Stainless Steel Coil Tube — Dual-Channel Heating Coiltube (Model Series JX-CT)
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., the JX-CT Series Stainless Steel Coil Tube represents a precision-engineered product category designed for high-performance thermal management applications. This technical specification document provides a comprehensive description of the product's material composition, dimensional specifications, manufacturing methodology, applicable domains, and quality assurance framework.
Product Overview
The JX-CT Series Coil Tube (盘管) is a continuously wound, helical stainless steel tubing product formed from precision cold-rolled or seamless stainless steel strip/pipe stock. Unlike straight-length piping, coil tubes are produced in continuous spooled configurations that offer significant material utilization advantages, reduced welding requirements, and superior flexibility for complex thermal circuit routing.
Central to the JX-CT product line is the Dual-Channel Heating Coil Tube architecture — a design configuration in which two concentric or parallel flow channels are integrated within a single coil structure. This dual-channel topology enables simultaneous heat exchange between two distinct fluid media (e.g., working fluid and heating medium), thereby maximizing thermal efficiency within a compact volumetric envelope. Advanced computational fluid dynamics (CFD) modeling and heat transfer effect analysis have been applied to optimize the geometric parameters, channel spacing, and flow dynamics of this configuration, yielding measurable improvements in overall heat transfer coefficient (OHTC) and pressure drop characteristics.
Key Design Philosophy
- Thermal Optimization: Dual-channel architecture maximizes heat transfer surface area per unit volume, achieving thermal performance metrics comparable to multi-pass shell-and-tube heat exchangers in a fraction of the footprint.
- Continuous Form Factor: Coiled delivery eliminates the need for field welding and reduces potential failure points associated with pipe joints and flanged connections.
- Material Integrity: Cold-forming processes preserve the metallurgical properties of austenitic stainless steel, ensuring long-term corrosion resistance and mechanical reliability under cyclic thermal loading.
Material & Properties
Available Stainless Steel Grades
The JX-CT Series is manufactured from a range of austenitic and austenitic-ferritic stainless steel grades, selected based on the specific thermal, chemical, and mechanical demands of the application:
- SAE 304 (UNS S30408): The standard general-purpose austenitic grade offering excellent corrosion resistance, formability, and weldability. Suitable for most industrial heat exchange and food-grade applications.
- SAE 316 / 316L (UNS S31608 / S31603): Enhanced pitting and crevice corrosion resistance due to the addition of 2–3% molybdenum. Recommended for marine, chemical processing, and pharmaceutical environments.
- SAE 321 (UNS S32108): Stabilized with titanium to prevent sensitization during welding. Ideal for elevated-temperature service (up to 870 °C) in heat exchangers and furnace applications.
- SAE 310S (UNS S31008): High-temperature grade with superior oxidation resistance, suitable for continuous service up to 1150 °C.
- SAE 316Ti (UNS S31635): Titanium-stabilized 316 variant combining molybdenum-enhanced corrosion resistance with improved weldability and resistance to intergranular corrosion.
Mechanical Properties (Annealed Condition, Representative — SAE 304)
| Property | Specification | Test Method |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ASTM A262 / EN 10204 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ASTM A262 / EN 10204 |
| Elongation (A50) | ≥ 40 % | ASTM A262 |
| Hardness (HV) | ≤ 210 HV | ASTM A262 |
| Density | 7.93 g/cm³ | — |
| Thermal Conductivity (at 20 °C) | 16.3 W/(m·K) | — |
| Thermal Conductivity (at 100 °C) | 16.3 W/(m·K) | — |
| Thermal Conductivity (at 500 °C) | 21.5 W/(m·K) | — |
| Linear Thermal Expansion (20–100 °C) | 17.3 × 10⁻⁶ /K | — |
| Specific Heat (at 20 °C) | 500 J/(kg·K) | — |
Chemical Composition (SAE 304, wt.%)
| Element | C | Mn | P | S | Si | Cr | Ni | N | Fe |
|---|---|---|---|---|---|---|---|---|---|
| Maximum / Range | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 18.0–20.0 | 8.0–10.5 | — | Balance |
Specifications
Dimensional Specifications
| Parameter | Specification / Range | Tolerance | Reference Standard |
|---|---|---|---|
| Outer Diameter (OD) | Φ3.0 mm – Φ38.0 mm | ± 0.1 mm (OD ≤ 12 mm); ± 0.15 mm (OD > 12 mm) | ASTM A269 / EN 10217-7 |
| Wall Thickness (WT) | 0.20 mm – 3.00 mm | ± 10 % of nominal | ASTM A269 / EN 10217-7 |
| Coil Diameter (CD) | Φ50 mm – Φ1500 mm | ± 1 % of nominal | Manufacturer Specification |
| Pitch / Spacing | 2.0 mm – 25.0 mm (configurable) | ± 0.5 mm | Manufacturer Specification |
| Number of Turns | 10 – 10,000+ (custom) | ± 1 turn | — |
| Tube Length (Developed) | 1.0 m – 500.0 m (continuous) | ± 0.5 % | — |
| Surface Finish (Ra) | 0.4 μm – 1.6 μm (standard); 0.1 μm (electropolished) | — | ASTM A269 / EN 10217-7 |
| End Condition | Plain, Beveled, Threaded, Flanged, or Custom | Per drawing | — |
| Surface Treatment | Pickled & Passivated, Electropolished, or Bright Annealed (BA) | — | ASTM A967 |
Dual-Channel Configuration Parameters
| Parameter | Description | Typical Value |
|---|---|---|
| Channel Configuration | Concentric (annular) or Parallel-dual-tube | Application-dependent |
| Inner Channel OD | Outer diameter of the inner tube | Φ3.0 – Φ19.0 mm |
| Outer Channel ID | Inner diameter of the outer tube | Φ5.0 – Φ35.0 mm |
| Annular Gap | Radial clearance between inner and outer channels | 1.0 – 8.0 mm |
| Heat Transfer Surface Area | Total effective exchange area per meter of coil | Calculated per geometry |
| Maximum Operating Pressure | Design pressure rating per channel | Up to 4.0 MPa (typical) |
| Maximum Operating Temperature | Grade-dependent continuous service limit | Up to 870 °C (321); 1150 °C (310S) |
Manufacturing Process
The production of the JX-CT Series Coil Tube follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Inspection & Verification: Incoming stainless steel strip or seamless tube stock is inspected for chemical composition (via XRF or spectroscopic analysis), mechanical properties, and surface quality. Mill test certificates (MTC) conforming to EN 10204 Type 3.1 are verified prior to processing.
- Surface Preparation & Cleaning: The raw material undergoes degreasing, pickling, and passivation treatment to remove scale, oils, and contaminants. This step is critical for ensuring uniform cold-forming behavior and subsequent corrosion resistance.
- Coil Winding (Helical Forming): Precision-wound coil tubes are produced using CNC-controlled coil winding machines. The winding parameters — including coil diameter, pitch, tension, and number of turns — are controlled to within tight tolerances. For dual-channel configurations, concentric tube assemblies are wound simultaneously to maintain precise annular spacing throughout the coil length.
- Cold Forming & Dimensional Stabilization: The formed coil undergoes controlled cold working to achieve the final geometric profile. Interpass annealing may be applied for severe forming conditions to prevent work hardening and maintain ductility.
- Heat Treatment (Annealing): Solution annealing is performed at 1010–1150 °C followed by rapid water quenching to restore full austenitic microstructure, relieve residual stresses, and achieve the specified mechanical properties in the annealed (soft) condition. For stabilized grades (321, 347, 316Ti), a stabilization anneal at 870–900 °C may be applied to precipitate carbides on alloying elements (Ti, Nb) rather than at grain boundaries.
- Pickling & Passivation: Post-annealing pickling removes oxide scale using a mixed acid bath (nitric acid + hydrofluoric acid). Subsequent passivation treatment (per ASTM A967) establishes a protective chromium oxide film on the surface, enhancing corrosion resistance to the maximum achievable level for the given alloy composition.
- Non-Destructive Testing (NDT): 100 % eddy current testing (ECT) is performed to detect internal and external surface discontinuities. Hydrostatic pressure testing (per ASTM A269) is conducted at 1.5× the maximum design pressure to verify leak-tight integrity. Visual inspection of surface finish and dimensional verification using laser scanning or coordinate measurement systems (CMM) complete the quality assurance protocol.
- End Processing & Finishing: Coil ends are cut to specified lengths, and end conditions (beveling, threading, flanging, or welding of fittings) are applied per customer specifications. Final cleaning and protective packaging are performed prior to shipment.
Process Optimization — Dual-Channel Heat Transfer Model
The design and manufacturing of dual-channel heating coil tubes are informed by advanced thermal analysis models. Optimization of the heat transfer effect involves computational simulation of fluid dynamics within both channels, accounting for natural and forced convection, turbulent flow development, and the thermal coupling between the two media across the shared tube wall. Key optimization variables include:
- Coil diameter and pitch — governing secondary flow patterns (Dean vortices) that enhance turbulent mixing and local heat transfer coefficients.
- Annular gap geometry — determining flow velocity, Reynolds number, and pressure drop in the outer channel.
- Material thermal conductivity and wall thickness — balancing conductive resistance against structural requirements.
- Flow rate and inlet temperature matching — ensuring optimal log-mean temperature difference (LMTD) across the exchanger length.
These analytical models enable the prediction of overall heat transfer coefficient (U-value), thermal efficiency (ε), and pressure drop (ΔP) with high fidelity, guiding the selection of optimal geometric and operational parameters for each specific application.
Applications
The JX-CT Series Stainless Steel Coil Tube is deployed across a broad spectrum of industrial, commercial, and specialized applications:
Thermal Management & Heat Exchange
- Industrial Heat Exchangers: Dual-channel coil tubes serve as compact heat exchange elements in process heaters, coolers, and recuperators within chemical, petrochemical, and power generation facilities.
- Refrigeration & HVAC Systems: Evaporator and condenser coils for commercial refrigeration units, air handling systems, and industrial cold storage applications.
- Automotive Thermal Systems: Engine coolant loops, intercooler assemblies, and exhaust gas recirculation (EGR) cooling circuits.
Process & Chemical Industry
- Chemical Processing: Reactor cooling jackets, distillation column internals, and process fluid heating/cooling circuits where corrosion resistance to aggressive media is critical.
- Pharmaceutical & Biotech: Clean-in-place (CIP) compatible coil assemblies for bioreactors, fermentation tanks, and sterile fluid transfer systems meeting FDA and GMP requirements.
- Food & Beverage