Stainless Steel Coil Tube — River Water Chilled Air Conditioning Fan Coil Tube
Product Overview
The Stainless Steel Coil Tube (Product No. 1036) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubing product designed for application in river-water-chilled central air conditioning fan coil units. This coil tube is specifically engineered to operate under dry-condition (dry operation) scenarios, where the coil functions primarily as a sensible heat exchanger without condensation formation. The product represents a specialized solution addressing the unique thermal and fluid dynamic requirements of river-water-cooled HVAC (Heating, Ventilation, and Air Conditioning) systems, offering superior corrosion resistance, thermal efficiency, and long-term operational reliability in challenging environmental conditions.
River water, while serving as a renewable and cost-effective cooling source, introduces challenges such as variable water quality, biological growth, and fluctuating temperatures. The stainless steel coil tube is designed to withstand these conditions while maintaining optimal heat transfer performance throughout the operational lifecycle of the fan coil unit.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its exceptional balance of mechanical strength, corrosion resistance, and thermal conductivity. The material composition and resulting properties are as follows:
- Base Material: Austenitic stainless steel (e.g., SUS304 / AISI 304 or SUS316 / AISI 316L), offering resistance to chloride-induced pitting corrosion commonly encountered in river water environments.
- Corrosion Resistance: The passive chromium oxide layer (Cr₂O₃) provides inherent protection against oxidation and biological fouling, critical for river water applications where dissolved oxygen and microbial activity are elevated.
- Thermal Conductivity: Approximately 16.3 W/(m·K) for SUS304, ensuring efficient sensible heat transfer between the river water coolant and the process air stream.
- Mechanical Properties: Tensile strength of ≥ 520 MPa and elongation of ≥ 40%, providing adequate formability for coil winding while maintaining structural integrity under operational pressure.
- Temperature Range: Operational suitability from −40°C to +400°C, accommodating seasonal variations in river water temperature.
- Surface Finish: Pickled and passivated interior and exterior surfaces to minimize scaling and biofilm adhesion, reducing maintenance frequency and preserving heat transfer efficiency over time.
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Product Category | Stainless Steel Coil Tube (Fan Coil Tube) | — |
| Product No. | 1036 | — |
| Material Grade | SUS304 / AISI 304 (standard); SUS316 / AISI 316L (upgrade option) | — |
| Outer Diameter (OD) | 8.0 / 9.52 / 12.7 | mm |
| Wall Thickness | 0.50 / 0.60 / 0.70 / 1.00 | mm |
| Coil Diameter | 600 – 1200 (customizable) | mm |
| Coil Length | Up to 100 | m |
| Operating Pressure | ≤ 1.6 | MPa |
| Design Pressure | ≤ 2.5 | MPa |
| Operating Temperature | −40 to +400 | °C |
| Thermal Conductivity | 16.3 (SUS304) / 14.6 (SUS316) | W/(m·K) |
| Surface Treatment | Pickled & Passivated (interior and exterior) | — |
| Tolerance (OD) | ±0.10 | mm |
| Tolerance (Wall Thickness) | ±0.05 | mm |
| Applicable Standard | GB/T 14976, ASTM A269, EN 10216-5 | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, surface quality, and mechanical performance:
- Raw Material Selection: High-purity stainless steel wire rod is sourced from certified mills, with each batch undergoing spectroscopic analysis to verify chemical composition compliance with the specified grade (SUS304 or SUS316).
- Wire Drawing: The steel wire is cold-drawn through precision tungsten carbide dies to achieve the required outer diameter and wall thickness with tight dimensional tolerances (±0.10 mm OD, ±0.05 mm wall thickness).
- Coil Winding: The drawn tubing is wound into coils of specified diameter using CNC-controlled winding machinery, ensuring uniform tension and consistent coil geometry to prevent ovality and distortion.
- Heat Treatment (if applicable): Solution annealing at 1050°C followed by rapid water quenching to relieve residual stresses introduced during cold drawing, restoring full austenitic microstructure and ductility.
- Pickling and Passivation: The coil tube undergoes acid pickling (using a mixed HNO₃/HF solution) to remove surface oxide scale, followed by passivation treatment to regenerate the protective chromium oxide passive layer.
- Quality Inspection: Each coil is subjected to dimensional measurement (OD, wall thickness, coil diameter), visual surface inspection, hydrostatic pressure testing (at 1.5× working pressure for 30 minutes), and sampling for mechanical testing (tensile, hardness, impact).
- Packaging and Labeling: Qualified coils are wrapped in protective packaging material and labeled with product identification, batch number, and traceability information.
Applications
The stainless steel coil tube is primarily designed for the following applications:
- River Water Chilled Central Air Conditioning Systems: The primary application, where the coil tube serves as the heat exchange element in fan coil units (FCUs) utilizing river water as the cooling medium. The dry-condition design ensures efficient sensible heat removal without moisture-related degradation.
- Industrial Process Cooling: Suitable for industrial HVAC applications where corrosion-resistant heat exchangers are required, including chemical processing plants, food and beverage facilities, and pharmaceutical manufacturing.
- Commercial Building HVAC: Deployed in commercial buildings with river water access, providing energy-efficient cooling with reduced reliance on conventional refrigeration systems.
- Marine and Coastal Environments: The superior corrosion resistance of SUS316 grade makes the coil tube suitable for HVAC applications in marine vessels and coastal facilities exposed to high-chloride environments.
- Geothermal and Ground Source Heat Exchange: Applicable in ground-coupled heat exchange systems where long-term exposure to groundwater necessitates corrosion-resistant tubing materials.
Unique Selling Points
- Enhanced Corrosion Resistance for River Water: The austenitic stainless steel composition provides superior resistance to the variable water quality, biological fouling, and dissolved oxygen content characteristic of river water cooling applications, significantly extending service life compared to carbon steel alternatives.
- Optimized for Dry-Condition Operation: Specifically engineered for sensible heat exchange scenarios where condensation is absent, ensuring consistent thermal performance without the efficiency degradation associated with wet coil fouling.
- Precision Dimensional Control: Tight manufacturing tolerances ensure optimal fin-to-tube contact and uniform air-side and water-side flow distribution, maximizing heat transfer efficiency.
- Full Traceability: Each product batch is traceable to raw material mill certifications, providing assurance of material integrity and compliance with applicable standards.
- Customizable Configurations: Available in multiple tube diameters, wall thicknesses, and coil dimensions to accommodate diverse system designs and capacity requirements.
Quality Certifications
The manufacturing facility and product line maintain compliance with the following quality standards and certifications:
- ISO 9001:2015 — Quality Management System certification, demonstrating systematic commitment to quality and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification, reflecting responsible environmental practices in production.
- GB/T 14976-2012 — Chinese national standard for seamless stainless steel tubes for general use, ensuring conformity with domestic regulatory requirements.
- ASTM A269/A269M — American standard for seamless austenitic stainless steel tubing, providing international recognition and compatibility.
- EN 10216-5 — European standard for welded austenitic stainless steel tubes, applicable for export markets within the European Economic Area.
- Third-Party Testing: Products are periodically verified by accredited independent testing laboratories for chemical composition, mechanical properties, and dimensional accuracy.
Note: The dry-condition design and operational analysis referenced in the product development documentation draws upon research into river water chilled central air conditioning fan coil systems, emphasizing the importance of material selection, coil geometry optimization, and operational parameter control in achieving reliable sensible cooling performance under variable river water conditions.