Stainless Steel Direct Evaporation Ice Storage Coil Tube (Coiltube)
Product Overview
The Direct Evaporation Ice Storage Coil Tube (also referred to as "Coiltube" or "Spiral Coil Pipe") is a precision-engineered stainless steel tubing product designed for direct evaporative ice storage and thermal energy management systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this product is specifically engineered to serve as the refrigerant flow channel within ice storage tanks, enabling the direct contact between refrigerant and water/ice during both the ice-making (charging) and ice-melting (discharging) cycles.
Unlike indirect (plate or shell-and-tube) ice storage systems, direct evaporation coil tubes provide a more compact and thermodynamically efficient approach to thermal energy storage. The coiled configuration maximizes the heat exchange surface area within a confined volume, facilitating rapid ice formation and controlled release of stored cooling capacity. This product represents the core heat transfer component in direct expansion (DX) ice thermal storage systems used across commercial and industrial applications.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, and mechanical integrity under cryogenic operating conditions.
- Base Material: Austenitic stainless steel conforming to ASTM A213 (Tubes, Heat-Exchanger, Condenser, and Refrigeration) or ASTM A269 (Welded Austenitic Stainless Steel Tubing) specifications.
- Common Grades:
- SUS304 / 304L (UNS S30400 / S30403): The standard grade offering excellent general corrosion resistance and weldability. Suitable for most refrigerant and water environments.
- SUS316 / 316L (UNS S31600 / S31603): Enhanced chlorides resistance; recommended for applications involving brine or environments with elevated chloride concentrations.
- SUS321 / 321H (UNS S32100 / S32109): Titanium-stabilized grade for elevated temperature service stability.
- Surface Finish: Electropolished or passivated internal surface to minimize friction losses and prevent biofilm formation, ensuring long-term hydraulic efficiency.
- Mechanical Properties:
- Yield Strength: ≥ 205 MPa (SUS304, annealed condition)
- Tensile Strength: ≥ 515 MPa
- Elongation: ≥ 40%
- Operating Temperature Range: −196°C to +450°C
- Corrosion Resistance: Excellent resistance to oxidation, pitting (with 316L), and stress corrosion cracking in typical refrigeration and HVAC environments.
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (SUS304), providing effective heat transfer between refrigerant and stored thermal medium.
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Direct Evaporation Ice Storage Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Product Code | 1105 |
| Material Grade | SUS304, SUS304L, SUS316, SUS316L, SUS321 (customizable) |
| Outer Diameter (OD) | φ6.0 mm – φ25.4 mm (standard); custom diameters available |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Pitch | 15 mm – 50 mm (adjustable per system design) |
| Coil Outer Diameter | φ100 mm – φ600 mm |
| Tube Length per Coil | 3 m – 30 m (customizable) |
| Refrigerant Compatibility | R22, R407C, R410A, R134a, R404A, CO₂ (R744), ammonia (NH₃) |
| Maximum Operating Pressure | ≤ 3.5 MPa (design-dependent) |
| Ice Storage Capacity | 50 – 500 kWh/m³ (system-level specification) |
| Surface Treatment | Electropolished / Passivated / Acetone cleaned |
| End Connection | Flared, brazed, threaded, or welded fittings (per application) |
| Standard References | ASTM A213, ASTM A269, GB/T 14976, GB/T 12771 |
Manufacturing Process
The production of high-quality direct evaporation ice storage coil tubes involves a multi-stage precision manufacturing workflow:
- Raw Material Selection & Inspection: Stainless steel seamless or welded tubes are sourced from certified mills and subjected to spectroscopic analysis (PMI), dimensional verification, and hydrostatic testing to ensure compliance with ASTM/GB standards.
- Dimensional Preparation: Tubes are cut to specified lengths with precision saws, and ends are deburred and chamfered to facilitate subsequent coiling and connection processes.
- Coiling / Spiraling: Tubes are formed into helical coils using CNC-controlled coiling machines. The coiling process maintains consistent pitch, ovality control (≤ 3% OD variation), and eliminates residual stress through controlled feed rates and die geometry. Multi-pass coiling may be employed for large-diameter or tight-pitch configurations.
- Heat Treatment (if required): For cold-worked coils requiring stress relief, annealing at 1050°C–1150°C followed by controlled cooling restores full austenitic microstructure and mechanical properties.
- Surface Treatment: Chemical pickling and passivation (nitric acid/citric acid process) removes scale and contaminants, establishing a protective chromium oxide film. Electropolishing may be applied to achieve Ra ≤ 0.4 μm internal surface roughness.
- Quality Inspection: Each coil undergoes dimensional verification (OD, wall thickness, pitch, coil diameter), pressure testing (1.5× working pressure), and visual inspection for surface defects. Leak testing using nitrogen or helium is performed on assembled systems.
- Packaging & Dispatch: Coils are individually wrapped in protective film, placed in ventilated crates, and labeled with material certificates and traceability codes.
Applications
The direct evaporation ice storage coil tube is integral to a broad spectrum of thermal energy storage and refrigeration systems:
- Commercial Ice Thermal Energy Storage (TES): Peak-shaving and load-shifting in commercial buildings, shopping malls, and office complexes to reduce peak electricity demand charges.
- Hospital & Data Center Cooling: Critical facilities requiring uninterrupted cooling capacity with backup thermal storage for emergency scenarios.
- Industrial Process Cooling: Temperature-controlled manufacturing environments, including pharmaceutical cold chains, food processing, and chemical plants.
- Cold Storage Warehouses: Efficient refrigeration systems for frozen food logistics and perishable goods preservation.
- Chiller Retrofitting: Integration into existing chiller systems to add ice storage capability without major infrastructure modification.
- Research & Development: As demonstrated in the experimental study "Experimental Study on the Refrigeration Process of Direct Evaporation Ice Coil Tube", these coils serve as critical components in academic research on ice formation kinetics, heat transfer optimization, and system performance evaluation.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality assurance systems to ensure product reliability:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System certification
- Material Certification: Each batch accompanied by Mill Test Reports (MTR) with chemical composition and mechanical property data
- Pressure Vessel Standards: Compliance with GB/T 150 (Pressure Vessel) and ASME BPVC Section VIII for pressure-containing applications
- Food Grade Compliance: Available in food-grade finish (Ra ≤ 0.25 μm) meeting 3-A Sanitary Standards and NSF/ANSI 61 for potable water contact applications
- Traceability: Full heat-lot traceability from raw material to finished product
Unique Selling Points
- Direct Evaporation Efficiency: Eliminates intermediate heat transfer surfaces, achieving higher coefficient of performance (COP) compared to indirect ice storage systems — experimentally validated in peer-reviewed research.
- Compact Footprint: Spiral coil geometry achieves maximum heat transfer area per unit volume, reducing tank size and installation space requirements.
- Corrosion-Resistant Construction: Stainless steel material ensures 20+ year service life in aggressive refrigerant and water environments without degradation.
- Custom Engineering: Flexible dimensional customization (pitch, coil diameter, tube specification) to match specific system thermodynamic requirements.
- Low Maintenance: Electropolished surfaces resist scaling and fouling, minimizing operational downtime and cleaning requirements.
- Refrigerant Versatility: Compatible with all major HCFC, HFC, and natural refrigerants, supporting transition to low-GWP refrigerant systems.
Note: All specifications are subject to engineering review based on specific application requirements. Wenzhou Jixing Metal Materials Co., Ltd provides customized design support and technical consultation for direct evaporation ice storage system integration.