Stainless Steel Evaporative Cooling Coil Tube (Coil Tube) — Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Precision Coil Tubes for Thermal Management Systems
Reference Study: "Research on the Influence of Different Water Distribution Configurations on the Uniformity of Evaporative Cooling Coil Tubes"
1. Product Overview
The Stainless Steel Evaporative Cooling Coil Tube is a precision-engineered tubular component designed for integration into evaporative cooling systems, heat exchangers, and fluid distribution networks. This product is manufactured by Wenzhou Jixing Metal Materials Co., Ltd., a specialized producer of stainless steel pipe and tube solutions with extensive expertise in metallurgical processing and thermal system components.
The coil tube is fabricated from high-grade austenitic stainless steel and formed into a helical or serpentine geometry optimized for maximum heat transfer surface area within a compact footprint. The product is particularly suited for evaporative cooling applications where water distribution uniformity is a critical performance parameter. Research conducted on this product class has demonstrated that the geometric configuration, surface finish, and material properties of the coil tube directly influence the uniformity of water film distribution across the tube surface, which in turn governs the overall cooling efficiency and thermal stability of the system.
Key performance characteristics include:
- Superior corrosion resistance in humid and chemically aggressive environments
- High thermal conductivity relative to other corrosion-resistant alloys
- Excellent dimensional accuracy and geometric consistency throughout the coil length
- Low surface roughness to promote uniform water film formation and distribution
- Long service life with minimal degradation under continuous thermal cycling
2. Material & Properties
2.1 Base Material Composition
The coil tube is primarily manufactured from Austenitic Stainless Steel conforming to international standards. The most commonly specified grades include:
| Grade | Standard Designation | Carbon (C) max % | Chromium (Cr) % | Nickel (Ni) % | Molybdenum (Mo) % | Key Application |
|---|---|---|---|---|---|---|
| 304 / 304L | ASTM A213 TP304 / EN 1.4301 | 0.08 / 0.03 | 18.0–20.0 | 8.0–10.5 | — | General evaporative cooling |
| 316 / 316L | ASTM A213 TP316 / EN 1.4401 | 0.08 / 0.03 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | Marine / chloride environments |
| 321 | ASTM A213 TP321 / EN 1.4541 | 0.08 | 17.0–19.0 | 9.0–12.0 | — | Elevated temperature service |
| 310S | ASTM A213 TP310S / EN 1.4845 | 0.08 | 19.0–21.0 | 25.0–30.0 | — | High-temperature thermal cycling |
2.2 Mechanical Properties
| Property | Specification (A270/ASME SA-213 Type 304) | Specification (A270/ASME SA-213 Type 316) |
|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa (75 ksi) | ≥ 515 MPa (75 ksi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (30 ksi) | ≥ 205 MPa (30 ksi) |
| Elongation (in 50 mm / 2 in.) | ≥ 40% | ≥ 40% |
| Density | 8.00 g/cm³ | 8.03 g/cm³ |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Thermal Conductivity (100°C) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Linear Thermal Expansion (20–100°C) | 17.3 × 10⁻⁶ /°C | 17.3 × 10⁻⁶ /°C |
2.3 Surface Characteristics
The internal and external surface finish of the coil tube is a critical parameter for evaporative cooling applications. The surface roughness directly affects the wettability and uniformity of the water film distributed across the tube surface. Research has confirmed that lower surface roughness values result in more uniform water distribution and enhanced evaporative cooling performance.
- External Surface Finish: Ra ≤ 0.8 μm (polished) or Ra ≤ 1.6 μm (pickled and passivated)
- Internal Surface Finish: Ra ≤ 0.4 μm (electropolished) for high-flow applications
- Passivation Treatment: Citric acid or nitric acid passivation per ASTM A967
3. Specifications
3.1 Geometric Dimensions
| Parameter | Range / Options | Notes |
|---|---|---|
| Outer Diameter (OD) | 6 mm – 50 mm (0.25" – 2.0") | Custom diameters available upon request |
| Wall Thickness | 0.5 mm – 3.0 mm (0.020" – 0.118") | Thicker walls for high-pressure service |
| Coil Pitch (Center-to-Center) | 10 mm – 60 mm | Affects water distribution uniformity |
| Coil Diameter | 100 mm – 2000 mm | Depends on system configuration |
| Tube Length (Total Unwound) | Up to 100 m per coil | Continuous coil or segmented |
| Tolerance on OD | ± 0.1 mm | Per ASTM A213 |
| Tolerance on Wall Thickness | ± 10% of nominal | Per ASTM A213 |
| Roundness | ≤ 1% of nominal OD | Ensures uniform water film coverage |
3.2 Operating Conditions
| Parameter | Type 304 | Type 316 |
|---|---|---|
| Maximum Operating Temperature | 870°C (1600°F) | 870°C (1600°F) |
| Minimum Operating Temperature | −196°C (−320°F) | −196°C (−320°F) |
| Recommended Water Temperature Range | 5°C – 80°C | 5°C – 80°C |
| Maximum Operating Pressure | Up to 1.6 MPa (standard) | Up to 1.6 MPa (standard) |
| Corrosion Resistance (Pitting) | PREN ≈ 18–20 | PREN ≈ 24–26 |
4. Manufacturing Process
The coil tube is manufactured through a multi-stage process combining precision metallurgy, cold working, and thermal treatment to achieve the required geometric accuracy, mechanical properties, and surface quality.
- Material Selection and Incoming Inspection: Virgin stainless steel strip or seamless tube blanks are selected based on the specified grade. Each batch undergoes spectroscopic analysis (OES) to verify chemical composition within ASTM/EN specification limits.
- Coil Forming: The tube blank is cold-formed around precision mandrels to achieve the desired helical or serpentine geometry. Computer Numerical Control (CNC) forming machines ensure consistent pitch, coil diameter, and tube cross-sectional roundness throughout the coil length.
- Welding (if applicable):strong> For welded coil tube configurations, orbital TIG (Tungsten Inert Gas) welding is employed with high-purity argon shielding (99.99% purity). Weld seam geometry and internal/external surface quality are inspected per ASME BPV Code Section IX.
- Solution Annealing: The formed coil is heated to 1050°C – 1150°C in a controlled atmosphere furnace and rapidly quenched to dissolve carbides and restore full austenitic structure, ensuring maximum corrosion resistance and ductility.
- Pickling and Passivation: The annealed coil undergoes acid pickling (HNO₃/HF or citric acid blend) to remove oxide scale, followed by passivation per ASTM A967 to restore the chromium oxide passive film. This step is critical for long-term corrosion performance.
- Surface Finishing: Depending on application requirements, the coil may undergo mechanical polishing, electropolishing (to achieve Ra ≤ 0.4 μm), or chemical mirror finishing to promote uniform water film distribution.
- Dimensional Inspection: Each coil is measured for OD, wall thickness, pitch, coil diameter, and total length using laser scanning, coordinate measuring machines (CMM), and ultrasonic wall thickness gauges.
- Non-Destructive Testing (NDT): Visual inspection (VT), dye penetrant testing (PT), and eddy current testing (ET) are performed to detect surface and subsurface defects. Hydrostatic pressure testing is conducted at 1.5× the maximum operating pressure for leak integrity verification.
- Packaging and Delivery: Coils are wrapped in moisture-proof protective film, placed in wooden or steel crates, and labeled with material certificates, heat numbers, and dimensional data for traceability.
5. Applications
The Stainless Steel Evaporative Cooling Coil Tube finds extensive application across multiple industries:
- Industrial Evaporative Cooling Systems: Primary application for air-side cooling in manufacturing plants, data centers, and commercial HVAC systems. The coil tube serves as the heat exchange surface where water evaporates to absorb latent heat.
- Refrigeration and Cryogenic Systems: Used as evaporator and condenser tubes in industrial refrigeration units operating across a wide temperature range.
- Food and Beverage Processing: Compliant with FDA and 3-A Sanitary Standards for heat exchangers in dairy, beverage, and pharmaceutical processing lines.
- Marine and Offshore Applications: Type 316 coil tubes resist chloride-induced pitting and crevice corrosion in seawater-cooled heat exchangers.
- Power Generation: Condenser tubes and cooling coils in thermal power plants and nuclear facilities.
- Chemical Processing: Heat exchange coils in reactors, distillation columns, and storage tank cooling systems handling corrosive media.
- Agricultural Applications: Evaporative cooling pads and coils for greenhouse climate control and livestock housing ventilation systems.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and product certifications to ensure international compliance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| ASTM A213 / ASME SA-213 | Standard specification for seamless austenitic stainless steel boiler, heat-exchanger, and heat-treating tubes |
| ASTM A269 / ASME SA-269 | Standard specification for welded austenitic stainless steel tubing |
| ASTM A270 / ASME SA-270 | Standard specification for cold-drawn austenitic stainless steel seamless tubing |
| EN 10216-5 | European standard for austenitic stainless steel seamless tubes |
| JIS G3446 | Japanese Industrial Standard for austenitic stainless steel tubes |
| PED 2014/68/EU | European Pressure Equipment Directive compliance (Category I–III) |
| CE Marking | Conformity with European health, safety, and environmental protection standards |
| NACE MR0175 / ISO 15156 | Resistance to sulfide stress cracking in sour service environments |
| Mill Test Reports (MTR) | Full chemical and mechanical test documentation for each heat number |
7. Unique Selling Points
Research-Validated Water Distribution Uniformity: The coil tube geometry and surface finish are optimized based on published research investigating the influence of water distribution configurations on evaporative cooling performance. This ensures that each coil delivers uniform water film coverage, maximizing evaporative heat transfer efficiency and minimizing dry spots that degrade cooling capacity.
- Precision Geometry: CNC-forming technology ensures consistent coil pitch