Stainless Steel Coil Tube for Air Conditioning Coil Sections
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component specifically designed for integration into air conditioning unit coil sections. These coil tubes serve as the core heat exchange elements within air handling units, chillers, condensers, and evaporators, facilitating efficient thermal transfer between refrigerants and ambient air or process fluids.
Coil tubes are fabricated as continuous lengths of stainless steel tubing, wound into serpentine or helical configurations to maximize surface area within a compact envelope. The design philosophy emphasizes optimal hydraulic flow characteristics, minimal pressure drop, and superior corrosion resistance to ensure long-term reliability in demanding HVAC (Heating, Ventilation, and Air Conditioning) environments.
Material & Properties
The coil tubes are constructed from high-grade austenitic stainless steel alloys, selected for their exceptional combination of mechanical strength, thermal conductivity, and resistance to corrosion and oxidation under elevated temperature and humidity conditions typical of air conditioning applications.
- Austenitic Stainless Steel: Primarily based on AISI 304 (UNS S30400) and AISI 316 (UNS S31600) grades, offering excellent formability, weldability, and corrosion resistance.
- Chromium Content: Minimum 18% Cr (Chromium) provides a passive oxide layer for atmospheric and chemical corrosion protection.
- Nickel Content: 8–10% Ni (Nickel) stabilizes the austenitic microstructure and enhances ductility at cryogenic and elevated temperatures.
- Molybdenum Addition (316 Grade): 2–3% Mo (Molybdenum) imparts superior resistance to pitting and crevice corrosion, particularly in chloride-containing environments.
- Surface Finish: Available in bright annealed (BA), 2B, or No. 4 finish depending on application requirements for optical clarity and fouling resistance.
- Thermal Conductivity: Approximately 14–16 W/(m·K) at 20°C, ensuring efficient heat transfer performance.
- Operating Temperature Range: −196°C to +870°C, accommodating extreme thermal cycling in HVAC systems.
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) |
| Material Grade | AISI 304 / 304L / 316 / 316L / 321 / 310S |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (¼" – 1") |
| Wall Thickness | 0.3 mm – 1.5 mm (0.012" – 0.059") |
| Tube Length (Continuous) | Up to 3,000 mm per coil section |
| Bend Radius | Minimum 2× OD (to prevent wall thinning and kinking) |
| Number of Passes | 1 to 12 (configurable per coil section design) |
| Tolerance on OD | ±0.05 mm (per ASTM A213 / EN 10216-5) |
| Tolerance on Wall Thickness | ±10% of nominal |
| End Preparation | Plain end, beveled, or expanded for header connection |
| Surface Treatment | Bright Annealed / Pickled & Passivated |
| Applicable Standards | ASTM A213, ASME SA-213, EN 10216-5, GB/T 14976 |
| Refrigerant Compatibility | R-134a, R-410A, R-32, R-407C, CO₂ (R-744) |
Manufacturing Process
The production of stainless steel coil tubes for air conditioning coil sections follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and performance reliability:
- Raw Material Selection & Inspection: Hot-rolled stainless steel strip or seamless tube stock is procured from certified mills. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition and mechanical testing to confirm yield strength and tensile properties.
- Cold Drawing / Piercing: Tube blanks are cold-drawn through precision dies to achieve the required outer diameter and wall thickness with tight tolerances. This process also imparts beneficial work hardening and surface finish.
- Intermediate Annealing: Periodic solution annealing at 1050–1100°C followed by controlled cooling relieves accumulated cold work stresses, restores ductility, and ensures uniform microstructure.
- Coil Winding / Forming: The straight tube is wound into the prescribed serpentine or helical geometry using CNC-controlled bending machinery. Bend radii are precisely maintained at ≥2× OD to prevent ovality, wrinkles, or wall thinning.
- Fin Attachment (if applicable): Integral or expanded aluminum/copper fins are attached to the coil tube to enhance external heat transfer area by up to 40–60× the bare tube surface.
- Welding to Headers: Tube ends are welded (TIG/Orbital) to stainless steel headers. Weld joints undergo helium leak testing to confirm hermetic integrity at pressures exceeding 1.5× design pressure.
- Pickling & Passivation: The completed coil assembly is subjected to acid pickling (HNO₃/HF blend) to remove oxide scale, followed by passivation treatment to regenerate the protective chromium oxide film.
- Pressure Testing & Leak Detection: Hydrostatic pressure testing at 1.5× maximum operating pressure for a minimum dwell time of 30 minutes, supplemented by soap-bubble or helium mass spectrometer leak detection.
- Final Inspection & Packaging: Dimensional verification, visual inspection, and material traceability documentation are completed prior to protective packaging for shipment.
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. are integral components in a wide spectrum of air conditioning and thermal management systems:
- Commercial Air Handling Units (AHUs): Serving as the primary heat exchange medium in chilled water coils and heating coils for large-scale commercial and industrial HVAC systems.
- Chillers & Condensers: Employed in shell-and-tube and plate-fin heat exchangers within centrifugal, screw, and reciprocating chiller systems.
- Evaporator Coils: Used in direct-expansion (DX) evaporator coils for precision temperature control in pharmaceutical, food processing, and semiconductor manufacturing facilities.
- Marine HVAC Systems: Leveraging the superior corrosion resistance of 316L grade coil tubes in saltwater and high-humidity marine environments.
- Cleanroom & Laboratory Cooling: Providing ultra-low particulate, high-purity heat exchange for semiconductor fab cleanrooms and research laboratories.
- Food & Beverage Processing: Ensuring hygienic, sanitary-grade heat transfer compliant with FDA and EHEDG standards in dairy, beverage, and pharmaceutical processing.
- Refrigeration Systems: Integral to evaporator and condenser coil assemblies in walk-in coolers, freezers, and blast chillers.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and certifications to assure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- EN 10204 3.1 Certificates — Material test certificates providing full traceability of chemical composition, mechanical properties, and heat treatment records for each production lot.
- ASME "U" Stamp / "S" Stamp — Authorization for fabrication of pressure vessels and heat exchangers in compliance with ASME Boiler and Pressure Vessel Code.
- CE Marking (PED 2014/68/EU) — Conformity with the European Pressure Equipment Directive for safe operation in EU member states.
- Hygienic Certification (EHEDG / 3-A) — For food-grade and pharmaceutical applications requiring sanitary design and surface finish standards.
- Mill Test Reports (MTR) — Provided with every shipment, documenting full chemical analysis, tensile testing, hardness testing, and non-destructive examination results.
Unique Selling Points
Engineering Excellence for Coil Section Design: Drawing upon extensive research in air conditioning coil section design optimization, Wenzhou Jixing Metal Materials Co., Ltd. delivers coil tubes engineered for maximum thermal efficiency, minimal pressure drop, and extended service life. The integration of advanced metallurgical understanding with precision manufacturing capabilities ensures that each coil tube assembly meets or exceeds the design parameters specified in rigorous HVAC engineering studies.
- Superior Corrosion Resistance: The austenitic stainless steel construction provides decades of service life without degradation, even in aggressive chemical or marine environments where carbon steel alternatives would fail prematurely.
- Optimized Thermal Performance: Precision-controlled wall thickness and surface finish maximize heat transfer coefficients while minimizing fouling resistance, resulting in higher COP (Coefficient of Performance) for the overall HVAC system.
- Customizable Configurations: Flexible manufacturing capabilities allow tailoring of tube OD, wall thickness, bend radius, pass count, and header arrangement to meet specific coil section design requirements.
- Full Traceability: Every coil tube is accompanied by comprehensive documentation including mill test reports, chemical analysis, and heat treatment records, ensuring complete supply chain traceability.
- Cost-Effective Lifecycle: While initial material cost may be higher than copper or aluminum alternatives, the extended service life, minimal maintenance, and energy savings from superior heat transfer performance deliver significantly lower total cost of ownership (TCO).