assemblies suffer from accelerated corrosion, frost formation, and thermal degradation.
Based on extensive thermal performance testing and analysis of fan coil units (FCU — Fan Coil Units) operating under low-temperature conditions, this coil tube product has been optimized for heat transfer efficiency, frost resistance, and long-term durability. The stainless steel construction provides an inherent corrosion-resistant barrier that significantly extends service life compared to traditional coil materials in humid, acidic, or cryogenic service environments.
Material & Properties
The coil tube is fabricated from austenitic stainless steel, predominantly Grade 304 (UNS S30400) or Grade 316L (UNS S31603), selected for their exceptional combination of mechanical strength, corrosion resistance, and thermal conductivity at low temperatures. Key material properties include:
- Austenitic microstructure — Ensures ductility and toughness retention at cryogenic temperatures (down to −196 °C), eliminating the risk of brittle fracture.
- Corrosion resistance — Chromium content of 18–20% forms a passive oxide layer (Cr₂O₃) that resists pitting, crevice corrosion, and intergranular attack in aggressive environments.
- Thermal conductivity — Approximately 16 W/(m·K) at 20 °C, providing reliable heat transfer performance while maintaining structural stability.
- Weldability — Excellent forming and welding characteristics enable seamless coil construction with minimal residual stress.
- Non-magnetic properties — The austenitic structure remains non-magnetic even after cold working, suitable for electromagnetic-sensitive installations.
Specifications
| Parameter | Specification |
|---|---|
| Product Category | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Product No. | 619 |
| Material Grade | SUS 304 / SUS 316L (Austenitic Stainless Steel) |
| Tube Outer Diameter (OD) | 6.35 mm – 19.05 mm (1/4" – 3/4") |
| Tube Wall Thickness | 0.5 mm – 1.2 mm |
| Fin Material | Aluminum (Al 1100) or Stainless Steel (SUS 304) |
| Fin Pitch | 2.0 mm – 3.5 mm |
| Fin Height | 8 mm – 15 mm |
| Operating Temperature Range | −40 °C to +120 °C |
| Cooling Capacity | Up to 15 kW (model-dependent) |
| Heat Transfer Efficiency | ≥ 95% (low-temperature condition, tested per GB/T 19232) |
| Refrigerant Compatibility | R410A, R32, R134a, R404A, Ammonia (NH₃) |
| Surface Treatment | Passivation, Anti-frost Coating (optional), Hydrophilic Coating |
| Connection Type | Flared, Brazed, or Threaded (G1/2" – G1") |
| Standard Compliance | GB/T 14976, ASTM A213, EN 10216-5, JIS G3445 |
Manufacturing Process
The production of this stainless steel coil tube follows a rigorous multi-stage manufacturing protocol designed to ensure dimensional accuracy, metallurgical integrity, and thermal performance consistency:
- Material Selection & Incoming Inspection — Raw stainless steel strip or tube stock is verified for chemical composition (via optical emission spectroscopy, OES) and mechanical properties before processing.
- Cold Drawing & Forming — Precision cold-drawing processes shape the tube to exact OD and wall thickness tolerances (±0.05 mm). The coil winding pattern is formed on CNC-controlled bending machines to achieve uniform pitch and consistent geometry.
- Fin Attachment — Aluminum or stainless steel fins are mechanically bonded or welded to the coil tubes using high-frequency resistance welding or brazing techniques, ensuring minimal thermal contact resistance.
- Welding & Brazing — U-bends and header connections are welded using TIG (Tungsten Inert Gas) welding or vacuum brazing under inert atmosphere to prevent oxidation and ensure leak-tight integrity.
- Surface Treatment — Electrochemical passivation removes free iron contamination and enhances the passive oxide layer. Optional hydrophilic coatings are applied to facilitate condensate drainage and reduce frost accumulation.
- Pressure Testing & Leak Detection — Each coil assembly undergoes hydrostatic pressure testing at 1.5× working pressure (minimum 2.5 MPa) and nitrogen leak testing to verify structural integrity.
- Thermal Performance Verification — Representative samples are subjected to low-temperature thermal performance testing in accordance with GB/T 19232 and AHRI 210/240 standards to validate heat transfer coefficients and capacity ratings.
Applications
This stainless steel coil tube is engineered for a wide range of industrial and commercial applications where low-temperature operation and corrosion resistance are critical requirements:
- Low-temperature Fan Coil Units (FCU) — Primary application for chilled water and refrigerant cooling systems operating below 5 °C, where anti-frost performance is essential.
- Industrial Refrigeration — Cold storage facilities, freeze-drying equipment, and cryogenic processing plants requiring reliable heat exchange at sub-zero temperatures.
- Pharmaceutical & Food Processing — Cleanroom HVAC systems, refrigerated processing lines, and sanitary-grade cooling applications demanding hygienic and corrosion-resistant materials.
- Chemical Processing — Heat exchangers handling aggressive or corrosive media where carbon steel coil assemblies would fail prematurely.
- Marine & Offshore — HVAC systems on vessels and offshore platforms exposed to salt-laden atmospheres requiring maximum corrosion protection.
- Commercial Air Conditioning — High-end commercial buildings, data centers, and laboratory environments requiring silent, efficient, and long-lasting cooling solutions.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems ensuring that every coil tube product meets international standards and regulatory requirements:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating environmental responsibility in manufacturing.
- CE Marking — Conformity with European Union directives for safety and performance.
- GB/T 14976 — Chinese national standard for seamless and welded stainless steel tubes.
- ASTM A213 — American standard for austenitic stainless steel tubes for heat exchangers.
- EN 10216-5 — European standard for welded austenitic stainless steel tubes for heat exchangers.
- GB/T 19232 — Thermal performance testing standard for air-water heat exchangers.
- AHRI 210/240 — Air-Conditioning, Heating, and Refrigeration Institute standard for unitary air-conditioning and air-source heat pump equipment.
Unique Selling Points
1. Proven Low-Temperature Performance: Validated through systematic thermal performance testing under low-temperature conditions, demonstrating heat transfer efficiency exceeding 95% even at operating temperatures as low as −40 °C — a capability that distinguishes this product from standard coil tube offerings.
2. Superior Corrosion & Frost Resistance: The austenitic stainless steel construction combined with optional anti-frost surface coatings provides dual protection against both chemical corrosion and ice accumulation, reducing maintenance frequency and extending operational lifespan by 3–5× compared to copper-fin-tube (CFT) alternatives.
3. Engineering-Driven Design: Informed by rigorous academic research on fan coil unit thermal dynamics under low-temperature conditions, this product embodies evidence-based design optimization for real-world application scenarios.
4. Versatile Refrigerant Compatibility: Designed to operate with next-generation low-GWP (Global Warming Potential) refrigerants including R32 and R410A, ensuring regulatory compliance with evolving environmental standards.
5. Precision Manufacturing: CNC-controlled coil forming with dimensional tolerances of ±0.05 mm ensures uniform airflow distribution and optimal heat transfer surface area utilization across the entire coil assembly.
Conclusion
The Stainless Steel Coil Tube (Product No. 619) from Wenzhou Jixing Metal Materials Co., Ltd. represents the convergence of metallurgical science, thermal engineering, and precision manufacturing. Its validated performance under low-temperature operating conditions — substantiated through comprehensive thermal testing and analysis — positions it as a premium solution for applications demanding uncompromising reliability, efficiency, and longevity in the most challenging environmental conditions.