Stainless Steel Coil Tube (盘管) for Fan Coil Units — Technical Specification
Product Overview
The Stainless Steel Coil Tube (盘管), manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 537), is a precision-engineered coiled tubing product designed primarily for integration into Fan Coil Units (FCUs, 风机盘管机组). Fan coil units are terminal air-conditioning devices widely deployed in commercial, industrial, and residential HVAC (Heating, Ventilation, and Air Conditioning) systems. The coil tube serves as the core heat-exchange element within these units, facilitating efficient thermal transfer between circulating refrigerant or hot water and the ambient air stream.
This product represents the culmination of decades of metallurgical innovation and process refinement in the stainless steel tube industry. Wenzhou Jixing Metal Materials Co., Ltd. leverages advanced cold-drawing, seamless tube forming, and multi-axis coiling technologies to deliver coil tubes that meet or exceed international performance benchmarks for thermal conductivity, pressure resistance, and long-term corrosion durability.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, corrosion resistance, and thermal performance characteristics.
Primary Alloy Grades
- SAE 304 (UNS S30408) — The standard grade for general-purpose HVAC applications, offering excellent corrosion resistance in moderate environments with a chromium (Cr) content of 18–20% and nickel (Ni) content of 8–10.5%.
- SAE 316 (UNS S31608) — Enhanced grade with 2–3% molybdenum (Mo) addition, providing superior resistance to chlorides, sulfates, and aggressive chemical environments. Preferred for coastal installations and industrial HVAC systems.
- SAE 321 (UNS S32108) — Stabilized with titanium (Ti), suitable for elevated-temperature service and applications requiring resistance to intergranular corrosion.
Key Physical & Mechanical Properties
- Density (密度): 8.0 g/cm³
- Thermal Conductivity (热导率): 14.6–16.3 W/(m·K) at 20°C
- Specific Heat Capacity (比热容): 500 J/(kg·K)
- Tensile Strength (抗拉强度): ≥ 520 MPa (SAE 304); ≥ 515 MPa (SAE 316)
- Yield Strength (屈服强度): ≥ 205 MPa
- Elongation (延伸率): ≥ 40%
- Operating Temperature Range (工作温度范围): −196°C to +870°C
- Maximum Working Pressure (最大工作压力): Up to 1.6 MPa (configurable up to 4.0 MPa upon request)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name (产品名称) | Stainless Steel Coil Tube (盘管) | — |
| Product Code (序号) | 537 | Internal Catalog |
| Tube Outer Diameter (外径) | 6.35 mm / 8.0 mm / 9.53 mm / 12.7 mm (customizable) | ASTM A269 / GB/T 12771 |
| Tube Wall Thickness (壁厚) | 0.5 mm – 1.0 mm (standard); up to 1.5 mm available | ASTM A269 / GB/T 12771 |
| Coil Diameter (盘管直径) | 500 mm – 1,200 mm (configurable) | Custom |
| Coil Height (盘管高度) | 100 mm – 400 mm (configurable) | Custom |
| Tube Length per Coil (单管长度) | 15 m – 120 m (configurable) | Custom |
| Fin Pitch (翅片间距) | 1.5 mm – 3.0 mm (for finned coil variants) | ASHRAE 34 |
| Fin Material (翅片材料) | Aluminum (Al 1100) or Stainless Steel (304/316) | ASTM B209 |
| Surface Finish (表面状态) | Bright Annealed (BA) or 2B Finish; Ra ≤ 0.8 μm | ASTM A473 |
| Heat Transfer Coefficient (传热系数) | 800 – 1,200 W/(m²·K) (air-side, typical) | ASHRAE Handbook |
| Refrigerant Compatibility (制冷剂兼容性) | R-410A, R-32, R-134a, R-404A, Water/Glycol Mixtures | ASHRAE 34 |
| Design Life (设计寿命) | ≥ 25 years (under normal operating conditions) | Manufacturer's Specification |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing protocol designed to ensure dimensional accuracy, metallurgical integrity, and consistent performance across every unit produced.
-
Raw Material Selection & Incoming Inspection (原材料选择与来料检验)
Stainless steel strips or seamless tubes are sourced from certified mills. Each batch undergoes spectroscopic analysis (spectrometer-based chemical composition verification), mechanical property testing (tensile, hardness, impact), and visual surface inspection to confirm compliance with ASTM A269 or GB/T 12771 requirements. -
Tube Forming & Cold Drawing (管材成型与冷拔)
Precise cold-drawing processes are employed to achieve the target outer diameter and wall thickness with tolerances within ±0.05 mm. This step eliminates surface defects, improves grain structure uniformity, and enhances mechanical properties through controlled work hardening. -
Intermediate Annealing (中间退火)
Tubes are subjected to controlled furnace annealing (typically at 1,050–1,100°C in a protective atmosphere or vacuum) to relieve residual stresses, restore ductility, and prevent cracking during subsequent forming operations. -
Coiling / Spiral Winding (盘绕成型)
Multi-axis CNC-controlled coiling machines wind the tube into the specified helical or spiral configuration. Precision servo motors ensure uniform coil pitch, consistent center-to-center spacing between tube passes, and accurate overall coil geometry. The coiling process is monitored in real-time via laser measurement systems to maintain dimensional tolerance within ±1.0 mm for coil diameter and ±0.5 mm for pass spacing. -
Fin Attachment (翅片装配) — if applicable
For finned coil variants, aluminum or stainless steel fins are pressed onto the coiled tube using high-speed finning machines. Fin engagement depth is controlled to ensure optimal thermal contact while minimizing flow resistance. -
Final Annealing & Passivation (最终退火与钝化处理)
A final low-temperature annealing cycle (400–500°C) stabilizes the microstructure without significantly reducing strength. Passivation treatment using nitric acid or citric acid solutions removes free iron contaminants and enhances the passive chromium oxide film, improving long-term corrosion resistance. -
Hydrostatic Pressure Testing (水压试验)
Every coil tube undergoes 100% hydrostatic pressure testing at 1.5× the maximum working pressure, with a minimum hold time of 30 seconds. Any unit exhibiting pressure drop beyond specified limits is immediately rejected. -
Final Inspection & Packaging (最终检验与包装)
Completed units undergo dimensional verification, visual surface inspection, and documentation review. Each coil tube is individually wrapped in protective film, boxed, and palletized for shipment, with accompanying material test reports (MTR) and certificates of conformity.
Applications
The Stainless Steel Coil Tube (Product No. 537) finds extensive application across multiple sectors, driven by its superior thermal performance, corrosion resistance, and design flexibility:
- Fan Coil Units (风机盘管机组, FCUs) — The primary application. Coil tubes serve as the evaporator or condenser heat-exchange core within FCUs installed in office buildings, hotels, hospitals, and residential complexes. The coil tube's geometry and material properties directly determine the unit's cooling/heating capacity, efficiency (EER/COP), and noise performance.
- Chilled Water & Hot Water Distribution Systems (冷冻水/热水系统) — Used in secondary loop heat exchangers for large-scale HVAC systems, including air handling units (AHUs) and variable air volume (VAV) systems.
- Industrial Process Cooling (工业过程冷却) — Deployed in chemical processing plants, pharmaceutical manufacturing facilities, and food processing operations where resistance to corrosive media is critical.
- Refrigeration & Cold Storage (制冷与冷链) — Utilized in evaporator coils for walk-in coolers, freezers, and industrial cold rooms operating at sub-zero temperatures.
- Renewable Energy Systems (可再生能源系统) — Integrated into solar thermal collectors and heat pump systems where long-term outdoor durability is essential.
Development Context — Fan Coil Unit Industry Evolution (风机盘管机组行业发展沿革)
The evolution of fan coil unit technology has been a defining trajectory in modern HVAC engineering. Early FCUs relied on simple copper-fin-and-tube (CFT) heat exchangers with limited efficiency and durability. The progressive adoption of stainless steel coil tubes — as championed by manufacturers like Wenzhou Jixing Metal Materials Co., Ltd. — has addressed longstanding challenges including corrosion-induced failure, refrigerant leakage, and reduced service life in humid or chemically aggressive environments. Contemporary FCU designs incorporating advanced stainless steel coil geometries achieve thermal efficiencies (COP) exceeding 4.0 for heat pump variants, representing a >40% improvement over first-generation systems. Looking forward, the integration of smart controls, variable-speed drives, and high-temperature superconducting (HTS) refrigerant circuits promises further performance gains, with stainless steel coil tubes remaining a foundational component due to their unmatched material versatility.
Quality Certifications & Standards Compliance
All products are manufactured in strict accordance with the following international and national standards, and the manufacturing facility holds the following certifications:
- ISO 9001:2015 — Quality Management System (质量管理体系)
- ISO 14001:2015 — Environmental Management System (环境管理体系)
- ISO 45001:2018 — Occupational Health and Safety Management System (职业健康安全管理体系)
- CE Marking — European Conformity for pressure equipment (Directive 2014/68/EU)
- ASME (American Society of Mechanical Engineers) — Certified for pressure vessel and heat exchanger components
- EN 10216-5 — European standard for non-alloy steel and stainless steel seamless tubes for technical purposes
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes for general industrial purposes
- GB/T 14976 — Chinese national standard for seamless stainless steel cold-drawn tubes
- ASTM A269 — Standard specification for austenitic stainless steel seamless, cold-drawn tubing
- ASTM A270 — Standard specification for austenitic stainless steel welded tubing
Traceability & Documentation
- Every production batch is accompanied by a Material Test Report (MTR, 材质证明书) including full chemical composition analysis (via optical emission spectrometry, OES), mechanical property test results, and heat treatment records.
- Unique batch identification codes enable full production traceability from raw material mill certificate through final product delivery.
- Third-party inspection by recognized agencies (SGS, TÜV, BV) is available upon customer request.
Unique Selling Points
- Superior Corrosion Resistance — Austenitic stainless steel construction with passivated surfaces delivers exceptional resistance to condensation water, chlorides, and aggressive HVAC fluids, extending service life beyond 25 years in demanding environments.
- Precision Dimensional Accuracy — CNC-controlled coiling ensures coil geometry tolerances within ±1.0 mm, enabling seamless integration into standardized and custom FCU housings without field modification.
- Enhanced Thermal Efficiency — Optimized tube pass configuration and optional fin geometry maximize the heat transfer surface area-to-volume ratio, achieving U-values of 800–1,200 W/(m²·K) and reducing fan power consumption by up to 15% compared to conventional copper alternatives.
- Full Refrigerant Compatibility — Certified for use with all current-generation refrigerants including R-32 and R-410A, ensuring future-proofing against regulatory phase-outs of high-GWP (Global Warming Potential) refrigerants.
- Customizable Engineering — Flexible configuration options for tube diameter, wall thickness, coil geometry, and fin specifications allow tailored solutions for specialized industrial and commercial applications.
- Comprehensive Quality Assurance — 100% hydrostatic testing, full-spectrum material traceability, and multi-system ISO certifications provide unparalleled confidence in product reliability and regulatory compliance.