Stainless Steel Coil Tube (Dry Coil System Chilled Water Tube)
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered coiled piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 912). This product is specifically designed for integration into Dry Coil Systems (also referred to as Direct Expansion or DX Cooling Systems), where it serves as the primary heat exchange conduit for chilled water or refrigerant circulation. The coil tube is formed into a compact, serpentine configuration that maximizes heat transfer surface area within a minimal footprint, making it ideal for applications requiring efficient thermal management under constrained spatial conditions.
Based on extensive research into Chilled Water Flow Regulation in dry coil systems, this product is engineered to maintain optimal hydraulic performance, minimize pressure drop, and ensure uniform flow distribution across the coil loop—critical factors for maintaining system efficiency and preventing thermal stratification.
2. Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical durability, and thermal conductivity—properties essential for long-term operation in HVAC and thermal management environments.
Primary Material Grades
- SUS 304 (AISI 304 / 1.4301) — General-purpose grade offering excellent corrosion resistance in most atmospheric and aqueous environments; contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- SUS 316 (AISI 316 / 1.4401) — Enhanced grade with 2–3% Molybdenum (Mo) addition, providing superior resistance to chlorides and aggressive chemical media.
- SUS 321 (AISI 321 / 1.4541) — Stabilized grade with Titanium (Ti) addition, offering improved resistance to intergranular corrosion at elevated temperatures.
Key Material Properties (Typical for SUS 304)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Specific Heat Capacity: 0.50 kJ/(kg·K)
- Density: 7.93 g/cm³
- Yield Strength: ≥ 205 MPa (annealed condition)
- Tensile Strength: 515–720 MPa
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Excellent resistance to atmospheric, water, and mild chemical environments
3. Specifications
| Parameter | Specification | Notes |
|---|---|---|
| Product No. | 912 | Manufacturer designation |
| Product Name | Coil Tube (盘管) | Dry coil system chilled water tube |
| Material | SUS 304 / SUS 316 / SUS 321 | Customizable per application requirements |
| Outer Diameter (OD) | 6 mm – 50 mm | Standard range; custom sizes available |
| Wall Thickness | 0.5 mm – 3.0 mm | Selected based on pressure rating |
| Coil Diameter | 100 mm – 2000 mm | Configurable per installation space |
| Coil Length | 0.5 m – 50 m | Custom cut lengths available |
| Surface Finish | Bright annealed / Polished (Ra ≤ 0.4 μm) | Smooth interior reduces flow resistance |
| Maximum Working Pressure | ≤ 1.6 MPa (standard); ≤ 4.0 MPa (reinforced) | Hydrostatic tested at 1.5× working pressure |
| Fluid Compatibility | Chilled water, glycol-water mixtures, light refrigerants | Not suitable for highly corrosive media without special treatment |
| End Connections | Flanged, threaded, welded, or crimped fittings | Configured per system design |
| Compliance Standards | GB/T 12771, EN 10217-7, ASTM A269 | See Quality Certifications section |
4. Manufacturing Process
The coil tube undergoes a rigorous multi-stage manufacturing process to ensure dimensional accuracy, structural integrity, and surface quality:
- Raw Material Inspection: Incoming stainless steel strip or seamless pipe stock is verified for chemical composition (via Optical Emission Spectrometry, OES) and mechanical properties, ensuring conformance to the specified grade.
- Blanking & Forming: For welded coil tube, precision slitting and edge preparation are performed, followed by roll-forming into the target tube geometry. Seamless variants are produced via cold drawing or piercing processes.
- Welding (if applicable): Longitudinal seams are welded using Automatic Submerged Arc Welding (SAW) or Laser Welding technology to achieve full-penetration welds with minimal heat-affected zone (HAZ).
- Bright Annealing: The formed tube is subjected to controlled-temperature bright annealing in a reducing atmosphere (typically hydrogen or endothermic gas) at 1050–1100°C, followed by rapid cooling. This process relieves residual stresses, restores ductility, and produces a clean, oxide-free surface.
- Coiling: The straightened tube is wound into the specified coil geometry using precision CNC-controlled coiling equipment. Tension is carefully managed to prevent distortion, kinking, or ovality.
- Surface Finishing: Optional polishing (electro-polishing or mechanical polishing) is applied to achieve the target surface roughness, reducing internal flow resistance and improving heat transfer efficiency.
- Pressure Testing: Each coil is hydrostatically tested at 1.5× the maximum working pressure for a minimum hold time of 5 minutes to verify leak-tightness and structural integrity.
- Final Inspection & Packaging: Dimensional verification, visual inspection, and material traceability documentation are completed. The coil is wrapped in protective film and secured for shipment.
5. Applications
The Stainless Steel Coil Tube (Product No. 912) is designed for demanding thermal management applications, with the following primary use cases:
- Dry Coil Chilled Water Systems: The primary application domain. The coil tube circulates chilled water through a serpentine coil, where ambient air drawn across the coil surface is cooled and dehumidified. This configuration eliminates the need for a secondary refrigerant loop, simplifying system architecture.
- HVAC (Heating, Ventilation, and Air Conditioning) Systems: Used in commercial and industrial air handling units (AHUs), rooftop units (RTUs), and packaged terminal air conditioners (PTACs) for precise temperature control.
- Cold Storage & Refrigeration: Deployed in walk-in coolers, freezers, and cold chain logistics facilities where reliable, corrosion-resistant heat exchange is critical.
- Industrial Process Cooling: Applied in chemical processing, food and beverage production, and pharmaceutical manufacturing where hygienic, non-reactive piping is required.
- Marine & Offshore Systems: The corrosion-resistant properties of SUS 316 grade make this product suitable for marine HVAC and cooling applications exposed to saline environments.
- Energy Recovery Systems: Integrated into heat recovery wheels and plate heat exchangers for energy-efficient building management systems.
Chilled Water Flow Regulation Considerations
Research into dry coil system chilled water flow regulation has identified several performance-critical design parameters that this product addresses:
- Uniform Flow Distribution: The coil geometry is optimized to ensure consistent flow velocity across all passes, preventing flow maldistribution that can lead to localized overheating or under-cooling.
- Minimal Pressure Drop: The smooth interior surface finish (Ra ≤ 0.4 μm) significantly reduces Darcy friction factor, lowering pumping energy requirements by up to 15–20% compared to standard finish tubes.
- Thermal Stratification Mitigation: The coil pitch and diameter ratios are engineered to promote turbulent mixing at the coil inlet and outlet, minimizing thermal stratification in the chilled water supply and return loops.
- Variable Flow Adaptability: The coil's hydraulic characteristics are designed to perform efficiently across a wide range of flow rates (0.5× to 1.5× design flow), accommodating variable-speed pumping systems and demand-responsive controls.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product reliability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering the full manufacturing and supply chain process.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- GB/T 12771 — Chinese national standard for stainless steel welded tubes for general applications.
- EN 10217-7 — European standard for stainless steel cold-drawn seamless and welded tubes.
- ASTM A269 — American standard for austenitic stainless steel welded tubing.
- CE Marking — Conformity with European Union safety and performance directives.
- Hydrostatic Test Report — Each batch is accompanied by a pressure test certificate confirming leak-tightness.
- Material Traceability Certificate — Full chemical and mechanical test reports (MTC) provided for every production lot, with heat-number traceability from raw material to finished product.
7. Unique Selling Points
Engineered for Dry Coil System Excellence: Unlike generic coil tubes, this product is specifically optimized based on research into chilled water flow regulation dynamics, ensuring superior thermal-hydraulic performance in dry coil applications.
- Superior Heat Transfer Efficiency: The combination of high thermal conductivity stainless steel and optimized coil geometry delivers heat transfer coefficients up to 25% higher than conventional carbon steel alternatives.
- Exceptional Durability: Austenitic stainless steel construction provides a service life exceeding 25 years under normal operating conditions, with resistance to scaling, pitting, and crevice corrosion.
- Low Lifecycle Cost: Reduced maintenance requirements, minimal fouling, and energy-efficient hydraulic design result in significantly lower total cost of ownership (TCO) over the system lifecycle.
- Customizable Configurations: Flexible manufacturing capabilities allow tailoring of coil diameter, pitch, tube size, and connection types to match specific system design requirements.
- Hygienic & Food-Grade Compatible: Available in electropolished finish suitable for food processing, pharmaceutical, and biomedical applications.
- Full Traceability & Compliance: Complete documentation chain from raw material to finished product, supporting regulatory audits and quality assurance programs.
8. Ordering & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including system integration consultation, coil layout design, flow simulation analysis, and post-installation performance verification. Custom engineering solutions are available upon request, with lead times typically ranging from 15 to 30 calendar days depending on order volume and specification complexity.