Stainless Steel Coiled Tube (Coiltube) for Internal-Melting Ice Storage Systems
Product Overview
The stainless steel coiled tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for integration into Internal-Melting Coiled Tube Ice Storage Systems (内融式盘管蓄冰系统). These systems represent an advanced thermal energy storage (TES) technology that leverages the latent heat of fusion of water to store cooling energy at near-constant temperatures, enabling peak-shaving and load-shifting in commercial and industrial HVAC applications.
Unlike conventional shell-and-tube or external-melting ice storage configurations, the internal-melting coiled tube system utilizes a continuous spiral coil geometry where refrigerant flows through the coiled tubes while ice forms on the outer surface. During the melting (discharge) cycle, warm secondary coolant flows through the same coiled tubes, absorbing stored thermal energy from the surrounding ice layer. This architecture offers superior heat transfer efficiency, compact footprint, and enhanced scalability compared to traditional ice storage approaches.
Material & Properties
The coiled tubes are fabricated from high-grade austenitic stainless steel, selected for their exceptional corrosion resistance, thermal conductivity, mechanical integrity under cryogenic cycling, and long-term durability in aqueous environments.
- Primary Alloy: AISI 304 / 304L (UNS S30400 / S30403) — the industry-standard grade for general ice storage applications, offering excellent weldability and resistance to chloride-induced pitting corrosion.
- Alternative Grade: AISI 316 / 316L (UNS S31600 / S31603) — recommended for applications involving brine-based secondary loops or coastal environments where elevated chloride concentrations are present.
- Corrosion Resistance: Maintains structural integrity across repeated freeze-thaw cycles (typically exceeding 10,000 cycles) without degradation of mechanical properties.
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 25°C for Grade 304, providing efficient heat exchange between the refrigerant and the ice/water medium.
- Operating Temperature Range: -40°C to +100°C, accommodating both the freezing (charging) phase and the melting (discharge) phase of the thermal storage cycle.
- Mechanical Strength: Yield strength ≥ 205 MPa; tensile strength ≥ 515 MPa for Grade 304 in the annealed condition, ensuring resistance to thermal stress and pressure loading during operation.
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Type | Continuous Stainless Steel Coiled Tube | — |
| Material Grade | AISI 304 / 304L (Standard); AISI 316 / 316L (Optional) | ASTM A213 / ASME SA-213 |
| Outer Diameter (OD) | 12 mm – 25 mm (customizable) | Per customer specification |
| Wall Thickness | 0.8 mm – 1.5 mm | ASTM A213 |
| Coil Pitch (Center-to-Center Spacing) | 15 mm – 35 mm (optimized for ice layer formation) | Thermal design requirement |
| Coil Diameter | Custom (typically 200 mm – 600 mm per layer) | System design specification |
| Coil Length per Module | Up to 500 m (continuous, no intermediate joints) | Manufacturing capability |
| Surface Finish | BA (Bright Annealed) or 2B Finish; Ra ≤ 0.8 μm | ASTM A478 |
| End Condition | Beveled, deburred, and sealed for welding | ASME B31.5 |
| Pressure Rating | Up to 1.6 MPa (design); burst pressure ≥ 4.0 MPa | ASME BPV Code Section VIII |
| Inspection | 100% Eddy Current Testing (ECT) + Hydrostatic Testing at 2.5× working pressure | ASTM E709 / ASTM A213 |
| Packaging | Coiled on protective wooden reel, wrapped in moisture-proof film | ISO 11607 (adapted) |
Manufacturing Process
The production of stainless steel coiled tubes for ice storage applications involves a multi-stage precision manufacturing sequence designed to ensure dimensional accuracy, metallurgical homogeneity, and defect-free integrity:
- Raw Material Selection: Cold-rolled stainless steel strip is sourced from certified mills, with full chemical composition verification (Spectroscopic Analysis per ASTM E415) and mechanical property validation.
- Tube Forming: High-precision cold-drawing or cold-rolling processes are employed to produce seamless tubes with tight dimensional tolerances (±0.05 mm on OD; ±0.02 mm on wall thickness).
- Coil Winding: A computer-controlled continuous coil winding machine forms the tube into the specified spiral geometry. The winding process maintains consistent pitch and alignment, critical for uniform ice formation and heat transfer performance.
- Welding (if applicable): Where tube length extension is required, orbital TIG welding (Gas Tungsten Arc Welding per ASME Section IX) is performed with full radiographic or ultrasonic inspection.
- Heat Treatment: Solution annealing at 1050°C – 1150°C followed by controlled cooling eliminates residual stresses introduced during forming and restores full corrosion resistance.
- Surface Treatment: Pickling and passivation (per ASTM A967) removes oxidation scale and establishes a protective chromium oxide layer on the inner and outer surfaces.
- Quality Inspection: Every coil undergoes 100% eddy current testing for wall thickness uniformity and defect detection, followed by hydrostatic pressure testing to verify structural integrity.
Applications
The coiled tube products are engineered for a wide range of thermal energy storage and heat exchange applications:
- Internal-Melting Ice Storage Systems: Primary application — coiled tubes serve as the heat transfer element within ice storage tanks, enabling efficient charging (ice formation) and discharging (ice melting) cycles for commercial HVAC peak-shaving.
- Commercial Building Cooling: Hotels, shopping malls, office complexes, and hospitals where demand-side management and energy cost optimization are critical.
- Industrial Process Cooling: Food and beverage processing, pharmaceutical manufacturing, and chemical plants requiring reliable backup cooling capacity.
- Geothermal Heat Exchange: Borehole heat exchanger applications where coiled stainless steel tubes are deployed underground for ground-source heat pump systems.
- Refrigeration Systems: Evaporator coils in commercial refrigeration units and walk-in coolers/freezers.
- Marine and Offshore Cooling: Ice storage systems on vessels and offshore platforms where space is limited and energy efficiency is paramount.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a rigorous quality management system ensuring full traceability and compliance with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing operations.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ASME SA-213 — Compliance with specifications for seamless austenitic stainless steel tubes for heat-transfer applications.
- ASTM A213 / A269 — Conformance with American material standards for stainless steel tubing.
- CE Marking — European conformity marking for products intended for the European Economic Area.
- MTC (Material Test Certificate) Type 3.1 — Independent third-party verification of chemical composition and mechanical properties for every production batch.
- Full Traceability: Heat number tracking from raw material mill to finished coil, enabling complete supply chain transparency.
Unique Selling Points
- Optimized for Ice Storage: Coil pitch and geometry are specifically engineered to promote uniform ice nucleation and formation, maximizing the effective thermal storage density of the system.
- Extended Cycle Life: The austenitic stainless steel matrix provides outstanding resistance to stress corrosion cracking (SCC) and intergranular corrosion during repeated thermal cycling, with proven performance exceeding 10,000 freeze-thaw cycles.
- Continuous Length Capability: Ability to produce coils up to 500 meters without intermediate welds eliminates potential leak points and reduces maintenance requirements throughout the system lifetime.
- Precision Dimensional Control: Tight tolerances on tube OD, wall thickness, and coil pitch ensure optimal fit within ice storage tank housings and maximize the surface-area-to-volume ratio for heat transfer.
- Customization: Full flexibility in tube diameter, wall thickness, coil pitch, and overall geometry to match specific system design requirements and performance targets.
- Cost-Effective Energy Management: The internal-melting coiled tube configuration enables 20–30% reduction in peak electrical demand charges while maintaining full cooling capacity, delivering significant ROI for building owners.
Note: All specifications are subject to confirmation based on the specific project requirements. Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive technical consultation and custom engineering support to ensure optimal system performance. Contact our technical team for application-specific design assistance and quotation.