Stainless Steel Spiral Coil Tube — Gradual-Transition Helical Coil for Thermal Energy Storage Systems
Product Overview
The Gradual-Transition Spiral Coil Tube (Model Reference: No. 426) is a high-performance stainless steel coil tube product engineered for advanced thermal energy storage (TES) systems. Developed and manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a cutting-edge application of helical coil geometry in conjunction with numerical simulation and experimental validation methodologies. The gradual-transition design ensures a smooth variation in coil pitch and diameter along the axial direction, optimizing heat transfer efficiency and fluid dynamics within thermal storage media.
This product is the result of extensive research in computational fluid dynamics (CFD) and thermofluid analysis, specifically informed by the study titled "Numerical Simulation and Experimental Research on the Heat Storage Process of Gradual Spiral Coil." The coil tube is designed to maximize the volumetric heat storage density while minimizing thermal stratification losses and pressure drop across the system.
Material & Properties
The coil tube is fabricated from high-grade stainless steel, selected for its superior combination of thermal conductivity, corrosion resistance, and mechanical integrity under cyclic thermal loading conditions.
- Primary Material Grade: Austenitic Stainless Steel (e.g., SUS304 / AISI 304, SUS316L / AISI 316L)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 25°C (SUS304); 14.6–16.3 W/(m·K) at 25°C (SUS316L)
- Maximum Service Temperature: Up to 870°C (SUS304); Up to 870°C (SUS316L)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion; suitable for aggressive chemical environments
- Mechanical Strength: Tensile strength ≥ 520 MPa (SUS304); ≥ 515 MPa (SUS316L)
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /K (25–300°C)
- Surface Finish: Electropolished or passivated surface (Ra ≤ 0.4 μm available upon request)
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) Range | 6 – 50 (customizable) | mm |
| Wall Thickness Range | 0.5 – 3.0 | mm |
| Coil Pitch (Gradual Transition) | Variable — linear or exponential taper profile | mm |
| Coil Diameter (Mean) | 50 – 500 (customizable) | mm |
| Overall Coil Length | Up to 2,000 (customizable) | mm |
| Number of Turns | 10 – 500+ | — |
| Maximum Operating Pressure | Up to 2.5 | MPa |
| Thermal Efficiency (Simulated) | ≥ 92% | % |
| Pressure Drop (Typical) | ≤ 0.05 (design-dependent) | MPa |
| Connection Type | Threaded / Flanged / Welded / Quick-Coupling | — |
| Surface Treatment | Passivation / Electropolishing / PTFE Coating (optional) | — |
| Standards Compliance | ASTM A269, ASTM A213, GB/T 12771, EN 10216-5 | — |
Manufacturing Process
The production of the Gradual-Transition Spiral Coil Tube follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical integrity, and consistent performance characteristics:
- Raw Material Selection and Verification: Stainless steel strip or seamless tube stock is sourced from certified mills and subjected to spectroscopic analysis (OES) and mechanical testing to confirm compliance with specified grades.
- Precision Coiling and Forming: Computer Numerical Control (CNC) coil winding machines are employed to achieve the gradual-transition geometry. The coil pitch and diameter are programmatically varied along the axial length according to pre-defined profiles derived from CFD optimization results.
- Heat Treatment (if applicable): Solution annealing at 1010–1150°C followed by rapid water quenching ensures full austenitic structure and optimal corrosion resistance, particularly for grades susceptible to sensitization (e.g., SUS304).
- Welding and Joint Fabrication: Where multi-segment coils are required, orbital TIG (Tungsten Inert Gas) welding is employed with full penetration and visual/NDT (Non-Destructive Testing) inspection of all weld seams.
- Surface Finishing: Electropolishing removes surface contaminants and establishes a uniform chromium oxide passive layer. Passivation treatment with nitric acid or citric acid solutions further enhances corrosion resistance.
- Quality Control and Testing: Each coil assembly undergoes hydrostatic pressure testing (at 1.5× maximum operating pressure), dimensional verification via laser scanning or coordinate measuring machine (CMM), and optional heat transfer performance bench testing.
Applications
The Gradual-Transition Spiral Coil Tube is designed for a wide range of industrial and commercial applications where efficient thermal energy storage, heat exchange, or fluid conditioning is required:
- Thermal Energy Storage (TES) Systems: Integration with molten salt, phase change material (PCM), or packed-bed sensible heat storage systems for solar thermal power plants, district heating networks, and industrial waste heat recovery.
- Heat Exchangers: Compact spiral coil heat exchangers for process heating/cooling in chemical processing, pharmaceutical manufacturing, and food & beverage industries.
- Refrigeration and HVAC: Evaporator and condenser coils for high-efficiency refrigeration systems and commercial heating, ventilation, and air conditioning (HVAC) installations.
- Geothermal Energy Systems: Borehole heat exchangers utilizing spiral coil configurations to maximize ground-coupled heat transfer area within constrained diameters.
- Power Generation: Feedwater preheating coils, economizers, and superheaters in combined heat and power (CHP) plants and cogeneration systems.
- Research and Development: Laboratory-scale prototypes for thermofluid research, CFD model validation, and experimental heat transfer studies.
Quality Certifications and Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and standards compliance:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- Material Certifications: Mill Test Certificates (MTC) conforming to EN 10204 Type 3.1 for each production batch
- Product Standards: ASTM A269 (Welded Austenitic Stainless Steel Tubing), ASTM A213 (Seamless Austenitic Stainless Steel Tubing), GB/T 12771 (Chinese National Standard for Welded Stainless Steel Tubing), EN 10216-5 (European Standard for Non-Alloy and Alloy Steel Tubes for Heat Exchangers)
- Non-Destructive Testing (NDT): 100% visual inspection, spot radiographic testing (RT), and eddy current testing (ET) for weld integrity verification
- Pressure Testing: Hydrostatic pressure testing per ASME BPV Code Section VIII compliance
Unique Selling Points
The Gradual-Transition Spiral Coil Tube by Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through several key technical advantages:
- CFD-Optimized Gradual-Transition Geometry: Unlike conventional constant-pitch helical coils, the gradual-transition design is derived from rigorous numerical simulation of the heat storage process, resulting in superior thermal stratification management and enhanced volumetric storage efficiency (≥ 92% simulated thermal efficiency).
- Reduced Pressure Drop: The tapered coil pitch profile minimizes flow resistance while maintaining high heat transfer coefficients, enabling lower pumping power requirements and improved system energy efficiency.
- Experimentally Validated Performance: The product design is backed by both numerical simulation and physical experimental validation, ensuring reliable real-world performance predictability.
- Full Customization Capability: Coil dimensions, transition profiles, material grades, and connection configurations are fully customizable to meet specific application requirements and system integration constraints.
- Superior Durability and Corrosion Resistance: High-grade austenitic stainless steel construction ensures long service life even in aggressive thermal and chemical environments, with minimal maintenance requirements.
- Compact Footprint: The helical coil geometry achieves maximum heat transfer surface area within a minimized volumetric envelope, making it ideal for space-constrained installations.
Technical Notes
The gradual-transition spiral coil geometry addresses a critical limitation of conventional constant-pitch helical coils in thermal energy storage applications: the tendency for early-stage thermal bypass and reduced effective storage capacity. By progressively varying the coil pitch along the flow direction, the fluid residence time distribution is optimized to ensure uniform heat release during discharge cycles, thereby maximizing the usable thermal energy fraction of the storage medium.
For detailed engineering consultation, custom design specifications, or batch production inquiries, please contact Wenzhou Jixing Metal Materials Co., Ltd. with your specific application parameters including operating temperature range, flow rate, desired storage capacity, and system pressure requirements.