Coil Tube (Floating Coil Tube) — Product Technical Specification

1. Product Overview

The Coil Tube, also referred to as a Floating Coil Tube (浮动盘管), is a specialized heat exchanger component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is engineered according to advanced design and manufacturing principles derived from industry-standard literature on copper and copper alloy floating coil tube systems, while leveraging the company's extensive expertise in stainless steel metallurgy and piping technology.

Floating coil tubes are characterized by their helical or serpentine geometry, which allows for enhanced heat transfer efficiency through increased surface area and turbulent fluid flow. The "floating" designation refers to the mechanical design that permits thermal expansion and contraction without inducing stress on the tube structure or its mounting supports. These coil tubes are widely employed in thermal management systems where compactness, efficiency, and durability are paramount.

Product Catalogue Reference No.: 1215

2. Material & Properties

2.1 Primary Materials

Copper and Copper Alloys (Cu, Cu-Ni, Cu-Al): As per the foundational design literature, copper and copper alloy materials are the primary construction materials for floating coil tubes. These offer exceptional thermal conductivity (up to 401 W/m·K for pure copper), excellent corrosion resistance, and superior formability for helical winding processes.
Stainless Steel Grades (AISI 304, 316, 316L, 321): Leveraging Wenzhou Jixing's core metallurgical expertise, stainless steel coil tubes are available for applications requiring higher mechanical strength, elevated temperature resistance, and resistance to aggressive chemical environments.

2.2 Key Material Properties

Property	Copper Alloy (Cu-Ni 90/10)	Stainless Steel (AISI 316L)
Thermal Conductivity (W/m·K)	42–45	14–16
Specific Heat Capacity (J/kg·K)	380	480
Tensile Strength (MPa)	240–310	515–620
Yield Strength (MPa)	100–140	205–310
Maximum Operating Temperature (°C)	300	870
Corrosion Resistance	Excellent (seawater, marine)	Superior (chemical, food-grade)
Density (g/cm³)	8.94	8.03

2.3 Metallurgical Characteristics

The floating coil tube design demands materials with specific metallurgical properties:

Cyclic Fatigue Resistance: The helical winding geometry subjects the tube wall to repeated bending stresses during operation. Materials must exhibit high fatigue limits under thermal cycling conditions.
Creep Resistance: At elevated operating temperatures, materials must resist time-dependent deformation to maintain dimensional stability of the coil geometry.
Weldability: End connections and header joints require reliable fusion or brazing compatibility without significant loss of mechanical integrity in the Heat-Affected Zone (HAZ).
Thermal Expansion Coefficient Compatibility: The floating design accommodates differential thermal expansion between the coil tube and the shell/vessel, reducing the need for expansion joints.

3. Specifications

3.1 Geometric Dimensions

Parameter	Specification
Tube Outer Diameter (OD)	Ø12 mm – Ø50 mm (standard); custom up to Ø80 mm
Tube Wall Thickness	0.5 mm – 3.0 mm
Coil Mean Diameter	Ø100 mm – Ø1,500 mm
Coil Height (Axial Length)	200 mm – 3,000 mm
Coil Pitch (Turn Spacing)	8 mm – 50 mm (adjustable for flow/heat transfer optimization)
Number of Turns	4 – 60 turns (custom configuration)
End Connection Type	Flanged, threaded (NPT/BSP), welded stub, or sanitary tri-clamp
Surface Finish	Bright annealed, pickled & passivated (Ra ≤ 0.8 μm), or electropolished (Ra ≤ 0.4 μm)

3.2 Performance Parameters

Parameter	Typical Value / Range
Heat Transfer Coefficient	2,500 – 6,000 W/m²·K (depending on fluid velocity and geometry)
Maximum Operating Pressure	1.6 – 6.4 MPa (design-dependent)
Hydrostatic Test Pressure	1.5× Maximum Operating Pressure
Reynolds Number Range	Re > 10,000 (fully turbulent flow regime)
Pressure Drop (per coil length)	15 – 80 kPa/m (optimized for specific application)

3.3 Standards & Compliance

Standard	Description
ASTM B330 / B365	Copper and copper alloy seamless tubing specifications
ASTM A213 / A269	Stainless steel seamless tubing specifications
ASME BPV Section VIII	Pressure vessel and heat exchanger construction code
EN 10217 / EN 10216	European seamless steel tube standards
GB/T 14976 / GB/T 21830	Chinese national standards for stainless steel seamless tubes
TEMA (Tubular Exchanger Manufacturers Association)	Heat exchanger design and manufacturing standards
ASME BPE	Bioprocessing Equipment (for pharmaceutical applications)

4. Manufacturing Process

4.1 Process Flow

Raw Material Selection & Inspection: Premium-grade copper alloys (Cu-Ni 90/10, Cu-Al) or stainless steel seamless tubes are procured with mill certification. Incoming material undergoes spectroscopic analysis (OES), tensile testing, and hydrostatic examination.
Cold Drawing & Annealing: Tubes are cold-drawn to precise dimensional tolerances (±0.05 mm on OD) and subsequently annealed to relieve residual stresses and restore ductility for subsequent forming operations.
Helical Forming / Coil Winding: The tube is wound into the specified helical geometry using CNC-controlled coiling machines. The winding process is executed at controlled speeds to prevent work-hardening and ensure uniform curvature throughout the coil length.
Stress Relief Annealing: Post-forming annealing (typically 400–650°C for stainless steel; 600–750°C for copper alloys) eliminates residual stresses introduced during coiling, ensuring dimensional stability and optimal fatigue life.
End Forming & Connection Fabrication: Tube ends are formed into flanges, threaded connections, or welded stubs. Brazing or TIG (Tungsten Inert Gas) welding is employed for joint fabrication.
Surface Treatment: Pickling and passivation (for stainless steel) or acid cleaning and descaling (for copper alloys) remove oxidation and contaminants. Electropolishing is available for sanitary-grade applications.
Quality Inspection: Comprehensive inspection including dimensional verification (CMM), pressure testing, dye penetrant testing (DPT) for weld integrity, and visual inspection.
Packaging & Delivery: Coils are protected with corrosion-inhibitive coatings, wrapped in protective film, and packaged for safe transport.

4.2 Design Principles (Floating Coil Tube)

Based on the foundational literature "Design and Manufacturing of Copper and Copper Alloy Floating Coil Tubes", the floating coil tube design incorporates the following critical engineering principles:

Thermal Expansion Accommodation: The coil tube is suspended or supported in a manner that permits free axial and radial expansion without imposing constraint stresses on the tube body or vessel wall. Support saddles are designed with sliding surfaces or roller bearings.
Flow Distribution Optimization: Inlet and outlet configurations are engineered to ensure uniform fluid distribution across the coil, preventing flow maldistribution that would reduce overall heat transfer effectiveness.
Compactness Factor: The helical geometry achieves a surface-area-to-volume ratio significantly higher than straight-tube designs, enabling compact heat exchanger packages.
Self-Cleaning Characteristics: The helical path generates secondary flows (Dean vortices) that enhance turbulence and minimize fouling deposition on the tube inner surface.

5. Applications

5.1 Primary Application Domains

Marine & Naval Engineering: Seawater cooling systems, shipboard condensers, and heat recovery units. Copper-nickel alloys provide outstanding resistance to marine biofouling and seawater corrosion.
Chemical Processing: Reactor cooling jackets, distillation column condensers, and heat recovery systems. Stainless steel grades resist aggressive chemical media.
Power Generation: Feedwater preheaters, economizers, and condenser tubes in thermal power plants and nuclear facilities.
Pharmaceutical & Bioprocessing: Sterile heat exchange systems requiring electropolished surfaces and compliance with ASME BPE standards.
Food & Beverage Industry: Pasteurization systems, CIP (Clean-in-Place) compatible heat exchangers, and refrigeration condensers.
HVAC & Refrigeration: Chiller coils, air-cooled condensers, and heat pump components.
Oil & Gas: Process heat exchangers, heat recovery steam generators (HRSG), and subsea thermal management systems.
Electronics Cooling: Immersion cooling loops and liquid-to-air heat exchangers for high-power computing and data center applications.

5.2 Unique Selling Points

Superior Heat Transfer Efficiency: The helical coil geometry generates Dean vortices that increase the heat transfer coefficient by 20–40% compared to straight-tube equivalents of the same diameter, reducing required heat transfer area and equipment footprint.
Compact Design: Achieves high thermal performance in a fraction of the volume required by conventional shell-and-tube heat exchangers, ideal for space-constrained installations.
Thermal Stress Mitigation: The floating design eliminates thermal stress accumulation at support points, extending service life and reducing maintenance frequency.
Multi-Material Capability: Available in both copper/copper alloy (for maximum thermal conductivity) and stainless steel (for maximum corrosion resistance and mechanical strength), allowing material selection optimized for specific service conditions.
Customizable Geometry: Coil pitch, diameter, number of turns, and end configurations are tailored to match specific process requirements and vessel geometries.
Low Fouling Tendency: Enhanced turbulence and secondary flow patterns within the helical path minimize deposit accumulation, reducing cleaning frequency and unplanned downtime.