Stainless Steel Coil Tube (Coiltube) — Low-Temperature Air Supply Cooling Coil Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous coil tubing product specifically designed for low-temperature air supply air conditioning systems (Low-Temperature Air Supply HVAC Systems). This product represents an advanced solution in heat exchange performance optimization, delivering superior thermal conductivity, corrosion resistance, and structural integrity under demanding cryogenic and sub-ambient operating conditions. The coil tube is supplied in continuous coil form (Coiltube) to facilitate seamless integration into coil winding, brazing, and fabrication processes without the need for butt-welding, thereby minimizing thermal resistance at joints and ensuring uniform heat transfer across the entire coil assembly.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, predominantly utilizing the following alloy grades:
- 304 (UNS S30400 / 1.4301): General-purpose grade offering excellent corrosion resistance and formability, suitable for standard cooling coil applications.
- 316 (UNS S31600 / 1.4401): Enhanced molybdenum-bearing grade providing superior resistance to chlorides and aggressive cooling media.
- 316L (UNS S31603 / 1.4404): Low-carbon variant optimized for weldability and resistance to intergranular corrosion in brazed coil assemblies.
- 321 (UNS S32100 / 1.4541): Titanium-stabilized grade for applications requiring elevated temperature stability.
Key mechanical and thermal properties include:
- Thermal Conductivity: 14.6–16.3 W/(m·K) at 20°C, ensuring efficient heat dissipation in low-temperature air supply systems.
- Tensile Strength: ≥ 520 MPa (minimum, as cold-worked).
- Yield Strength: ≥ 205 MPa.
- Elongation: ≥ 40% (guaranteeing excellent deep-drawing and coil-winding capability).
- Operating Temperature Range: −196°C to +450°C, accommodating extreme low-temperature air supply conditions.
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, condensate, and mildly acidic cooling media (pH 4–9).
Specifications
| Parameter | Specification |
|---|---|
| Product Type | Stainless Steel Coil Tube (Coiltube) — Continuous Coil Form |
| Material Grades | SUS 304, SUS 316, SUS 316L, SUS 321 (custom grades available) |
| Outer Diameter (OD) | 3.0 mm – 25.0 mm (customizable up to 50.0 mm) |
| Wall Thickness | 0.3 mm – 2.5 mm |
| Coil Inner Diameter | 150 mm – 600 mm (standard packaging coil ID) |
| Coil Length per Spool | 50 m – 500 m (continuous, weld-free) |
| Surface Finish | Pickled & Passivated (2B), Bright Annealed (BA), or Custom Polished |
| Inner Surface Roughness | ≤ Ra 0.8 μm (ensuring low flow resistance for refrigerant/circulating fluid) |
| Dimensional Tolerance | OD: ±0.05 mm; Wall Thickness: ±0.02 mm |
| Pressure Rating | Up to 4.0 MPa (depending on OD and wall thickness) |
| Standards Compliance | ASTM A269/A269M, ASTM A312/A312M, EN 10217-7, GB/T 12771 |
| Maximum Continuous Operating Temperature | 450°C |
| Minimum Operating Temperature | −196°C (LN₂ compatible) |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional precision, metallurgical homogeneity, and surface integrity:
- Hot Rolling & Annealing: Stainless steel strip (coil) is hot-rolled to the target gauge and subsequently annealed to relieve residual stresses and refine grain structure.
- Pickling & Passivation: The hot-rolled coil undergoes acid pickling to remove oxide scale, followed by passivation to form a protective chromium oxide layer.
- Cold Forming (Tube Milling): The strip is fed through precision-matched roll sets in a continuous tube mill, forming the tubular geometry without longitudinal weld seams (seamless) or with a controlled helical weld (welded coil tube, depending on grade and size).
- Cold Drawing & Sizing: Tubes are drawn through calibrated dies to achieve precise outer diameter and wall thickness tolerances (±0.05 mm / ±0.02 mm).
- Intermediate Annealing: Periodic annealing cycles are performed to restore ductility during multi-pass cold working, preventing cracking and maintaining formability for subsequent coil winding.
- Final Cold Drawing & Straightening: Final dimensional refinement and straightening ensure the coil tube meets exact specification requirements.
- Final Annealing & Passivation: A controlled atmosphere anneal (protective atmosphere or vacuum) eliminates cold-work hardening, followed by final passivation for maximum corrosion protection.
- Coil Winding & Packaging: The finished tube is wound onto precision steel spools in continuous coil form, protected with anti-condensation packaging and moisture-absorbing desiccants.
This process ensures that the coil tube maintains superior heat transfer performance in low-temperature air supply cooling coil applications, as validated by research on heat exchange optimization in low-temperature HVAC systems.
Applications
The Stainless Steel Coil Tube is engineered for a broad spectrum of high-performance thermal management applications:
- Low-Temperature Air Supply HVAC Systems: Primary application — cooling coils in chilled beam systems, dedicated outdoor air systems (DOAS), and low-temperature air distribution networks requiring efficient heat exchange at supply air temperatures as low as −10°C to +5°C.
- Refrigeration & Cryogenic Systems: Evaporator and condenser coils in industrial refrigeration, food processing, and cryogenic storage facilities.
- Commercial & Industrial Air Conditioning: Chilled water coils, fan coil units (FCUs), air handling units (AHUs), and rooftop units (RTUs).
- Food & Beverage Industry: Sanitary-grade cooling coils for breweries, dairy processing, and beverage pasteurization systems (316L grade).
- Pharmaceutical & Biotechnology: Cleanroom HVAC cooling coils requiring non-reactive, easy-to-sanitize surfaces.
- Marine & Offshore: Seawater-cooled heat exchanger coils leveraging 316/316L chloride resistance.
- Automotive & Aerospace: Precision cooling circuits and thermal management coils.
- Data Center Cooling: High-efficiency cooling coils for server room thermal management.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality assurance framework to ensure every coil tube product meets international standards:
- ISO 9001:2015 — Quality Management System certification.
- ISO 14001:2015 — Environmental Management System certification.
- ISO 45001:2018 — Occupational Health & Safety Management System.
- CE Marking — Compliance with European directives for construction products and machinery integration.
- EN 10204 3.1 — Third-party material inspection certificates available upon request.
- Material Testing: Each batch undergoes spectroscopic chemical analysis (OES), tensile testing, hardness testing, hydrostatic pressure testing, and intergranular corrosion testing (ASTM A923 Method A).
- Dimensional Inspection: 100% in-line OD and wall thickness monitoring via laser measurement systems with statistical process control (SPC).
- Surface Quality: Visual and dye penetrant inspection (ASTM E709) to ensure freedom from cracks, laps, and surface defects.
- Traceability: Full heat number and lot traceability from raw material mill to final coil packaging.
Unique Selling Points
- Optimized Heat Transfer Performance: Precision inner surface roughness (Ra ≤ 0.8 μm) reduces flow resistance by up to 15%, enhancing the overall heat exchange efficiency of low-temperature air supply cooling coils — a finding validated through dedicated research on cooling coil heat transfer optimization.
- Weld-Free Continuous Coil Supply: Eliminates the need for butt welding during coil fabrication, reducing thermal resistance at joints and improving system reliability.
- Ultra-Low Temperature Capability: Maintains mechanical integrity and ductility down to −196°C, making it suitable for extreme low-temperature air supply applications.
- Customization Flexibility: Full range of OD, wall thickness, and material grade customization to match specific HVAC system design parameters.
- Superior Corrosion & Condensate Resistance: Austenitic stainless steel composition ensures long service life in humid, condensate-rich low-temperature air environments without degradation of heat transfer surfaces.
- Hygienic & Sanitary Grade Available: 316L coil tube with electropolished interior suitable for food-grade and pharmaceutical HVAC applications.
Technical Note: The performance data and specifications presented herein are derived from research into the heat transfer optimization of cooling coil tubes in low-temperature air supply air conditioning systems (低温送风空调系统冷却盘管换热性能优化研究). These findings confirm that the material selection, surface finish, and geometric precision of the coil tube are critical determinants of overall system COP (Coefficient of Performance) improvement, with measured enhancements of 8–12% in heat exchange efficiency compared to standard-grade coil tubing.