Stainless Steel Coil Tube — HVAC Fan Coil Unit Heat Exchanger Tube
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular heat exchange component designed for integration into advanced Fan Coil Units (FCUs) equipped with multi-functional thermal and humidity treatment capabilities. This product represents a critical structural and thermal element within HVAC (Heating, Ventilation, and Air Conditioning) systems, where it facilitates efficient heat transfer between refrigerant or hydronic fluid and ambient air streams.
Drawing upon research principles from the development of multi-functional fan coil units with combined sensible and latent heat treatment, this coil tube is engineered to support dehumidification, heating, and cooling cycles simultaneously, meeting the demanding requirements of modern climate control systems in commercial, industrial, and residential environments.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, and long-term mechanical integrity under cyclic thermal stress.
- Base Material: Austenitic Stainless Steel (typically AISI 304 / AISI 316 depending on application requirements)
- Corrosion Resistance: Excellent resistance to oxidation, chemical attack, and condensation-induced pitting
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, enabling efficient heat exchange
- Operating Temperature Range: −40°C to +150°C (continuous)
- Mechanical Strength: Yield strength ≥ 205 MPa (0.2% offset); tensile strength ≥ 515 MPa
- Surface Finish: Polished or passivated interior/exterior to minimize flow resistance and prevent biofilm accumulation
- Hygienic Compliance: Suitable for potable water and food-grade applications where specified
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Code | No. 1137 — Coiltube |
| Outer Diameter (OD) | 6.35 mm / 9.52 mm / 12.7 mm (available configurations) |
| Wall Thickness | 0.5 mm – 1.0 mm |
| Tube Length (per coil) | Standard lengths: 300 mm, 600 mm, 900 mm, 1200 mm; custom lengths available |
| Coil Diameter | Customizable per FCU design requirements |
| Bend Radius | Minimum 1.5× OD to prevent kinking and maintain structural integrity |
| Heat Transfer Efficiency | Optimized for combined sensible and latent heat exchange in multi-function FCU systems |
| Pressure Rating | Up to 1.6 MPa (working); 2.4 MPa (test) |
| Connection Type | Flared, brazed, or threaded fittings compatible with standard FCU manifolds |
| Coating / Surface Treatment | Optional hydrophilic or anti-corrosion coating for enhanced dehumidification performance |
| Standards Compliance | ASTM A213, ASTM A269, EN 10216-5, ISO 15767 |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, thermal performance, and long-term reliability:
- Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis to verify alloy composition (Cr ≥ 18%, Ni ≥ 8% for 304 grade).
- Precision Forming: High-precision tube forming machinery produces seamless tubes with tight tolerance on wall thickness (±0.05 mm) and outer diameter (±0.1 mm).
- Coil Bending: CNC-controlled bending equipment forms the tube into the required coil geometry with controlled bend radii to prevent wall thinning or ovality exceeding 2%.
- Welding & Brazing: Where multi-pass configurations are required, TIG (Tungsten Inert Gas) welding or silver brazing is employed to create leak-tight joints between tube passes and header connections.
- Surface Treatment: Interior and exterior surfaces undergo mechanical polishing or chemical passivation (nitric acid passivation) to achieve a smooth finish (Ra ≤ 0.4 μm) and enhanced corrosion protection.
- Quality Testing: Each coil assembly undergoes 100% pneumatic pressure testing, dimensional verification, and visual inspection for defects.
- Final Assembly & Packaging: Coils are fitted with end fittings, protected with anti-condensation wrapping, and packaged for shipment.
5. Applications
The stainless steel coil tube is specifically designed for use in the following applications:
- Multi-Function Fan Coil Units: FCUs capable of simultaneous cooling, heating, and dehumidification — the primary design reference for this product, as described in the research literature on thermal-humidity integrated treatment systems.
- Commercial HVAC Systems: Air handling units (AHUs), rooftop units, and constant-volume (CV) or variable-air-volume (VAV) systems in office buildings, hospitals, and hotels.
- Industrial Climate Control: Precision temperature and humidity regulation in pharmaceutical manufacturing, electronics fabrication, and laboratory environments.
- Residential Comfort Systems: Ducted and ductless split air conditioning units, radiant cooling panels, and underfloor heating loops.
- Food & Beverage Processing: Hygienic-grade heat exchangers where stainless steel construction is mandated by food safety regulations.
- Marine & Coastal Environments: Corrosion-resistant coil assemblies for HVAC installations in high-humidity, salt-spray environments (AISI 316 grade recommended).
6. Unique Selling Points
- Multi-Function Thermal Performance: Engineered specifically for FCUs with integrated sensible and latent heat treatment, enabling superior dehumidification efficiency without sacrificing cooling capacity.
- Extended Service Life: Stainless steel construction eliminates the corrosion and scaling issues associated with copper or carbon steel alternatives, providing a design life exceeding 25 years.
- Hygienic Design: Smooth, passivated internal surfaces prevent microbial growth and condensate stagnation — critical for healthcare and food-grade applications.
- Custom Configurability: Flexible coil geometry, tube count, and pass arrangement tailored to specific FCU heat load calculations.
- Energy Efficiency: Optimized tube-to-finned surface area ratio reduces fan power requirements while maximizing heat transfer coefficient (U-value).
- Sustainability: Stainless steel is 100% recyclable, contributing to reduced lifecycle carbon footprint in accordance with green building standards (LEED, Green Star).
7. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management Systems certification
- ISO 14001:2015 — Environmental Management Systems certification
- CE Marking — Conformity with European Machinery and Pressure Equipment Directives
- ASTM / EN Compliance — Material and fabrication standards (ASTM A213, A269; EN 10216-5)
- Hydrostatic Pressure Testing — 100% batch testing to 1.5× working pressure
- NDT (Non-Destructive Testing) — Helium leak detection or dye penetrant inspection on critical welds
- Mill Test Reports (MTR) — Full chemical and mechanical property documentation supplied with each shipment
Note: The design philosophy of this coil tube product is informed by advanced research into multi-functional thermal and humidity treatment in fan coil units. By integrating principles of simultaneous sensible heat removal and latent heat (moisture) extraction, the product enables next-generation climate control solutions that achieve superior indoor air quality (IAQ) with minimal energy consumption.