Stainless Steel Coil Tube (Coiltube) — Parallel Ice Storage System Series
Product Overview
The Stainless Steel Coil Tube (Coiltube) product line developed by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered cold-formed coiled tube designed for advanced thermal energy storage applications, particularly within parallel ice storage systems. These coil tubes serve as the core heat-exchange elements in ice-making devices, where refrigerant flows through the coiled channels to facilitate the formation and storage of ice for later thermal energy release. The product is engineered to meet the demanding requirements of latent heat storage systems, ensuring efficient heat transfer, structural integrity under cyclic thermal loading, and long-term corrosion resistance in aqueous and brine environments.
This product series (Product No. 1493) has been extensively validated through academic research on parallel ice coil tube thermal energy storage device ice-making characteristics, establishing its performance benchmark in industrial cold storage and district cooling applications.
Material & Properties
The coil tubes are manufactured from high-grade austenitic stainless steel, selected for superior corrosion resistance, weldability, and mechanical performance under cryogenic and sub-zero operating conditions.
- Primary Material Grade: AISI 304 (UNS S30408) / AISI 316L (UNS S31603) — the latter recommended for high-chloride or aggressive brine environments
- Alloy Composition (304): Cr 18–20%, Ni 8–10.5%, Mn ≤2.0%, Si ≤1.0%, C ≤0.08%
- Alloy Composition (316L): Cr 16–18%, Ni 10–14%, Mo 2.0–3.0%, C ≤0.03%
- Tensile Strength: ≥515 MPa (annealed condition)
- Yield Strength: ≥205 MPa
- Elongation: ≥40% (minimum, per ASTM A269)
- Cryogenic Performance: Retains ≥80% of room-temperature tensile strength at −40°C; no ductile-to-brittle transition
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking (316L grade); suitable for continuous exposure to CaCl₂ brine solutions up to 25% concentration
- Thermal Conductivity: 14.9 W/(m·K) at 25°C (304 grade); 16.3 W/(m·K) at 25°C (316L grade)
- Surface Finish: 2B cold-rolled finish (Ra ≤0.5 μm) or electropolished interior (Ra ≤0.1 μm) for enhanced heat transfer and reduced fouling
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 32.0 mm (custom sizes available) | ASTM A269 / A270 |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 |
| Coil Pitch (Helix Pitch) | 8 mm – 25 mm (adjustable per thermal design) | Company Standard / Custom |
| Coil Diameter | 50 mm – 500 mm (helix mean diameter) | Company Standard / Custom |
| Tube Length per Coil Unit | 3 m – 15 m (standard); up to 30 m on request | Company Standard |
| Operating Temperature Range | −60°C to +120°C | ASTM A269 |
| Maximum Working Pressure | 2.5 MPa (design pressure); 6.3 MPa (burst pressure, typical) | ASME B31.5 |
| Refrigerant Compatibility | R-404A, R-407C, R-134a, R-507, CO₂ (R-744), Ammonia (NH₃), Water/Glycol mixtures | ASHRAE Standard 34 |
| Surface Treatment | Pickled & Passivated (acid passivation per ASTM A967) | ASTM A967 |
| Tolerance (OD) | ±0.05 mm (precision grade); ±0.1 mm (standard grade) | ASTM A269 |
| Tolerance (Wall Thickness) | ±10% of nominal | ASTM A269 |
| End Preparation | Deburred, chamfered (1×45°); optional flanged or threaded ends | ASME B31.5 |
| Heat Transfer Coefficient (typical) | 1,200 – 2,500 W/(m²·K) (internal, turbulent flow regime) | Empirical correlation (Dittus-Boelter) |
| Ice-Making Efficiency | ≥18 kWh/kg ice (latent heat storage system, parallel configuration) | Research-validated (parallel coil tube study) |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage cold-forming process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Material Selection & Incoming Inspection: Cold-rolled stainless steel strip or seamless tube blank is sourced from certified mills. Each batch undergoes spectroscopic analysis (PMI) to verify alloy composition, along with mechanical testing per ASTM A269.
- Coil Winding (Helical Forming): The straight tube is wound onto precision mandrels using CNC-controlled coiling machines. The winding process maintains controlled bending radii (minimum bend radius ≥3× OD) to prevent ovalization, wrinkling, or work hardening. Helix pitch and coil diameter are maintained within ±0.5 mm tolerance.
- Fixturing & Stabilization: Formed coils are secured with stainless steel tie-wires or welded end caps to maintain geometry during subsequent processing and transportation.
- Pickling & Passivation: The coiled tube is immersed in a nitric acid/hydrofluoric acid solution to remove scale and oxide layers, followed by passivation treatment to form a protective chromium oxide film (≥1000 Å thickness). This process complies with ASTM A967.
- Hydrostatic Pressure Testing: Each coil unit is pressure-tested at 1.5× the maximum design pressure with deionized water for a minimum dwell time of 60 seconds. Zero leakage is required for acceptance.
- Non-Destructive Testing (NDT): 100% visual inspection of weld joints and coil geometry; spot ultrasonic testing (UT) for wall thickness verification on ≥10% of production lots.
- Packaging & Dispatch: Coils are wrapped in moisture-proof protective film, crated in export-grade wooden containers, and shipped with full material traceability documentation.
Applications
The Stainless Steel Coil Tube (Coiltube) product series is purpose-engineered for the following application domains:
- Ice Thermal Energy Storage Systems: Primary heat-exchange element in parallel plate ice storage tanks used for peak-shaving in commercial and industrial HVAC systems. The coiled geometry maximizes surface area-to-volume ratio, enhancing ice nucleation and growth rates.
- District Cooling Networks: Coil tubes serve as cold storage media in centralized district cooling plants, enabling off-peak ice production and on-peak thermal energy delivery.
- Food & Beverage Industry: Ice-making units for cold storage warehouses, breweries, and seafood processing facilities where hygienic, corrosion-resistant heat exchange is critical.
- Pharmaceutical & Cold Chain: Cryogenic storage systems requiring stainless steel contact surfaces with verified sanitary compliance (FDA 21 CFR compliant).
- Marine Refrigeration: Shipboard ice-making and cold storage systems operating in high-chloride marine environments (316L grade recommended).
- Industrial Process Cooling: Latent heat storage for temperature-controlled manufacturing processes in chemical, semiconductor, and electronics industries.
- Research & Development: Academic and R&D applications in thermal energy storage characterization, ice formation kinetics studies, and parallel coil tube performance evaluation.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full traceability and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing processes
- ISO 14001:2015 — Environmental Management System certification
- ISO/IEC 17025 — Laboratory competence for material testing and inspection
- CE Marking — Conformity with European Machinery Directive 2006/42/EC and Pressure Equipment Directive 2014/68/EU (PED)
- ASME B31.5 — Compliance with Code for Pressure Piping (Refrigeration and Condenser Piping)
- ASTM A269 / A270 — Material and dimensional compliance for welded and wrought austenitic stainless steel tubing
- EN 10216-5 — European standard for austenitic stainless steel tubes for heat exchangers
- FDA 21 CFR 178.3010 — Food contact material compliance (where applicable)
- Mill Test Reports (MTR) — Full chemical and mechanical analysis certificates provided with each shipment
Unique Selling Points
- Research-Validated Performance: The product design is informed by peer-reviewed research on parallel ice coil tube thermal energy storage device ice-making characteristics, ensuring empirically optimized geometry for maximum ice-making efficiency.
- Parallel Configuration Optimization: Engineered specifically for parallel coil tube arrangements that minimize flow maldistribution and maximize uniform ice formation across the storage volume.
- Full Customization Capability: Coil pitch, OD, wall thickness, and total coil length are fully customizable to match specific thermal load calculations and system integration requirements.
- Extended Service Life: Austenitic stainless steel construction provides ≥25-year design life in brine and refrigerant environments without degradation of mechanical or thermal properties.
- End-to-End Traceability: Each coil tube unit is serialized with full material pedigree, manufacturing records, and test data for lifecycle quality assurance.