Stainless Steel Coil Tube for Microchannel Condenser Applications (Coiltube)
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubular component specifically designed for integration into external-winding microchannel condenser (MWCC) structures within heat pump water heater (HPWH) systems. This product leverages advanced stainless steel metallurgy to deliver superior thermal performance, extended service life, and enhanced system efficiency in demanding refrigeration and heat pump applications.
The coil tube serves as the primary heat transfer medium within the condenser assembly, where refrigerant flows through the coiled stainless steel tubing while ambient air or a secondary fluid exchanges thermal energy across the tube walls. The external winding configuration of the microchannel condenser structure optimizes the surface-area-to-volume ratio, enabling compact and high-efficiency thermal exchange. The coil geometry, winding pitch, and tube diameter are critical parameters that directly influence the overall coefficient of performance (COP) of the heat pump water heater system.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, mechanical strength, and formability. The primary material grades employed are as follows:
- SAE 304 (UNS S30408): General-purpose austenitic stainless steel with 18% Chromium (Cr) and 8% Nickel (Ni), offering excellent resistance to atmospheric and aqueous corrosion. This grade is the standard selection for most condenser coil tube applications.
- SAE 316 (UNS S31608): Enhanced austenitic stainless steel with the addition of 2–3% Molybdenum (Mo), providing superior resistance to pitting and crevice corrosion in chloride-rich environments. This grade is recommended for coastal or industrial applications where aggressive chemical exposure is anticipated.
- SAE 321 (UNS S32103): Titanium-stabilized austenitic stainless steel with intergranular corrosion resistance, suitable for applications involving elevated operating temperatures.
Key Material Properties
| Property | SAE 304 | SAE 316 |
|---|---|---|
| Density (kg/m³) | 8,000 | 8,000 |
| Thermal Conductivity (W/m·K, at 20°C) | 16.3 | 14.6 |
| Specific Heat (kJ/kg·K, at 20°C) | 502 | 500 |
| Tensile Strength (MPa, minimum) | 515 | 515 |
| Yield Strength (MPa, minimum) | 205 | 205 |
| Elongation (% in 50 mm, minimum) | 40 | 40 |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 |
| Corrosion Resistance (Pitting Equivalent Number, PEN) | 19 | 24–26 |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Product Catalog No. | 484 |
| Material Grade | SAE 304 / SAE 316 / SAE 321 (customizable) |
| Outer Diameter (OD) | φ2.0 mm – φ12.7 mm (customizable per application) |
| Wall Thickness | 0.3 mm – 1.2 mm (tolerance ±0.05 mm) |
| Coil Pitch (Winding Spacing) | 1.5 mm – 6.0 mm (adjustable based on thermal load requirements) |
| Coil Diameter (Mean) | φ50 mm – φ300 mm (customizable) |
| Surface Finish | Mirror polished (Ra ≤ 0.05 μm) / Matte passivated / Custom |
| End Condition | Deburred, chamfered, or flanged per drawing specification |
| Winding Configuration | External winding for microchannel condenser integration |
| Maximum Working Pressure | Up to 4.0 MPa (depending on OD and wall thickness) |
| Hydrostatic Test Pressure | 1.5× maximum working pressure (minimum 6.0 MPa) |
| Refrigerant Compatibility | R-134a, R-410A, R-32, R-1234yf, R-290 (propane), ammonia (NH₃) |
| Packaging | Anti-corrosion coated, individually bagged, export-grade wooden crates |
Manufacturing Process
The production of precision stainless steel coil tubes for microchannel condenser applications involves a rigorously controlled multi-stage manufacturing sequence:
- Raw Material Selection and Incoming Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis (per ASTM E1473) to verify chemical composition compliance with the specified grade.
- Slitting and Leveling: The strip is slit to the required width and leveled to ensure uniform flatness and dimensional accuracy prior to forming.
- Tube Forming (Seamless or Welded): Tubes are produced via either cold-drawn seamless forming (for higher pressure applications) or orbital TIG welding of slitted strip (per ISO 13919 for welding procedure qualification). Welded joints are ground flush to minimize flow resistance and turbulence.
- Cold Drawing and Sizing: Tubes undergo multiple passes through precision tungsten carbide (WC) dies to achieve the target outer diameter, wall thickness, and concentricity tolerances (concentricity ≤ 0.1 mm).
- Coil Winding: The formed tubes are wound around precision-machined mandrels using computerized CNC winding machines. The winding process is controlled to maintain consistent coil pitch, layer-to-layer alignment, and minimum inter-layer stress. Tension control is maintained within ±5% to prevent ovality or kinking.
- Heat Treatment (if applicable): Solution annealing at 1050–1150°C followed by controlled air or water quenching may be performed to relieve residual stresses and restore full austenitic microstructure and mechanical properties.
- Surface Passivation and Polishing: Chemical passivation using nitric acid or citric acid solutions removes free iron and forms a protective chromium oxide layer. Mirror polishing is achieved through mechanical buffing and electrolytic polishing (EP) processes.
- Quality Inspection: Each coil tube batch undergoes hydrostatic pressure testing, dimensional verification (OD, wall thickness, coil diameter, pitch), visual inspection for surface defects, and magnetic particle inspection (MPI) for weld integrity where applicable.
Applications
The stainless steel coil tube is engineered for integration into external-winding microchannel condenser structures, with primary applications including:
- Heat Pump Water Heaters (HPWH): The coil tube serves as the refrigerant circuit within the condenser, transferring heat from the refrigerant to the domestic hot water storage tank. The microchannel design reduces refrigerant charge by 30–50% compared to conventional fin-and-tube condensers, improving COP and reducing greenhouse gas impact.
- Residential and Commercial HVAC Systems: High-efficiency condensers for air-source heat pumps, chiller units, and air conditioning systems.
- Automotive Thermal Management: Electric vehicle (EV) battery cooling and heating systems where stainless steel coil tubes provide durable, lightweight heat exchange surfaces.
- Industrial Process Cooling: Refrigeration systems in food processing, pharmaceutical, and chemical manufacturing facilities where corrosion resistance is paramount.
- Marine and Offshore Equipment: Condenser coils for shipboard HVAC and refrigeration systems operating in high-salinity environments.
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and certification frameworks to ensure product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and post-sale service processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Conformity with European Union machinery and pressure equipment directives.
- ASME / PED 2014/68/EU — Compliance with pressure vessel and piping standards for high-pressure refrigerant applications.
- Material Certifications: EN 10204 3.1 material test certificates provided with every shipment, verifying chemical composition and mechanical properties per ASTM A213 / EN 10216-5 / JIS G3459 standards.
- RoHS and REACH Compliance: Products are free from restricted hazardous substances as defined by EU directives 2011/65/EU and 1907/2006/EC.
Unique Selling Points
- Superior Thermal Performance: The precision-wound coil geometry maximizes heat transfer surface area while minimizing pressure drop, directly contributing to improved system COP in heat pump water heater applications.
- Exceptional Durability: Austenitic stainless steel construction eliminates the risk of rust and scale formation, extending condenser service life beyond 20 years even in aggressive water environments.
- Reduced Refrigerant Charge: Microchannel condenser architecture enables 30–50% reduction in refrigerant inventory compared to conventional designs, aligning with international environmental regulations (Montreal Protocol, Kigali Amendment).
- Customization Capability: Full customization of tube OD, wall thickness, coil pitch, coil diameter, and surface finish to match specific OEM design requirements.
- Consistent Quality: CNC-controlled winding and multi-stage inspection ensure dimensional accuracy and batch-to-batch consistency critical for automated assembly lines.
- Comprehensive Technical Support: Wenzhou Jixing provides engineering consultation, prototype development, and thermal simulation support to optimize coil tube specifications for target application performance.
Note: All specifications are subject to revision based on the latest engineering data and customer-specific requirements. For detailed technical inquiries, custom design requests, or sample procurement, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Product performance data referenced in this specification is derived from controlled laboratory testing conditions and may vary under field operating conditions.