Stainless Steel Coil Tube — Fan Coil Unit (FCU) Heat Exchange Series
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubing product specifically designed for use in Fan Coil Unit (FCU) air conditioning systems, heat exchangers, and hydronic heating/cooling circuits. This product represents an advanced integration of metallurgical expertise and thermal-fluid engineering principles, optimized to meet the rigorous demands of modern HVAC (Heating, Ventilation, and Air Conditioning) system design and operation.
The coil tube is formed from high-grade austenitic stainless steel wire through a continuous cold-coiling process, producing a helical tube geometry that maximizes heat transfer surface area per unit volume. Its application in fan coil air conditioning systems has been extensively studied and validated through systematic design calculation methodologies, ensuring predictable and reliable thermal performance across a broad range of operating conditions.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, selected for their outstanding combination of corrosion resistance, thermal conductivity, mechanical strength, and long-term durability in humid and corrosive environments typical of HVAC systems.
Base Material Specifications
- Primary Grade: AISI 304 / SUS304 (Austenitic Stainless Steel, 18% Cr, 8% Ni)
- Alternative Grade: AISI 316 / SUS316 (with 2% Mo for enhanced pitting resistance)
- Wire Form: Cold-drawn seamless stainless steel tube, annealed and pickled
- Surface Finish: 2B (cold-rolled, annealed) or BA (Bright Annealed) for high thermal contact efficiency
Key Material Properties
| Property | Grade 304 | Grade 316 | Test Standard |
|---|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ≥ 485 MPa | ASTM A270 / GB/T 12771 |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ≥ 170 MPa | ASTM A270 |
| Elongation (A₅₀) | ≥ 40% | ≥ 35% | ASTM A270 |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | ASTM A270 |
| Corrosion Resistance | Excellent (general) | Superior (chloride/pitting) | ASTM A967 (Pickling) |
| Operating Temperature Range | −196°C to +870°C | −196°C to +870°C | — |
| Chromium Content | 18.0–20.0% | 16.0–18.0% | ASTM A270 |
| Nickel Content | 8.0–10.5% | 10.0–14.0% | ASTM A270 |
| Molybdenum Content | — | 2.0–3.0% | ASTM A270 |
Specifications
The following table presents the dimensional and geometric specifications available for this coil tube product line, tailored to meet the requirements of fan coil unit and hydronic heat exchange system design:
| Parameter | Specification | Notes |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 22.0 mm | Incremental selection per system design |
| Wall Thickness | 0.50 mm – 1.50 mm | Optimized for pressure rating and heat transfer |
| Coil Pitch (Helical Spacing) | 8.0 mm – 25.0 mm | Determines airflow resistance and heat transfer area |
| Coil Diameter (Bundle) | 150 mm – 600 mm | Adaptable to FCU casing dimensions |
| Tube Length (Developed) | 3.0 m – 50.0 m | Continuous coil or custom-cut assemblies |
| Pressure Rating | Up to 1.6 MPa (16 bar) | Hydrostatic tested per batch |
| Surface Roughness (Ra) | ≤ 0.8 μm | Minimizes flow resistance in hydronic circuits |
| End Treatment | Cut, deburred, or flanged | Custom per customer specification |
| Coil Quantity per Package | 1 – 200 pcs | Customized per order volume |
| Applicable Standards | ASTM A270, GB/T 12771, EN 10217 | Conforms to multi-regional code requirements |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and consistent thermal performance:
- Raw Material Selection: Hot-rolled stainless steel strip or seamless pipe blanks are procured from certified mills, with full chemical composition verification via Spectroscopy (Optical Emission Spectrometry, OES) analysis.
- Cold Drawing: The seamless tube or strip is cold-drawn through precision tungsten carbide dies to achieve the target outer diameter and wall thickness with tight dimensional tolerances (±0.05 mm).
- Intermediate Annealing: Periodic solution annealing (1050–1100°C) is performed during cold working to relieve residual stresses and restore ductility, preventing cracking during subsequent forming operations.
- Precision Coiling (Forming): The drawn tube is fed through a CNC-controlled coiling head that produces a uniform helical coil with controlled pitch, coil diameter, and spring-back compensation. The forming process maintains full material properties without localized thinning.
- Final Annealing & Pickling: The formed coil undergoes final bright annealing (BA) or acid pickling (per ASTM A967) to remove surface scale, restore the passive chromium oxide layer, and achieve the required surface finish.
- Quality Inspection: Each batch undergoes dimensional verification (OD, wall thickness, pitch), hydrostatic pressure testing, visual surface inspection, and periodic mechanical property testing.
- End Processing & Packaging: Tubes are cut to length, ends are deburred or flanged as specified, and products are packaged in protective wraps with moisture-absorbent desiccants for export readiness.
Applications
The stainless steel coil tube is engineered for a wide range of thermal-fluid applications, with particular emphasis on the following sectors:
- Fan Coil Unit (FCU) Air Conditioning Systems: The primary design application. The coil tube serves as the heat exchange element within fan coil units, transferring thermal energy between circulating water (hot or chilled) and the air stream. System design calculations — including coil performance ratings, air-side and water-side pressure drops, and capacity derating factors — are performed using validated engineering methodologies to ensure optimal system performance.
- Chilled Water & Hot Water Heat Exchangers: Used in shell-and-coil heat exchangers for district heating, chilled water distribution, and process cooling systems.
- Commercial & Industrial HVAC: Air handling units (AHUs), rooftop units (RTUs), and unitary air conditioners in commercial buildings, hospitals, and manufacturing facilities.
- Refrigeration & Cryogenic Systems: Low-temperature heat exchangers where austenitic stainless steel retains ductility and strength at sub-ambient temperatures.
- Food & Pharmaceutical Processing: Hygienic-grade heat exchangers where corrosion resistance and cleanability are critical requirements.
- Marine & Coastal HVAC: Grade 316 coil tubes provide superior resistance to chloride-induced pitting corrosion in humid, salt-laden coastal environments.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that all stainless steel coil tube products meet or exceed international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and supply chain processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating environmental responsibility in production.
- CE Marking (EN 10217) — European conformity marking for pressure equipment components.
- ASTM A270 Compliance — Full compliance with American Society for Testing and Materials specifications for austenitic stainless steel seamless and welded tubing.
- GB/T 12771 Compliance — Chinese national standard for stainless steel seamless and welded tubing for general engineering purposes.
- Material Test Reports (MTR) — Each production batch is accompanied by a full mill test certificate documenting chemical composition, mechanical properties, and heat treatment records.
- Hydrostatic Pressure Testing — 100% batch testing at 1.5× working pressure, with documented test records.
- Third-Party Inspection — Available upon customer request (SGS, BV, TÜV verification programs).
Unique Selling Points
- System-Integrated Design: Product specifications are developed with full consideration of fan coil unit design calculation methodologies, ensuring that coil geometry, material properties, and flow characteristics are harmonized for optimal thermal-hydraulic performance.
- Full Traceability: Every coil tube batch is traceable from raw steel mill origin through final inspection, providing complete supply chain transparency.
- Custom Engineering Support: Technical consultation is available for custom coil configurations, including pitch optimization, bundle layout design, and system-level thermal performance modeling.
- Corrosion-Durability Advantage: Stainless steel coil tubes eliminate the need for internal coatings or cathodic protection, reducing lifecycle maintenance costs in aggressive HVAC water chemistries.
- Multi-Grade Flexibility: Availability in both Grade 304 and Grade 316 provides customers with cost-optimized material selection based on specific application environment and corrosion requirements.
Note: All specifications are subject to verification against the latest product data sheets issued by Wenzhou Jixing Metal Materials Co., Ltd. Customers are advised to consult with our engineering team for project-specific material selection and dimensional configuration recommendations based on the thermal load, flow rate, and environmental conditions of their intended application.