Stainless Steel Coil Tube — Fan Coil Unit Simulation-Optimized Design
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for integration into Fan Coil Unit (FCU) systems and HVAC (Heating, Ventilation, and Air Conditioning) applications. This product line incorporates findings from advanced Computer-Aided Simulation Design and Performance Analysis Systems, leveraging Computational Fluid Dynamics (CFD) modeling and thermodynamic simulation to optimize coil geometry, heat transfer efficiency, and pressure drop characteristics.
Unlike conventional coil tubes, this product represents a paradigm shift in manufacturing methodology — where digital twin simulation precedes physical production, ensuring that every coil geometry is validated for optimal thermal-hydraulic performance before fabrication begins. This approach minimizes design iterations, reduces material waste, and guarantees consistent performance across production batches.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for their superior corrosion resistance, thermal conductivity, and mechanical integrity under cyclic thermal loading conditions.
- Primary Grade: AISI 304 / SUS304 (18Cr-8Ni) — General purpose HVAC applications with excellent resistance to atmospheric and waterborne corrosion
- High-Performance Grade: AISI 316L / SUS316L (18Cr-10.5Ni-2Mo) — Enhanced chloride resistance for marine environments and aggressive chemical service
- Heat-Transfer Optimized Grade: AISI 321 (18Cr-10Ni-Ti stabilized) — Superior resistance to intergranular corrosion during brazing and welding operations
Key Material Properties
| Property | AISI 304 | AISI 316L | AISI 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K, 20°C) | 16.3 | 14.6 | 16.3 |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 | −196 to +900 |
| Pitting Resistance (PREN) | 18–20 | 24–26 | 18–20 |
| Density (g/cm³) | 7.93 | 8.00 | 7.93 |
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | SS-FCU-CT Series (Fan Coil Unit Coil Tube) |
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.53 mm (3/8"), 12.70 mm (1/2") |
| Wall Thickness | 0.50 mm – 1.20 mm (customizable) |
| Coil Pitch (Turn Spacing) | 12.7 mm – 25.4 mm (simulation-optimized per application) |
| Coil Diameter (Mean) | 100 mm – 500 mm |
| Number of Turns | 4 – 24 turns per circuit |
| Tube Length (Uncoiled) | Up to 15,000 mm continuous |
| Surface Finish | Electropolished (Ra ≤ 0.4 μm) or Brushed (Ra ≤ 1.6 μm) |
| Manufacturing Standard | ASTM A213 / ASTM A269 / EN 10216-5 |
| Design Validation | CFD-verified thermal-hydraulic performance (ANSYS Fluent / CFD-Post) |
| Pressure Rating | Up to 1.6 MPa (232 psi) working pressure |
| Heat Transfer Coefficient | ≥ 2,800 W/m²·K (simulated and field-validated) |
| Pressure Drop (Design) | ≤ 35 kPa at nominal flow rate |
Manufacturing Process
The production of this coil tube product follows a rigorously controlled multi-stage process, integrating simulation-driven design with precision manufacturing:
- Computational Simulation & Design Optimization: Each coil geometry is modeled using CFD software (ANSYS Fluent, COMSOL Multiphysics) to predict flow distribution, thermal gradients, and pressure drop characteristics. Design parameters — including coil pitch, tube diameter, and turn count — are iteratively optimized to maximize the coefficient of performance (COP) while minimizing pressure losses.
- Hot/Roll Forming of Stainless Steel Strip: High-purity austenitic stainless steel strip is cold-rolled to precise thickness tolerances (±0.02 mm) and formed into seamless tube via roll-forming technology. The material undergoes solution annealing at 1050–1100°C followed by rapid quenching to achieve a fully austenitic microstructure free of carbide precipitation.
- Coil Bending & Forming: The formed tube is bent into the simulation-optimized spiral geometry using CNC-controlled coil bending machinery. Bend radii are controlled to prevent wall thinning exceeding 5% and to eliminate residual stress concentrations. Finite Element Analysis (FEA) of the bending process ensures dimensional accuracy within ±0.3 mm.
- Heat Treatment & Stress Relief: Post-forming annealing at 1040°C in a controlled atmosphere eliminates residual stresses introduced during bending, restoring full mechanical properties and preventing stress corrosion cracking (SCC) susceptibility.
- Surface Treatment: Electropolishing removes a controlled depth (0.02–0.05 mm) of surface material, revealing a clean, passive oxide layer with Cr₂O₃ enrichment. This step is critical for hygiene applications and long-term corrosion resistance.
- Performance Verification: Each production batch undergoes hydrostatic pressure testing (1.5× working pressure for 30 minutes) and thermal performance validation against simulation predictions. Deviations exceeding 5% from simulated values trigger design review and process adjustment.
Applications
The simulation-optimized stainless steel coil tube serves a broad range of thermal management applications:
- Fan Coil Units (FCU): Primary application — serving as the heat exchanger coil in commercial and residential HVAC systems, delivering superior heating and cooling capacity with reduced pumping power.
- Chilled Water Distribution Systems: Used in secondary-loop coil assemblies for large-scale commercial buildings, data centers, and process cooling applications.
- Food Processing & Pharmaceutical Equipment: Hygienic-grade electropolished coils for pasteurization, sterilization, and clean-in-place (CIP) compatible heat exchange systems.
- Marine & Offshore HVAC: 316L-grade coils resistant to saltwater-induced pitting and crevice corrosion in shipboard and platform air conditioning systems.
- Industrial Process Heating: Steam-heated coil assemblies for chemical reactors, drying ovens, and thermal oil systems requiring corrosion-resistant heat transfer surfaces.
Quality Certifications & Compliance
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Design, Manufacturing, and Supply Chain |
| ISO 14001:2015 | Environmental Management System |
| ASTM A213 / A269 | Material specifications for seamless stainless steel tubing |
| EN 10216-5 | European standard for welded stainless steel tubes |
| NSF/ANSI 61 | Drinking water system components — material safety |
| 3-A Sanitary Standards | Food-grade surface finish and hygiene compliance |
| CE Marking (EU) | Compliance with European Machinery Directive and Pressure Equipment Directive (PED 2014/68/EU) |
| ASME B31.9 | Refrigeration and air-conditioning pressure piping |
Unique Selling Points
Simulation-First Engineering Philosophy: Every coil tube geometry is validated through full-scale CFD simulation before physical production, ensuring that thermal performance predictions match field results within ±5%. This eliminates the traditional trial-and-error approach and guarantees optimal performance from the first unit.
- Superior Heat Transfer Efficiency: Simulation-optimized coil pitch and geometry deliver up to 15% higher heat transfer coefficient compared to conventionally designed coils of equivalent size.
- Reduced Pumping Power: CFD-validated flow channel design minimizes pressure drop, reducing fan and pump energy consumption by 10–20%.
- Full Traceability: Each production lot is traceable to its material heat number, simulation run ID, and final performance test data — enabling complete lifecycle documentation.
- Extended Service Life: Electropolished surfaces with validated passive film integrity provide 2–3× longer service life in corrosive environments compared to standard mill-finish alternatives.
- Customizable to Application: The simulation platform enables rapid design adaptation to specific thermal loads, flow rates, and space constraints without compromising performance predictability.
Technical Notes
Wenzhou Jixing Metal Materials Co., Ltd. maintains a dedicated Computer Simulation and Performance Analysis Laboratory equipped with high-performance computing (HPC) clusters capable of running transient CFD simulations with mesh resolutions exceeding 5 million elements. This infrastructure supports rapid design iteration cycles of 48–72 hours per concept, significantly accelerating time-to-market while maintaining engineering rigor.
All products are manufactured in compliance with the company's internally developed FCU-Coil Performance Verification Protocol (FCPVP), which mandates cross-validation of simulation predictions against empirical test data from a calibrated thermal performance test rig (capacity: 50–500 kW heating/cooling range).