Spiral Coil Tube for Shell-and-Tube Phase Change Thermal Storage Units
Product Overview
The Spiral Coil Tube (Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 337) is a precision-engineered stainless steel tube product specifically designed for integration into shell-and-tube heat exchanger assemblies, with particular emphasis on its application in ladder-type Phase Change Material (PCM) thermal storage units. This product represents a critical structural and functional component in advanced thermal energy storage (TES) systems, where the coil tube serves as the working fluid channel within the shell-and-tube configuration, facilitating efficient heat transfer between the circulating heat transfer fluid (HTF) and the surrounding phase change material.
The spiral coil geometry provides a significantly increased heat transfer surface area per unit volume compared to conventional straight-tube designs, enabling superior thermal performance in compact shell-and-tube arrangements. The ladder-type configuration allows for cascaded phase change at multiple temperature levels, maximizing the utilization of stored thermal energy and improving the overall system efficiency through multi-stage energy release.
Material and Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical integrity under cyclic thermal loading conditions.
- Base Material: Austenitic stainless steel conforming to ASTM A213/A213M or equivalent standards
- Typical Grades: SUS304 (18-8 Cr-Ni), SUS316L (low-carbon 18-10 Cr-Ni-Mo), or SUS321 (stabilized with titanium)
- Corrosion Resistance: Excellent resistance to oxidizing environments, aqueous corrosion, and chemical attack from common heat transfer fluids including water, organic heat transfer oils, and molten salts
- Thermal Conductivity: 14–16 W/(m·K) at 20°C for Grade 304, ensuring efficient conductive heat transfer through the tube wall
- Mechanical Properties: Yield strength ≥ 205 MPa; ultimate tensile strength ≥ 515 MPa; elongation ≥ 40% (minimum)
- Temperature Range: Operational range from cryogenic temperatures to 800°C in air; suitable for continuous operation in the 0–450°C range typical of thermal storage applications
- Surface Finish: Mill finish or electropolished (Ra ≤ 0.4 μm) to minimize fouling and pressure drop
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Type | Spiral Coil Tube (盘管) | — |
| Tube Outer Diameter (OD) | 6.35 mm – 50.8 mm (1/4" – 2") | ASTM A213 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 3.0 mm | — |
| Coil Winding Diameter | 50 mm – 500 mm (configurable) | Per application design |
| Coil Length | Up to 500 m (continuous coil) | — |
| Winding Pitch | 1.05× OD – 2.0× OD (adjustable) | — |
| Helix Angle | 3° – 15° from perpendicular plane | — |
| End Connection | Plain end, beveled end, or threaded connection | ASME B1.20.1 |
| Pressure Rating | Up to 15 MPa (design dependent) | ASME VIII Div.1 |
| Surface Treatment | Passivated, pickled, or electropolished | ASTM A967 |
| Applicable PCM Range | Paraffin-based (20–80°C), Salt hydrate (40–120°C), Molten salt (200–565°C) | Per PCM selection |
| Shell-and-Tube Configuration | Ladder-type multi-stage arrangement | Custom design |
Manufacturing Process
The production of precision spiral coil tubes involves a carefully controlled multi-step process to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Material Selection and Inspection: Cold-rolled stainless steel coil is procured from certified suppliers with full mill test certificates (MTC) per EN 10204 Type 3.1. Incoming material undergoes spectroscopic verification (PMI) and mechanical property testing.
- Tube Forming: The flat stainless steel strip is cold-formed through a series of calibrated rollers into seamless tube stock, or alternatively, seamless drawn-and-pearced (DPC) tube is used for higher pressure applications.
- Spiral Coiling: The straight tube is wound onto a precision CNC-controlled coiling machine. The winding diameter, pitch, and helix angle are programmatically controlled to achieve tight dimensional tolerances (±0.5 mm on coil diameter). The coiling process is performed at controlled speeds to prevent work hardening and residual stress accumulation.
- Heat Treatment (if required): For applications requiring stress relief, the coiled tube undergoes solution annealing at 1050–1100°C followed by controlled cooling to restore full austenitic microstructure and relieve cold-work stresses.
- End Preparation: Tube ends are cut square, deburred, and beveled or threaded per the specified connection type.
- Surface Cleaning and Passivation: The coil tube is cleaned of all contaminants and passivated per ASTM A967 to establish a protective chromium oxide layer, ensuring maximum corrosion resistance.
- Quality Inspection: Each coil undergoes dimensional verification (laser measurement of OD, wall thickness, and coil diameter), hydrostatic pressure testing per ASTM A269, and visual inspection for surface defects.
- Packaging: Coiled tubes are wrapped in protective film, secured with banding, and packed in export-grade wooden cases or metal containers for shipment.
Applications
The spiral coil tube is a versatile component with applications spanning multiple thermal engineering domains:
- Phase Change Thermal Energy Storage (PCM-TES): The primary application domain—integrated into shell-and-tube ladder-type PCM thermal storage units for solar thermal energy storage, industrial waste heat recovery, and district heating systems. The coil tube acts as the heat transfer surface between the HTF and PCM, enabling charge/discharge cycles at defined temperature levels.
- Solar Thermal Power Plants: Used in intermediate heat exchangers and storage tank internals for concentrating solar power (CSP) facilities, handling molten salt heat transfer fluids at temperatures up to 565°C.
- Industrial Waste Heat Recovery: Deployed in heat recovery units (HRUs) for capturing low-grade waste heat from industrial processes and storing it in PCM matrices for later use.
- Building Heating and Cooling Systems: Employed in latent heat thermal storage tanks for building energy management, utilizing paraffin-based or salt hydrate PCMs for peak-shaving and load management.
- Automotive Thermal Management: Compact coil tube designs used in battery thermal management systems (BTMS) for electric vehicles, leveraging PCM for thermal buffering.
- Food and Pharmaceutical Processing: Sanitary-grade coil tubes (316L) used in pasteurization heat exchangers and process heating systems requiring hygienic conditions.
- Cryogenic Applications: Stainless steel coil tubes in cryogenic heat exchangers and LNG (Liquefied Natural Gas) processing facilities.
Unique Selling Points
- Optimized Spiral Geometry: The helical coil configuration maximizes heat transfer area within the shell volume, achieving 2–5 times the surface area density of conventional U-tube or straight-tube arrangements, directly enhancing PCM charge/discharge rates.
- Ladder-Type Multi-Stage Compatibility: Engineered for integration into cascaded thermal storage systems where multiple PCM phases at different melting temperatures are sequentially activated, enabling high-temperature-difference energy storage with improved exergy efficiency.
- Thermal Cycling Durability: Austenitic stainless steel retains full mechanical properties after thousands of thermal cycling events, ensuring long-term reliability in repeated charge/discharge operations typical of TES applications.
- Wide Temperature and PCM Compatibility: Suitable for organic PCMs (paraffins, fatty acids), inorganic salt hydrates, and molten salt systems, covering the full spectrum of PCM-based thermal storage from ambient to high-temperature applications.
- Corrosion-Free Service: The passive oxide layer on stainless steel eliminates internal corrosion concerns, preventing tube degradation and PCM contamination over the system lifetime.
- Custom Engineering Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil dimensions, tube specifications, and end preparations tailored to specific thermal storage system designs.
Quality Certifications and Standards Compliance
All products manufactured by Wenzhou Jixing Metal Materials Co., Ltd. adhere to internationally recognized quality standards and are backed by comprehensive certification documentation:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- Material Standards: ASTM A213/A213M (seamless wrought austenitic stainless steel tubing), GB/T 12771 (welded stainless steel tubes), EN 10216-5 (welded austenitic stainless steel tubes)
- Pressure Vessel Compliance: Tubes designed for use in pressure vessels conform to ASME BPV Code Section VIII Division 1 and PED 2014/68/EU requirements
- Hydrostatic Testing: Performed per ASTM A269 at 1.5× the maximum design pressure with zero leakage tolerance
- Mill Test Certification: EN 10204 Type 3.1 certificates provided for each batch, including chemical composition, mechanical properties, and heat treatment records
- NDT (Non-Destructive Testing): Eddy current inspection per ASTM E709 and ultrasonic testing per ASTM E309 available upon request for critical applications
- Food-Grade Compliance: 316L grade tubes available with compliance to FDA 21 CFR 184.5090 and EC Regulation 1935/2004 for food processing applications
Note: All specifications are subject to final confirmation based on specific application requirements. Wenzhou Jixing Metal Materials Co., Ltd. provides engineering consultation and custom design support to ensure optimal coil tube selection and integration for each thermal storage system application.