Stainless Steel Coil Tube for Fan Coil Unit (FCU) Air-Conditioning Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular component designed specifically for integration into Fan Coil Unit (FCU) air-conditioning systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube serves as a critical heat-exchange element within segmented linear regression–optimized demand response frameworks, enabling efficient thermal transfer in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications. The product combines high-performance austenitic stainless steel with advanced coil-forming technology to deliver superior corrosion resistance, thermal conductivity, and mechanical durability under cyclic thermal loading conditions.
Material & Properties
- Base Material: Austenitic Stainless Steel (AISI 304 / AISI 316L), conforming to ASTM A213 / ASTM A269 standards
- Corrosion Resistance: Excellent resistance to chlorides, dehumidified condensate, and atmospheric pollutants; superior pitting resistance (PREN ≥ 19 for 316L grade)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C, ensuring efficient heat transfer between refrigerant and ambient air
- Mechanical Properties: Tensile strength ≥ 520 MPa; elongation ≥ 40%; yield strength ≥ 205 MPa
- Operating Temperature Range: −196°C to +870°C (austenitic grade dependent)
- Surface Finish: 2B cold-rolled finish, Ra ≤ 0.8 μm; optional electropolished finish for hygienic applications
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.35 mm / 9.53 mm / 12.7 mm (custom available) | ASTM A213 |
| Wall Thickness | 0.5 mm – 1.5 mm | ASTM A269 |
| Coil Pitch | 10 mm – 25 mm (configurable per system design) | Manufacturer Specification |
| Coil Diameter | φ150 mm – φ600 mm | EN 10217 |
| Tube Length (Uncoiled) | 3 m – 30 m (continuous) | GB/T 14976 |
| Material Grade | SUS304 / SUS304L / SUS316 / SUS316L | JIS G4314 |
| Pressure Rating | ≤ 1.6 MPa (standard); ≤ 4.0 MPa (reinforced) | ISO 11114 |
| Surface Roughness | Ra ≤ 0.8 μm (2B); Ra ≤ 0.2 μm (electropolished) | ISO 1302 |
| Heat Exchanger Efficiency | ≥ 85% (NTU method, segmented linear regression validated) | ASHRAE Standard 90.1 |
| Compliance | EN 10217-1, ASTM A213, GB/T 14976 | Multi-standard certified |
Manufacturing Process
- Hot-Rolled Billet Preparation: Primary steel is cast and hot-rolled into seamless tube blanks with controlled chemistry (low carbon, controlled chromium-nickel ratios).
- Pilot Milling & Piercing: Blanks are heated to 1150°C–1250°C and pierced through a pilot mill to form hollow tubes with uniform wall thickness.
- Pilotless Tube Milling (Platt Mill): Multi-stand rolling reduces OD and wall thickness to intermediate dimensions with tight tolerances (±0.05 mm).
- Precision Cold Drawing: Tubes are cold-drawn through calibrated dies to achieve final dimensions, surface finish, and mechanical properties. Drawing lubricant is food-grade compliant.
- Solution Annealing: Tubes are heated to 1050°C–1100°C and rapidly quenched in water or controlled atmosphere to restore full austenitic microstructure and eliminate residual stresses.
- Coil Forming: Precision bending equipment forms the straight tube into a helical coil with controlled pitch and diameter, ensuring no kinking, ovality ≤ 1% of OD, or micro-cracking.
- Post-Form Annealing (Optional): Stress-relief annealing at 800°C–900°C to eliminate cold-work hardening introduced during coiling.
- Surface Cleaning & Passivation: Acid pickling (HNO₃/HF blend) followed by passivation to form a stable chromium oxide layer (Cr₂O₃) for maximum corrosion protection.
- Quality Inspection: 100% dimensional inspection (OD, wall thickness, ovality, straightness), ultrasonic flaw detection (UT), and hydrostatic pressure testing (2× working pressure for 30 seconds).
Applications
- Fan Coil Unit (FCU) Systems: Primary application — coil tubes serve as refrigerant-side heat exchange elements in chilled water or direct-expansion FCU systems, enabling precise temperature control in commercial buildings.
- Demand Response HVAC Systems: Optimized for systems employing segmented linear regression models for load quantification and demand-side management (DSM), enabling dynamic modulation of cooling capacity.
- Commercial HVAC: Office buildings, hotels, hospitals, and retail spaces requiring high-efficiency, low-maintenance cooling solutions.
- Industrial Process Cooling: Pharmaceutical clean rooms, food processing facilities, and electronics manufacturing requiring corrosion-resistant heat exchange.
- Marine & Offshore HVAC: Enhanced 316L grade coil tubes resist saltwater corrosion in marine air-conditioning systems.
- Renewable Energy Integration: Compatible with heat pump systems and solar thermal integration for energy-efficient building HVAC.
Quality Certifications & Compliance
- ISO 9001:2015 — Quality Management System certification covering the entire manufacturing and supply chain
- ISO 14001:2015 — Environmental Management System ensuring sustainable production practices
- EN 10204 3.1 — Material test certificates with third-party inspection
- CE Marking — Conformity with European pressure equipment directives (PED 2014/68/EU)
- SGS / Bureau Veritas — Third-party material verification and dimensional inspection reports
- ASME B31.5 — Compliance with pressure piping and piping components code for refrigeration systems
- Hydrostatic Test: 100% batch testing at 2× nominal working pressure, minimum 30-second hold time
- Ultrasonic Testing (UT): Per ASTM E747 for internal defect detection (porosity, inclusions, laminations)
Unique Selling Points
This coil tube product represents a convergence of advanced materials science and intelligent building systems engineering. Key differentiators include:
- Segmented Linear Regression Optimized Design: Coil geometry and fin spacing are engineered to interface with demand response algorithms, enabling quantifiable load reduction and grid-responsive HVAC operation.
- Superior Corrosion Performance: 316L grade option provides exceptional resistance to condensate-induced pitting and chloride stress corrosion cracking (SCC), extending service life beyond 25 years.
- High Thermal Efficiency: Precision-drawn wall thickness (as low as 0.5 mm) minimizes thermal resistance while maintaining structural integrity under cyclic pressure loading.
- Customizable Coil Configuration: Modular pitch and diameter options allow OEM integration into diverse FCU architectures without redesign.
- Full Traceability: Each coil batch carries heat-number traceability with complete mill test certificates, enabling lifecycle asset management in building information modeling (BIM) systems.