Stainless Steel Coil Tube (盘管 Coiltube) — Residential Fan Coil Unit Series
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Catalog No.: 1336
Classification: Literature Study & Technical Reference — Novel Residential Fan Coil Unit Design
Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping component designed primarily for integration into residential fan coil units (FCUs) within heating, ventilation, and air conditioning (HVAC) systems. This product represents a significant advancement in thermal exchange technology, combining the superior corrosion resistance and mechanical durability of austenitic stainless steel with an optimized helical coil geometry that maximizes heat transfer efficiency in compact residential installations.
The coil tube is engineered to address the growing demand for energy-efficient, long-service-life air conditioning components in residential buildings. By leveraging a novel design philosophy documented in the study "A Design of a Novel Residential Fan Coil Unit", this product achieves enhanced thermal performance while reducing overall system footprint and maintenance requirements.
Material Composition & Mechanical Properties
Primary Material Grades
- 304 Stainless Steel (UNS S30400): The standard grade offering excellent general corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- 316L Stainless Steel (UNS S31603): Enhanced grade with 2–3% Molybdenum (Mo) addition, providing superior resistance to pitting and crevice corrosion in aggressive environments such as coastal residential areas or chlorinated water systems.
- 321 Stainless Steel (UNS S32100): Titanium-stabilized variant suitable for elevated-temperature applications where intergranular corrosion resistance is critical.
Key Mechanical & Physical Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa (304 grade) | ASTM A269 / GB/T 12771 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ASTM A269 |
| Elongation (伸长率) | ≥ 40% | ASTM A269 |
| Hardness (硬度) | ≤ 230 HV (annealed condition) | ASTM E92 |
| Thermal Conductivity (导热系数) | ~16.3 W/(m·K) at 20°C | ASTM E153 |
| Density (密度) | 7.93 g/cm³ | — |
| Operating Temperature Range | −196°C to +870°C | — |
| Surface Finish (表面光洁度) | Ra ≤ 0.8 μm (electropolished option available) | ASTM A967 |
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name (产品名称) | Stainless Steel Coil Tube (盘管 Coiltube) |
| Product Catalog No. | 1336 |
| Outer Diameter (OD) Range | 6.0 mm – 25.4 mm (1/4" – 1") |
| Wall Thickness Range | 0.5 mm – 1.5 mm |
| Coil Pitch (螺旋节距) | 15 mm – 40 mm (configurable per application) |
| Coil Diameter (盘管外径) | Φ100 mm – Φ500 mm |
| Number of Turns (圈数) | Customizable, typically 8 – 60 turns |
| End Connection Type | Flared, Threaded (BSP/NPT), Soldered, or Welded |
| Maximum Working Pressure | ≤ 2.5 MPa (cold water); ≤ 1.6 MPa (hot water) |
| Hydrostatic Test Pressure | 3.0 MPa (sustained for 30 minutes) |
| Refrigerant Compatibility | R410A, R32, R134a, R290, R407C, R404A |
| Corrosion Resistance | Equivalent to ASTM G48 (Pitting), ASTM G15 (Erosion-Corrosion) |
| Insulation Option | EPDM foam jacket or PVC wrap (available upon request) |
| Coating (Optional) | Passivation treatment per ASTM A967; Passivation solution per ASTM A380 |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection & Inspection: Stainless steel strip or seamless tube stock is procured from certified mills (e.g., POSCO, Outokumpu, Baosteel) and subjected to incoming quality inspection including chemical composition verification (spectroscopic analysis) and mechanical property testing.
- Coil Forming (盘管成型): High-precision CNC coil forming machines are employed to wind the tube into the specified helical geometry. The forming process is carefully controlled to prevent work hardening, ovality, or residual stress accumulation. Multi-axis servo control ensures consistent coil pitch and diameter throughout the entire length.
- Stress Relief Annealing (去应力退火): Formed coils undergo controlled annealing at 800–1050°C in a protective atmosphere to relieve residual stresses introduced during cold forming, thereby restoring full ductility and corrosion resistance.
- Precision Bending & Shaping: Where specific inlet/outlet configurations are required, CNC bending stations produce precise bends with controlled bend radii (typically ≥ 3× tube OD) to minimize flow restriction and avoid wall thinning.
- Welding & Joining: End connections are fabricated using either orbital TIG welding (GTAW) for seamless joints or brazing with silver-based filler alloys. Weld quality is verified through visual inspection and, where applicable, dye penetrant testing (PT) per ASTM E709.
- Surface Treatment: All finished coils receive passivation treatment per ASTM A967 to enhance surface corrosion resistance. Optional electropolishing (ASTM B919) is available for applications requiring ultra-clean internal surfaces.
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Quality Assurance & Testing: Every production batch undergoes comprehensive testing including:
- Dimensional verification (CMM or laser scanning)
- Hydrostatic pressure testing
- Helium leak detection (for refrigerant applications)
- Chemical composition verification (OES spectroscopy)
- Corrosion testing (salt spray per ASTM B117, 24-hour minimum)
- Packaging & Dispatch: Finished coils are protected with anti-corrosion wrapping, placed in moisture-absorbent packaging, and shipped with full traceability documentation.
Applications
Primary Applications
- Residential Fan Coil Units (住宅用风机盘管): The primary design application, serving as the thermal exchange core in wall-mounted or ceiling-cassette fan coil units for single-family homes, apartments, and small commercial spaces.
- HVAC Chilled Water Systems: Integration into hydronic air distribution systems where the coil tube serves as the heat exchange element between chilled/hot water and the circulated air stream.
- Refrigeration Systems: Use as evaporator or condenser coils in compact refrigeration units for residential food storage, wine cellars, and medical cold storage.
Secondary Applications
- Industrial heat exchange systems requiring corrosion-resistant coiled piping
- Process cooling/heating in pharmaceutical and food-grade equipment
- Geothermal heat pump systems (closed-loop configurations)
- Marine HVAC systems in residential yachts and vessels
- Solar thermal systems as heat collection coils
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent production quality and process control |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| CE Marking (EU) | Compliance with European health, safety, and environmental protection standards |
| EN 10217-7 | European standard for stainless steel tubes for pressure purposes |
| ASTM A269/A269M | Standard specification for welded austenitic stainless steel tubing |
| GB/T 12771 | Chinese national standard for welded stainless steel tubes for general purposes |
| GB/T 14976 | Chinese national standard for seamless stainless steel tubes for fluid transport |
| JIS G3446 | Japanese Industrial Standard for stainless steel tubes |
| ASME B31.5 | American standard for hydronic piping (where applicable) |
Unique Selling Points
1. Novel Residential-Grade Design Optimization: This coil tube is specifically engineered based on the innovative design principles documented in "A Design of a Novel Residential Fan Coil Unit", incorporating optimized coil pitch, tube diameter, and arrangement that maximizes heat transfer coefficient (U-value) while minimizing pressure drop — a critical balance for residential applications where fan power is limited.
2. Superior Corrosion Longevity: The use of high-grade austenitic stainless steel (304/316L) provides a design service life exceeding 25 years in residential HVAC environments, significantly outperforming traditional copper-aluminum coil alternatives in terms of resistance to condensation corrosion and scale buildup.
3. Enhanced Thermal Performance: The precision-formed helical geometry, combined with optional internal surface enhancement (low-fin or micro-channel treatment), achieves thermal efficiency gains of 15–25% compared to conventional coil designs, directly translating to lower energy consumption and reduced operating costs.
4. Full Traceability & Quality Assurance: Each coil tube is produced under a fully traceable quality system with documented material certifications, process parameters, and test results — providing end-users with complete confidence in product reliability and compliance.
5. Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers full customization of coil geometry, dimensions, end connections, and surface treatments to meet specific OEM requirements, enabling seamless integration into diverse residential HVAC system architectures.
Design & Engineering Notes
Based on the study "A Design of a Novel Residential Fan Coil Unit", the following engineering considerations are incorporated into the coil tube design:
- Flow Distribution Optimization: The coil layout is designed to ensure uniform fluid distribution across all passes, minimizing flow maldistribution that degrades overall heat transfer performance.
- Condensate Management: Surface geometry and orientation are optimized to facilitate efficient condensate drainage, preventing waterlogging and associated corrosion risks in cooling mode operation.
- Compact Footprint: The coil tube geometry is designed for maximum heat transfer area per unit volume, enabling integration into space-constrained residential installations.
- Low Refrigerant Charge: Optimized tube diameter and coil arrangement minimize refrigerant charge volume, contributing to environmental sustainability and system cost reduction.
- Acoustic Performance: Tube-to-finned surface interaction is optimized to minimize vibration-induced noise generation, supporting quiet residential operation.
Document Classification: Literature Study & Technical Reference (文献学习)
Source Company: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司)
Product Reference No.: 1336