Stainless Steel Coiltube for Evaporative Ice Storage Systems
Product Code: JX-CT-1155 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coiltube (JX-CT-1155) is a precision-engineered continuous-loop tubing product specifically designed for evaporative ice storage systems and thermal energy storage applications. Unlike conventional straight pipe segments, the coiltube is manufactured as a pre-formed helical or serpentine coil configuration, enabling direct integration into evaporative ice makers, ice slurry generators, and latent heat thermal energy storage (LTES) tanks without the need for on-site bending or welding.
This product is manufactured according to rigorous industrial standards and is optimized for the demanding conditions of evaporative ice storage processes, where the coil tube serves as the primary heat exchange surface through which refrigerant (typically ethylene glycol-water solution or ammonia) transfers thermal energy to the surrounding water medium, inducing controlled ice nucleation and crystallization. The coiltube design maximizes the heat transfer area per unit volume, significantly enhancing the efficiency of the ice storage cycle.
2. Material and Properties
2.1 Base Material
The coiltube is fabricated from austenitic stainless steel conforming to the following material grades:
- Primary Grade: SUS304 (ASTM A213 TP304 / EN 1.4301) — the standard choice for general ice storage applications requiring excellent corrosion resistance and formability.
- High-Performance Grade: SUS316L (ASTM A213 TP316L / EN 1.4401) — recommended for applications involving chloride-containing refrigerant solutions or where enhanced pitting and crevice corrosion resistance is required.
- High-Temperature Grade: SUS321 (ASTM A213 TP321 / EN 1.4845) — titanium-stabilized variant suitable for elevated temperature cycling scenarios.
2.2 Mechanical and Physical Properties
| Property | SUS304 | SUS316L | Test Standard |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 480 MPa | ASTM A213 / GB/T 228 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa | ASTM A213 / GB/T 228 |
| Elongation (A50mm) | ≥ 40% | ≥ 35% | ASTM A213 / GB/T 228 |
| Density | 7.93 g/cm³ | 8.00 g/cm³ | — |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | ASTM E1530 |
| Operating Temperature Range | −196°C to +870°C | −196°C to +870°C | — |
| Cryogenic Impact Strength | ≥ 47 J (at −196°C) | ≥ 47 J (at −196°C) | ASTM A370 |
2.3 Chemical Composition (Typical)
| Element | SUS304 (Max %) | SUS316L (Max %) |
|---|---|---|
| Carbon (C) | 0.08 | 0.03 |
| Chromium (Cr) | 18.0–20.0 | 16.5–18.5 |
| Nickel (Ni) | 8.0–10.5 | 10.0–14.0 |
| Molybdenum (Mo) | — | 2.0–3.0 |
| Chloride (Cl) | 0.03 | 0.03 |
| Sulfur (S) | 0.03 | 0.03 |
3. Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | φ12.7 mm / φ15.8 mm / φ19.0 mm / φ25.4 mm | ±0.15 mm |
| Wall Thickness | 0.5 mm / 0.8 mm / 1.0 mm / 1.2 mm / 1.5 mm | ±0.05 mm |
| Coil Diameter (Mean) | φ300 mm to φ1200 mm (customizable) | ±3 mm |
| Coil Pitch (Spacing) | 15 mm to 50 mm (adjustable per design) | ±1.0 mm |
| Coil Length (Uncoiled) | Up to 3000 m per coil (standard); custom on request | ±1% |
| Surface Finish | Electropolished (Ra ≤ 0.4 μm) or Brushed (Ra ≤ 1.6 μm) | — |
| End Configuration | Plain cut, beveled, or pre-welded fittings (flange/threaded) | — |
| Pressure Rating | Up to 1.6 MPa (standard); up to 4.0 MPa (heavy wall) | — |
| Heat Treatment | Solution annealed (1050–1100°C) followed by water quench | — |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel strip or seamless tube stock is verified for chemical composition (via XRF spectroscopy), mechanical properties, and surface quality in accordance with ASTM A213 and GB/T 12771 requirements.
- Cold Drawing / Rolling: Seamless tube stock is cold-drawn through precision dies to achieve the target OD and wall thickness with tight dimensional tolerances. This process induces beneficial work hardening that enhances fatigue resistance.
- Intermediate Annealing: Periodic solution annealing is performed during multi-pass cold drawing to relieve accumulated residual stresses and restore ductility, preventing cracking during subsequent forming operations.
- Coil Forming (Helical Bending): The straight tube is fed through a CNC-controlled helical coiling machine that imparts a uniform helical geometry. The machine employs synchronized feed and rotation mechanisms to maintain constant coil diameter and pitch throughout the entire length. For serpentine configurations, a multi-axis bending station is utilized.
- Post-Coil Annealing: The formed coil undergoes solution annealing at 1050–1100°C followed by rapid water quenching to eliminate bending-induced residual stresses, restore full austenitic microstructure, and ensure uniform corrosion resistance.
- Surface Treatment: Depending on the application specification, the coiltube receives either electropolishing (removing surface impurities and creating a smooth passive layer) or mechanical brushing. A final passivation treatment (citric acid or nitric acid bath) is applied to enhance the chromium oxide passive film.
- Precision Cutting and End Preparation: Coils are cut to specified lengths using plasma or laser cutting systems. End faces are ground flat, chamfered, or fitted with pre-welded connectors to facilitate field installation.
- Hydrostatic Pressure Testing: Each coil undergoes 100% hydrostatic testing at 1.5× the maximum design pressure for a minimum dwell time of 30 seconds to verify structural integrity and weld soundness.
- Final Inspection and Packaging: Coils are inspected for dimensional accuracy, surface quality, and material certification traceability. Each unit is packaged on a wooden pallet with protective wrapping and accompanied by a full material test report (MTR) and certificate of conformity (CoC).
4.2 Key Manufacturing Advantages
- The continuous coil configuration eliminates the need for field welding, reducing potential leak points by up to 95% compared to straight-pipe assemblies.
- CNC helical coiling ensures geometric uniformity critical for consistent heat transfer coefficient distribution across the entire coil surface.
- Post-coil annealing preserves the full mechanical and corrosion performance of the austenitic microstructure.
5. Applications
5.1 Evaporative Ice Storage Systems
The primary application of the JX-CT-1155 coiltube is in evaporative ice storage systems, where the coil is submerged in a water-filled tank. A chilled secondary fluid (ethylene glycol-water solution at −10°C to −20°C, or ammonia at −15°C to −30°C) circulates through the coiltube, causing water on the tube surface to freeze and form ice layers. The high surface-area-to-volume ratio of the coil geometry maximizes the rate of ice nucleation and growth, enabling efficient latent heat storage. During the discharge phase, ambient or process water flows over the ice-covered coil, absorbing stored thermal energy for peak-load shifting in district cooling systems.
5.2 Additional Applications
- Ice Slurry Generation: Coiltube configurations with optimized pitch and diameter are used in slurry ice makers where controlled ice crystal formation is required for secondary refrigerant transport.
- Thermal Energy Storage (TES) Tanks: Coiltubes serve as embedded heat exchange elements in molten salt or phase-change material (PCM) storage systems for solar thermal and waste heat recovery.
- Food and Beverage Processing: Rapid cooling coils for juice, dairy, and beverage pasteurization and cooling lines.
- Pharmaceutical and Biotech: Cryogenic storage coils for vaccine cold-chain systems and laboratory freezer units.
- HVAC Peak Shaving: Integration into chiller plants for time-of-use energy cost optimization through off-peak ice making.
6. Quality Certifications and Standards Compliance
| Standard / Certification | Description |
|---|---|
| ASTM A213 | Standard Specification for Seamless and Wrought Austenitic Stainless Steel Tubing |
| ASME B31.3 | Process Piping Design Code — verified pressure and stress ratings |
| GB/T 12771 | Chinese National Standard for Stainless Steel Tubes for General Purposes |
| ISO 9001:2015 | Quality Management System Certification |
| ISO 14001:2015 | Environmental Management System Certification |
| CE Marking | Conformity with European pressure equipment and machinery directives |
| EN 10216-5 | European Standard for Heat-Exchange and Heat-Sink Tubing |
| 3-A Sanitary Standard | Available for food-grade and pharmaceutical applications |
7. Unique Selling Points
1. Zero-Weld Continuous Coil Architecture: The pre-formed coiltube design eliminates field welding entirely, providing a hermetically sealed heat exchange element with dramatically reduced failure risk and extended service life exceeding 20 years under normal operating conditions.
2. Optimized Helical Geometry for Evaporative Freezing: The coil pitch, diameter, and tube cross-section are engineered specifically for the physics of evaporative ice nucleation. CFD-validated designs ensure uniform ice layer thickness distribution, preventing localized blockage and maintaining consistent heat transfer throughout the ice storage cycle.
3. Full Material Traceability: Every coil is accompanied by a complete mill test report (MTR) with heat number, chemical analysis, mechanical test results, and heat treatment documentation, ensuring full traceability from raw steel mill to final installation.
4. Customizable Configuration: Wenzhou Jixing Metal Materials offers fully customizable coil geometries — including variable pitch sections, transition curves, and integrated flow distribution headers — tailored to specific evaporative ice maker designs and tank configurations.
5. Enhanced Corrosion Performance: The SUS316L option with molybdenum alloying provides superior resistance to chloride-induced pitting in glycol-based refrigerant solutions, extending maintenance intervals and reducing lifecycle costs.