Stainless Steel Coil Tube for Continuous Flow Microwave Heating Systems
Product Overview
This product is a precision-engineered stainless steel coil tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for applications involving continuous flow microwave heating of liquids. The coil tube geometry facilitates uniform electromagnetic energy absorption by the fluid medium as it traverses the helical channel, enabling efficient thermal processing, pasteurization, and sterilization. The design principle is grounded in rigorous research on the dielectric heating behavior of continuously flowing liquids within confined tubular geometries, ensuring reproducible and scalable microwave-assisted thermal processing performance.
The coil tube configuration provides a high surface-area-to-volume ratio, which is critical for maximizing microwave coupling efficiency. As liquid flows through the coiled channel, the extended path length within the microwave field ensures sufficient residence time for complete thermal activation, making this product ideal for food-grade pasteurization, pharmaceutical sterilization, chemical reaction enhancement, and industrial heat exchange systems.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its exceptional corrosion resistance, mechanical integrity under thermal cycling, and compatibility with food-grade and pharmaceutical processing environments.
- Base Material: Austenitic Stainless Steel (SS304 / SS316L / SS321, depending on application requirements)
- Corrosion Resistance: Excellent resistance to organic acids, chlorides, and alkaline solutions; passivation layer (Cr₂O₃) provides long-term oxidation protection
- Mechanical Properties: Yield strength ≥ 205 MPa (SS304); tensile strength ≥ 520 MPa; elongation ≥ 40%
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, suitable for rapid heat transfer applications
- Temperature Range: Continuous operation from −196°C to +870°C (SS304); up to +925°C (SS321)
- Electromagnetic Compatibility: Non-magnetic (relative permeability μᵣ ≈ 1.005), ensuring minimal eddy current losses and optimal microwave field penetration into the fluid medium
- Surface Finish: Electropolished inner surface (Ra ≤ 0.4 μm) to minimize biofilm formation and fluid flow resistance
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code | No. 372 |
| Material Grade | SS304 / SS316L / SS321 (customizable) |
| Outer Diameter (OD) | 6 mm – 50 mm (standard); up to 100 mm (special order) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch | 10 mm – 50 mm (adjustable per thermal load requirements) |
| Coil Diameter | 50 mm – 500 mm |
| Tube Length per Coil | 1 m – 50 m (continuous or modular) |
| Pressure Rating | Up to 4.0 MPa (PN40) at 20°C |
| Flow Velocity Range | 0.5 – 10 m/s |
| Surface Treatment | Electropolishing / Passivation / Pickling |
| End Connection | Flanged / Threaded / Welding Ends / Tri-Clamp |
| Applicable Frequency | 915 MHz / 2.45 GHz (industrial microwave bands) |
| Hygienic Standard | 3-A Sanitary / FDA 21 CFR / EC 1935/2004 |
Manufacturing Process
The production of the stainless steel coil tube follows a multi-stage precision manufacturing protocol to ensure dimensional accuracy, material homogeneity, and surface integrity:
- Material Selection & Inspection: Virgin stainless steel strip or seamless tube stock is procured from certified mills, accompanied by mill test certificates (MTC) verifying chemical composition and mechanical properties in accordance with ASTM A269 / EN 10216 standards.
- Cold Forming & Coiling: The tube is cold-drawn and helically coiled using precision CNC-controlled forming machinery to achieve exact pitch, diameter, and wall thickness tolerances (±0.05 mm). Cold working enhances yield strength while preserving the non-magnetic austenitic microstructure.
- Heat Treatment (Stress Relief): Post-forming annealing at 1050°C – 1150°C followed by rapid water quenching eliminates residual stresses introduced during cold coiling, restores full ductility, and ensures uniform grain structure.
- Pickling & Passivation: The coiled tube is subjected to acid pickling (HNO₃/HF blend) to remove scale and contamination, followed by nitric acid passivation to establish a protective chromium oxide layer.
- Electropolishing: Inner surface is electropolished using anodic dissolution to achieve a mirror-like finish (Ra ≤ 0.4 μm), critical for hygienic applications and minimizing flow turbulence effects on microwave heating uniformity.
- End Finishing & Assembly: Tube ends are cut, deburred, and fitted with the selected connection type (flange, thread, or welding preparation).
- Final Quality Inspection: Each coil tube undergoes dimensional verification (OD, wall thickness, pitch), hydrostatic pressure testing (1.5× working pressure), surface defect inspection (eddy current / visual), and material traceability verification.
Applications
The stainless steel coil tube is engineered for demanding applications where continuous flow microwave heating and sterilization are required:
- Food & Beverage Industry: Continuous flow pasteurization and sterilization of liquid foods (milk, juice, sauces, beverages) using microwave-assisted thermal processing. The coil geometry ensures uniform temperature distribution, eliminating hot spots and cold zones that compromise product safety and quality.
- Pharmaceutical Industry: Sterilization of aqueous pharmaceutical solutions, injection-grade fluids, and bioprocessing media. The non-toxic, non-leaching properties of austenitic stainless steel ensure product purity compliance with GMP standards.
- Chemical Processing: Microwave-assisted catalytic reactions, solvent recovery, and continuous flow chemical synthesis where rapid and uniform heating is essential for reaction kinetics and selectivity.
- Industrial Heat Exchange: Use as a heat exchanger element in processes requiring rapid thermal cycling, leveraging the high surface-to-volume ratio of the coiled configuration.
- Biomedical Equipment: Component in microwave-based sterilization systems for medical device decontamination and endoscope reprocessing.
- Research & Development: Laboratory-scale and pilot-scale studies on microwave heating mechanisms, dielectric property characterization of fluids, and sterilization efficacy evaluation.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full product traceability and compliance with international standards:
- ISO 9001:2015 – Quality Management System Certification
- ISO 14001:2015 – Environmental Management System Certification
- ISO 45001:2018 – Occupational Health and Safety Management System
- CE Marking – European Conformity (Directive 2014/68/EU Pressure Equipment Directive)
- 3-A Sanitary Standards – U.S. Dairy Products Sanitary Standards
- NSF/ANSI 61 – Drinking Water System Components
- FDA 21 CFR – U.S. Food and Drug Administration compliance for food-contact materials
- EC 1935/2004 – European Framework Regulation on food-contact materials
- EN 10204-3.1 – Third-party inspection and material testing certificates
- PED (Pressure Equipment Directive) – Applicable for pressure-containing applications
Unique Selling Points
- Scientifically Validated Geometry: Coil pitch and diameter are optimized based on peer-reviewed research into microwave heating uniformity of continuously flowing liquids, ensuring predictable thermal profiles and sterilization efficacy.
- Non-Magnetic Material Selection: Austenitic stainless steel (μᵣ ≈ 1.005) eliminates parasitic electromagnetic interference, maximizing microwave energy transfer to the fluid medium rather than the tube wall.
- Hygienic Inner Surface: Electropolished finish (Ra ≤ 0.4 μm) prevents biofilm accumulation, ensuring consistent flow characteristics and long-term sterilization reliability.
- Modular Scalability: Available in standard coil lengths and diameters, easily integrated into continuous flow processing lines from pilot-scale to full industrial production.
- Full Material Traceability: Every coil tube is accompanied by a complete material traceability dossier including mill certificates, heat treatment records, and final inspection reports.
- Custom Engineering Support: Tailored coil geometry, material grade, and connection specifications available to match specific process parameters (flow rate, residence time, target temperature, sterilization D-value requirements).