Stainless Steel Coil Tube — Dry Coil Evaporative Cooling System Component
Product Overview
The Stainless Steel Coil Tube (Product No. 444) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coil tube is specifically designed for dry coil evaporative cooling systems, representing a significant advancement over conventional indirect evaporative cooling (IEC) technologies. The dry coil evaporative cooling approach eliminates the need for a water-immerged heat exchanger, thereby reducing energy consumption, minimizing water usage, and virtually eliminating the risk of biological contamination (e.g., Legionella). The coil tube serves as the core heat transfer element, enabling highly efficient air-to-air heat exchange through a closed-loop dry coil configuration.
As a "terminator" of traditional indirect evaporative cooling systems, this product addresses longstanding industry challenges including fouling, scaling, high maintenance costs, and energy inefficiency associated with wet-surface heat exchangers. The stainless steel coil tube delivers superior thermal performance, exceptional corrosion resistance, and extended service life in demanding industrial and commercial HVAC applications.
Material & Properties
Base Material Composition
- Primary Alloy: Austenitic stainless steel, typically grades 304 (UNS S30408) or 316 (UNS S31608), selected for optimal balance of mechanical strength, thermal conductivity, and corrosion resistance.
- Alternative Grades: 321 (UNS S32108) for high-temperature applications; 316L (UNS S31603) for enhanced resistance in chloride-rich environments.
- Surface Finish: Electropolished or mechanically polished to achieve surface roughness (Ra) ≤ 0.4 μm, facilitating easy cleaning and reducing fouling propensity.
Mechanical and Thermal Properties
- Tensile Strength: ≥ 520 MPa (Grade 304); ≥ 515 MPa (Grade 316)
- Yield Strength: ≥ 205 MPa
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (Grade 304); 14.6 W/(m·K) at 20°C (Grade 316)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Operating Temperature Range: −196°C to +870°C (Grade 304); −196°C to +870°C (Grade 316)
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, acidic and alkaline environments; superior chloride pitting resistance (Grade 316)
- Non-Magnetic: Austenitic microstructure ensures non-magnetic properties
Key Alloying Elements (Typical % by Mass — Grade 304)
| Element | Minimum (%) | Maximum (%) | Function |
|---|---|---|---|
| Carbon (C) | — | 0.08 | Controlled to prevent intergranular corrosion |
| Chromium (Cr) | 18.0 | 20.0 | Passive oxide layer formation; primary corrosion resistance |
| Nickel (Ni) | 8.0 | 10.5 | Stabilizes austenitic structure; enhances ductility |
| Molybdenum (Mo) | — | — | Grade 316: 2.0–3.0% for pitting resistance |
| Iron (Fe) | Balance | — | Base matrix element |
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Code | 444 | Internal catalog designation |
| Product Name | Stainless Steel Coil Tube (盘管) | — |
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (¼" – 1") | Customizable per project requirements |
| Wall Thickness | 0.5 mm – 1.5 mm | ASME B36.19M |
| Bend Radius | ≥ 1.5 × OD (standard); ≥ 1.0 × OD (tight radius) | ASTM A213 |
| Coil Length | Up to 120 m per continuous coil | Custom lengths available |
| Surface Treatment | Electropolished / Passivated / Brushed | ASTM A967 |
| Tolerance (OD) | ±0.05 mm (precision grade) | ISO 1307 |
| End Condition | Plain end / Flared / Threaded / Brazed fitting | Per customer specification |
| Pressure Rating | Up to 4.0 MPa (working pressure) | ASME B31.3 |
| Weight | 0.42 kg/m (6.0 mm OD × 0.5 mm WT) | Calculated per geometry |
| Manufacturing Origin | Wenzhou, Zhejiang, China | — |
| Coil Form | Continuous spiral coil / S-bend / U-bend configurations | Custom layouts |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection and Inspection: Certified stainless steel seamless tubes (ASTM A213 TP304/TP316) or precision-welded tubes (ASTM A269 TP304/TP316) are procured from accredited mills. Each batch undergoes spectrographic analysis (OES) for chemical composition verification and mechanical testing (tensile, hardness) for conformance confirmation.
- Dimensional Preparation and Cutting: Tubes are cut to the specified length using precision plasma or laser cutting systems. Cut ends are deburred and chamfered to prevent flow disruption and facilitate assembly.
- Tube Bending (Coil Forming): CNC-controlled rotary draw bending machines form the tubes into the designated coil geometry. The bending process employs internal mandrel support to prevent ovality (cross-section distortion) beyond 2% of nominal OD. Bend radius is precisely controlled to optimize turbulent flow characteristics and maximize heat transfer coefficients.
- Welding and Joining: Where continuous coils require interconnection, orbital TIG welding (GTAW — Gas Tungsten Arc Welding) is employed with inert gas (Argon) shielding on both inside and outside surfaces. Weld quality is verified through visual inspection and, where required, helium leak testing at sensitivity ≤ 1×10⁻⁹ Pa·m³/s.
- Surface Finishing: Electropolishing removes a controlled layer of surface material (0.01–0.05 mm), smoothing micro-roughness and enhancing the passive chromium oxide layer. Passivation treatment (per ASTM A967) ensures maximum corrosion resistance.
- Quality Control and Testing: Each coil assembly undergoes hydrostatic pressure testing (1.5× working pressure, held for minimum 30 seconds), dimensional verification via coordinate measuring machine (CMM), and surface defect inspection. Non-destructive testing (NDT) methods including magnetic particle inspection (MPI) and dye penetrant testing (PT) are applied as applicable.
- Packaging and Shipping: Coils are wrapped in protective plastic film, secured on wooden pallets or custom cradles to prevent deformation during transit. Material traceability documentation accompanies each shipment.
Applications
The Stainless Steel Coil Tube is engineered for high-efficiency thermal management applications, with particular emphasis on the following sectors:
- Dry Coil Evaporative Cooling Systems: Serves as the primary heat exchange medium in dry coil configurations where air-to-air heat exchange replaces traditional water-immerged indirect evaporative cooling. Eliminates Legionella risk and reduces water consumption by up to 95% compared to conventional evaporative coolers.
- Data Center Cooling: High-density server room thermal management requiring reliable, low-maintenance heat rejection with minimal water usage.
- Commercial and Industrial HVAC: Large-scale air handling units, rooftop cooling units, and process cooling systems in food processing, pharmaceutical manufacturing, and semiconductor fabrication facilities.
- Food and Beverage Processing: Sanitary-grade heat exchangers for pasteurization, refrigeration, and temperature-controlled processing where hygienic design (EHEDG-compliant) is mandatory.
- Chemical and Petrochemical Industries: Heat recovery and process cooling in aggressive chemical environments where corrosion resistance is critical.
- Marine and Offshore Applications: Cooling systems exposed to high-salinity environments requiring Grade 316 or duplex stainless steel construction.
- Agricultural Greenhouse Climate Control: Precision temperature regulation systems utilizing evaporative cooling principles.
- Automotive and Aerospace Thermal Management: Compact heat exchanger assemblies requiring lightweight, high-performance coil configurations.
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and certifications to ensure product excellence:
| Certification / Standard | Scope | Description |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Ensures consistent product quality and continuous improvement processes |
| ISO 14001:2015 | Environmental Management System | Demonstrates environmental responsibility in manufacturing operations |
| ISO 45001:2018 | Occupational Health & Safety | Worker safety and health management compliance |
| CE Marking | European Conformity | Product compliance with EU health, safety, and environmental protection standards |
| ASTM A213 / A269 | Material Standards | Specification for seamless and welded austenitic stainless steel tubing |
| EN 10216-5 | European Material Standard | Technical delivery conditions for stainless steel tubes for general purposes |
| ASME B31.3 | Piping Code Compliance | Process piping design and fabrication standards |
| NSF/ANSI 61 | Drinking Water Systems | Health effects certification for materials in potable water applications |
| 3-A Sanitary Standards | Food Industry Hygiene | Sanitary design and fabrication for food-grade equipment |
Unique Selling Points
1. Dry Coil Technology Leadership: This coil tube is purpose-built for next-generation dry coil evaporative cooling systems, positioning it as a definitive solution replacing legacy indirect evaporative cooling. The design eliminates the "wet surface" failure mode inherent in traditional systems, delivering superior reliability and hygiene.
2. Zero Water Contamination Risk: By operating as a fully dry heat exchanger medium, the coil tube eliminates Legionella growth potential and water quality concerns, simplifying compliance with stringent health and safety regulations.
3. Precision Coil Geometry: CNC rotary draw bending ensures consistent bend radius, minimal ovality, and optimized internal flow characteristics. The controlled geometry maximizes turbulence intensity, enhancing convective heat transfer coefficients (h) by up to 30% over standard bent tubing.
4. Ultra-Low Surface Roughness: Electropolished finish (Ra ≤ 0.4 μm) reduces fouling accumulation, maintains heat transfer performance over extended operating cycles, and facilitates CIP (Clean-In-Place) sanitation protocols.
5. Full Traceability: Each coil tube batch is traceable from raw material mill certificate through final product testing, providing complete quality documentation for regulatory and audit purposes.
6. Custom Engineering Capability: Flexible manufacturing infrastructure supports bespoke coil configurations—varying OD, wall thickness, bend patterns, and total coil length—to meet specific thermal performance targets and spatial constraints.
Technical Performance Summary
| Performance Metric | Dry Coil Configuration | Conventional Indirect Evaporative Cooling | Improvement |
|---|---|---|---|