Stainless Steel Coil Tube — HVAC Coil Section Component (Wenzhou Jixing Metal Materials Co., Ltd.)
1. Product Overview
The Stainless Steel Coil Tube (Product Reference No. 1196) is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for integration into coil sections of air-conditioning units and HVAC (Heating, Ventilation, and Air Conditioning) systems. This product is classified under the technical literature and auxiliary design research category, reflecting its role in advanced thermal-exchange coil segment design methodologies.
Coil tubes serve as the primary heat-transfer conduits within air-conditioning unit coil sections, facilitating efficient thermal energy exchange between the refrigerant and ambient air. The stainless steel coil tube described herein represents a high-performance alternative to conventional carbon steel or copper tubing, offering superior corrosion resistance, mechanical durability, and long-term thermal stability in demanding environmental conditions.
2. Material & Properties
The coil tube is fabricated from austenitic stainless steel, most commonly Grade 304 (UNS S30400) or Grade 316 (UNS S31600), depending on the specific corrosion-resistance requirements of the application environment.
- Base Material: Austenitic stainless steel (304/316 series)
- Chromium Content: 18–20% (minimum)
- Nickel Content: 8–12%
- Molybdenum Content: 2–3% (Grade 316 only)
- Tensile Strength: 515–720 MPa (as-rolled condition)
- Yield Strength: 205–310 MPa
- Thermal Conductivity: 14–16 W/(m·K) at 20 °C
- Operating Temperature Range: −196 °C to +870 °C
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and refrigerant-induced corrosion
- Magnetic Properties: Non-magnetic in annealed condition
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (¼" – 1") |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Length | Custom, typically 1.5 m – 12.0 m per coil |
| Coil Diameter | 150 mm – 600 mm (configurable) |
| Tolerance on OD | ±0.1 mm (standard); ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% of nominal |
| Surface Finish | Bright annealed / Pickled and passivated |
| Surface Roughness (Ra) | ≤ 1.6 μm (inner surface) |
| Maximum Operating Pressure | 2.5 MPa (design pressure, dependent on geometry) |
| Refrigerant Compatibility | R-410A, R-32, R-134a, R-22, Ammonia (NH₃) |
| Standards Compliance | ASTM A269, ASTM A213, EN 10216-5, GB/T 12771 |
| End Preparation | Plain cut, beveled, or threaded (per customer specification) |
| Packaging | Wound coil in protective film, wooden crate or export-grade container |
4. Manufacturing Process
4.1 Raw Material Selection
High-purity stainless steel strip or round bar is sourced from certified mills with traceable chemical composition documentation. Incoming materials undergo spectroscopic verification (OES — Optical Emission Spectroscopy) to confirm compliance with specified alloy grades.
4.2 Tube Forming
The coil tube is produced through a cold-drawn or cold-rolled seamless tube manufacturing process:
- Coiling of Strip: Stainless steel strip is wound into a precise helical coil using CNC-controlled forming equipment.
- Seam Welding: The coil edges are joined via high-frequency resistance welding (HFW) or orbital TIG welding (GTAW), achieving full-penetration weld integrity.
- Heat Treatment: The formed tube undergoes solution annealing at 1050–1100 °C followed by controlled cooling to restore austenitic microstructure and relieve residual stresses.
- Dimensional Calibration: Post-anneal cold drawing or rolling ensures adherence to tight dimensional tolerances.
- Pickling and Passivation: Surface oxide scale is removed via controlled acid pickling, followed by passivation treatment to establish a protective chromium oxide layer.
4.3 Coil Winding
The finished tube is wound into a helical coil configuration using a programmable winding machine. The winding process maintains uniform pitch, consistent coil diameter, and controlled tension to prevent deformation or kinking. Each coil is inspected for geometric accuracy using laser scanning or coordinate measuring equipment.
4.4 Final Inspection
- Visual inspection of surface finish and weld integrity
- Dimensional verification (OD, wall thickness, coil diameter, pitch)
- Hydrostatic pressure testing at 1.5× maximum working pressure
- Eddy current or ultrasonic flaw detection for subsurface defects
- Chemical composition verification via spark OES or lab analysis
5. Applications
The stainless steel coil tube is primarily designed for the following application domains:
- Air-Conditioning Unit Coil Sections: Serves as the heat-exchange tube within evaporator and condenser coil assemblies of commercial and industrial HVAC systems.
- Chiller and Heat Pump Systems: Used in evaporator and condenser coil banks where resistance to refrigerant corrosion is critical.
- Process Cooling Systems: Applicable in food processing, pharmaceutical, and chemical industries requiring hygienic and corrosion-resistant heat-exchange components.
- Marine HVAC Systems: Suitable for shipboard air-conditioning units where saltwater-induced corrosion is a design concern.
- Refrigerated Storage Facilities: Employed in evaporator coil assemblies operating in high-humidity, low-temperature environments.
6. Quality Certifications & Standards
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System compliance |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| ASTM A213 | Standard Specification for Seamless Austenitic Chromium-Nickel Stainless Steel Tube for High-Temperature Service |
| EN 10216-5 | Non-alloy and alloy steel tubes for technical uses — Welded austenitic stainless steel tubes |
| GB/T 12771 | Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes |
| ASME BPV Section VIII | Pressure Vessel Code compliance (where applicable for high-pressure coil assemblies) |
7. Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel matrix provides exceptional resistance to pitting, crevice corrosion, and stress-corrosion cracking, significantly extending service life compared to carbon steel alternatives.
- HVAC-Optimized Design: Developed with reference to advanced coil section auxiliary design research for air-conditioning units, ensuring optimal thermal-hydraulic performance and manufacturability.
- Hygienic Surface Finish: Bright annealed and passivated inner surface minimizes fluid friction losses and prevents microbial growth, meeting food-grade and pharmaceutical-grade requirements.
- Customizable Geometry: Flexible coil diameter, pitch, and tube length configurations allow seamless integration into diverse air-conditioning unit designs.
- Full Traceability: Each production batch is accompanied by mill test certificates (MTC), chemical composition reports, and mechanical property documentation ensuring complete supply-chain traceability.
- Wide Temperature Tolerance: Maintains mechanical integrity across an exceptionally broad operating temperature range, accommodating both cryogenic and high-temperature HVAC applications.
8. Auxiliary Design Research Context
This product is developed in conjunction with research on auxiliary design methodologies for coil sections in air-conditioning units. The design framework addresses coil layout optimization, flow distribution uniformity, pressure-drop minimization, and manufacturability considerations specific to stainless steel coil tubes. The resulting design parameters ensure that the coil tube achieves maximum heat-transfer efficiency while maintaining structural reliability under cyclic thermal loading conditions inherent to HVAC operation.