Stainless Steel Spiral Coil Tube — Coiltube Series (Model No. 596)
1. Product Overview
The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed in a continuous spiral geometry, forming a helical winding configuration that maximizes the heat transfer surface area per unit volume. The spiral coil architecture is widely recognized in thermal engineering for its superior convective heat transfer characteristics, particularly under conditions of gas-phase flow within confined helical passages.
Based on the principles established in numerical simulation studies of helium gas flow and heat transfer within spiral coil heat exchangers (《螺旋盘管换热器内氦气流动传热的数值模拟研究》), the Coiltube product line is engineered to optimize the interplay between fluid dynamics and thermal performance. The helical curvature induces secondary Dean vortices within the flowing medium, which enhance turbulence intensity and disrupt the thermal boundary layer, thereby significantly improving the overall heat transfer coefficient compared to straight-tube configurations.
Wenzhou Jixing Metal Materials Co., Ltd. positions this product within the literature-study classification (一级分类: 文献学习), indicating that the design parameters and performance benchmarks are derived from rigorous academic research and computational fluid dynamics (CFD) simulation data, ensuring a science-based approach to product development.
2. Material & Properties
2.1 Base Alloy Composition
The Coiltube product line is primarily fabricated from austenitic stainless steel grades conforming to international standards. The principal material options include:
- AISI 304 / SUS304 (ASTM A213 TP304): Contains 18–20% Chromium (Cr) and 8–10.5% Nickel (Ni), offering excellent general corrosion resistance and formability.
- AISI 316 / SUS316 (ASTM A213 TP316): Contains 2–3% Molybdenum (Mo) in addition to Cr and Ni, providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- AISI 321 / SUS321 (ASTM A213 TP321): Stabilized with Titanium (Ti), suitable for elevated-temperature applications up to 870°C (1600°F) with resistance to intergranular corrosion.
- AISI 316L / SUS316L (ASTM A213 TP316L): Low-carbon variant (C ≤ 0.03%) for enhanced weldability and resistance to sensitization during welding operations.
2.2 Mechanical Properties (Typical Values for Annealed Condition)
| Property | ASTM A213 TP304 | ASTM A213 TP316 | ASTM A213 TP321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 | ≥ 515 |
| Yield Strength (MPa, 0.2% offset) | ≥ 205 | ≥ 170 | ≥ 205 |
| Elongation (% in 50 mm / 2 in.) | ≥ 40 | ≥ 40 | ≥ 40 |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 |
| Specific Heat at 100°C (J/kg·K) | 502 | 500 | 502 |
| Thermal Expansion Coefficient (20–100°C, μm/m·K) | 17.3 | 17.3 | 17.3 |
2.3 Corrosion Resistance
The austenitic microstructure of the selected grades provides exceptional resistance to atmospheric corrosion, oxidizing acids, and a wide range of aqueous environments. The passive chromium oxide film (Cr₂O₃) self-heals in the presence of oxygen, maintaining long-term surface integrity. For applications involving helium gas flow — as studied in the referenced numerical simulation research — the material exhibits negligible reactivity with noble gases, ensuring no degradation of tube wall integrity under high-temperature, high-pressure helium service conditions.
3. Specifications
3.1 Geometric Dimensions
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ3.0 mm – Φ50.8 mm | ASTM A213 / ASME B36.19M |
| Wall Thickness | 0.3 mm – 6.0 mm | ASTM A269 / EN 10217-7 |
| Helix Diameter (Center-to-Center) | Φ50 mm – Φ2000 mm | Custom / Project-Specific |
| Pitch (Turn Spacing) | 5 mm – 100 mm | Custom / Project-Specific |
| Number of Turns | 1 – 500+ | Custom / Project-Specific |
| Tube Length (Unwound) | 1 m – 500 m | Custom / Project-Specific |
| Surface Finish (Ra) | 0.4 μm – 1.6 μm (Polished/Baught) | ASTM A269 / Custom |
3.2 Pressure and Temperature Ratings
| Parameter | Typical Value | Notes |
|---|---|---|
| Maximum Operating Temperature (304/321) | 870°C (1600°F) | Continuous service; short-term up to 1100°C |
| Maximum Operating Temperature (316/316L) | 593°C (1100°F) | With consideration of carbide precipitation |
| Cryogenic Service Temperature | -196°C (-320°F) | Maintains ductility; no brittle fracture |
| Maximum Working Pressure (Φ12 mm × 1 mm, 304) | ~35 MPa (5000 PSI) | At 20°C ambient; pressure-temperature dependent |
| Hydrostatic Test Pressure | 1.5 × Working Pressure | Per ASME BPV Section VIII |
3.3 Applicable Standards
- ASTM A213 — Specification for Seamless Austenitic Stainless Steel Tubing for Heat-Exchanger and Heat-Sink Service
- ASTM A269 — Specification for Welded Austenitic Stainless Steel Tubing
- ASME SA-213 — Seamless Austenitic Chromium-Nickel Stainless Steel Tubing for High-Service Temperatures
- EN 10217-7 — Non-Alloy and Alloy Steel Tubes for Heat Exchangers and Similar Heat-Exchange Equipment
- GB/T 12771 — Stainless Steel Tubes for Heat Exchangers and Heat Sinks (Chinese National Standard)
- ASME BPV Section VIII — Boiler and Pressure Vessel Code (for pressure-containing applications)
4. Manufacturing Process
4.1 Raw Material Preparation
Manufacturing commences with the procurement of certified stainless steel seamless tube stock or precision-welded pipe conforming to ASTM A213 or ASTM A269 specifications. Each incoming lot undergoes spectrometric analysis (Optical Emission Spectroscopy, OES) to verify chemical composition, along with mechanical testing (tensile, hardness) and non-destructive examination (Eddy Current Testing, ECT) to confirm conformance to material specifications.
4.2 Coil Forming (Spiral Winding)
The helical geometry is achieved through a controlled cold-forming process utilizing a precision spiral coiling machine. The process involves:
- End Preparation: Tube ends are deburred, chamfered, and inspected for dimensional accuracy to ensure proper engagement with the forming tooling.
- Progressive Winding: The straight tube is fed through a rotating die assembly that imparts a continuous helical curvature. The mandrel diameter, tooling radius, and feed rate are precisely controlled to achieve the target helix diameter and pitch with dimensional tolerances of ±0.5 mm.
- Spring-Back Compensation: Computational models account for elastic recovery (spring-back) of the austenitic stainless steel during forming, ensuring the final geometry matches design specifications after unloading.
- Continuous Monitoring: In-process dimensional measurement systems (laser profilometry or optical scanning) verify helix diameter and pitch consistency throughout production.
4.3 Heat Treatment (if required)
For applications requiring restoration of full annealed properties after cold-forming, a solution annealing treatment is performed at 1050–1150°C (1922–2092°F) followed by rapid water quenching. This eliminates strain hardening effects and restores the uniform austenitic microstructure, ensuring maximum ductility and corrosion resistance.
4.4 Surface Treatment
Optional surface finishing includes:
- Pickling and Passivation: Removal of mill scale and formation of a stable chromium oxide passive layer per ASTM A380.
- Electrolytic Polishing: Achieves surface roughness values as low as Ra 0.2 μm for applications requiring ultra-clean internal surfaces (e.g., pharmaceutical, food-grade, or high-purity gas service).
- Passivation Verification: Confirmed via ferrite content testing (ferrite number ≤ 4 FN for 304/316 grades) and surface cleanliness inspection.
4.5 Quality Inspection
- Dimensional Inspection: Helix diameter, pitch, tube OD, wall thickness, and overall length verified per drawing tolerances.
- Non-Destructive Testing (NDT): Eddy current testing (ASTM E309) for wall thickness uniformity; dye penetrant testing (ASTM E709) for surface discontinuities.
- Pressure Testing: Hydrostatic or pneumatic pressure testing at 1.5× the maximum working pressure with a minimum hold time of 30 seconds.
- Chemical Analysis: Final lot verification via OES or wet chemical analysis.
- Performance Simulation Validation: CFD-based verification of flow and heat transfer characteristics for critical applications, referencing the numerical simulation methodology from the referenced helium gas flow study.
5. Applications
The Stainless Steel Spiral Coil Tube finds extensive application across multiple high-performance engineering sectors:
5.1 Heat Exchanger Systems
- Shell-and-Coil Heat Exchangers: The spiral coil serves as the tube bundle within a pressure shell, providing compact heat exchange for liquid-liquid, gas-liquid, and gas-gas applications.
- Plate and Coil Heat Exchangers: Integrated into modular heat exchange units for industrial process cooling and heating.
- Cryogenic Heat Exchangers: Utilized in helium liquefaction systems and cryogenic natural gas (LNG) processing, where the referenced numerical simulation study on helium flow heat transfer directly informs design optimization.
5.2 Energy and Nuclear Industry
- Reactor Coolant Systems: Helium-cooled reactors (High-Temperature Gas Reactors, HTGR; Very High Temperature Reactors, VHTR) utilize stainless steel spiral coils as intermediate heat exchanger (IHX) elements for primary-to-secondary loop heat transfer.
- Supercritical CO₂ Brayton Cycles: Compact spiral coil recuperators for next-generation power generation systems.
5.3 Chemical and Petrochemical Processing
- Process Reactor Cooling/Heating: Internal coil inserts for jacketed reactors requiring controlled temperature profiles.
- Distillation Column Reboilers and Condensers: Compact spiral coil designs for high-efficiency phase-change heat transfer.
- Corrosive Fluid Handling: 316/316L grade coils for acid service, chlorinated water treatment, and chemical synthesis.
5.4 Aerospace and Defense
- Hydraulic Cooling Systems: Lightweight spiral coils for aircraft hydraulic fluid temperature regulation.
- Fuel Preheating Systems: Jet engine fuel cooling/heat recovery loops.
5.5 Food and Pharmaceutical Industry
- Pasteurization and Sterilization: Electropolished 316L spiral coils for milk, beverage, and pharmaceutical fluid processing.
- High-Pressure Homogenizers: Cooling coils for temperature control during homogenization.
5.6 Refrigeration and HVAC
- Evaporator/Condenser Coils: Spiral wound coils for compact refrigeration units, cold storage systems, and industrial chiller applications.
6. Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management and certification framework:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System — Design, Manufacturing, and Supply of Stainless Steel Tubular Products |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| CE Marking (EU) | Conformance with European Pressure Equipment Directive (PED 2 |