Stainless Steel Coil Tube for Ice Storage Thermal Energy Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered heat exchange component designed specifically for ice storage thermal energy storage (TES) systems. This product series is engineered to operate under the demanding conditions of incomplete-freezing ice storage tanks, where it facilitates both internal ice melting and external ice melting cold-storage retrieval cycles. The coil tube serves as the primary heat transfer medium between the refrigerant brine solution and the ice matrix, enabling efficient thermal energy accumulation and dispatch for peak-load shifting applications in commercial and industrial HVAC systems.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional resistance to chloride-induced pitting corrosion in brine environments (typically calcium chloride or ethylene glycol solutions at concentrations of 10–30 wt%). The material exhibits the following key properties:
- Corrosion Resistance: Superior resistance to galvanic and crevice corrosion in aqueous brine media, with a minimum pitting resistance equivalent number (PREN) of 24, ensuring long-term structural integrity in aggressive electrochemical environments.
- Mechanical Strength: High yield strength and tensile strength even at sub-zero operating temperatures (down to −40°C), maintaining dimensional stability during repeated freeze-thaw cycles.
- Thermal Conductivity: Optimized thermal conductivity to minimize heat transfer resistance between the refrigerant fluid and the ice layer, maximizing cold-storage retrieval efficiency.
- Cryogenic Performance: Retains ductility and toughness at cryogenic temperatures, preventing brittle fracture during thermal cycling.
- Hygienic Surface Finish: Mirror-polished or electropolished internal surface (Ra ≤ 0.4 μm) to minimize fouling and biofilm accumulation.
Specifications
| Parameter | Specification |
|---|---|
| Material Grade | 304 / 316L / 316Ti Stainless Steel |
| Outer Diameter (OD) | 12 mm – 50 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Pitch (Turn-to-Turn Spacing) | 8 mm – 25 mm |
| Coil Length | Up to 500 m per continuous coil |
| Surface Finish (Internal) | Electropolished, Ra ≤ 0.4 μm |
| Surface Finish (External) | No. 4 Brushed or Mirror Polished |
| Operating Temperature Range | −40°C to +80°C |
| Maximum Operating Pressure | 1.6 MPa (design), 2.5 MPa (test) |
| Tolerance on OD | ±0.1 mm |
| Tolerance on Wall Thickness | ±10% |
| Standards Compliance | ASTM A269, ASTM A270, EN 10217-7, GB/T 12771 |
| Connection Type | Welded, Flanged, or Threaded (per project specification) |
Manufacturing Process
The coil tube is produced through a multi-stage precision manufacturing process to ensure dimensional accuracy, mechanical reliability, and surface quality:
- Raw Material Procurement: Hot-rolled stainless steel strip or seamless tube stock is sourced from certified mills, with each batch accompanied by a mill test certificate (MTC) verifying chemical composition and mechanical properties.
- Precision Forming: The tube is cold-formed into a helical coil configuration using CNC-controlled coiling machines. The forming process is optimized to prevent work hardening, ovality, and wall thinning at the coil bend radii. Multi-pass coiling ensures uniform plastic deformation and consistent dimensional tolerances.
- Heat Treatment: Solution annealing (at 1050–1100°C with rapid water quench) is performed to relieve residual stresses introduced during forming, restore full austenitic microstructure, and maximize corrosion resistance.
- Surface Treatment: Internal surfaces undergo electropolishing to achieve a mirror finish, removing surface contaminants and creating a passivated chromium oxide layer. External surfaces are mechanically polished or passivated via chemical treatment.
- Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification using laser measurement systems, and hydrostatic pressure testing at 1.5× the maximum design pressure for a minimum dwell time of 5 minutes. Eddy current testing may be employed for wall thickness verification.
- End Preparation: Tube ends are cut square, deburred, and prepared for welding or connection fitting installation. Protective caps are applied to prevent contamination during shipping and storage.
Applications
The stainless steel coil tube is specifically designed for the following applications:
- Ice Storage Thermal Energy Systems: Primary heat exchanger element in incomplete-freezing ice storage tanks, enabling both internal ice melting (where ice forms on the inside of the coil tube) and external ice melting (where ice forms on the outside of the coil tube) cold retrieval modes.
- Peak-Load Shifting: Facilitates off-peak ice formation and on-peak cooling dispatch in commercial buildings, reducing electrical demand charges by 30–50%.
- Chilled Water Systems: Used in large-scale HVAC systems for hospitals, data centers, shopping malls, and industrial facilities requiring high-capacity cooling.
- Process Cooling: Applicable in food and beverage processing, pharmaceutical manufacturing, and chemical production where precise temperature control is required.
- Cryogenic Applications: Suitable for low-temperature storage and transport of cryogenic liquids due to excellent low-temperature mechanical properties.
Quality Certifications & Standards
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and certifications to ensure product reliability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health and Safety Management System certification
- EN 10204 3.1 — Material Test Certificates provided with each shipment
- CE Marking — Conformity with European health, safety, and environmental protection standards
- ASME Standards — Compliance with ASME B31.5 (Hydraulic and Pneumatic Piping) and ASME B31.3 (Process Piping) where applicable
- NSF/ANSI 61 — Drinking Water System Components certification for potable water applications
- Third-Party Inspection: Available upon request — SGS, Bureau Veritas, or TÜV Rheinland inspection services
Unique Selling Points
The coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. offers several distinguishing advantages for ice storage thermal energy applications:
- Proven Performance in Incomplete-Freezing Systems: Engineered and validated through experimental research on cold retrieval characteristics of both internal and external ice melting configurations, ensuring optimal heat transfer efficiency in real-world operating conditions.
- Extended Service Life: Superior corrosion resistance in chloride-containing brine solutions eliminates the need for costly replacement or rehabilitation, with a design service life exceeding 20 years.
- Customizable Geometry: Coil pitch, tube diameter, and wall thickness can be tailored to specific system requirements, enabling optimization of heat transfer area-to-volume ratio and pressure drop characteristics.
- Low-Fouling Surface: The electropolished internal surface minimizes scale formation and biofilm growth, maintaining high heat transfer coefficients throughout the operational lifecycle.
- Thermal Cycling Durability: Designed to withstand thousands of freeze-thaw cycles without degradation of mechanical properties or dimensional integrity.