Semi-Circular Coil Tube for Floating Coil Heat Exchangers
Product Overview
The Semi-Circular Coil Tube (Half-Round Coil Tube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a specialized stainless steel coil tube engineered for use in floating coil heat exchangers. This product represents an advanced solution in thermal exchange technology, leveraging the geometric advantages of a semi-circular cross-section to optimize heat transfer efficiency while maintaining structural integrity under dynamic thermal cycling conditions.
Unlike conventional round coil tubes, the semi-circular (half-round) profile provides superior surface-to-volume ratio characteristics and enhanced fluid dynamics within the heat exchanger shell. The floating coil design allows the coil assembly to expand and contract freely within the shell, accommodating thermal differential expansion without inducing mechanical stress on the tube-sheet or shell walls.
Material & Properties
Base Material Composition
The coil tubes are fabricated from high-grade austenitic stainless steel, conforming to internationally recognized standards including ASTM A213 (Tubing, Seamless Austenitic Stainless Steel), EN 10216-5, and GB/T 12771. The primary material grade employed is SUS316L (UNS S31603) or SUS304L (UNS S30403), selected for their exceptional corrosion resistance, weldability, and high-temperature performance.
Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (SUS316L) / ≥ 515 MPa (SUS304L)
- Yield Strength (0.2% Proof): ≥ 205 MPa
- Elongation: ≥ 40% (at fracture)
- Hardness (HBW): ≤ 217
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient (α): 16.0–17.5 × 10⁻⁶ /°C (20–100°C)
Corrosion Resistance
The addition of molybdenum (2.0–3.0%) in the SUS316L grade provides superior resistance to pitting and crevice corrosion in chloride-containing environments. The low carbon (≤ 0.03%) composition ensures resistance to intergranular corrosion following welding operations.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Tube Cross-Section Shape | Semi-Circular (Half-Round) | Custom / OEM |
| Tube Outer Dimension (A × B) | 12 × 6 mm / 15 × 7.5 mm / 19 × 9.5 mm (typical) | Manufacturer Spec. |
| Wall Thickness | 0.8 – 1.5 mm | ASTM A213 |
| Coil Outer Diameter | Φ200 – Φ800 mm | Custom |
| Coil Pitch (Turn-to-Turn) | 6 – 15 mm (adjustable per design) | Design-Specific |
| Tube Length (Total Developed) | 15 – 60 m | Custom |
| Number of Coils per Assembly | 1 – 200 (configurable) | Heat Exchanger Design |
| Surface Finish | BA (Bright Annealed) / Pickled / Mirror (Ra ≤ 0.4 μm) | ASTM A270 |
| End Preparation | Flat End / Beveled / Threaded / Weld Prep | ASME B31.3 |
| Maximum Operating Temperature | −196°C to +870°C | Material Dependent |
| Maximum Operating Pressure | ≤ 4.0 MPa (design dependent) | ASME Section VIII |
| Heat Transfer Coefficient Enhancement | 15 – 30% over conventional round coil | Empirical Data |
Manufacturing Process
Process Flow
- Raw Material Procurement: Selection of certified seamless stainless steel tube stock (ERW or seamless) from accredited mills, with full mill test certificates (MTC) per EN 10204 Type 3.1.
- Flattening / Semi-Circular Forming: The round tube is precisely flattened to a semi-circular profile using a multi-roll forming machine with servo-controlled roll gap adjustment. The forming process employs cold work to maintain material strength while achieving dimensional accuracy within ±0.1 mm tolerance.
- Coil Winding: The formed semi-circular tube is wound into a helical coil using a CNC-controlled coil winding machine. The winding process ensures uniform pitch, concentricity within ±1 mm, and controlled spring-back compensation.
- Welding (if segmented): For longer coil assemblies, butt-welding is performed using TIG (Tungsten Inert Gas) welding with argon shielding (99.999% purity). Weld procedures are qualified per AWS D1.6 / ISO 15614.
- Surface Treatment: Bright annealing (BA) in a vacuum or controlled-atmosphere furnace to remove cold-work stresses and achieve a smooth, corrosion-resistant surface finish suitable for hygienic and chemical applications.
- Quality Inspection: Dimensional verification using laser scanning, hydrostatic pressure testing per ASTM A530, and surface inspection via visual and penetrant testing (PT) per ASTM E165.
- End Preparation & Packaging: Coil ends are prepared per drawing specifications. Final product is packaged with desiccant protection and shipped in wooden crates or palletized configurations.
Applications
Primary Application Domain: Floating Coil Heat Exchangers
The semi-circular coil tube is the core heat transfer element in floating coil heat exchangers, which find extensive application in the following industries:
- Chemical Processing: Heat exchange for reactive chemicals, acids, and caustic solutions where fouling resistance and ease of cleaning are critical. The floating design allows complete coil removal for maintenance without dismantling the shell.
- Food & Beverage Industry: Pasteurization, sterilization, and cooling of dairy products, beverages, and food slurries. The smooth semi-circular profile minimizes dead zones and product retention.
- Pharmaceutical Manufacturing: CIP (Clean-in-Place) compatible designs for processing solvents, APIs, and sterile fluids under GMP requirements.
- Petrochemical & Refining: Heat recovery in process streams, condensers, and reboilers handling hydrocarbons and process fluids.
- Textile Industry: Dyeing and finishing equipment requiring precise temperature control with fouling-resistant coil designs.
- Central Heating & HVAC: Floating coil designs for district heating networks and industrial heating systems.
Unique Selling Points
- Enhanced Heat Transfer Efficiency: The semi-circular cross-section creates a natural flow channel that promotes turbulent flow at lower Reynolds numbers, achieving 15–30% higher heat transfer coefficients compared to equivalent round coil tubes.
- Superior Fouling Resistance: The half-round geometry eliminates stagnant fluid pockets, reducing fouling accumulation by up to 40% in viscous or particulate-laden fluids.
- Thermal Expansion Accommodation: The floating coil design, combined with the semi-circular profile's flexibility, allows free axial and radial movement during thermal cycling, eliminating stress concentrations at tube-sheet joints.
- Ease of Maintenance: Complete coil assemblies can be withdrawn from the heat exchanger shell for inspection and cleaning without requiring shell removal or flange disassembly.
- Compact Design: Higher heat transfer per unit volume enables smaller equipment footprint and reduced capital expenditure.
- Material Versatility: Available in SUS304L, SUS316L, SUS321, and duplex grades (2205/2507) to suit diverse corrosive environments.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring products meet international standards:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| ASME "U" Stamp | Pressure Vessel Components |
| PED (CE) 2014/68/EU | Pressure Equipment Directive Compliance |
| EN 10204 Type 3.1 | Mill Test Certificate (MTC) — Product-Specific |
| 3-A Sanitary Standards | Food-Grade Surface Quality (where applicable) |
| API 5L / ASTM A213 | Material Conformance |
| ASME BPE | Biopharmaceutical Equipment (for pharma applications) |
Inspection & Testing Protocols
- Dimensional Inspection: Laser profilometry for cross-sectional accuracy (tolerance ±0.1 mm)
- Hydrostatic Testing: Per ASTM A530, test pressure = 1.5 × design pressure, hold time ≥ 30 seconds
- Chemical Analysis: Spectrographic verification (OES) of material composition
- Mechanical Testing: Tensile and hardness testing per ASTM A370
- Non-Destructive Testing: Dye penetrant testing (PT) per ASTM E165 for weld integrity
- Surface Roughness: Verification via contact profilometry (Ra ≤ 0.4 μm for sanitary applications)
- Coating/Passivation Test: Blue dye test per ASTM A967 for passivation layer verification
Technical Notes & Design Considerations
When selecting semi-circular coil tubes for floating coil heat exchanger applications, engineers should consider the following design parameters:
- Clearance Design: The gap between the flat side of the semi-circular tube and the adjacent coil or shell wall should be maintained at a minimum of 1.5× the tube thickness to ensure adequate flow and prevent vibration-induced fretting.
- Thermal Fatigue: For applications with frequent thermal cycling (>10,000 cycles), fatigue life assessment per ASME Section VIII Div. 2 Part 5 is recommended.
- Flow Distribution: Inlet and outlet headers must be designed to ensure uniform flow distribution across all coil elements; maldistribution exceeding 10% may reduce overall exchanger effectiveness.
- Support Spacing: Coil support rings or guide plates should be positioned at intervals not exceeding 600 mm to prevent excessive coil deflection under operating loads.
This product represents the convergence of advanced materials science, precision manufacturing, and thermal engineering, delivering reliable performance in demanding industrial heat exchange applications across global markets.