Stainless Steel Internal-Threading Air Conditioning Coil Tube (Product No. 1504)
Product Overview
The Stainless Steel Internal-Threading Air Conditioning Coil Tube is a precision-engineered seamless tube product designed specifically for high-efficiency air conditioning and refrigeration heat exchanger systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a significant advancement in coil tube technology, incorporating an internal micro-fin (threaded) surface structure that dramatically enhances heat transfer performance. The product line is classified under the technical literature and research category (Reference No. 1504), reflecting its development through rigorous R&D processes including the successful commissioning of a dedicated internal-thread coil tube drawing machine.
The integration of internal threading technology into stainless steel coil tubes addresses the long-standing challenge of balancing thermal efficiency with mechanical durability in HVAC (Heating, Ventilation, and Air Conditioning) applications. This product leverages advanced cold-drawing and roll-forming techniques to create a controlled internal geometry that increases the effective heat exchange surface area without proportionally increasing material consumption or pressure drop.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity suitable for refrigerant service.
- Primary Material Grades: SUS304 (UNS S30400), SUS316 (UNS S31600), and SUS316L (UNS S31603)
- Corrosion Resistance: Superior resistance to chlorides, ammonia-based refrigerants, and condensate corrosion in humid environments
- Mechanical Strength: Yield strength of 205–310 MPa (depending on grade and temper condition), ensuring structural integrity under cyclic pressure loads
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, providing reliable heat transfer capability
- Temperature Range: Operational from −196°C to +870°C, accommodating extreme thermal cycling in refrigeration cycles
- Hygienic Surface: Food-grade passivated surface (Ra ≤ 0.4 μm) suitable for pharmaceutical and food processing applications
- Non-magnetic: Austenitic microstructure ensures non-magnetic properties for electronic and medical applications
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 19.05 mm (⅛" – ¾") | ASTM A269 / A213 |
| Wall Thickness | 0.30 mm – 1.50 mm | ASTM A269 |
| Coil Length (per spool) | 100 m – 500 m (configurable) | Manufacturer specification |
| Internal Thread Pitch | 0.25 mm – 1.00 mm (adjustable) | Proprietary design |
| Internal Thread Depth | 0.05 mm – 0.20 mm | Proprietary design |
| Number of Internal Threads | 4 – 16 (configurable per application) | Proprietary design |
| Heat Transfer Enhancement | 30% – 65% improvement over smooth-bore equivalent | Measured per ASHRAE guidelines |
| Pressure Drop Increase | 15% – 35% (optimized ratio) | Darcy-Weisbach analysis |
| Maximum Operating Pressure | 4.0 MPa (580 psi) | ASME B31.5 |
| Surface Finish (Internal) | Ra ≤ 0.8 μm (post-threading) | ASTM A269 |
| Surface Finish (External) | Ra ≤ 0.4 μm (electropolished) | ASTM A269 |
| Refrigerant Compatibility | R-134a, R-410A, R-32, R-1234yf, R-290, R-717 (NH₃) | ASHRAE 34 |
| Tolerance (OD) | ±0.05 mm | ISO 2852 |
| Tolerance (Wall Thickness) | ±10% | ASTM A269 |
| Delivery Condition | Annealed (Solution Heat Treated) | ASTM A269 |
Manufacturing Process
The production of this stainless steel internal-threading coil tube involves a multi-stage precision manufacturing sequence, integrating advanced metallurgical processing with proprietary forming technology:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition compliance with the designated grade specification. Incoming material undergoes 100% visual inspection and sampling for mechanical property verification.
- Slitting & Leveling: The coil strip is precision-slitted to the target width with edge-quality inspection. Automated leveling ensures flatness tolerance of ≤0.5 mm/m to prevent downstream forming defects.
- Forming (Welding): High-precision multi-roller forming stations shape the strip into a circular cross-section. TIG (Tungsten Inert Gas) welding or friction welding is employed to create the longitudinal seam, with weld penetration verified via ultrasonic testing (UT) or eddy current detection.
- Coil Drawing (Reduction): The formed tube passes through sequential cold-drawing dies to achieve target outer diameter and wall thickness dimensions. This stage also enhances mechanical strength and surface finish through work hardening.
- Internal Threading (Roll Forming): Using the proprietary internal-thread coil tube drawing machine developed by the manufacturer, precision roller tools are inserted into the tube bore and rotated under controlled axial feed to form the micro-fin/thread geometry on the internal surface. This process is performed at controlled speeds and temperatures to prevent material work-hardening and surface cracking.
- Heat Treatment (Annealing): The threaded coil tube is solution-annealed at 1050–1150°C followed by rapid water quenching to restore full austenitic structure, relieve residual stresses, and optimize corrosion resistance. This ensures the material returns to the annealed (soft) condition per ASTM A269 requirements.
- Passivation & Cleaning: A citric acid or nitric acid-based passivation treatment removes surface iron contamination and forms a protective chromium oxide layer. Final cleaning ensures freedom from lubricants, cutting fluids, and particulate contamination.
- Quality Control & Testing: Comprehensive inspection includes dimensional verification (OD, wall thickness, thread geometry), hydrostatic pressure testing, internal bore profiling (laser or optical), and surface defect detection. Samples are tested for intergranular corrosion per ASTM A262 Practice No. 1A.
- Packaging & Coiling: The finished product is wound onto protected cores, wrapped in moisture-barrier packaging, and labeled with full traceability documentation including heat number, batch code, and certification records.
Applications
The stainless steel internal-threading air conditioning coil tube finds application across a broad spectrum of thermal management systems:
- Residential & Commercial Air Conditioning: Evaporator and condenser coils in split systems, central air handlers, and heat pump units where enhanced heat transfer reduces compressor energy consumption.
- Automotive Air Conditioning: Lightweight, high-efficiency heat exchangers for vehicle HVAC systems, particularly in electric vehicles (EVs) where thermal management efficiency is critical.
- Industrial Refrigeration: Cold storage systems, refrigerated transport, and process cooling where ammonia (R-717) or hydrocarbon refrigerants are employed.
- Heat Pump Systems: Air-to-water and air-to-air heat pumps operating in demanding environments requiring corrosion-resistant components.
- Commercial Food Equipment: Freezers, chillers, and display cases requiring hygienic, non-toxic materials in direct food-contact environments.
- Marine & Offshore Applications: HVAC systems in marine environments where chloride-induced corrosion resistance is paramount.
- Pharmaceutical & Medical Equipment: Temperature-controlled storage, laboratory refrigeration, and medical device cooling systems requiring biocompatible materials.
Quality Certifications & Standards Compliance
The product and manufacturing facility adhere to internationally recognized quality and industry standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and continuous improvement
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- ASTM A269 / A269M — Standard Specification for Seamless and Wrought Stainless Steel Tubing for Chemical and General Applications
- ASTM A213 — Standard Specification for Seamless Austenitic Stainless Steel Tubing for High-temperature Service
- EN 10217-7 — European standard for austenitic stainless steel tubing
- ASME B31.5 — Pressure Piping, Process Piping (for pressure design verification)
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes for fluid transport
- GB/T 4237 — Chinese national standard for cold-rolled stainless steel strips and plates
- RoHS Compliance — Restriction of Hazardous Substances directive compliance for environmental safety
- REACH Compliance — Registration, Evaluation, Authorization, and Restriction of Chemicals compliance for EU market access
Unique Selling Points
- Proprietary Internal-Threading Technology: The manufacturer's independently developed internal-thread coil tube drawing machine enables precise, consistent micro-fin formation at production speeds previously unattainable, ensuring uniform thread geometry along the entire coil length.
- Significant Energy Efficiency Gains: The 30–65% heat transfer enhancement translates directly to reduced compressor runtime and energy consumption, contributing to lower operating costs and reduced carbon footprint for end-users.
- Full Traceability: Every coil is accompanied by a complete material test certificate (MTC) traceable to the mill heat number, ensuring supply chain transparency and compliance with regulated industry requirements.
- Customization Capability: Thread pitch, depth, and number of threads can be tailored to specific application requirements, enabling optimized performance for particular refrigerant types, flow velocities, and heat exchanger configurations.
- Superior Corrosion Longevity: The austenitic stainless steel matrix combined with controlled internal surface finish provides extended service life in aggressive chemical and environmental conditions, reducing lifecycle replacement costs.
- Lightweight Design: Enhanced heat transfer per unit length permits smaller diameter tubes and reduced overall heat exchanger mass, advantageous for weight-sensitive applications such as automotive and portable equipment.
Technical Note: The development of the internal-thread coil tube drawing machine represents a key intellectual property asset of Wenzhou Jixing Metal Materials Co., Ltd. The machine's design integrates precision servo-controlled roller feeding, real-time dimensional monitoring via laser displacement sensors, and adaptive speed regulation to maintain consistent thread quality throughout variable-length coil production runs. This technological capability positions the manufacturer as a leading supplier of advanced heat-transfer-enhanced tubing solutions in the Asian market.