Stainless Steel Coil Tube for HVAC Fan Coil Unit Systems
Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component specifically designed for integration into Fan Coil Unit (FCU) heating, ventilation, and air conditioning (HVAC) systems. This product, catalogued under reference number 784, represents an advanced solution for thermal energy transfer applications where energy efficiency, corrosion resistance, and long-term reliability are paramount.
The coil tube is formed by continuous bending of stainless steel seamless or welded pipe into a serpentine or spiral configuration, creating an optimized heat exchange surface area within a compact volumetric envelope. This geometry is fundamental to the operation of fan coil units, which serve as terminal units in hydronic heating and cooling distribution systems. The design principles incorporated in this product align with current research on Fan Coil Unit Heating Energy-Saving and Heat-Saving Control Modes, ensuring that the coil tube contributes to maximum thermodynamic efficiency in both heating and cooling operational cycles.
As a member of the literature and technical study classification (一级分类: 文献学习), this product embodies the latest advancements in coil tube design derived from academic research into energy-saving control strategies for HVAC terminal units. The manufacturing methodology and material selection reflect findings from studies examining optimal heat transfer coefficients, pressure drop minimization, and thermal stratification control within fan coil unit systems.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, thermal conductivity, and corrosion resistance properties essential for HVAC applications involving water-based heat transfer media.
Primary Material Grades
- ASTM A269 / ASME SA-269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service
- ASTM A312 / ASME SA-312 — Standard Specification for Austenitic Stainless Steel Welded Tubing for Chemical and Heat-Transfer Applications
- EN 10216-5 — European Standard for Heat Exchangers and Radiators — Stainless Steel Tubes
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport
Typical Material Composition (Grade 304 / 316)
| Element | Grade 304 (%) | Grade 316 (%) |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.08 |
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 10.0 – 14.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 |
| Manganese (Mn) | ≤ 2.0 | ≤ 2.0 |
| Silicon (Si) | ≤ 1.0 | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.03 | ≤ 0.03 |
Mechanical and Thermal Properties
| Property | Grade 304 | Grade 316 |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 515 MPa | ≥ 485 MPa |
| Yield Strength (屈服强度) | ≥ 205 MPa | ≥ 170 MPa |
| Thermal Conductivity (热导率) at 20°C | 16.3 W/(m·K) | 14.6 W/(m·K) |
| Specific Heat Capacity (比热容) at 20°C | 0.500 J/(g·K) | 0.500 J/(g·K) |
| Density (密度) at 20°C | 8.00 g/cm³ | 8.03 g/cm³ |
| Operating Temperature Range (工作温度范围) | -196°C to +870°C | -196°C to +870°C |
| Elongation (伸长率) | ≥ 40% | ≥ 40% |
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Designation | Stainless Steel Coil Tube (盘管) | — |
| Catalogue Number | 784 | — |
| Outer Diameter (OD) (外径) | 6.0 mm / 8.0 mm / 9.53 mm / 12.7 mm | ASTM B564 |
| Wall Thickness (壁厚) | 0.50 mm / 0.80 mm / 1.00 mm / 1.50 mm | ASTM B564 |
| Coil Pitch (盘管间距) | 15 mm – 25 mm (adjustable) | — |
| Number of Rows (排数) | 2 – 6 rows (configurable) | — |
| Tube Length (管长) | Up to 6000 mm (customizable) | — |
| Bend Radius (弯曲半径) | ≥ 3× OD (minimum) | — |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (interior); Ra ≤ 1.6 μm (exterior) | ASTM A240 |
| End Treatment (端部处理) | Deburred, chamfered, or threaded (per customer specification) | — |
| Maximum Operating Pressure (最大工作压力) | 1.6 MPa – 4.0 MPa (depending on configuration) | EN 10216-5 |
| Hydrostatic Test Pressure (水压试验压力) | 1.5× Maximum Operating Pressure | ASME SA-269 |
| Heat Transfer Coefficient (传热系数) | 1500 – 3500 W/(m²·K) (typical range) | ASHRAE Handbook |
| Pressure Drop (压降) | ≤ 25 kPa at rated flow velocity | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, structural integrity, and optimal thermal performance. The process integrates advanced forming technology with comprehensive quality control at each stage.
- Raw Material Inspection (原材料检验) — Incoming stainless steel pipe or tubing is verified for chemical composition, mechanical properties, and surface quality in accordance with ASTM A312 or EN 10216-5. Each batch is accompanied by a mill test certificate (MTC) confirming conformance to specified grades.
- Cutting and End Preparation (切割与端部处理) — The straight tube stock is cut to the required coil length using precision plasma or mechanical saw cutting. End faces are deburred and chamfered to ensure proper fluid flow entry and prevent turbulence at connection points.
- Coil Forming / Bending (盘管成型/弯曲) — The tube is formed into the serpentine coil configuration using CNC-controlled rotary draw bending (RDB) machines. The bending process employs precision tooling with internal mandrels and external dies to maintain consistent bend radii (≥ 3× OD) and prevent tube wall thinning or ovalization. The coil pitch is maintained within ±0.5 mm tolerance to ensure uniform airflow distribution across the heat exchange surface.
- Welding and Header Assembly (焊接与集管组装) — Individual coil circuits are connected to inlet and outlet headers (集管) using orbital TIG welding (GTAW) or automated laser welding. The welding parameters are optimized to minimize heat-affected zone (HAZ) width and prevent sensitization of the stainless steel microstructure. Post-weld passivation treatment is applied to restore the protective chromium oxide layer.
- Fin Attachment (翅片安装) — Where applicable, aluminum or stainless steel fins (翅片) are mechanically expanded onto the coil tube using a hydraulic fin-tube expander. The expansion process ensures a tight metal-to-metal bond between the tube and fins, minimizing contact thermal resistance and enhancing the overall heat transfer coefficient.
- Surface Treatment and Passivation (表面处理与钝化) — The assembled coil tube undergoes chemical passivation using nitric acid or citric acid solutions to remove surface contaminants and promote the formation of a stable, self-healing chromium oxide passive film. This treatment enhances long-term corrosion resistance, particularly in humid HVAC environments.
- Non-Destructive Testing (NDT) (无损检测) — All weld joints are inspected using dye penetrant testing (DPT) or ultrasonic testing (UT) to verify weld integrity and detect any subsurface defects. The coil tube assembly undergoes a hydrostatic pressure test at 1.5× the maximum rated operating pressure for a minimum dwell time of 30 minutes to confirm leak-tightness.
- Performance Verification (性能验证) — Each production batch is subjected to thermal performance testing in accordance with ARI Standard 270/470 or equivalent, measuring total cooling capacity, sensible cooling capacity, heating capacity, and air-side/water-side pressure drops at rated and part-load operating conditions.
Applications
The stainless steel coil tube is specifically engineered for use in Fan Coil Unit (FCU) systems and related HVAC applications. The product's design parameters are informed by research into Fan Coil Unit Heating Energy-Saving and Heat-Saving Control Modes (风机盘管采暖节电与节热控制模式), ensuring optimal performance across diverse operating scenarios.
Primary Applications
- Commercial HVAC Systems (商业暖通空调系统) — Terminal heating and cooling units in office buildings, hotels, hospitals, and educational facilities where precise temperature and humidity control is required.
- Residential Heating and Cooling (住宅采暖与制冷) — Concealed and exposed fan coil units in residential apartments, villas, and multi-family housing complexes.
- Industrial Process Cooling (工业过程冷却) — Temperature-controlled environments in pharmaceutical manufacturing, food processing, semiconductor fabrication, and laboratory facilities.
- Energy-Saving Control Systems (节能控制系统) — Integration with variable speed drives (VSD) and smart thermostatic control systems to optimize part-load efficiency and minimize energy consumption during heating and cooling cycles.
- Chilled Water Distribution Systems (冷冻水分配系统) — Connection to central chilled water or hot water distribution networks in large-scale commercial and institutional buildings.
- Marine and Offshore HVAC (船舶与海上暖通) — Corrosion-resistant coil tubes for HVAC systems in marine environments where exposure to saltwater and high humidity demands superior material performance.
Energy-Saving Integration Features
Research findings on fan coil unit energy-saving control modes have directly informed the design of this coil tube product. Key energy optimization features include:
- Optimized Coil Geometry — The serpentine coil configuration with precisely controlled pitch and row count maximizes heat exchange surface area while minimizing air-side pressure drop, reducing fan energy consumption.
- Part-Load Performance Enhancement — The tube dimensions and material properties are selected to maintain high heat transfer efficiency across a wide range of water flow rates, supporting variable flow control strategies.
- Low Thermal Mass Design — The stainless steel material's relatively low specific heat capacity enables rapid thermal response to control signals, facilitating faster temperature stabilization and reduced cycling losses.
- Anti-Fouling Surface Characteristics — The passivated stainless steel surface resists scale and biofilm formation, maintaining long-term heat transfer performance and reducing energy penalties associated with fouling.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that all coil tube products meet or exceed international standards. The following certifications and compliance frameworks are applicable:
Management System Certifications
- ISO 9001:2015 — Quality Management Systems (质量管理体系)
- ISO 14001:201