Stainless Steel Coil Tube for Semi-Centralized Air Conditioning Systems — Wenzhou Jixing Metal Materials Co., Ltd.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this Stainless Steel Coil Tube (Product No. 1072) is engineered specifically for integration into hybrid semi-centralized air conditioning systems that combine evaporative cooling with dry chilled water coil technology. The product represents a high-performance heat transfer component designed to deliver superior thermal efficiency, corrosion resistance, and long-term operational reliability in demanding HVAC (Heating, Ventilation, and Air Conditioning) environments.
1. Product Overview
The Stainless Steel Coil Tube is a precision-formed tubular component used within dry-type fan coil units that operate in conjunction with evaporative cooling subsystems. In this hybrid architecture, the dry coil serves as the primary sensible heat removal element while the evaporative stage handles latent heat and pre-cooling of the return air. This division of labor significantly improves the overall Coefficient of Performance (COP) of the system and reduces total energy consumption compared to conventional all-mechanical cooling approaches.
The coil tube is manufactured from austenitic stainless steel, ensuring exceptional resistance to corrosion in high-humidity environments where evaporative cooling is present. Unlike traditional copper or carbon steel tubing, stainless steel coil tubes eliminate the risk of galvanic corrosion when exposed to condensate, humid air streams, and the mildly acidic water films generated during evaporative cooling cycles.
2. Material and Properties
2.1 Base Material Composition
The coil tube is fabricated from SUS304 (AISI 304) or SUS316L (AISI 316L) austenitic stainless steel, selected based on the specific corrosion environment of the installation. Key material properties include:
- Chromium (Cr) Content: 18.0–20.0 wt% — provides a stable passive oxide layer for corrosion resistance.
- Nickel (Ni) Content: 8.0–11.0 wt% — stabilizes the austenitic crystal structure and enhances ductility.
- Molybdenum (Mo) Content (316L grade): 2.0–3.0 wt% — further improves resistance to pitting and crevice corrosion in chloride-rich environments.
- Carbon (C) Content (316L grade): ≤ 0.030 wt% — minimizes intergranular corrosion susceptibility during welding.
2.2 Mechanical Properties
| Property | Unit | Typical Value (SUS304) | Typical Value (SUS316L) |
|---|---|---|---|
| Tensile Strength (Ultimate) | MPa | ≥ 520 | ≥ 515 |
| Yield Strength (0.2% Offset) | MPa | ≥ 205 | ≥ 170 |
| Elongation at Break | % | ≥ 40 | ≥ 45 |
| Thermal Conductivity (20°C) | W/(m·K) | 16.3 | 14.6 |
| Density | kg/m³ | 7930 | 8000 |
| Linear Thermal Expansion Coefficient (20–100°C) | × 10⁻⁶ /K | 17.3 | 16.6 |
| Maximum Service Temperature | °C | 870 | 870 |
2.3 Corrosion Resistance
The stainless steel coil tube exhibits outstanding resistance to atmospheric corrosion, condensate attack, and the mildly corrosive water films encountered in evaporative cooling systems. The self-healing chromium oxide passive film (Cr₂O₃) maintains integrity even under cyclic wet-dry conditions, which is a critical advantage over copper tubing that is susceptible to ammonia and sulfur compound attack in evaporative environments.
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 Coiltube) |
| Product No. | 1072 |
| Material Grade | SUS304 / SUS316L (AISI 304 / AISI 316L) |
| Tube Outer Diameter (OD) | 9.52 mm (3/8") / 12.70 mm (1/2") — configurable |
| Tube Wall Thickness | 0.5 mm / 0.6 mm / 0.8 mm (selectable per application) |
| Fin Material | Stainless Steel (SUS304) or Aluminum (with isolation treatment) |
| Fin Thickness | 0.10 mm – 0.20 mm |
| Fin Spacing | 2.0 mm – 3.5 mm (pitch, adjustable for airflow/heat transfer optimization) |
| Tube Pitch (Center-to-Center) | 16 mm – 25 mm |
| Coil Configuration | Single-row, Double-row, or Multi-row serpentine arrangement |
| Welding Method | Automatic TIG (Tungsten Inert Gas) Welding or Brazing with stainless-compatible filler |
| Operating Pressure (Design) | ≤ 1.6 MPa (liquid side); ≤ 0.6 MPa (gas side) |
| Operating Fluid | Water, Glycol-Water Mixture (up to 60% ethylene glycol), Chilled Water |
| Operating Temperature Range | −20°C to +120°C |
| Surface Treatment | Pickling and Passivation (酸洗钝化); optional coating for enhanced corrosion protection |
| Customization | Available — dimensions, row count, fin density, and material grade customizable per OEM specifications |
4. Manufacturing Process
The production of the Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Selection and Inspection: Stainless steel strip or tube stock is sourced from certified mills and subjected to incoming quality inspection including spectroscopic composition analysis (OES — Optical Emission Spectroscopy) and mechanical property verification.
- Cutting and Blanking: Precise laser cutting or shearing operations produce tube segments to the required length with tolerances within ±0.1 mm.
- Forming and Bending: CNC-controlled (Computer Numerical Control) bending machines form the tubes into the specified serpentine coil configuration. Bend radii are carefully controlled to prevent wall thinning or ovality exceeding 5% of nominal diameter.
- Fin Insertion or Coiling: Pre-formed stainless steel fins are inserted through the tubes at the specified pitch, or finned tube is coiled directly during production. Fin-to-tube bonding is achieved through mechanical interference fit and, where required, high-frequency welding.
- Welding: All tube-to-tube and tube-to-header joints are welded using automatic TIG welding with argon shielding gas. Weld beads are uniform and free of porosity, cracks, or incomplete fusion defects.
- Pickling and Passivation (酸洗钝化): The welded assembly undergoes acid pickling to remove heat-affected zone discoloration and mill scale, followed by passivation treatment to restore and strengthen the chromium oxide passive film. This step is critical for ensuring long-term corrosion resistance.
- Pressure Testing: Each coil tube assembly undergoes hydrostatic pressure testing at 1.5 times the maximum design pressure for a minimum of 30 minutes to verify leak-tightness and structural soundness.
- Final Inspection and Quality Control: Visual inspection, dimensional verification, and surface quality assessment are performed in accordance with ISO 9001 quality management system requirements.
- Packaging and Shipping: Finished coil tubes are protected with anti-corrosion packaging materials and moisture barriers to prevent damage during transit.
5. Applications
The Stainless Steel Coil Tube is designed for deployment in a wide range of HVAC applications, with particular suitability for the following systems:
- Semi-Centralized Air Conditioning Systems: Integrated into dry-type fan coil units that work in tandem with evaporative cooling pre-treatment stages, as described in the technical study "Evaporative Cooling and Dry Chilled Water Coil Combined Semi-Centralized Air Conditioning System". This configuration achieves significant energy savings by leveraging the latent heat of evaporation for pre-cooling while the dry coil handles the remaining sensible cooling load.
- Commercial Building HVAC: Office buildings, retail spaces, and hospitality facilities where high humidity control and energy efficiency are critical.
- Industrial Process Cooling: Food processing, pharmaceutical manufacturing, and chemical plants where stainless steel's corrosion resistance is essential and the product meets sanitary and hygienic requirements.
- Light Industrial Ventilation: Workshops, warehouses, and cold storage facilities requiring robust and low-maintenance cooling solutions.
- Specialty Cooling Applications: Data centers, laboratory environments, and precision air conditioning systems where air quality and equipment longevity are paramount.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance programs and holds the following certifications and standards compliance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| GB/T 14976 | Chinese National Standard for cold-rolled seamless stainless steel tubes — dimensional and mechanical requirements. |
| ASTM A269 / A270 | American Society for Testing and Materials standards for austenitic stainless steel seamless and welded tubes. |
| EN 10216-5 | European Standard for non-ferrous metal tubes — stainless steel welded tubes. |
| GB/T 12771 | Chinese National Standard for stainless steel welded tubes for general purposes. |
| SGS Testing | Independent third-party material and performance verification. |
All coil tube products are traceable to the mill heat number of the raw material, and complete test reports — including chemical composition analysis, mechanical test results, and pressure test records — are provided with each shipment upon request.
7. Unique Selling Points
Exceptional Corrosion Resistance in Hybrid Cooling Environments: Unlike conventional copper or carbon steel coil tubes, the stainless steel construction provides immunity to corrosion from condensate, humid air streams, and the mildly acidic conditions inherent in evaporative cooling systems. This dramatically extends service life and eliminates maintenance-related downtime.
Energy Efficiency Enhancement: When integrated into the semi-centralized system architecture described in the referenced technical literature, the dry stainless steel coil operates exclusively on the sensible cooling load. This eliminates the need for deep sub-cooling of the refrigerant and reduces compressor energy consumption by an estimated 20%–35% compared to conventional all-mechanical cooling configurations.
Hygienic and Food-Grade Compatible: The austenitic stainless steel surface, following pickling and passivation, is non-toxic, non-porous, and resistant to microbial growth. This makes the coil tube suitable for food processing, pharmaceutical, and laboratory applications where air quality standards are stringent.
Full Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers complete design flexibility, including tube diameter, wall thickness, fin geometry, row configuration, and material grade selection. OEM (Original Equipment Manufacturer) specifications are accommodated with rapid prototyping and volume production support.
Environmental Sustainability: Stainless steel is 100% recyclable with no loss of material properties. The extended service life of stainless steel coil tubes compared to copper alternatives reduces total material consumption and waste generation over the lifecycle of the installation, contributing to sustainable building operations.
8. Conclusion
The Stainless Steel Coil Tube (Product No. 1072) from Wenzhou Jixing Metal Materials Co., Ltd. represents a technically advanced and economically advantageous solution for modern semi-centralized air conditioning systems. Its integration with evaporative cooling technology enables significant energy savings while maintaining superior indoor air quality and system reliability. Backed by rigorous manufacturing standards, comprehensive quality certifications, and full customization capabilities, this product is an ideal choice for OEM manufacturers and engineering firms seeking high-performance heat transfer components for the next generation of sustainable HVAC systems.