Stainless Steel Coil Tube for VRV HVAC Heating Systems
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 877 | Category: Technical Documentation & Application Engineering
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) is a precision-engineered serpentine heat exchanger tube designed for integration into Variable Refrigerant Volume (VRV) air conditioning systems that incorporate combined hot water heating loops for winter operation. This product represents a critical component in hybrid HVAC architectures where refrigerant-based cooling is supplemented by hydronic heating during cold-season operation, enabling seamless transition between cooling and heating modes within a single system envelope.
Unlike conventional copper coil tubes, the stainless steel construction provides superior resistance to corrosion, thermal fatigue, and chemical degradation, significantly extending service life in demanding commercial and industrial environments. The coil geometry maximizes surface-area-to-volume ratio, ensuring efficient heat transfer between the circulating hot water medium and the ambient air stream drawn through the unit.
2. Material & Properties
2.1 Base Material
- Grade: SUS304 / SUS316L (ASTM A269 / ASTM A213 equivalent)
- Carbon Content (C): ≤ 0.08% (SUS304) / ≤ 0.03% (SUS316L)
- Chromium (Cr): 18.0–20.0%
- Nickel (Ni): 8.0–11.0% (SUS304) / 10.0–14.0% (SUS316L)
- Molybdenum (Mo): 2.0–3.0% (SUS316L only)
2.2 Mechanical & Thermal Properties
| Property | SUS304 | SUS316L |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa | ≥ 520 MPa |
| Yield Strength (屈服强度) | ≥ 205 MPa | ≥ 205 MPa |
| Elongation (延伸率) | ≥ 40% | ≥ 40% |
| Thermal Conductivity (热导率) at 100°C | 16.3 W/(m·K) | 14.6 W/(m·K) |
| Operating Temperature Range (工作温度范围) | −196°C to +870°C | −196°C to +870°C |
| Corrosion Resistance (耐腐蚀性) | Excellent (general environments) | Superior (chloride-rich environments) |
2.3 Surface Finish
The coil tube surface undergoes precision polishing to achieve a roughness value (表面粗糙度) of Ra ≤ 0.8 μm, minimizing fluid friction losses and reducing fouling accumulation. Optional electropolishing (电解抛光) is available to further enhance hygiene and corrosion resistance for food-grade or pharmaceutical applications.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) (外径) | 6 mm, 8 mm, 10 mm, 12 mm, 15 mm, 19 mm (customizable) |
| Wall Thickness (壁厚) | 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm |
| Coil Pitch (管间距) | 8 mm – 25 mm (configurable per thermal load requirements) |
| Coil Width (盘管宽度) | 150 mm – 800 mm (standard); up to 1200 mm (custom) |
| Coil Depth (盘管深度) | 100 mm – 600 mm |
| Tube Length per Coil (单排管长) | 2 m – 12 m |
| Number of Rows (排数) | 1 – 6 rows |
| End Connections (接口形式) | Threaded (NPT / BSP), Flanged, Welded (TIG), or Quick-Connect |
| Operating Pressure (工作压力) | ≤ 1.6 MPa (standard); ≤ 4.0 MPa (reinforced) |
| Test Pressure (试验压力) | 1.5× operating pressure (hydrostatic); 2.0× (pneumatic) |
| Heat Transfer Coefficient (传热系数) | ≥ 85 W/(m²·K) (air-water configuration) |
| Weight (重量) | 1.2 kg – 28 kg (depending on configuration) |
| Standard Compliance (执行标准) | GB/T 14976, GB/T 13296, ASTM A269, EN 10216-5 |
4. Manufacturing Process
- Raw Material Inspection (原材料检验): Incoming stainless steel seamless tubes are verified against mill certificates for chemical composition, mechanical properties, and dimensional tolerance. Spectroscopic analysis (光谱分析) ensures grade conformance.
- Cutting & Deburring (切割与去毛刺): Precision CNC cutting to specified lengths with automated deburring to eliminate edge burrs that could impede fluid flow or damage downstream components.
- Hydroforming & Coil Bending (液压成型与盘绕): Computer-controlled bending machines form the serpentine coil geometry with precise pitch control (±0.5 mm tolerance). Hydraulic forming prevents work-hardening and maintains uniform wall thickness throughout the bend radius.
- Welding (焊接): TIG (Tungsten Inert Gas) welding is employed for header connections and end-fitting attachment. Weld seams are ground and polished to flush with the tube surface to minimize flow disturbance.
- Heat Treatment (热处理): Solution annealing at 1050–1100°C followed by rapid water quenching relieves residual stresses from forming and restores full corrosion resistance. Stress-relief annealing at 450–550°C is applied to welded assemblies.
- Surface Finishing (表面处理): Mechanical polishing (mechanical polishing) or electropolishing achieves the specified surface roughness. Optional passivation treatment (钝化处理) with citric acid or nitric acid solutions enhances passive film integrity.
- Pressure Testing (压力测试): Each coil tube undergoes 100% hydrostatic pressure testing at 1.5× the rated operating pressure with a minimum hold time of 30 minutes. Zero-leakage acceptance criterion is enforced.
- Dimensional & Visual Inspection (尺寸与目视检验): Final quality control includes OD/wall-thickness measurement (ultrasonic thickness gauge), coil pitch verification, and visual examination for surface defects, weld integrity, and finish quality.
- Packaging & Shipping (包装与运输): Coils are individually wrapped in protective film, placed in corrugated boxes with desiccant, and palletized for shipment to prevent mechanical damage and moisture exposure during transit.
5. Applications
5.1 Primary Application: VRV Combined Heating Systems
The principal application domain for this coil tube is the winter heating mode of Variable Refrigerant Volume (VRV) air conditioning systems that integrate a hot water heating loop. In this configuration:
- The stainless steel coil tube functions as the air-side heat exchanger (风侧换热器), transferring thermal energy from the circulating hot water (typically 45–75°C) to the indoor air stream.
- During summer cooling, the coil tube is bypassed or isolated from the hydronic loop, and the refrigerant circuit operates independently.
- During winter heating, the hot water coil supplements or replaces refrigerant-based heating, particularly in extreme cold conditions where heat pump COP (Coefficient of Performance) degrades.
- The hybrid approach achieves Seasonal Energy Efficiency Ratio (SEER) improvements of 15–30% compared to pure refrigerant heating.
5.2 Additional Applications
- Commercial HVAC Systems: Rooftop units (RTUs), air handling units (AHUs), and fan coil units (FCUs) in office buildings, hotels, hospitals, and retail facilities.
- Industrial Process Heating: Precise temperature control in manufacturing environments requiring corrosion-resistant heat exchange (e.g., chemical processing, food and beverage production, pharmaceutical manufacturing).
- Marine & Offshore Systems: Saltwater-resistant heating coils for shipboard HVAC and offshore platform climate control, leveraging SUS316L's superior chloride resistance.
- Geothermal & Solar Thermal Integration: Coil tubes connected to ground-source heat pumps (GSHP) or solar thermal collectors for sustainable building heating.
- Chilled Beam Systems: Perforated coil tubes used in chilled/hot water beam systems for high-performance commercial buildings.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent manufacturing quality and process control |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices |
| CE Marking (EU) | Compliance with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU) |
| GB/T 14976 | Chinese national standard for cold-rolled stainless steel seamless tubes |
| GB/T 13296 | Chinese national standard for seamless stainless steel tubes for pressure purposes |
| ASTM A269 | American standard for welded austenitic stainless steel tubing |
| EN 10216-5 | European standard for welded stainless steel tubes for heat exchangers |
| TÜV / SGS Inspection | Third-party quality inspection and testing reports available upon request |
| Mill Test Reports (MTR) | Batch-specific material traceability documentation provided with every shipment |
7. Unique Selling Points (USP)
Why Choose Wenzhou Jixing Stainless Steel Coil Tubes for VRV Heating Systems:
- Exceptional Corrosion & Durability: Stainless steel construction eliminates the risk of corrosion-induced failure that plagues copper and aluminum coil tubes, especially in high-humidity or chemically aggressive environments. Expected service life exceeds 25 years under normal operating conditions.
- VRV System Integration Expertise: Deep application engineering knowledge in Variable Refrigerant Volume systems with combined hot water heating loops, enabling optimized coil design for peak thermal performance in winter heating mode.
- Precision Manufacturing Tolerance: CNC-controlled coil bending ensures ±0.5 mm pitch accuracy, guaranteeing uniform airflow distribution and consistent heat transfer performance across the entire coil face.
- Customizable Configurations: Flexible design parameters (OD, wall thickness, pitch, dimensions, connection types) allow tailoring to specific thermal load calculations and equipment constraints.
- Hygienic Surface Quality: Ra ≤ 0.8 μm surface finish with optional electropolishing meets food-grade (FDA/3-A) and pharmaceutical (GMP) requirements, expanding application scope beyond standard HVAC.
- Full Traceability: Every coil tube is accompanied by a Mill Test Report (MTR) and pressure test certificate, providing complete material and performance traceability for compliance and warranty purposes.
- Energy Efficiency Contribution: Optimized coil geometry and high thermal conductivity stainless steel grade deliver superior heat transfer coefficients, reducing pump energy consumption and lowering total cost of ownership (TCO).
8. Technical Learning Reference
This product documentation is informed by the technical study of "Application of VRV Air Conditioning Combined Hot Water Coil Tube Technology in Winter Heating" (《VRV空调联合热水盘管技术在冬季采暖中的应用》), which provides critical insights into:
- Thermal performance optimization of hybrid VRV + hydronic heating configurations