Stainless Steel Coil Tube — High-Performance Air Conditioning Chilled Water System Component
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd
Product Category: Coil Tube (盘管) for HVAC (Heating, Ventilation, and Air Conditioning) Applications
Reference Document: Technical Study on the Effect of Large Temperature Differences in Air Conditioning Chilled Water on Fan Coil Unit Performance
1. Product Overview
The stainless steel coil tube produced by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered heat exchange component designed for use in fan coil units (FCUs), chiller systems, and large temperature-difference (LTD) air conditioning applications. The coil tube is manufactured from high-grade austenitic stainless steel, offering superior corrosion resistance, thermal conductivity, and mechanical integrity under demanding operating conditions.
This product is specifically engineered to address the performance challenges associated with large temperature differentials (typically ΔT ≥ 10°C) in chilled water systems, where conventional materials may suffer from thermal stress fatigue, scaling, and accelerated corrosion. The coil tube maintains stable thermal performance and structural integrity even under fluctuating flow velocities and temperature gradients.
2. Material & Properties
The coil tube is fabricated from austenitic stainless steel conforming to international standards, ensuring long-term serviceability in aggressive chemical environments commonly found in HVAC systems.
- Primary Material Grade: SUS304 (UNS S30408) / SUS316L (UNS S31603) austenitic stainless steel
- Chromium (Cr) Content: 18.0%–20.0% — provides excellent oxidation and corrosion resistance
- Nickel (Ni) Content: 8.0%–10.5% — enhances ductility and toughness at low temperatures
- Molybdenum (Mo) Content (316L grade): 2.0%–3.0% — imparts superior resistance to pitting and crevice corrosion
- Carbon (C) Content: ≤ 0.03% (in 316L) — minimizes intergranular sensitization during welding
- Tensile Strength: ≥ 520 MPa (0.2% proof stress ≥ 205 MPa)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C
- Operating Temperature Range: −196°C to +870°C
- Surface Finish: 2B cold-rolled finish or polished (Ra ≤ 0.8 μm available upon request)
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm, 9.52 mm, 12.7 mm (standard); custom sizes available | GB/T 14976, ASTM A269 |
| Wall Thickness | 0.5 mm – 1.2 mm (typical range) | ISO 1127 |
| Coil Pitch | 12 mm – 25 mm (configurable based on heat transfer requirements) | Manufacturer specification |
| Coil Length | 10 m – 100 m (customizable) | — |
| Material Grade | SUS304 / SUS316L / SUS321 / SUS316Ti | GB/T 20878, ASTM A270 |
| Surface Treatment | Pickled & passivated; optional electropolishing | ASTM A967 |
| Maximum Working Pressure | 1.6 MPa (standard); 2.5 MPa (reinforced) | GB/T 10409 |
| Tolerance on OD | ±0.1 mm | ISO 4287 |
| Tolerance on Wall Thickness | ±10% of nominal | GB/T 14976 |
| Hydrostatic Test Pressure | 2.0 × working pressure, minimum 10 minutes hold | ISO 1127 |
| Coil Forming Method | Cold spiral winding with precision die forming | — |
| End Preparation | Flat-cut, beveled, or flanged (as specified) | — |
| Applicable Standards | GB/T 14976, ASTM A269/A270, ISO 1127, EN 10216-5 | — |
4. Manufacturing Process
The coil tube is produced through a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical soundness, and consistent surface quality:
- Raw Material Selection: Certified stainless steel seamless tubes or welded tubes are sourced from approved suppliers with full material traceability and mill test certificates (MTC).
- Dimensional Inspection: Incoming tubes undergo ultrasonic testing (UT) and dimensional verification to confirm compliance with specified tolerances.
- End Preparation & Straightening: Tube ends are deburred, chamfered, and the tube stock is straightened to eliminate residual bending stresses.
- Coil Forming: Precision cold spiral winding is performed using CNC-controlled forming equipment with calibrated dies to achieve exact pitch, diameter, and concentricity tolerances.
- Welding (if applicable): Butt welds or brazed joints are performed using inert gas shielding (TIG welding, AWS D17.1) to maintain material integrity.
- Pickling & Passivation: The formed coil undergoes chemical pickling to remove oxide scale, followed by passivation treatment to restore the protective chromium oxide film (per ASTM A967).
- Hydrostatic Pressure Testing: Each coil is subjected to hydrostatic testing at 2.0 × the maximum working pressure to verify structural integrity and absence of leaks.
- Final Quality Inspection: Comprehensive inspection including visual examination, dimensional verification, and optional eddy current testing (ECT) for wall thickness mapping.
- Packaging & Labeling: Coils are wrapped in moisture-proof protective film, packaged in wooden or steel crates, and labeled with product identification, material grade, and batch traceability information.
5. Applications
This stainless steel coil tube is specifically designed for demanding HVAC and thermal management applications, including:
- Fan Coil Units (FCUs): Primary heat exchange element in commercial and industrial FCUs operating under large temperature-difference (LTD) chilled water conditions (supply temperature 7°C–12°C, return temperature 17°C–22°C).
- Chiller Systems: Evaporator and condenser coil assemblies in absorption chillers and electric chillers.
- Heat Recovery Systems: Total energy recovery ventilators (TERVs) and heat exchangers in energy-efficient building systems.
- Cleanroom HVAC: High-purity air handling units in pharmaceutical, semiconductor, and biotechnology facilities requiring corrosion-resistant heat exchange surfaces.
- Marine & Offshore HVAC: Corrosion-resistant coil assemblies for shipboard and offshore platform climate control systems.
- Food & Beverage Processing: Sanitary-grade heat exchangers in pasteurization, refrigeration, and temperature control systems.
- Industrial Process Cooling: Temperature regulation in chemical processing, electronics manufacturing, and data center cooling systems.
6. Performance Under Large Temperature Difference Conditions
Based on technical studies regarding the impact of large temperature differences in air conditioning chilled water systems on fan coil unit performance, this coil tube demonstrates the following advantages:
- Thermal Stress Resistance: The austenitic microstructure provides excellent resistance to thermal fatigue under cyclic temperature variations of up to 15°C differential, preventing crack initiation and propagation.
- Scaling Mitigation: The smooth surface finish (Ra ≤ 0.8 μm) reduces mineral scale deposition, maintaining heat transfer efficiency over extended operating cycles.
- Corrosion Inhibition: Enhanced chromium oxide passive film resists electrochemical corrosion from chlorides and dissolved oxygen in chilled water circuits.
- Stable Flow Characteristics: Precision coil geometry ensures uniform flow distribution, minimizing dead zones that promote biofilm growth and localized corrosion.
- Long Service Life: Expected operational lifespan of 15–25 years under standard HVAC operating conditions with proper maintenance.
7. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health & Safety Management System certification
- CE Marking — Compliance with European directives for pressure equipment (PED 2014/68/EU)
- Material Certifications: Mill Test Certificates (MTC) per EN 10204 Type 3.1 for all material grades
- Third-Party Inspection: Available upon request (SGS, BV, or TÜV)
8. Unique Selling Points
1. Superior Large ΔT Performance: Engineered specifically for large temperature-difference chilled water applications, maintaining optimal heat transfer coefficients even under extreme thermal cycling conditions.
2. Precision Manufacturing: CNC-controlled coil forming ensures ±0.1 mm dimensional accuracy, guaranteeing uniform flow distribution and maximum thermal efficiency.
3. Material Excellence: Use of 316L and 304 austenitic stainless steel provides unmatched corrosion resistance in aggressive HVAC water environments, extending system service life significantly.
4. Customization Capability: Flexible production parameters (OD, wall thickness, pitch, length) allow tailored solutions for specific system designs and performance requirements.
5. Full Traceability: Every product batch is accompanied by comprehensive documentation including material certificates, process records, and test reports for complete quality traceability.
6. Industry Expertise: Backed by extensive research into HVAC thermal performance optimization, ensuring products meet the evolving demands of energy-efficient building systems.
9. Ordering Information
Customers are advised to specify the following parameters when placing orders:
- Material grade (SUS304 / SUS316L / SUS321 / SUS316Ti)
- Outer diameter and wall thickness
- Coil pitch and total coil length
- Surface finish requirements (2B / polished / electropolished)
- End preparation type
- Applicable standard or specification
- Quantity and delivery schedule
Wenzhou Jixing Metal Materials Co., Ltd — Engineering Excellence in Stainless Steel Coil Tube Solutions for HVAC and Industrial Applications.