Stainless Steel Cooling Coil Tube for Low-Temperature Air Distribution Systems
Supplier: Wenzhou Jixing Metal Materials Co., Ltd. | Product No.: 1435
Product Overview
The Stainless Steel Cooling Coil Tube is a precision-engineered coiled tubing product specifically designed for low-temperature air supply systems (Low-Temperature Air Distribution Systems, LTADS). This product serves as the core heat exchange element within chilled water and refrigerant-based cooling coil assemblies, enabling efficient thermal transfer between the working fluid and the airstream. The coil tube is manufactured to support rigorous mathematical modeling requirements, including convective heat transfer coefficient determination, pressure drop analysis, and energy balance calculations inherent to the thermodynamic performance characterization of cooling coils.
Unlike conventional carbon steel or copper coil tubes, the stainless steel construction provides superior corrosion resistance, extended service life, and compliance with stringent hygienic requirements demanded by modern HVAC (Heating, Ventilation, and Air Conditioning) installations in commercial, industrial, and institutional environments.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards. The primary material specifications are detailed below:
- Material Grade: SUS304 / SUS316 (AISI 304 / AISI 316L)
- Standard Compliance: ASTM A213 / ASME SA-213, GB/T 12771, EN 10217-7
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, chlorinated water, and mild chemical environments
- Thermal Conductivity: Approximately 16.3 W/(m·K) for SUS304 at 20°C, ensuring adequate heat transfer performance
- Operating Temperature Range: −196°C to +870°C
- Surface Treatment: Passivated and polished finish (Ra ≤ 0.4 μm available upon request)
- Mechanical Properties: Tensile strength ≥ 515 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
Specifications
| Parameter | Specification | Unit | Standard / Reference |
|---|---|---|---|
| Outer Diameter (OD) | 3.18 / 4.00 / 6.35 / 8.00 / 9.53 | mm | ASTM B791 |
| Wall Thickness | 0.30 – 1.20 | mm | — |
| Bend Radius | ≥ 1.5 × OD | — | GB/T 12771 |
| Coil Length (Standard) | 20 / 30 / 50 / 100 (customizable) | m | — |
| Coil Inner Diameter | 150 / 200 / 250 / 300 | mm | — |
| Surface Roughness | ≤ 0.8 Ra (standard); ≤ 0.4 Ra (premium) | μm | ASTM A967 |
| Pressure Rating | Up to 1.6 MPa (design); 2.4 MPa (hydrostatic test) | MPa | ASME B31.9 |
| Refrigerant / Chilled Water Flow Velocity | 0.5 – 3.0 | m/s | ASHRAE Handbook |
| Dimensional Tolerance | ± 0.1 mm (OD); ± 10% (wall thickness) | mm | EN 10217-7 |
| Helix Pitch | 12 – 25 | mm | — |
| Winding Tolerance | ± 0.5 mm | mm | — |
Manufacturing Process
The production of the stainless steel cooling coil tube follows a multi-stage precision manufacturing workflow:
- Raw Material Selection: Cold-rolled stainless steel strip (SUS304/316) is sourced from certified mills and undergoes incoming inspection for chemical composition (via XRF or optical emission spectrometry) and mechanical properties.
- Coil Forming: The strip is fed through a high-precision forming station where it is progressively shaped into the specified circular cross-section tube. The forming process is controlled to prevent wall thinning and ovality exceeding tolerance limits.
- Welding: The longitudinal seam is welded using automatic TIG (Tungsten Inert Gas) or laser welding technology, ensuring a hermetic seal with minimal heat-affected zone (HAZ). Weld penetration is verified via radiographic testing (RT) or ultrasonic testing (UT) at defined intervals.
- Coil Winding: The formed tube is helically wound around a precision mandrel using CNC-controlled winding machinery. The winding parameters — pitch, bend radius, and coil diameter — are maintained within ± 0.5 mm tolerance through real-time servo feedback control.
- Post-Forming Heat Treatment: Solution annealing at 1050–1100°C followed by rapid water quenching restores the austenitic microstructure, relieves residual stresses, and maximizes corrosion resistance.
- Surface Finishing: Mechanical polishing or electropolishing is applied to achieve the specified surface roughness, facilitating lower pressure drop and enhanced heat transfer coefficients.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing at 1.5× design pressure for a minimum of 30 seconds, dimensional verification, and visual surface inspection.
Applications
The stainless steel cooling coil tube is integral to a wide range of HVAC and refrigeration applications:
- Low-Temperature Air Supply Systems (LTADS): Serves as the primary heat exchanger element in chilled water coils operating at supply air temperatures below 13°C, delivering high-sensible-cooling loads with reduced latent load.
- Commercial HVAC Systems: Used in air handling units (AHUs), fan coil units (FCUs), and rooftop units (RTUs) for office buildings, hospitals, and educational facilities.
- Industrial Process Cooling: Applicable in food processing, pharmaceutical manufacturing, and semiconductor fabrication environments requiring hygienic-grade heat exchange components.
- Chilled Water Distribution: Functions within secondary chilled water loops in district cooling systems and large-scale commercial complexes.
- Mathematical Modeling & Research: Provides standardized geometric and material parameters for the establishment and validation of cooling coil mathematical models, including the ε-NTU (Effectiveness-Number of Transfer Units) method and finite volume-based numerical simulations.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity and traceability:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- CE Marking — Conformity with European Directive 2014/68/EU (Pressure Equipment Directive, PED)
- ASME "S" Stamp — Section I Boiler and Pressure Vessel Code compliance (for applicable pressure-containing assemblies)
- Material Traceability: Each batch is accompanied by a Mill Test Certificate (MTC) conforming to EN 10204 3.1, including chemical analysis, mechanical test results, and heat number identification.
- Third-Party Inspection: Available upon request through SGS, Bureau Veritas, or TÜV Rheinland for lot-by-lot verification.
Unique Selling Points
1. Precision Geometric Consistency: CNC-controlled winding ensures dimensional accuracy critical for reliable mathematical modeling of heat transfer and pressure drop characteristics, enabling engineers to predict system performance with high confidence.
2. Superior Corrosion Resistance: The austenitic stainless steel construction eliminates concerns of internal corrosion and scale formation, maintaining design heat transfer coefficients over the full service life without degradation.
3. Hygienic Compliance: Smooth internal surfaces (Ra ≤ 0.4 μm) prevent microbial colonization, making the product suitable for food-grade and pharmaceutical applications where sanitary design is mandatory.
4. Customizable Configuration: Flexible manufacturing capabilities allow for tailored coil dimensions, pitch, and length to match specific thermal load requirements and AHU/FCU housing constraints.
5. Full Documentation Support: Comprehensive technical documentation, including MTCs, dimensional drawings, and heat transfer performance data, supports engineering validation and regulatory submission.
Mathematical Model Integration
In the context of low-temperature air supply system design, the cooling coil tube parameters directly influence the governing equations of the thermal performance model. Key relationships include:
- Heat Transfer Equation: Q = U × A × LMTD, where U is the overall heat transfer coefficient, A is the total heat transfer surface area (determined by tube OD, length, and coil geometry), and LMTD is the Logarithmic Mean Temperature Difference.
- Pressure Drop: ΔP = f × (L/D) × (ρ × v²/2), where f is the Darcy friction factor dependent on surface roughness and Reynolds number, L is the developed tube length, and D is the hydraulic diameter.
- Effectiveness-NTU Method: ε = f(NTU, C_r), where NTU = UA/C_min and C_r = C_min/C_max, enabling rapid performance prediction under varying flow rate and temperature conditions.
The geometric precision and material consistency of this product ensure that theoretical model predictions align closely with field performance, reducing commissioning time and operational uncertainty in LTADS installations.