Stainless Steel Coil Tube for Ice-Storage Low-Temperature Air Supply Systems
Product Overview
The Stainless Steel Coil Tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered piping component specifically designed for ice-storage low-temperature air supply systems (Ice Storage Low Temperature Air Supply System). This product series, catalogued under reference number 1168, represents an advanced solution for thermal energy storage and distribution applications where superior heat transfer performance, corrosion resistance, and long-term reliability are paramount.
Unlike conventional coil tubes fabricated from carbon steel or copper, the stainless steel coil tube leverages the inherent metallurgical advantages of austenitic and duplex stainless steels to deliver exceptional performance in cryogenic and low-temperature environments. The product has been extensively validated through academic research on heat transfer performance characteristics within ice-storage systems, establishing its suitability for demanding HVAC (Heating, Ventilation, and Air Conditioning) and thermal energy storage applications.
Material & Properties
The coil tube is fabricated from high-grade stainless steel alloys selected specifically for their performance under low-temperature conditions. The primary material grades include:
- Austenitic Stainless Steel (e.g., AISI 304 / AISI 316) — Offers excellent corrosion resistance, ductility, and cryogenic toughness. The austenitic microstructure (face-centered cubic, FCC) ensures the material retains full mechanical integrity at temperatures as low as −196°C (liquid nitrogen temperature).
- Duplex Stainless Steel (e.g., AISI 2205) — Provides enhanced yield strength (approximately 450–550 MPa) and superior resistance to chloride-induced stress corrosion cracking (SCC), making it ideal for marine and coastal applications.
- Super-Austenitic Stainless Steel (e.g., Alloy 6 / 904L) — Selected for extreme corrosion environments with high chloride concentrations or aggressive chemical media.
Key Mechanical Properties (Typical for AISI 316L):
- Tensile Strength (UTS): ≥ 515 MPa
- Yield Strength (0.2% offset): ≥ 205 MPa
- Elongation (at break): ≥ 40%
- Hardness: ≤ 230 HB (Brinell)
- Thermal Conductivity (at 20°C): 16.3 W/(m·K)
- Linear Expansion Coefficient: 17.3 × 10⁻⁶ /K
Specifications
| Parameter | Specification / Range | Unit | Standard Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 – 50.8 | mm | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.5 – 3.0 | mm | ASTM A269 / EN 10217 |
| Coil Diameter | 300 – 2000 | mm | — |
| Coil Length (per coil) | 10 – 100 | m | — |
| Surface Finish (Ra) | 0.2 – 1.6 | μm | ASTM A270 |
| Operating Temperature Range | −196 to +400 | °C | — |
| Design Pressure (max) | — | MPa | ASME B31.9 |
| Material Grades | 304, 304L, 316, 316L, 321, 347, 2205 | — | ASTM A213 / A269 |
| Tolerance on OD | ±0.05 – ±0.15 | mm | ASTM A213 |
| Tolerance on Wall Thickness | ±10% | — | ASTM A213 |
| End Condition | Plain / Beveled / Flanged | — | ASME B16.25 |
| Heat Treatment | Solution Annealed + Water Quenched | — | ASTM A213 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Slit Coiling (Slitting & Re-coiling): Cold-rolled stainless steel strip (coil) is slit to the required width using precision slitting lines with laser-guided edge alignment. The slit coil is then re-coiled to the target coil diameter.
- Forming (Roll Forming / Hydroforming): The flat strip is cold-formed into a circular cross-section through a series of progressive roll stations. For larger diameters, hydroforming (hydrostatic forming) may be employed to achieve precise dimensional tolerances without work hardening.
- Welding (TIG / Laser Welding): The longitudinal seam is welded using Gas Tungsten Arc Welding (GTAW/TIG) or fiber laser welding under inert gas (argon) shielding to prevent oxidation. Weld parameters are computer-controlled for consistent bead quality.
- Heat Treatment (Solution Annealing): The welded tube is solution-annealed at 1050–1150°C followed by rapid water quenching to dissolve carbides, restore full austenitic structure, and maximize corrosion resistance.
- Pickling & Passivation: The tube surface is treated with mixed acid (nitric/hydrofluoric) pickling to remove oxide scale, followed by passivation to establish a stable chromium oxide passive film (Cr₂O₃).
- Dimensional Inspection & Coiling: Final OD, wall thickness, and straightness are verified using ultrasonic (UT) and optical measurement systems. The tube is then coiled to the required coil diameter and packaged.
Applications
The stainless steel coil tube is primarily engineered for the following application domains:
- Ice-Storage Low-Temperature Air Supply Systems: Serves as the heat exchanger coil within ice storage units, enabling thermal energy storage during off-peak hours and discharge during peak cooling demand. The high thermal conductivity and cryogenic toughness of stainless steel ensure efficient heat exchange between the refrigerant and ice/water medium.
- Commercial & Industrial HVAC Systems: Used in large-scale air conditioning systems for commercial buildings, hospitals, data centers, and manufacturing facilities requiring reliable thermal management.
- Refrigeration & Cryogenic Systems: Suitable for ammonia (NH₃), carbon dioxide (CO₂), and hydrofluorocarbon (HFC) refrigerant circuits operating under sub-zero conditions.
- Food & Pharmaceutical Processing: Compliant with sanitary standards (FDA, 3-A Sanitary), the tube is used in dairy processing, beverage pasteurization, and pharmaceutical cold-chain systems.
- Marine & Offshore Applications: The superior chloride corrosion resistance of duplex and super-austenitic grades makes this product suitable for shipboard cooling systems and offshore platform HVAC installations.
- Geothermal & District Cooling Systems: Employed in geothermal heat exchangers and district cooling networks where long service life and minimal maintenance are required.
Unique Selling Points
- Exceptional Cryogenic Performance: Retains full mechanical integrity and ductility at temperatures as low as −196°C, eliminating the risk of brittle fracture common in carbon steel alternatives.
- Superior Corrosion Resistance: The passive chromium oxide film provides resistance to atmospheric, acidic, and chloride environments, extending service life beyond 25 years in most applications.
- High Heat Transfer Efficiency: Validated through academic research (Ice Storage Low Temperature Air Supply System Design Software and Ice Coil Tube Heat Transfer Performance Study), the coil geometry and material combination achieve optimized Nusselt number (Nu) and heat transfer coefficients.
- Sanitary Compliance: Available in electropolished finish (Ra ≤ 0.2 μm) meeting FDA and 3-A Sanitary standards for food and pharmaceutical applications.
- Customizable Geometry: Flexible coil diameter, length, and cross-sectional dimensions enable tailored integration into diverse system architectures.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- EN 10204 3.1 / 3.2 — Material test certificates (MTC) per European standard
- ASME Section IX — Welding procedure qualifications (WPQ) and welder performance qualifications (WPQ)
- CE Marking — Conformity with European Directives (PED 2014/68/EU)
- NACE MR0175 / ISO 15156 — Compliance for sour service (H₂S-containing environments)
- Mill Test Reports (MTR): Full chemical composition and mechanical property documentation provided with each batch
- NDT Testing: 100% radiographic testing (RT) or ultrasonic testing (UT) of weld seams per ASTM E1647 / ASTM E2785
Disclaimer: The specifications listed above represent typical values for reference purposes. Actual product dimensions, tolerances, and performance characteristics are subject to the specific order requirements and applicable engineering codes. Wenzhou Jixing Metal Materials Co., Ltd. reserves the right to modify specifications without prior notice. All products comply with the applicable national and international standards in force at the time of manufacture.