Stainless Steel Coil Tube for Fan Coil Units — Technical Specification
Product Overview
The Stainless Steel Coil Tube (Product No. 231) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange component designed for integration into fan coil units (FCUs) and air handling systems. This product is developed in accordance with the performance testing methodologies outlined in GB/T 19232 (National Standard of the People's Republic of China — Performance Testing of Fan Coil Units) and AHRI 440 (Air-Conditioning, Heating, and Refrigeration Institute Standard — Performance Rating for Fan Coil Units), ensuring compliance with both Chinese national standards and internationally recognized HVAC performance criteria.
Coil tubes serve as the primary heat transfer medium in fan coil systems, facilitating efficient thermal exchange between the refrigerant or hot water circulating through the tube and the ambient air passing over the external fin surfaces. The adoption of stainless steel as the base material provides superior corrosion resistance, mechanical durability, and long-term thermal conductivity stability compared to traditional carbon steel or copper alternatives.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional resistance to pitting, crevice corrosion, and stress corrosion cracking in humid and chemically aggressive environments typical of HVAC applications.
- Base Material: Austenitic stainless steel (e.g., SUS304 / SUS316L equivalents per ASTM A270 or EN 10216-5)
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and microbiological corrosion; suitable for both potable water and non-potable water service
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C — balanced thermal performance with corrosion resistance
- Operating Temperature Range: −196 °C to +870 °C (material capability); typical HVAC service range: −40 °C to +120 °C
- Mechanical Strength: Yield strength ≥ 205 MPa (SUS304); tensile strength ≥ 515 MPa
- Surface Finish: Passivated and cleaned to achieve a low-roughness interior (Ra ≤ 0.8 μm) to minimize flow resistance and fouling
Specifications
| Parameter | Specification | Test / Reference Standard |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube) | GB/T 19232; AHRI 440 |
| Tube Outer Diameter (OD) | 6.35 mm (¼"), 9.53 mm (⅜"), 12.7 mm (½") | ASTM A213 / EN 10216-5 |
| Tube Wall Thickness | 0.5 mm – 1.2 mm (selectable) | Manufacturer tolerance ±10% |
| Coil Diameter | 150 mm – 600 mm (configurable) | Per AHRI 440 dimensional requirements |
| Fin Type | Aluminum or stainless steel corrugated / louvered fins | Fin spacing: 1.5 mm – 3.0 mm |
| Number of Rows | 1 – 4 rows (depending on capacity requirement) | GB/T 19232 performance classification |
| Cooling Capacity Range | 2.0 kW – 15.0 kW (per unit) | GB/T 19232 test conditions |
| Heating Capacity Range | 2.5 kW – 18.0 kW (per unit) | AHRI 440 rated conditions |
| Rated Water Pressure | 1.0 MPa (10 bar); test pressure 1.5 MPa | Hydrostatic pressure test |
| Design Service Life | ≥ 20 years (indoor HVAC application) | Accelerated corrosion testing |
| Connection Type | Flared, brazed, or threaded fittings | Per ASME B31.9 piping standards |
| Weight | Varies by configuration; typical unit weight 3.5 – 12.0 kg | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, material integrity, and performance compliance:
- Material Selection & Incoming Inspection: Stainless steel tubes are sourced from certified suppliers and subjected to chemical composition analysis (per ASTM E1), dimensional verification, and visual surface inspection prior to processing.
- Precision Cutting & Forming: Tubes are cold-formed and coiled using CNC-controlled forming equipment to achieve the specified coil diameter and pitch with tolerances within ±0.5 mm.
- Fin Attachment: Aluminum or stainless steel fins are mechanically inserted or welded onto the coil tubes using automated fin-stamping and brazing lines, ensuring uniform fin spacing and secure bonding.
- Welding & Brazing: Header connections and tube-to-fin joints are completed using TIG (Tungsten Inert Gas) welding or vacuum brazing to maintain material purity and prevent oxidation.
- Surface Treatment & Passivation: The assembled coil tube undergoes acid pickling and passivation to remove scale, restore the chromium oxide passive layer, and enhance long-term corrosion resistance.
- Performance Testing: Each batch is tested for cooling capacity, heating capacity, air-side pressure drop, water-side flow resistance, and acoustic performance in accordance with the test procedures defined in GB/T 19232 and AHRI 440.
- Pressure & Leak Testing: Hydrostatic pressure testing at 1.5 MPa for a minimum dwell time of 30 minutes, supplemented by helium leak detection to verify hermetic integrity.
- Final Inspection & Packaging: Visual inspection, dimensional verification, and protective packaging to prevent transit damage.
Applications
The stainless steel coil tube is engineered for a broad spectrum of commercial and industrial HVAC applications, including but not limited to:
- Commercial Building HVAC Systems: Fan coil units for office buildings, retail spaces, and hospitality facilities requiring precise temperature and humidity control.
- Cleanroom & Pharmaceutical Environments: Applications demanding high-purity air handling with zero risk of metallic contamination or corrosion-induced particulate generation.
- Food Processing & Dairy Industries: Environments where aggressive cleaning chemicals (CIP — Clean-in-Place systems) require corrosion-resistant heat exchange components.
- Marine & Coastal Applications: HVAC systems in coastal regions or marine vessels where high humidity and salt-laden air accelerate corrosion in conventional materials.
- Healthcare Facilities: Hospitals, laboratories, and cleanrooms requiring hygienic, easily sanitized heat exchange surfaces with long service life.
- Industrial Process Cooling: Precision temperature control in manufacturing processes where reliability and minimal maintenance are critical.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product consistency and regulatory compliance:
- GB/T 19232: Product performance verified against the Chinese national standard for fan coil unit testing, covering cooling capacity, heating capacity, air-side resistance, water-side resistance, and noise levels.
- AHRI 440: Performance data validated in accordance with AHRI standard rating procedures, enabling international market recognition and interoperability with globally sourced HVAC components.
- ISO 9001:2015: Quality Management System certification covering all stages of design, manufacturing, inspection, and after-sales service.
- ISO 14001:2015: Environmental Management System certification ensuring sustainable and responsible manufacturing practices.
- Material Certification: Each production lot accompanied by a Mill Test Certificate (MTC) confirming chemical composition, mechanical properties, and traceability per ASTM / EN standards.
- Pressure Vessel & Piping Compliance: Adherence to ASME B31.9 for industrial process piping applications and relevant pressure equipment directives.
Unique Selling Points
1. Dual-Standard Performance Validation: The coil tube is the only product in its category validated against both GB/T 19232 and AHRI 440 simultaneously, providing manufacturers with confidence for both domestic and international market deployment.
2. Superior Corrosion Resistance: Unlike copper or carbon steel coil tubes, the stainless steel construction eliminates galvanic corrosion risk when paired with aluminum fins, extending service life by an estimated 40–60% in aggressive environments.
3. Hygienic Surface Integrity: The passivated interior surface prevents biofilm formation and microbial growth, making the product ideal for pharmaceutical, food, and healthcare applications where contamination risk is paramount.
4. Precision Engineering: CNC-driven coil forming ensures uniform tube pitch and fin spacing, resulting in optimized airflow distribution and up to 12% improvement in overall heat transfer efficiency compared to manually coiled alternatives.
5. Full Traceability: Every unit is traceable to its raw material lot through a documented quality chain, supporting regulatory audits and post-installation performance analysis.
Comparison: GB/T 19232 vs. AHRI 440 Test Methodology
A key technical differentiator of this product is its validated compliance with two distinct international testing frameworks. The following table summarizes the primary methodological differences:
| Parameter | GB/T 19232 (China) | AHRI 440 (International) |
|---|---|---|
| Test Chamber Type | Indoor/outdoor temperature chamber | Calibrated air and water test chambers |
| Cooling Test Condition | DB 27 °C / WB 19.5 °C; water inlet 7 °C | DB 80 °F / WB 67 °F; water inlet 55 °F |
| Heating Test Condition | DB 20 °C / dry air; water inlet 50 °C | DB 70 °F / dry air; water inlet 130 °F |
| Capacity Reporting | Total cooling capacity; sensible heat ratio | Total capacity; sensible capacity; COP |
| Acoustic Testing | Sound power level at nominal fan speed | Sound power level at each fan speed setting |
| Applicability | Mandatory for China market entry | Required for North American and global markets |
This dual-standard compliance ensures that the stainless steel coil tube is suitable for OEM integration in HVAC systems targeting both the Chinese domestic market and international export markets without the need for re-engineering or re-testing.