Stainless Steel Coil Tube for Low-Temperature Air Supply Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchanger component specifically designed for low-temperature air supply systems (Low-Temperature Air Distribution Systems, LTADS). These coil tubes serve as the core thermal exchange elements within cooling coils, facilitating efficient heat transfer between refrigerant fluids and ambient air streams. The product has been validated through rigorous mathematical modeling of cooling coil performance, ensuring optimal thermal-hydraulic characteristics under varying operational conditions.
Coil tubes are fabricated into continuous helical or serpentine geometries, maximizing surface area within compact spatial footprints. This configuration is particularly advantageous in applications requiring high cooling capacity within constrained installation dimensions, such as commercial HVAC systems, industrial process cooling, and specialized low-temperature environments.
Material & Properties
Material Grades
- Austenitic Stainless Steel 304 (UNS S30400): Contains 18% Chromium and 8% Nickel, offering excellent corrosion resistance and formability for general-purpose cooling applications.
- Austenitic Stainless Steel 316 (UNS S31600): Enhanced with 2–3% Molybdenum for superior resistance to chlorides and aggressive environments.
- Duplex Stainless Steel 2205 (UNS S32205): Provides yield strength approximately twice that of 304/316, suitable for high-pressure and cryogenic applications.
Mechanical & Thermal Properties
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, ensuring efficient heat transfer performance.
- Operating Temperature Range: −196°C to +450°C, accommodating cryogenic and elevated-temperature service.
- Yield Strength: ≥205 MPa (304 grade); ≥450 MPa (2205 grade).
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical media through passive chromium oxide film formation.
- Hygienic Surface: Achievable surface roughness of Ra ≤ 0.4 μm for sanitary and pharmaceutical applications.
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) | 6.35 – 25.4 (1/4" – 1") | mm |
| Wall Thickness | 0.5 – 1.5 | mm |
| Coil Pitch | 10 – 50 | mm |
| Coil Diameter | 50 – 500 | mm |
| Tube Length (per coil) | 1 – 30 | m |
| Number of Passes | 1 – 12 | — |
| End Connection Type | Flared, Flanged, Welded (TIG), Threaded (BSP/NPT) | — |
| Surface Treatment | Pickled & Passivated, Electropolished, or Mill Finish | — |
| Maximum Working Pressure | 1.6 – 6.4 | MPa |
| Hydrostatic Test Pressure | 1.5 × Working Pressure | MPa |
| Tolerance on OD | ±0.05 | mm |
| Tolerance on Wall Thickness | ±10% | — |
Manufacturing Process
Process Flow
- Raw Material Inspection: Incoming stainless steel strip or seamless tube undergoes chemical composition analysis (via Optical Emission Spectroscopy, OES) and mechanical property verification.
- Coil Forming: Precision roll-forming or CNC bending equipment shapes the tube into the required helical or serpentine geometry. Computer Numerical Control (CNC) systems ensure dimensional accuracy within ±0.5 mm tolerance.
- Heat Treatment (if applicable): Solution annealing at 1050–1100°C followed by controlled cooling to restore austenitic microstructure and eliminate residual stresses.
- Surface Finishing: Pickling and passivation remove scale and oxide layers, establishing a protective chromium-rich passive film. Electropolishing may be applied for critical hygiene applications.
- End Preparation: Tube ends are cut, deburred, and formed into the specified connection type (flared, flanged, or welded fittings).
- Quality Testing: Hydrostatic pressure testing, dimensional measurement (via Coordinate Measuring Machine, CMM), and visual inspection confirm compliance with specifications.
- Packaging: Tubes are wrapped in protective film, placed in wooden crates or steel containers, and labeled with material certificates and traceability codes.
Applications
Primary Application Domains
- Low-Temperature Air Supply Systems: Core component in cooling coils for commercial and industrial HVAC systems utilizing chilled water or refrigerant circuits. Mathematical modeling of these systems confirms optimal heat transfer coefficients (U-values of 60–120 W/(m²·K)) when employing precision-formed stainless steel coil tubes.
- Refrigeration & Cryogenics: Evaporators and condensers in food processing, pharmaceutical cold chains, and industrial refrigeration plants operating at temperatures as low as −40°C.
- Process Cooling: Heat exchangers in chemical processing, petrochemical, and power generation facilities requiring corrosion-resistant thermal management.
- Sanitary & Pharmaceutical: Clean-in-place (CIP) compatible coil assemblies for dairy, beverage, and biopharmaceutical manufacturing.
- Automotive & Transportation: Compact heat exchangers for electric vehicle battery thermal management and hybrid powertrain cooling systems.
- Marine & Offshore: Seawater-cooled heat exchangers where chloride resistance and durability are critical.
Quality Certifications & Standards Compliance
Applicable Standards
- ASTM A213/A213M: Standard Specification for Seamless Austenitic Stainless Steel Tubing for Heat-Transfer and Similar Applications.
- ASTM A269/A269M: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Heat-Transfer Service.
- EN 10216-5: Seamless heat exchanger tubes and heat-treatment tubes of non-ferrous metals and alloys — Austenitic stainless steel tubes.
- ASME BPV Section VIII: Boiler and Pressure Vessel Code for pressure-containing applications.
- GB/T 12771: Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport.
Certifications
- ISO 9001:2015: Quality Management System certification ensuring consistent manufacturing quality.
- ISO 14001:2015: Environmental Management System certification for sustainable production practices.
- PED 2014/68/EU: European Pressure Equipment Directive compliance for pressure vessel components.
- NSF 61: Safe Drinking Water System Components certification for potable water applications.
- Mill Test Certificates (MTC): EN 10204 Type 3.1 certificates provided with each shipment, documenting chemical composition and mechanical properties.
Unique Selling Points
Technical Advantages
- Mathematical Model-Validated Performance: Product design is informed by rigorous computational modeling of low-temperature air supply system cooling coils, enabling prediction of thermal efficiency, pressure drop, and flow distribution with high accuracy. This ensures that coil geometry parameters (pitch, diameter, number of passes) are optimized for target thermal loads before manufacturing.
- Superior Corrosion Resistance: Austenitic and duplex stainless steel grades provide long service life in aggressive environments without degradation of mechanical properties or thermal performance.
- Customizable Geometry: Flexible manufacturing capabilities allow tailoring of coil pitch, tube diameter, pass count, and end configurations to meet specific system design requirements.
- Cryogenic Capability: Maintains ductility and mechanical integrity at extremely low temperatures, eliminating the risk of brittle fracture that affects carbon steel alternatives.
- Hygienic & Cleanable: Smooth internal surfaces prevent biofilm accumulation and facilitate CIP/SIP procedures, meeting pharmaceutical and food-grade requirements.
- Full Traceability: Each coil tube batch is traceable to its raw material heat number, with complete documentation of manufacturing parameters and test results.
Design Note: For low-temperature air supply systems, the thermal performance of cooling coil tubes is governed by the interplay between air-side and fluid-side heat transfer coefficients, tube geometry, and flow arrangement. Wenzhou Jixing Metal Materials Co., Ltd. applies computational fluid dynamics (CFD) and mathematical modeling methodologies to optimize coil configurations, achieving heat transfer effectiveness (ε) values exceeding 85% under design conditions.