Stainless Steel Coil Tube — Dual-Coil Temperature and Humidity Independent Control System Component
Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered heat exchange element designed for integration into dual-coil cooling source temperature and humidity independent control systems (T&H Independent Control System). This product serves as the core thermal transfer component within advanced HVAC (Heating, Ventilation, and Air Conditioning) applications where simultaneous and independent regulation of air temperature and humidity is required. The coil tube is formed into a continuous serpentine or spiral configuration that maximizes surface area-to-volume ratio, enabling superior thermal efficiency in both sensible and latent heat exchange processes.
Unlike conventional single-coil systems, the dual-coil architecture employs two distinct coil tubes — a primary coil for sensible heat removal and a secondary coil for latent heat (moisture) extraction — allowing decoupled control of indoor air temperature and relative humidity. This product is catalogued under reference number 759 in the manufacturer's literature study and technical documentation series.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, mechanical strength, and long-term durability in aggressive HVAC environments.
- Base Material: Austenitic Stainless Steel (奥氏体不锈钢), conforming to ASTM A269 / ASTM A270 standards
- Common Grades: SUS304 (UNS S30400), SUS316L (UNS S31603) for high-chloride environments
- Chromium Content: 18.0% – 20.0% (minimum), providing passive oxide film stability
- Nickel Content: 8.0% – 10.5%, ensuring austenitic microstructure and ductility
- Surface Finish: Electropolished or passivated (Ra ≤ 0.4 μm), minimizing fouling and biofilm adhesion
- Operating Temperature Range: −40 °C to +250 °C (continuous); short-term peak tolerance up to 300 °C
- Corrosion Resistance: Superior resistance to condensation water corrosion, chlorides, and organic acids common in HVAC condensate environments
- Thermal Conductivity: 14.9 – 16.3 W/(m·K) at 20 °C, ensuring efficient heat transfer between refrigerant and process air
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20 °C – 100 °C), compatible with expansion joint design
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Category | Coil Tube (盘管) — Heat Exchanger Element | — |
| Reference No. | 759 | Manufacturer Catalog |
| Tube Outer Diameter (OD) | 7.0 mm / 8.0 mm / 9.52 mm / 12.0 mm | ASTM A270 |
| Tube Wall Thickness | 0.5 mm – 1.2 mm | ASTM A270 |
| Fin Material | Aluminum (1100-H14) or Stainless Steel (SUS304) | GB/T 3190 |
| Fin Pitch | 1.8 mm – 3.0 mm (adjustable per thermal load) | — |
| Fin Density | 21 – 56 fins per inch (FPI) | — |
| Tube Layout | Double-row, Triple-row, or Multi-row serpentine | — |
| Coil Length | Custom (typically 1.5 m – 6.0 m per section) | — |
| Working Pressure | 1.6 MPa (refrigerant side); 0.6 MPa (water side) | GB/T 151 |
| Hydrostatic Test Pressure | 2.4 MPa (refrigerant); 0.9 MPa (water) | GB/T 151 |
| Refrigerant Compatibility | R410A, R32, R134a, R22, R407C | ASHRAE 34 |
| Cooling Capacity Range | 2.0 kW – 50.0 kW (per coil unit, dependent on configuration) | — |
| Temperature/Humidity Control | Independent sensible and latent heat control via dual-coil architecture | ASHRAE 62.1 |
| Weight | 0.8 kg – 8.5 kg (per standard unit) | — |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd (温州吉兴金属材料有限公司) | — |
Manufacturing Process
The production of this stainless steel coil tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and thermal performance:
- Material Selection and Inspection: Stainless steel seamless or welded tubes are sourced from certified mills and subjected to incoming inspection including chemical composition analysis (OES spectroscopy), mechanical property testing, and visual surface examination.
- Cutting and Forming: Tubes are precision-cut to specified lengths using automated laser or plasma cutting systems. Tubes are then formed into serpentine or spiral configurations using CNC-controlled tube bending machinery, maintaining a minimum bend radius of 2.5× the tube OD to prevent ovalization and wall thinning.
- Fin Insertion / Finning: Aluminum or stainless steel fins are inserted into the tube array using automated fin-insertion machinery, or the tubes are mechanically finned using rotary finning tools. Fin-to-tube contact resistance is minimized through crimping or brazing processes.
- Header Assembly: Inlet and outlet headers (manifolds) are fabricated from stainless steel plate or tube, and joined to the coil tubes via high-integrity brazing (phosphorus-copper or silver-based filler) or TIG (Tungsten Inert Gas) welding with argon shielding.
- Pressure Testing: Each completed coil unit undergoes hydrostatic pressure testing at 1.5× the maximum working pressure, held for a minimum of 30 minutes with no visible leakage or pressure drop exceeding 0.5%.
- Surface Treatment: Post-weld passivation or electropolishing is performed to restore the passive chromium oxide film, ensuring long-term corrosion resistance. All surfaces are cleaned of flux residues and contaminants.
- Final Quality Assurance: Dimensional verification, leak testing (helium or nitrogen), and thermal performance validation are conducted prior to packaging and shipment.
Applications
The dual-coil stainless steel tube system is designed for advanced HVAC applications requiring precise, independent control of both air temperature and humidity. Key application domains include:
- Commercial and Institutional HVAC Systems: Office buildings, hospitals, laboratories, and educational facilities where occupant comfort and indoor air quality (IAQ) are critical. The dual-coil configuration enables the primary coil to handle sensible cooling while the secondary coil manages dehumidification, eliminating the overcooling and reheat energy penalty inherent in single-coil systems.
- Industrial Process Cooling: Pharmaceutical cleanrooms, semiconductor fabrication facilities, and food processing plants requiring stringent temperature and humidity control to ensure product quality and regulatory compliance.
- Fresh Air Supply Systems (新风系统): As studied in the referenced literature on dual-coil cooling source fresh air supply methods, the coil tube serves as the heat exchange medium in dedicated outdoor air systems (DOAS), treating incoming fresh air independently of recirculated indoor air for optimal ventilation efficiency.
- Energy-Efficient Retrofitting: Replacement of legacy single-coil systems with dual-coil stainless steel coil tubes in existing buildings to achieve energy savings of 15% – 30% through elimination of reheat loads and improved part-load performance.
- Corrosive Environments: Coastal facilities, chemical processing plants, and data centers where the stainless steel construction provides superior longevity compared to copper or carbon steel alternatives.
Unique Selling Points
- Dual-Coil Independent Control Architecture: Enables decoupled sensible and latent heat management, achieving superior indoor air quality and energy efficiency compared to conventional single-coil systems.
- Premium Stainless Steel Construction: Eliminates corrosion-related failure modes common with copper coil tubes in condensate-rich environments, extending service life beyond 20 years with minimal maintenance.
- Modular and Scalable Design: Coil tube units are available in standardized sizes and can be configured in series or parallel arrangements to match varying thermal loads, simplifying system design and commissioning.
- High Surface-to-Volume Ratio: Precision-engineered fin geometry and tube layout maximize heat transfer area while maintaining acceptable air-side pressure drop (typically ΔP < 250 Pa at design airflow).
- Environmental Compliance: Compatible with low Global Warming Potential (GWP) refrigerants including R32 and R134a, supporting compliance with Montreal Protocol and EU F-Gas Regulation requirements.
Quality Certifications and Standards
Products manufactured by Wenzhou Jixing Metal Materials Co., Ltd comply with the following international and national standards and certifications:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- GB/T 151 — National standard for heat exchangers (China)
- GB/T 12771 — Stainless steel seamless and welded tubes for general purposes
- ASTM A269 / ASTM A270 — Seamless and welded austenitic stainless steel tubing
- ASHRAE 34 — Designation and safety classification of refrigerants
- EN 12730 — European standard for air-conditioning and heat pump equipment
- SGS / TÜV Inspection Reports — Third-party material and performance verification
Technical Note: The dual-coil temperature and humidity independent control system (双盘管冷源温湿度独立控制系统) represents a paradigm shift in HVAC design philosophy. By separating the cooling coil (primary, for sensible heat) from the dehumidification coil (secondary, for latent heat), this architecture eliminates the thermodynamic inefficiency of overcooling and reheating air. The stainless steel coil tube, as the critical heat transfer element, must be engineered to withstand continuous cycling between dew-point and above-dew-point operating conditions — a condition to which austenitic stainless steel is uniquely suited due to its resistance to condensation-induced pitting and crevice corrosion.