Stainless Steel Fan Coil Tube — Coiltube Series (Model No. 1110)
Product Overview
The Stainless Steel Fan Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange tube specifically designed for integration into Fan Coil Units (FCUs) operating within hydronic air-conditioning and ventilation systems. This product is engineered to meet the rigorous demands of both wet-bulb and dry-condition operation scenarios, ensuring optimal thermal transfer performance while maintaining structural integrity under prolonged exposure to water-carrying refrigerant loops and condensing environments.
The Coiltube series represents a critical component in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) infrastructure, where it serves as the primary medium for heat exchange between circulating water (or glycol-based fluids) and ambient air. Its design philosophy centers on maximizing surface area-to-volume ratio, minimizing pressure drop across the coil assembly, and resisting corrosion under dry-condition operation — a condition in which the coil surface temperature remains above the dew point of the passing air, thereby eliminating condensation formation.
Material & Properties
The Coiltube product line is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability in hydronic service.
- Primary Alloy Grade: AISI 304 (UNS S30400) — Chromium-Nickel Stainless Steel, containing 18–20% Chromium (Cr) and 8–10.5% Nickel (Ni), with maximum 2.0% Carbon (C) content.
- Alternative Grade: AISI 316L (UNS S31603) — Low-carbon variant with 2–3% Molybdenum (Mo) addition for enhanced resistance to chloride-induced pitting and crevice corrosion.
- Surface Finish: No. 2B cold-rolled finish with surface roughness (Ra) ≤ 0.8 μm, or electropolished finish for hygienic applications requiring Ra ≤ 0.4 μm.
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (standard 304 grade).
- Operating Temperature Range: −196°C to +870°C (theoretical); recommended continuous service range: −40°C to +250°C.
- Corrosion Resistance: Superior resistance to atmospheric, aqueous, and chemical corrosion; passivation layer self-repairs under oxidizing conditions.
- Mechanical Properties: Minimum tensile strength 515 MPa (304 annealed); minimum yield strength 205 MPa; elongation ≥ 40%.
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Tube Outer Diameter (OD) | 8.0 mm / 9.52 mm / 12.0 mm (configurable) | ISO 3505 |
| Tube Wall Thickness | 0.50 mm – 1.20 mm (standard: 0.70 mm) | ASTM A269 / ASTM A213 | Coil Pitch (Row Spacing) | 12.7 mm – 25.4 mm (typical: 19.05 mm) | Manufacturer specification |
| Coil Depth (Face-to-Face) | 250 mm / 375 mm / 500 mm / 625 mm (standard configurations) | ASHRAE Handbook — HVAC Systems and Equipment |
| Fin Type | Aluminum V-fin or corrugated fin; fin density 10–14 fins per inch (FPI) | EN 12974 |
| Fin Thickness | 0.10 mm – 0.20 mm | ISO 22976 |
| Hydraulic Circuit Configuration | Single-pass, double-pass, or multi-pass (2–8 passes typical) | ASHRAE 90.1 |
| Design Pressure | 1.0 MPa (10 bar) working; 1.5 MPa (15 bar) hydrostatic test | EN 12828 |
| Maximum Operating Flow Velocity | ≤ 2.5 m/s (water); ≤ 3.0 m/s (glycol-water mix) | ASHRAE Guideline 34 |
| Heat Transfer Capacity (Typical) | 1.5 kW – 45.0 kW (depending on coil size and face velocity) | ANSI/ASHRAE Standard 34 |
| Face Velocity (Air-Side) | 1.5 m/s – 3.5 m/s (variable speed fan operation) | ISO 5167 |
| Dry-Condition Operation Capability | Surface temperature control ≥ dew point + 2°C margin | ASHRAE 62.1 / CIBSE Guide C |
| Refrigerant/Water Connection | 1/2" BSP / 3/4" BSP threaded or flanged inlet and outlet | BS 4504 / EN 10253 |
| Weight (Typical, 500mm Depth Unit) | 8.5 kg – 14.0 kg (excluding fan assembly) | — |
| Coating / Protection | Optional epoxy or fluoropolymer (PTFE) anti-corrosion coating | ISO 12944 |
Manufacturing Process
The production of the Stainless Steel Coiltube follows a multi-stage precision manufacturing protocol to ensure dimensional accuracy, material homogeneity, and reliable long-term performance:
- Raw Material Preparation: Cold-rolled stainless steel strip (304 or 316L grade) is inspected for chemical composition via Optical Emission Spectroscopy (OES) and mechanical properties via tensile testing per ASTM A999.
- Tube Forming (Seamless or Welded): Strip material is cold-formed into tubular cross-section using roll-forming machinery. For welded variants, Transverse Resistance Welding (TRW) or TIG (Tungsten Inert Gas) welding is employed with 100% seam inspection via ultrasonic testing (UT) per ASTM E164.
- Heat Treatment: Solution annealing at 1040°C – 1120°C followed by rapid quenching to restore full austenitic microstructure and maximize corrosion resistance.
- Coil Winding: Formed tubes are helically wound around precision-machined mandrels to achieve exact pitch and row alignment. Tension-controlled winding ensures uniform tube-to-fin contact.
- Fin Insertion: Pre-slotted aluminum fins are inserted into the tube matrix using automated fin-stacking equipment, achieving consistent fin density and alignment within ±0.05 mm tolerance.
- Hydrostatic Pressure Testing: Each completed coil assembly undergoes hydrostatic testing at 1.5× design pressure (1.5 MPa) for a minimum dwell time of 30 minutes to verify leak-tightness and structural integrity.
- Surface Finishing & Passivation: Chemical passivation using citric acid or nitric acid solution establishes a stable chromium oxide (Cr₂O₃) passive film on all exposed surfaces.
- Final Quality Inspection: Dimensional verification via Coordinate Measuring Machine (CMM); visual inspection for surface defects; air-side pressure drop measurement per AMCA (Air Movement and Control Association) 210 standard.
Applications
The Stainless Steel Coiltube is deployed across a broad spectrum of HVAC applications where reliable, corrosion-resistant heat exchange is paramount:
- Commercial HVAC Systems: Fan Coil Units in office buildings, hotels, hospitals, and retail facilities — particularly in zones requiring dry-condition operation to maintain indoor humidity control and prevent Legionella risk.
- Residential Air Conditioning: Concealed ceiling-mounted or wall-mounted FCUs in high-end residential developments where silent operation and minimal maintenance are desired.
- Industrial Process Cooling: Precision temperature control in pharmaceutical manufacturing, food processing, and semiconductor fabrication cleanrooms (Class 100 – Class 10,000 per ISO 14644).
- Marine & Offshore Environments: 316L-grade Coiltube variants for shipboard HVAC systems where chloride exposure and salt spray corrosion are significant concerns.
- Data Center Cooling: High-density heat rejection in server room containment systems requiring continuous operation with glycol-water heat transfer fluids.
- Dry-Condition Fan Coil Operation: Specifically optimized for water-cooled FCUs operating above dew point, eliminating condensate drainage requirements, reducing mold growth risk, and improving indoor air quality (IAQ) — a critical consideration for healthcare facilities and sensitive manufacturing environments.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management infrastructure ensuring product compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- EN 12974 — Conformity with European standard for air-conditioning coils and heat exchangers.
- ANSI/ASHRAE Standard 34-2016 — Rating and performance testing methodology for air-cooled heat exchangers.
- CE Marking (EU) — Compliance with European Machinery Directive (2006/42/EC) and Pressure Equipment Directive (PED 2014/68/EU) for components operating above 0.5 bar.
- Material Certification: Each production batch accompanied by Mill Test Certificate (MTC) per EN 10204 Type 3.1, verifying chemical composition and mechanical properties.
- Hydrostatic Test Report: Individual unit test documentation available upon request, including test pressure, dwell time, and inspector identification.
- RoHS & REACH Compliance: Freedom from restricted hazardous substances per EU Directive 2011/65/EU and Regulation (EC) No 1907/2006.
Unique Selling Points
The Coiltube Series distinguishes itself through several key performance advantages:
- Superior Dry-Condition Performance: Engineered specifically for operation above dew point, eliminating condensate-related maintenance issues, reducing energy consumption associated with condensate pumping, and significantly improving indoor air quality by preventing microbial growth on coil surfaces.
- Extended Service Life: Austenitic stainless steel construction provides 2–3× the service life of conventional carbon steel alternatives in corrosive or humid environments, translating to total cost of ownership (TCO) savings of 35–50% over a 15-year design life.
- Low Pressure Drop Design: Optimized internal hydraulic geometry and smooth surface finish minimize friction losses, reducing pump energy consumption by up to 20% compared to standard tube geometries.
- Modular Configurations: Available in multiple depths, pass counts, and fin densities to precisely match system design loads, enabling engineers to optimize performance without oversized equipment.
- Full Traceability: Each unit is serialized with complete manufacturing documentation, including raw material mill certificates, process parameters, and final test results, supporting lifecycle management and warranty claims.