Stainless Steel Coil Tube for Fan Coil Unit Heat Exchange Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Code: JX-CT-507
1. Product Overview
The JX-CT-507 Stainless Steel Coil Tube is a precision-engineered coiled tubing product specifically designed for heat exchange applications in fan coil unit (FCU) systems. Based on extensive research into heat transfer characteristics under variable flow conditions, this product has been optimized to deliver superior thermal performance across a wide range of operating parameters. The coil tube serves as the core heat transfer medium in HVAC (Heating, Ventilation, and Air Conditioning) systems, where it facilitates efficient heat exchange between the circulating fluid and the ambient air stream.
Through rigorous testing and analysis of variable flow rate conditions, Wenzhou Jixing Metal Materials has developed a coil tube geometry and material configuration that maintains stable heat transfer coefficients even when flow rates fluctuate significantly. This makes the product particularly well-suited for modern energy-efficient building systems that employ variable speed drives and demand-controlled ventilation strategies.
2. Material & Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel conforming to AISI 304 / AISI 316L
- Alternative Grades: AISI 321 (Ti-stabilized), AISI 316Ti
- Corrosion Resistance: Excellent resistance to chloride-induced pitting and intergranular corrosion
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (AISI 304); 14.6 W/(m·K) at 20°C (AISI 316L)
- Operating Temperature Range: -196°C to +870°C
- Surface Finish: Electropolished (Ra ≤ 0.4 μm) or brushed finish available
Key Performance Characteristics
- Thermal Stability: Maintains consistent heat transfer performance across variable flow rates from 10% to 100% of nominal capacity
- Pressure Drop Optimization: Internal geometry designed to minimize pressure losses under low-flow conditions
- Fouling Resistance: Smooth inner surface reduces scale and biofilm accumulation
- Mechanical Durability: Withstands repeated thermal cycling without deformation or fatigue failure
3. Technical Specifications
| Parameter | Specification | Unit | Standard/Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.35 / 8.00 / 9.53 / 12.70 | mm | ASTM A269 |
| Wall Thickness | 0.50 / 0.80 / 1.00 / 1.20 | mm | ASTM A269 |
| Coil Pitch (Spacing) | 15.00 – 30.00 (adjustable) | mm | ISO 4533 |
| Coil Length | Up to 12,000 | mm | Custom |
| Coil Diameter (Bundle) | 300 / 400 / 500 / 600 | mm | ASHRAE 34 |
| Maximum Working Pressure | 1.6 / 2.5 / 4.0 | MPa | EN 10217 |
| Heat Transfer Coefficient (Nominal) | ≥ 1,800 | W/(m²·K) | Internal Test Standard |
| Pressure Drop at Nominal Flow | ≤ 45 | kPa | Internal Test Standard |
| Variable Flow Performance Ratio | ≥ 0.85 (at 20% flow rate) | — | ASTM D6618 |
| Surface Roughness (Inner) | ≤ 0.4 | μm (Ra) | ASTM A696 |
| Minimum Bend Radius | ≥ 3 × OD | — | ISO 10988 |
| Applicable Fluids | Water, Glycol solutions (≤ 50%), Brine | — | ASHRAE 34 |
4. Manufacturing Process
- Material Selection & Inspection: Ingot analysis via Optical Emission Spectrometry (OES) and Positive Material Identification (PMI) to verify alloy composition and reject off-grade materials.
- Hot Rolling & Annealing: Continuous hot rolling followed by solution annealing at 1050–1100°C with rapid water quenching to achieve full austenitic microstructure and maximum corrosion resistance.
- Cold Drawing & Sizing: Multi-stage cold drawing through tungsten carbide dies to achieve precise dimensional tolerances (±0.05 mm) and enhanced mechanical properties.
- Coil Forming: Precision CNC-driven coiling machine with hydraulic tension control ensures uniform coil pitch and consistent bend geometry. Forming is performed at controlled strain rates to prevent work-hardening-induced brittleness.
- Internal Cleaning & Passivation: High-pressure acid cleaning followed by citric acid passivation treatment to remove all processing residues and establish a stable chromium oxide passive film.
- Electropolishing (Optional): Electrochemical polishing to achieve mirror-smooth internal surface (Ra ≤ 0.4 μm), enhancing heat transfer efficiency and reducing fouling potential.
- Hydrostatic Pressure Testing: 100% of coils subjected to hydrostatic pressure test at 1.5× working pressure for a minimum of 60 seconds to verify structural integrity.
- Final Inspection & Packaging: Dimensional verification, visual surface inspection, and protective packaging with desiccant to prevent corrosion during transit.
5. Applications
Primary Applications
- Commercial HVAC Systems: Fan coil units for office buildings, hotels, hospitals, and retail spaces — particularly in systems employing variable flow control strategies
- Industrial Process Cooling: Precision temperature control in pharmaceutical manufacturing, food processing, and electronics fabrication
- Chilled Water Distribution: Terminal units in large-scale central air conditioning systems
- Heat Recovery Systems: Energy recovery ventilators and heat exchanger cores in net-zero energy buildings
Specialized Applications
- Marine HVAC systems (AISI 316L grade for seawater proximity)
- Cleanroom environments requiring ultra-low particulate emission
- High-purity fluid handling in semiconductor manufacturing
- Low-temperature applications using glycol-water mixtures down to -35°C
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering all manufacturing processes |
| ISO 14001:2015 | Environmental Management System — reduced carbon footprint and waste minimization |
| EN 10217 | European standard for welded and seamless stainless steel tubes |
| ASTM A269 | Standard specification for seamless austenitic stainless steel tubing |
| CE Marking | Compliance with European Conformity requirements for pressure equipment |
| PED 2014/68/EU | Pressure Equipment Directive compliance for Category I and II applications |
| NORSOK M-001 | Offshore materials standard (for marine applications) |
| NSF/ANSI 61 | Health effects testing for materials in contact with potable water |
7. Unique Selling Points
- Variable Flow Optimization: Unlike conventional coil tubes designed for fixed-flow operation, the JX-CT-507 maintains ≥85% of nominal heat transfer performance even at 20% flow rate, enabling significant energy savings in variable-speed HVAC systems.
- Extended Service Life: The combination of high-grade austenitic stainless steel and precision electropolished surfaces results in a design life exceeding 25 years under normal operating conditions.
- Reduced Maintenance Intervals: Smooth internal surface finish reduces fouling accumulation by up to 60%, extending cleaning intervals from 12 months to 36 months.
- Customizable Geometry: Modular coil pitch and bundle diameter options allow system integrators to optimize heat transfer area for specific load profiles.
- Full Traceability: Every coil tube is assigned a unique batch code linked to raw material mill certificates, process parameters, and test results for complete supply chain traceability.
8. Technical Reference: Heat Transfer Performance Under Variable Flow
Based on experimental testing and analysis of fan coil unit heat transfer characteristics under variable flow conditions, the JX-CT-507 coil tube demonstrates a heat transfer coefficient ratio (HTR) that remains above 0.85 across flow rates from 20% to 100% of design capacity. This performance significantly outperforms standard coil tubes, which typically exhibit HTR values dropping below 0.60 at 20% flow rate due to laminar flow transition and boundary layer thickening.
The optimized internal geometry and surface finish of the JX-CT-507 promote early turbulence onset at lower Reynolds numbers, maintaining convective heat transfer enhancement even under part-load conditions. This characteristic directly translates to reduced fan energy consumption and improved system COP (Coefficient of Performance) in real-world operating scenarios.
9. Ordering Information
For detailed quotations, custom specification development, and technical consultation, please contact Wenzhou Jixing Metal Materials Co., Ltd. Engineering Support Team. Provide the following information for accurate quotation:
- Required outer diameter and wall thickness
- Preferred alloy grade (AISI 304, 316L, 321, or 316Ti)
- Total coil length and bundle diameter
- Surface finish requirement (standard, electropolished, or custom)
- Operating pressure and temperature range
- Applicable fluid type and concentration
- Quantity and required delivery schedule