Stainless Steel Coil Tube for Fan Coil Unit Temperature Control Systems
1. Product Overview
The stainless steel coil tube (盘管) is a critical heat exchange component employed in fan coil unit (FCU) systems, designed to facilitate precise temperature regulation in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) applications. This product, designated as Model No. 320 by Wenzhou Jixing Metal Materials Co., Ltd., is engineered to optimize thermal transfer efficiency while maintaining structural integrity under continuous cyclic thermal loading. The coil tube serves as the primary medium for transferring thermal energy between a working fluid (water or refrigerant) and ambient air, enabling advanced energy-saving strategies in building climate control systems.
Unlike conventional copper or brass coil assemblies, this stainless steel coil tube offers superior corrosion resistance, extended service life, and enhanced hygiene characteristics, making it particularly suitable for high-performance temperature control applications where long-term reliability and energy efficiency are paramount.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, thermal conductivity, and resistance to oxidative and chemical degradation.
- Primary Material: AISI 304 / SUS 304 (18Cr-8Ni) or AISI 316 / SUS 316 (18Cr-10Ni-2Mo), depending on application requirements
- Alloy Composition: Chromium (Cr) 18–20%, Nickel (Ni) 8–12%, Molybdenum (Mo) 2–3% (for 316 grade), Carbon (C) ≤ 0.08%
- Thermal Conductivity: 14–16 W/(m·K) at 20°C
- Operating Temperature Range: -200°C to +870°C
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC)
- Hygienic Performance: Non-toxic, non-contaminating surface suitable for potable water and food-grade applications
- Mechanical Strength: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Model | 320 | Wenzhou Jixing Internal Designation |
| Tube Outer Diameter (OD) | 6.35 mm / 9.52 mm / 12.7 mm (configurable) | ISO 286 / ASME B36.19M |
| Wall Thickness | 0.50 mm – 1.50 mm | ASTM A269 / ASTM A213 |
| Coil Diameter | 150 mm – 500 mm | Custom per application |
| Tube Length per Coil | 3 m – 20 m | Custom per application |
| Fins per Inch (FPI) | 6 – 12 | ASHRAE Standard 90.1 |
| Fins Material | Aluminum (Al) or Stainless Steel (SS) | — |
| Heat Exchange Efficiency | ≥ 85% (NTU method) | ASHRAE Standard 22 |
| Maximum Working Pressure | 1.6 MPa (232 psi) | EN 12729 |
| Test Pressure | 2.4 MPa (348 psi) | Hydrostatic test |
| Surface Finish | BA (Bright Annealed) or No. 4 Brushed | ASTM A473 |
| End Connection | Flared, Threaded, or Welded | ISO 14284 |
| Weight (Typical) | 0.8 kg – 4.5 kg per unit | — |
4. Manufacturing Process
The production of this stainless steel coil tube follows a rigorous, multi-stage manufacturing protocol designed to ensure dimensional accuracy, surface quality, and thermal performance:
- Raw Material Selection: Certified stainless steel wire rod (AISI 304/316) undergoes incoming inspection for chemical composition (spectrometric analysis) and mechanical properties.
- Cold Drawing: Wire rod is cold-drawn through precision dies to achieve the required tube OD and wall thickness with tight tolerances (±0.05 mm).
- Solution Annealing: Drawn tubes are annealed at 1050–1150°C in a protective atmosphere to relieve residual stresses and restore full austenitic microstructure.
- Coil Forming: Tubes are precisely coiled using CNC-controlled bending equipment to achieve uniform bend radii without wall thinning or ovality exceeding 2%.
- Finning: Aluminum or stainless steel fins are mechanically or brazed onto the coil surface to maximize heat transfer area.
- Hydrostatic Pressure Testing: Each coil assembly undergoes 100% hydrostatic testing at 2.4 MPa to verify leak-tightness.
- Surface Treatment: Final cleaning and passivation (citric acid or nitric acid pickling) to ensure a clean, corrosion-resistant surface.
- Quality Inspection: Dimensional verification, visual inspection, and ultrasonic testing (UT) for internal defects.
5. Applications
This coil tube is designed for integration into fan coil unit systems and is applicable across a broad spectrum of HVAC and thermal management scenarios:
- Commercial HVAC Systems: Precise temperature control in office buildings, hotels, hospitals, and retail spaces
- Industrial Process Cooling/Heating: Temperature regulation in manufacturing facilities, cleanrooms, and laboratories
- Energy-Saving Fan Coil Units: Core component in high-efficiency FCU designs implementing variable temperature control strategies (e.g., modulating valve control, bypass control, and adaptive setpoint scheduling)
- Refrigeration Systems: Evaporator and condenser coils in commercial refrigeration and cold storage
- Chilled Water Systems: Heat exchange in secondary chilled water loops for zonal climate control
- Food and Pharmaceutical Processing: Sanitary-grade heat exchange where hygiene and non-contamination are critical
- Green Building Applications: Contributing to LEED and Green Star certification through improved energy efficiency in building HVAC systems
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure conformance with international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification covering the entire production lifecycle |
| ISO 14001:2015 | Environmental Management System ensuring sustainable manufacturing practices |
| CE Marking | European Conformity for compliance with EU health, safety, and environmental protection standards |
| EN 12729 | European standard for radiators and convectors (applicable to heat exchange coil assemblies) |
| ASTM A269 / A213 | American standards for welded and seamless austenitic stainless steel tube |
| ASME B36.19M | Welded stainless steel pipe and tube dimensions |
| GB/T 14976 | Chinese national standard for cold-rolled seamless stainless steel tubes |
| GB/T 21832 | Chinese national standard for heat exchangers and radiators |
7. Unique Selling Points
Enhanced Energy Efficiency: The high thermal conductivity and precision engineering of this stainless steel coil tube enable superior heat transfer performance, directly contributing to energy-saving strategies in fan coil unit temperature control systems. Studies on fan coil unit temperature control energy-saving strategies demonstrate that optimized coil design can reduce HVAC energy consumption by 15–30%.
- Exceptional Durability: Stainless steel construction provides a service life exceeding 25 years, significantly outperforming copper coil alternatives in corrosive environments.
- Corrosion Resistance: Immune to internal scaling and external oxidation, maintaining consistent thermal performance over the product lifetime without degradation.
- Hygienic Surface: Smooth, non-porous surface prevents biofilm formation, making it ideal for healthcare and food-grade applications.
- Environmental Sustainability: Stainless steel is 100% recyclable, aligning with green building and sustainable manufacturing objectives.
- Customization Capability: Flexible manufacturing allows tailoring of coil dimensions, fin configurations, and end connections to meet specific system requirements.
- Low Maintenance: Eliminates the need for periodic coil replacement or anti-corrosion treatments, reducing total cost of ownership (TCO).
8. Technical Notes on Temperature Control Energy-Saving Integration
When integrated into fan coil units employing advanced temperature control strategies, this coil tube contributes to energy optimization through the following mechanisms:
- Variable Flow Control: The coil's high heat transfer coefficient enables efficient operation at reduced flow rates, allowing variable frequency drive (VFD) pumps to operate at lower energy consumption.
- Adaptive Setpoint Control: Precise thermal response characteristics support dynamic setpoint adjustments based on occupancy, weather, and schedule.
- Bypass Control: The coil's rapid thermal response facilitates effective bypass damper control strategies, minimizing energy waste during part-load conditions.
- Free Cooling Integration: Suitable for systems that utilize outside air or ground-source heat exchange for natural cooling, reducing mechanical cooling load.
This product represents a state-of-the-art solution for energy-efficient thermal management in modern building systems, combining proven material science with precision manufacturing to deliver reliable, high-performance temperature control.