Stainless Steel Coil Tube — HVAC Fan Coil Unit Series (Model Ref. 917)
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Category: Literature Study / Technical Reference | Series Reference: 917
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) is a precision-engineered tubular component designed primarily for use in Fan Coil Units (FCU) integrated with Fresh Air Air Conditioning Systems. This product represents a critical heat exchange element within commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) infrastructure. The coil tube is manufactured to exacting dimensional tolerances and material specifications to ensure optimal thermal transfer efficiency while addressing acoustic performance requirements inherent to modern indoor climate control systems.
Wenzhou Jixing Metal Materials Co., Ltd. specializes in the production of stainless steel coil tubes that meet international standards for corrosion resistance, mechanical integrity, and long-term operational reliability. The product line is particularly suited for environments demanding low-noise operation, such as hospitals, office buildings, hotels, and precision manufacturing facilities where acoustic comfort is a design priority.
2. Material & Properties
2.1 Base Material Composition
- Primary Alloy: Austenitic Stainless Steel (奥氏体不锈钢) — Grade 304 (UNS S30400) and Grade 316 (UNS S31600)
- Alternative Grades: 321 (UNS S32100), 304L (UNS S30403), 316L (UNS S31603) — low-carbon variants for enhanced weldability
- Key Alloying Elements: Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, Molybdenum (Mo) 2–3% (Grade 316 only), Carbon (C) ≤0.08% (L-grades)
2.2 Mechanical Properties
- Tensile Strength (抗拉强度): ≥520 MPa (Grade 304); ≥550 MPa (Grade 316)
- Yield Strength (屈服强度): ≥205 MPa
- Elongation (延伸率): ≥40%
- Hardness (硬度): ≤200 HB (Brinell)
- Impact Toughness (冲击韧性): ≥47 J at 20°C
2.3 Physical & Corrosion Resistance Properties
- Density (密度): 7.93 g/cm³
- Thermal Conductivity (导热系数): 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient (热膨胀系数): 17.3 × 10⁻⁶ /°C (20–100°C)
- Pitting Resistance (耐点蚀性): PREN (Pitting Resistance Equivalent Number) ≥19 (Grade 316)
- Operating Temperature Range (工作温度范围): -196°C to +870°C
- Corrosion Resistance (耐腐蚀性): Superior resistance to atmospheric corrosion, waterborne contaminants, and mild chemical exposure
3. Specifications
| Parameter (参数) | Specification / Value | Standard / Reference |
|---|---|---|
| Outer Diameter (外径) | 6.0 mm, 7.0 mm, 8.0 mm, 9.53 mm (3/8"), 12.7 mm (1/2") | ASME B36.19M / GB/T 12771 |
| Wall Thickness (壁厚) | 0.5 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm | ASME B36.19M / EN 10216-5 |
| Coil Pitch (盘管间距) | 12 mm, 16 mm, 20 mm, 25 mm (adjustable per design) | ISO 5189 / AHRI 210/240 |
| Coil Length per Bank (每排盘管长度) | 300 mm – 1,200 mm (customizable) | Manufacturer Specification |
| Number of Rows (排数) | 2, 3, 4, 6, 8 rows (configurable) | AHRI 210/240 |
| Material Grade (材料牌号) | SUS 304 / 304L / 316 / 316L / 321 | ASTM A213 / ASTM A269 |
| Surface Finish (表面状态) | Mirror Polish (Ra ≤0.2 μm), Bright Annealed (BA), Pickled & Passivated | ASTM A478 |
| Dimensional Tolerance (尺寸公差) | OD: ±0.1 mm; Wall Thickness: ±0.05 mm | GB/T 14976 / ASTM A213 |
| Pressure Rating (压力等级) | Up to 1.6 MPa (232 psi) working pressure | EN 10216-5 / GB/T 12771 |
| Operating Medium (工作介质) | Water, Glycol-Water Solution (up to 50%), Chilled Water | ASHRAE Standard 90.1 |
| Design Service Life (设计使用寿命) | ≥20 years (under normal operating conditions) | ISO 15510 |
| Acoustic Performance (声学性能) | Sound Power Level ≤35 dB(A) at nominal operating conditions | ISO 3741 / ISO 3744 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection (原材料选择): Cold-rolled stainless steel strip (冷轧不锈钢带) sourced from certified mills, subjected to incoming chemical composition verification (光谱分析) and mechanical testing.
- Tube Forming (制管): Precision roll-forming of strip into seamless tube geometry using multi-stand rotary forming equipment with inline diameter and wall-thickness monitoring (在线壁厚检测).
- Welding (焊接): High-frequency induction welding (高频感应焊接) or laser welding for longitudinal seam closure, ensuring weld integrity with minimum heat-affected zone (HAZ).
- Coil Winding (盘绕成型): Controlled bending of the formed tube into helical coil geometry using CNC-controlled coiling machines to achieve uniform pitch and minimal residual stress (残余应力).
- Heat Treatment (热处理): Solution annealing (固溶处理) at 1010–1150°C followed by rapid air cooling to restore full austenitic microstructure and maximize corrosion resistance.
- Pickling & Passivation (酸洗钝化): Removal of scale and oxide layers via nitric acid/hydrofluoric acid solution, followed by passivation treatment to form protective chromium oxide film (Cr₂O₃).
- Surface Finishing (表面处理): Optional electropolishing (电解抛光) or mechanical polishing to achieve specified surface roughness for enhanced flow characteristics and reduced noise generation.
- Quality Inspection (质量检验): Hydrostatic pressure testing (液压试验), eddy current testing (涡流检测), dimensional verification, and visual inspection per applicable standards.
4.2 Noise Control Integration (噪声控制集成)
Based on technical literature study regarding Fan Coil Unit plus Fresh Air System noise control measures (风机盘管加新风空调系统噪声控制措施), the coil tube design incorporates the following acoustic optimization principles:
- Flow Channel Optimization: Smooth internal surfaces and uniform coil geometry minimize turbulent flow noise (湍流噪声) and reduce aerodynamic sound generation.
- Vibration Damping: Appropriate wall thickness selection and support spacing prevent resonant vibration (共振振动) at fan operating frequencies.
- Hydraulic Balance: Even distribution of flow across coil rows prevents localized high-velocity zones that contribute to fluid-borne noise.
- Material Selection: Stainless steel's inherent damping characteristics (阻尼特性) contribute to reduced structure-borne noise transmission.
5. Applications
5.1 Primary Applications
- Commercial HVAC Systems (商业暖通空调系统): Fan Coil Units in office buildings, shopping malls, hotels, and hospitals
- Residential Climate Control (住宅温控系统): Multi-zone air conditioning systems in high-end residential developments
- Industrial Process Cooling (工业过程冷却): Temperature-controlled environments in electronics manufacturing, pharmaceutical production, and food processing
- Marine & Offshore Applications (海洋及离岸应用): Corrosion-resistant HVAC systems on vessels and offshore platforms (Grade 316/316L)
- Food & Beverage Industry (食品饮料行业): Sanitary-grade coil tubes for temperature-controlled storage and processing areas
5.2 System Integration Context
The coil tube functions as the primary heat exchange surface within a Fan Coil Unit system integrated with a dedicated Fresh Air System (新风系统). In this configuration, the coil tube absorbs or releases thermal energy from the circulating water/glycol medium, transferring this energy to or from the indoor air stream. The noise control measures documented in the associated technical literature ensure that the integrated system operates within acceptable acoustic limits (typically ≤35–40 dB(A) per ASHRAE guidelines for occupied spaces).
6. Quality Certifications & Standards Compliance
6.1 International Standards
- Material Standards: ASTM A213 (Seamless Austenitic Stainless Steel Tubing), ASTM A269 (Welded Austenitic Stainless Steel Tubing)
- Dimensional Standards: ASME B36.19M, EN 10216-5, ISO 1127
- HVAC Performance Standards: AHRI 210/240 (Unitary Air-Conditioning and Air-Source Heat Pump Equipment), ISO 15510 (Fan Coil Units)
- Acoustic Standards: ISO 3741 (Sound Power Measurement), ISO 3744 (Outdoor Sound Power Determination), ASHRAE Handbook — HVAC Applications
- Pressure Testing: ASME Section VIII / EN 10207
6.2 Chinese National Standards
- GB/T 12771: Stainless steel seamless tubes for fluid transport
- GB/T 14976: Cold-rolled (drawn) stainless steel seamless tubes
- GB/T 4237: Cold-rolled stainless steel sheets and strips
- GB/T 1245: General technical conditions for stainless steel bars, rods, and profiles
6.3 Quality Management Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — European Conformity for mechanical equipment
- PED Directive 2014/68/EU — Pressure Equipment Directive compliance (where applicable)
7. Unique Selling Points
7.1 Acoustic-Optimized Design: This coil tube product line is uniquely informed by systematic noise control methodology for Fan Coil Unit + Fresh Air integrated systems, incorporating flow channel optimization and vibration damping principles directly into the coil geometry design.
7.2 Superior Corrosion Resistance: The use of high-grade austenitic stainless steel (304/316/316L) ensures exceptional resistance to condensation water corrosion, chlorides, and aggressive indoor air environments — significantly extending service life beyond carbon steel alternatives.
7.3 Precision Manufacturing: CNC-controlled coiling and tight dimensional tolerances (±0.1 mm OD) ensure consistent performance, predictable hydraulic characteristics, and reliable integration into pre-engineered FCU assemblies.
7.4 Thermal Efficiency: The combination of stainless steel's adequate thermal conductivity with optimized coil geometry and surface finish maximizes heat transfer coefficient (换热系数) while minimizing pressure drop (压降), contributing to energy-efficient system operation per ASHRAE 90.1 requirements.
7.5 Full Traceability: Each coil tube batch is accompanied by mill certificates, chemical analysis reports (化学成分报告), mechanical test results, and dimensional inspection records, ensuring complete quality traceability from raw material to finished product.
8. Technical Literature Reference
This product specification is informed by the technical study document: "浅谈风机盘管加新风空调系统噪声控制措施" (A Brief Discussion on Noise Control Measures for Fan Coil Unit Plus Fresh Air Air Conditioning Systems). The insights derived from this literature have been systematically incorporated into the coil tube design philosophy, particularly regarding:
- Reduction of aerodynamic noise through optimized flow channel geometry
- Minimization of structure-borne vibration via appropriate material properties and support design
- System-level acoustic performance optimization through coordinated component selection
- Compliance with indoor acoustic environment standards (《民用建筑隔声设计规范》GB 50118)
Document Classification: Technical Product Specification | Revision: 1.0 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd