Stainless Steel Coil Tube for HVAC Fan Coil Units
Product Overview
The Stainless Steel Coil Tube (also referred to as Coil Tube or Coiled Tubing) is a precision-engineered stainless steel tubing product specifically designed for use in HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly in Fan Coil Units (FCU). Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube is formed into continuous spiral or serpentine configurations that maximize heat transfer surface area within a compact footprint, making it an essential component in modern air conditioning systems.
Unlike conventional straight pipe assemblies, coil tubes are manufactured in a continuous coil form, which eliminates the need for extensive field welding or brazing joints, thereby reducing potential leak points and improving overall system reliability. The product is engineered in accordance with the principles outlined in Computer-Aided Design (CAD) for Fan Coil Units, ensuring optimal hydraulic and thermal performance through rigorous computational modeling and simulation.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical durability in demanding HVAC environments.
Material Grades
- 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability; suitable for most commercial and residential HVAC applications.
- 316 (UNS S31600) — Enhanced corrosion resistance grade with molybdenum (Mo) addition; recommended for environments with high humidity, salt exposure, or aggressive chemical conditions.
- 304L / 316L (Low-Carbon Variants) — Reduced carbon content grades designed to minimize intergranular corrosion risk during welding operations.
Key Physical & Mechanical Properties
| Property | Specification |
|---|---|
| Density (密度) | 8.0 g/cm³ |
| Thermal Conductivity (热导率) at 20°C | 16.3 W/(m·K) (304) / 14.6 W/(m·K) (316) |
| Thermal Expansion Coefficient (热膨胀系数) | 17.3 × 10⁻⁶ /°C (20–100°C) |
| Tensile Strength (抗拉强度) | ≥ 520 MPa (304) / ≥ 515 MPa (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 |
| Corrosion Resistance (耐腐蚀性) | Excellent resistance to oxidation, acid, and chloride environments |
| Surface Finish (表面光洁度) | Mirror polished (Ra ≤ 0.4 μm) or electropolished available |
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name (产品名称) | Stainless Steel Coil Tube (盘管) |
| Product Catalog No. (序号) | 1543 |
| Outer Diameter (OD, 外径) | 6.35 mm (1/4") to 25.4 mm (1") |
| Wall Thickness (壁厚) | 0.5 mm to 2.0 mm |
| Coil Pitch (盘管节距) | Customizable; typically 12 mm to 40 mm |
| Coil Diameter (盘管直径) | 50 mm to 300 mm (standard); custom sizes available |
| Tube Length (管长) | Up to 50 m continuous coil length |
| Coil Configuration (盘管形式) | Spiral coil, serpentine coil, double-pass coil, multi-row coil |
| End Connection (端部连接) | Flared, threaded (NPT/BSP), flanged, or brazed fittings |
| Working Pressure (工作压力) | Up to 2.5 MPa (standard); high-pressure variants up to 4.0 MPa |
| Hydrostatic Test Pressure (水压试验压力) | 1.5× working pressure (per ASME standards) |
| Applicable Media (适用介质) | Water, glycol-water mixtures, refrigerants (R22, R410A, R32, R134a) |
| Tolerance on OD (外径公差) | ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness (壁厚公差) | ±10% of nominal |
Manufacturing Process
The production of high-quality stainless steel coil tubes for HVAC applications involves a multi-stage manufacturing process that integrates traditional metalworking techniques with modern computer-aided design and engineering (CAE) methodologies:
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Raw Material Selection & Inspection (原材料选择与检验)
High-purity stainless steel strip or seamless tube stock is sourced from certified mills. Incoming materials undergo spectroscopic analysis (PMI — Positive Material Identification) to verify chemical composition compliance with ASTM, EN, or JIS standards.
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Computer-Aided Design & Simulation (计算机辅助设计与仿真)
Following the methodology described in CAD for Fan Coil Units, each coil tube geometry is designed using advanced CAD software (e.g., AutoCAD, SolidWorks, CATIA). Computational Fluid Dynamics (CFD) simulations are performed to optimize coil pitch, tube count, and layout for maximum heat exchange efficiency while minimizing pressure drop (ΔP) across the coil assembly.
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Coiling & Forming (盘管成型)
Stainless steel tube is precisely coiled using CNC-controlled coiling machines that maintain consistent coil diameter, pitch, and spring-back compensation. The forming process is designed to avoid work hardening, material thinning, or ovality beyond acceptable tolerance limits.
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Welding & Joining (焊接与连接)
Where multi-pass or multi-row configurations are required, tube joints are fabricated using Orbital TIG (Tungsten Inert Gas) welding or Laser Welding to ensure full-penetration, leak-tight seams. Weld parameters are calibrated to prevent chromium carbide precipitation (sensitivity) at heat-affected zones (HAZ).
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Heat Treatment & Stress Relief (热处理与去应力)
Post-forming annealing (solution treatment) is performed at 1050°C–1100°C followed by controlled cooling to restore full solution-hardened properties, relieve residual stresses, and ensure dimensional stability.
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Surface Finishing & Cleaning (表面处理与清洁)
Inner and outer surfaces are cleaned using ultrasonic degreasing and, if required, electropolishing to achieve a smooth, hygienic surface suitable for potable water or food-grade HVAC applications. Surface roughness is verified using profilometry.
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Quality Control & Testing (质量控制与检测)
Each coil tube undergoes comprehensive non-destructive testing (NDT), including:
- Hydrostatic Pressure Testing — Verifies integrity at 1.5× rated pressure for a minimum of 30 seconds.
- Helium Leak Testing — Detects micro-leaks at sensitivity levels of 1 × 10⁻⁹ mbar·L/s.
- Dye Penetrant Testing (DPT) — Inspects weld seams and formed bends for surface discontinuities.
- Dimensional Inspection — Verified using coordinate measuring machines (CMM) and laser scanning.
Applications
The stainless steel coil tube is a critical heat exchanger component in a wide range of HVAC and thermal management systems:
Primary Applications
- Fan Coil Units (风机盘管, FCU) — The primary application domain. The coil tube serves as the air-side heat exchange element in both cooling and heating modes, transferring thermal energy between the circulating fluid (water or glycol) and the ambient air.
- Air Conditioners (空调器) — Used in central air conditioning systems, split systems, and rooftop units (RTU) as the evaporator or condenser coil.
- Chilled Water Systems (冷冻水系统) — High-performance coil tubes for large-scale commercial and industrial chilled water distribution networks.
Secondary Applications
- Heat Recovery Ventilators (HRV) & Energy Recovery Ventilators (ERV) — Coil tubes used in cross-flow or run-around loop heat exchangers for energy-efficient ventilation.
- Industrial Process Cooling — Precision temperature control coils in semiconductor manufacturing, pharmaceutical production, and food processing facilities.
- Automotive HVAC — Miniaturized coil tubes for vehicle climate control systems requiring corrosion-resistant, lightweight heat exchangers.
- Marine HVAC Systems — 316-grade coil tubes for shipboard air conditioning where saltwater corrosion resistance is paramount.
- Refrigeration Systems — Evaporator and condenser coils in commercial refrigeration units for supermarkets, cold storage, and ice-making equipment.
Unique Selling Points
- Superior Corrosion Resistance — Austenitic stainless steel construction provides exceptional resistance to corrosion from humid air, condensate, and chemical contaminants, significantly extending service life compared to copper or aluminum coils.
- Hygienic & Food-Grade Compatible — Smooth inner bore surface (Ra ≤ 0.4 μm) inhibits bacterial growth and biofilm formation, making the coil tube suitable for cleanroom HVAC and food processing applications.
- CAD-Optimized Performance — Each coil geometry is designed using advanced computational methods to maximize heat transfer coefficient (U-value) and minimize fluid-side pressure drop, resulting in lower energy consumption and reduced fan motor sizing.
- Elimination of Leak-Prone Joints — Continuous coil design minimizes the number of connections, reducing the probability of refrigerant or water leaks in the field.
- Wide Operating Envelope — Capable of withstanding extreme temperatures (−196°C to +870°C), pressure fluctuations, and thermal cycling without degradation of mechanical properties.
- Customizability — Fully customizable OD, wall thickness, coil pitch, row count, and end-fitting configuration to meet specific OEM (Original Equipment Manufacturer) requirements.
- Environmental Sustainability — Stainless steel is 100% recyclable and fully compatible with low Global Warming Potential (GWP) refrigerants (R32, R410A, R1234ze), supporting compliance with international environmental regulations.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a rigorous quality management system ensuring that all coil tube products meet or exceed international standards:
| Standard / Certification | Scope of Compliance |
|---|---|
| ISO 9001:2015 (质量管理体系) | Quality Management System certification for design, manufacturing, and supply chain processes |
| ISO 14001:2015 (环境管理体系) | Environmental Management System covering waste reduction, emissions control, and sustainable manufacturing practices |
| ASTM A269 / A270 (美国材料与试验协会标准) | Standard specification for seamless and welded austenitic stainless steel tubing |
| EN 10216-5 (欧洲标准) | Non-alloy and alloy steel tubes for heat exchangers and similar heat transfer apparatus |
| ASME B31.5 (美国机械工程师学会) | Pressure piping and components for refrigeration and air-conditioning equipment |
| GB/T 14976 (中国国家标准) | Specification for seamless stainless steel tubes for fluid transport |
| NSF/ANSI 61 (美国国家卫生基金会) | Drinking water system components — Health effects certification (where applicable for potable water systems) |
| RoHS / REACH (欧盟指令) | Restriction of Hazardous Substances and Regulation on chemicals — Ensuring compliance with EU environmental and health regulations |
Quality Commitment: Every coil tube produced by Wenzhou Jixing Metal Materials Co., Ltd is traceable to its raw material heat number and undergoes a documented inspection protocol. Full material test reports (MTR), dimensional inspection certificates, and NDT reports are provided with each shipment to ensure complete supply chain transparency and regulatory compliance.
Technical Summary
The Stainless Steel Coil Tube (Product No. 1543) from Wenzhou Jixing Metal Materials Co., Ltd represents the convergence of advanced metallurgical engineering, precision manufacturing, and computer-aided thermal design. By leveraging CAD-optimized coil geometries, high-grade austenitic stainless steel materials, and rigorous quality assurance protocols, this product delivers outstanding thermal performance, exceptional durability, and long-term reliability for HVAC fan coil units and related heat exchange applications. Its compliance with international standards (ASTM, EN,