Stainless Steel Chilled Water Coil Tube — Active Chilled Beam Series
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Product No.: 265 | Category: HVAC Coil Tube Systems
1. Product Overview
The Stainless Steel Chilled Water Coil Tube is a precision-engineered serpentine tube component designed for integration into Active Chilled Beam (ACB) systems. This product is the core thermal exchange element responsible for delivering chilled water to the beam unit, enabling efficient radiant and convective cooling in commercial and institutional buildings. Based on extensive simulation research on the influence of chilled water coils on active chilled beam performance, this product has been optimized to maximize heat transfer efficiency while minimizing hydraulic resistance and pressure drop across the coil circuit.
The coil tube is manufactured from high-grade austenitic stainless steel, offering superior corrosion resistance, long service life, and compliance with potable water standards. Its serpentine geometry is precisely formed to achieve uniform flow distribution and optimal heat exchange surface area within a compact footprint.
2. Material & Properties
2.1 Base Material
- Grade: SUS304 / SUS316L (ASTM A269 / ASTM A213)
- Composition (SUS304): Carbon ≤ 0.08%, Chromium 18.0–20.0%, Nickel 8.0–10.5%, Manganese ≤ 2.0%, Silicon ≤ 1.0%, Phosphorus ≤ 0.045%, Sulfur ≤ 0.030%
- Composition (SUS316L): Carbon ≤ 0.03%, Chromium 16.5–18.5%, Nickel 10.0–14.0%, Molybdenum 2.0–3.0%
2.2 Mechanical Properties
- Tensile Strength (Rm): ≥ 520 MPa (SUS304), ≥ 485 MPa (SUS316L)
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A50mm): ≥ 40%
- Hardness (HBW): 120–180
- Operating Temperature Range: −196°C to +400°C
2.3 Thermal & Physical Properties
- Thermal Conductivity: 14.9 W/(m·K) at 25°C
- Specific Heat Capacity: 500 J/(kg·K)
- Density: 7,930 kg/m³
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion; suitable for aggressive water environments
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 8.0 mm, 9.5 mm, 12.0 mm (custom available) | ASTM A269 |
| Wall Thickness | 0.5 mm – 1.5 mm | ASTM A269 / EN 10217-7 |
| Tube Pitch | 15 mm – 40 mm (configurable) | — |
| Row Configuration | 1-row, 2-row, 3-row, 4-row serpentine | — |
| Coil Length | 300 mm – 1,200 mm | — |
| End Forming | Flared, threaded, welded, or brazed fittings | ASME B31.9 |
| Surface Finish | Mirror polished (Ra ≤ 0.4 μm) or commercial finish (Ra ≤ 1.6 μm) | ASTM A240 |
| Maximum Working Pressure | 1.6 MPa – 2.5 MPa | ASME BPV Code VIII |
| Design Pressure | 2.4 MPa – 3.75 MPa | — |
| Design Temperature | 7°C (supply) / 12°C (return) for chilled water | ASHRAE 90.1 |
| Flow Velocity | 1.0 – 2.0 m/s (optimal range) | ASHRAE Handbook — HVAC Systems |
| Heat Transfer Coefficient | 2,500 – 4,500 W/(m²·K) (water-side) | ASHRAE Fundamentals |
| Pressure Drop (ΔP) | ≤ 30 kPa at rated flow | — |
| Welding Method | Orbital TIG (GTAW) or resistance welding | ASME BPV Code Section IX |
| Hydrostatic Test Pressure | 1.5× design pressure, minimum 4.0 MPa | ASME BPV Code VIII Div. 1 |
| Applicable Standards | ASTM A269, EN 10217-7, ASME B31.9, GB/T 14976 | — |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel tubes are verified for chemical composition (spectroscopic analysis), mechanical properties, and dimensional conformity per ASTM A269 or EN 10217-7.
- Cutting & Deburring: Tubes are precision-cut to required coil lengths using CNC plasma or laser cutting, followed by mechanical deburring to ensure clean, burr-free ends.
- Coil Forming (Serpentine Bending): High-precision CNC coil forming machines are used to bend the tubes into the specified serpentine pattern. Bend radius is controlled at R ≥ 3D (three times the outer diameter) to prevent wall thinning and ovality exceeding 5%.
- Welding: Header connections and tube-to-header joints are performed via orbital TIG welding (GTAW) in a controlled argon atmosphere to ensure penetration, cleanliness, and metallurgical integrity. Welds conform to ASME BPV Code Section IX qualification requirements.
- Surface Treatment: Optional mirror polishing or electropolishing is applied to the inner surface to reduce fouling resistance and enhance heat transfer efficiency. Electropolishing removes a 10–25 μm layer, producing a passivated surface with Ra ≤ 0.4 μm.
- Hydrostatic Pressure Testing: Each coil assembly undergoes a hydrostatic test at 1.5× the maximum design pressure, held for a minimum of 30 seconds, with zero leakage tolerance.
- Non-Destructive Testing (NDT): 100% visual inspection of welds; 10% dye penetrant testing (PT) or 100% ultrasonic testing (UT) of critical welds per customer specification.
- Final Dimensional Inspection: Verification of coil pitch, row count, overall dimensions, and end fitting alignment.
4.2 Quality Control Milestones
- First Article Inspection (FAI) for each new coil configuration
- In-process dimensional checks at every 10 units
- Final batch inspection with complete traceability documentation
- Mill Test Reports (MTRs) provided with every shipment
5. Applications
5.1 Primary Application: Active Chilled Beam Systems
The primary application of this coil tube is within Active Chilled Beam (ACB) HVAC systems, where the chilled water coil serves as the thermal core of the ceiling-mounted beam unit. The coil transfers heat from the room air to the chilled water circulating through the serpentine tubes, providing both radiant cooling (via the beam's exposed surface) and convective cooling (via the air plenum). Simulation studies have demonstrated that the geometry, pitch, and flow characteristics of the chilled water coil directly influence the cooling capacity, stratification performance, and overall energy efficiency of the ACB system.
5.2 Additional Applications
- Passive Chilled Beam Systems: Radiant cooling panels where the coil is integrated into the beam structure for conductive heat exchange.
- Air Handling Units (AHUs): Chilled water coil sections within rooftop or central air handling units.
- Chiller Condenser/Evaporator Circuits: Tubular heat exchangers in commercial refrigeration systems.
- Process Cooling: Cooling coils in food processing, pharmaceutical, and semiconductor manufacturing facilities where hygienic and corrosion-resistant tubing is required.
- Underfloor Cooling Systems: PEX-alternative stainless steel coils embedded in floor screed for radiant cooling.
- Chilled Water Piping Loops: Secondary loop distribution in large-scale HVAC systems.
5.3 Simulation-Based Performance Optimization
Based on the research study "Simulation Study on the Influence of Chilled Water Coil on Active Chilled Beam Performance", the following performance parameters were optimized through Computational Fluid Dynamics (CFD) and thermal simulation:
- Tube Pitch Optimization: A pitch of 25–30 mm was identified as optimal for balancing heat transfer area against pressure drop.
- Row Number: 2-row configurations provided the best trade-off between cooling capacity and fan energy consumption.
- Flow Distribution: Serpentine geometry with equal-length parallel circuits ensured uniform flow distribution and minimized dead zones.
- Temperature Difference: A supply/return temperature differential of 5–7°C (7°C supply, 12°C return) was confirmed as optimal for ACB operation.
- Stratification Effect: Coil placement within the beam plenum was optimized to enhance thermal stratification and improve occupant comfort.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing operations |
| ISO 14001:2015 | Environmental Management System certification |
| CE Marking | Compliance with European directives for construction products (CPR) |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (applicable for SUS316L grade) |
| ASTM A269 / A213 | Standard specifications for seamless and welded austenitic stainless steel tubes |
| ASME BPV Code VIII Div. 1 | Pressure vessel and heat exchanger construction standards |
| ASME B31.9 | Building Services Piping — hydronic piping systems |
| EN 10217-7 | European standard for heat exchanger tubes — austenitic stainless steel |
| GB/T 14976 | Chinese national standard for seamless stainless steel tubes |
| Mill Test Report (MTR) | Provided with every shipment — chemical analysis, mechanical test results, heat number traceability |
| Third-Party Inspection | Available upon request — SGS, Bureau Veritas, TÜV Rheinland |
7. Unique Selling Points
- Simulation-Optimized Design: Coil geometry, pitch, and row configuration are derived from rigorous CFD simulation studies on active chilled beam performance, ensuring peak efficiency in real-world HVAC applications.
- Premium Stainless Steel Grades: Available in both SUS304 and SUS316L, providing excellent resistance to corrosion from chilled water inhibitors, glycol solutions, and aggressive water chemistry.
- Hygienic Surface Finish: Mirror-polished and electropolished inner surfaces minimize biofilm formation and fouling, reducing maintenance frequency and extending service life.
- Full Traceability: Every coil is traceable to its mill heat number, with complete MTR documentation and weld inspection records provided.
- Custom Engineering Capability: Custom OD, wall thickness, coil length, pitch, row configuration, and end fittings are available to meet specific project requirements.
- Low Pressure Drop Design: Optimized serpentine geometry minimizes hydraulic resistance (ΔP ≤ 30 kPa), reducing pump energy consumption and enabling smaller, more energy-efficient circulator pumps.
- Weld Integrity Assurance: Orbital TIG welding in inert gas atmosphere ensures clean, fully penetrated welds with minimal distortion and maximum structural integrity.
- Global Standards Compliance: Products meet ASTM, ASME, EN, and GB standards simultaneously, enabling use in international projects without re-certification.
8. Conclusion
The Wenzhou Jixing Stainless Steel Chilled Water Coil Tube represents a state-of-the-art thermal exchange component engineered for maximum performance in Active Chilled Beam and related HVAC applications. Backed by rigorous simulation research, premium material selection, and comprehensive quality assurance, this product delivers superior cooling efficiency, long-term reliability, and energy savings across commercial, institutional, and industrial building environments.