Stainless Steel Coil Tube (Coiltube) — Ice Storage Cold Extraction System
Product Code: 1289 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered spiral-wound tube assembly designed primarily for external-melting ice storage systems (External Melting Ice Storage, EMIS) and thermal energy storage applications. This product serves as the core heat exchange element within cold extraction subsystems, where phase-change materials (typically water-to-ice) absorb and release latent heat during charging and discharging cycles. The coil tube is fabricated from high-purity austenitic stainless steel to ensure long-term durability under repeated freeze-thaw conditions, corrosive environments, and thermal cycling loads.
Based on experimental research into the cold extraction characteristics of external-melting ice coil tubes, the performance of these coil assemblies is governed by fluid flow distribution, coil geometry, heat transfer coefficient, and the interplay between the coil wall temperature and the phase-change front propagation. The design philosophy integrates findings from laboratory-scale cold extraction experiments to optimize thermal efficiency, pressure drop, and structural integrity.
2. Material & Properties
2.1 Base Material
The coil tube is manufactured from austenitic stainless steel conforming to international standards, with the following typical grades available:
- SUS304 / AISI 304 (UNS S30400): Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%, Molybdenum (Mo) ≤ 0.08%. Suitable for general-purpose ice storage and low-chloride environments.
- SUS316L / AISI 316L (UNS S31603): Cr 16–18%, Ni 10–14%, Mo 2–3%. Enhanced resistance to chloride-induced pitting and crevice corrosion, recommended for brine-based or marine-influenced applications.
- SUS321 / AISI 321 (UNS S32100): Ti-stabilized austenitic grade, offering superior resistance to intergranular corrosion at elevated temperatures and improved thermal fatigue life.
2.2 Mechanical Properties (SUS304 Annealed Condition)
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 520 MPa | ASTM A213 / GB/T 12771 |
| Yield Strength (0.2% Offset) | ≥ 205 MPa | ASTM A213 / GB/T 12771 |
| Elongation (at Break) | ≥ 40% | ASTM A213 / GB/T 12771 |
| Hardness (Rockwell B) | ≤ 95 HRB | ASTM E18 |
| Density | ~ 8.00 g/cm³ | — |
2.3 Thermal & Physical Properties
| Property | Value (at 20 °C) | Value (at −20 °C) |
|---|---|---|
| Thermal Conductivity | ~ 16.3 W/(m·K) | ~ 12.5 W/(m·K) |
| Specific Heat Capacity | ~ 0.50 J/(g·K) | ~ 0.46 J/(g·K) |
| Thermal Expansion Coefficient | ~ 17.3 × 10⁻⁶ /K | ~ 14.0 × 10⁻⁶ /K |
| Cryogenic Impact Toughness | Excellent (no ductile-to-brittle transition) | Retains full ductility |
2.4 Corrosion Resistance
The austenitic microstructure, stabilized by chromium and nickel alloying, provides:
- Resistance to atmospheric corrosion, dilute acids, and alkaline solutions.
- For SUS316L: Superior resistance to chloride pitting (Pitting Resistance Equivalent Number, PREN ≥ 24).
- Resistance to intergranular corrosion when properly stabilized or low-carbon (L-grade) variants are selected.
3. Specifications
| Parameter | Specification / Range | Notes |
|---|---|---|
| Outer Diameter (OD) | 6 mm – 50 mm (customizable) | Standard increments: 6, 8, 10, 12, 15, 19, 25, 32, 38, 50 mm |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm | Typical: 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm |
| Coil Pitch (Center-to-Center Spacing) | 15 mm – 60 mm | Optimized per cold extraction efficiency studies |
| Coil Length / Developed Length | Up to 200 m per assembly | Custom lengths available |
| Operating Temperature Range | −40 °C to +150 °C | Continuous operation |
| Operating Pressure | Up to 1.6 MPa (16 bar) standard | High-pressure variants available |
| Surface Finish | 2B (mill finish) or BA (bright annealed) | Electropolished available on request |
| End Preparation | Plain end, threaded (G/BSP), flanged (ANSI/GB) | Per customer drawing |
| Heat Treatment | Solution annealed + water/quench cooled | Stress-relieved for dimensional stability |
| Standards Compliance | ASTM A213, ASTM A269, GB/T 12771, GB/T 13296 | EN 10216-5 available on request |
4. Manufacturing Process
The production of stainless steel coil tubes for ice storage cold extraction systems follows a rigorous multi-stage process:
- Coil Uncoiling & Straightening: Cold-rolled stainless steel coil stock is uncoiled, straightened, and inspected for surface defects and dimensional accuracy.
- Tube Forming & Sizing: The flat strip is formed into round or oval cross-section tubing using precision rolling mills, followed by sizing to exact OD and wall thickness tolerances (± 0.05 mm).
- Spiral Winding (Coiling): The formed tube is wound into a helical coil using CNC-controlled coiling machines. The coil pitch, diameter, and number of turns are programmatically set to match the thermal design requirements of the specific ice storage system. Experimental data on cold extraction efficiency directly informs the optimal coil geometry parameters.
- Welding: Spiral-wound coils are joined by Gas Tungsten Arc Welding (GTAW / TIG) for single-layer welds or Gas Metal Arc Welding (GMAW) for thicker sections. Weld seams are ground flush and subjected to 100% visual and dye penetrant inspection (DPI) per ASTM E709.
- Solution Annealing: The welded assembly is solution-annealed at 1050–1150 °C followed by rapid quenching to restore full austenitic microstructure, eliminate welding sensitization, and ensure maximum corrosion resistance.
- Precision Coiling & Fixturing: Post-annealing, the tube is recoiled to final geometry with precise pitch control. End fixtures, inlet/outlet manifolds, and support brackets are fabricated and welded as sub-assemblies.
- Pressure Testing & Leak Detection: Each coil assembly undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure, held for a minimum of 30 minutes, with zero permissible leakage. Helium leak detection (ASTM E2191) is available for critical applications.
- Surface Treatment & Passivation: Final passivation treatment per ASTM A967 removes free iron from the surface and establishes a protective chromium oxide passive film. Optional electropolishing reduces surface roughness to Ra ≤ 0.4 μm for enhanced heat transfer.
- Final Inspection & Packaging: Dimensional verification, material certification review, and protective packaging with desiccant for shipment.
5. Applications
The Stainless Steel Coil Tube is a versatile component deployed across multiple thermal management and cold storage domains:
- Ice Storage Cold Extraction Systems: Core heat exchange element in external-melting ice storage systems (EMIS), where the coil extracts latent heat from melting ice during peak demand periods, shifting energy consumption to off-peak hours.
- Commercial & Industrial Refrigeration: Evaporator coils in cold rooms, blast freezers, and process cooling loops requiring reliable low-temperature operation.
- Chilled Water Systems: Coil assemblies for district cooling networks and large-scale HVAC (Heating, Ventilation, and Air Conditioning) installations.
- Food & Beverage Processing: Pasteurization coils, juice cooling, dairy processing heat exchangers — where sanitary-grade stainless steel (SUS304L/SUS316L) is mandated.
- Pharmaceutical & Biotech: GMP-compliant cooling loops for bioreactors, vaccine storage, and cryogenic sample preservation.
- Marine & Offshore: Corrosion-resistant coil heat exchangers in shipboard HVAC and offshore platform cooling systems (SUS316L grade).
- Cryogenic Applications: Low-temperature coil assemblies for liquid nitrogen (LN₂) and liquid oxygen (LOX) handling, leveraging the excellent cryogenic toughness of austenitic stainless steel.
- Geothermal & Renewable Energy: Coil heat exchangers in ground-source heat pump systems and solar thermal storage installations.
6. Quality Certifications & Standards
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity and traceability:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System — covers all manufacturing processes |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| EN 10204 3.1 | Third-party material test certificates for each batch |
| ASTM A213 / A269 | Material specifications for seamless and welded stainless steel tubes |
| GB/T 12771 | Chinese national standard for welded stainless steel tubes |
| ASME BPV Code Section VIII | Pressure vessel code compliance for high-pressure coil assemblies (available) |
| CE Marking (PED 2014/68/EU) | European Pressure Equipment Directive compliance (available for export) |
7. Unique Selling Points
Performance-Optimized Coil Geometry: Coil pitch, diameter, and turn density are engineered based on experimental research into external-melting ice storage cold extraction characteristics, maximizing heat transfer coefficient while minimizing pressure drop and ensuring uniform ice melting front propagation.
Cryogenic-Grade Material Selection: Austenitic stainless steel retains full ductility and toughness at temperatures as low as −196 °C (LN₂ temperature), eliminating the risk of brittle fracture during thermal cycling — a critical advantage over carbon steel alternatives in freeze-thaw duty.
Custom Engineering Capability: Full parametric customization of OD, wall thickness, coil pitch, developed length, end preparation, and surface finish to match specific thermal system design requirements and installation constraints.
Traceable Quality Assurance: Every coil assembly ships with EN 10204 3.1 material certificates, full welding procedure specifications (WPS) and procedure qualifications (PQR), and batch-level chemical and mechanical test reports, ensuring complete supply-chain traceability.
Corrosion-Resistant Longevity: With proper grade selection (SUS316L for aggressive environments), the coil tube delivers a service life exceeding 25 years in continuous operation, with minimal maintenance requirements — significantly reducing total cost of ownership (TCO).
8. Technical Summary
The Stainless Steel Coil Tube (Product Code 1289) from Wenzhou Jixing Metal Materials Co., Ltd represents a high-performance thermal exchange solution engineered for demanding cold storage and refrigeration applications. By combining precision manufacturing, scientifically informed coil geometry design, and premium austenitic stainless steel materials, this product delivers superior cold extraction efficiency, exceptional durability under thermal cycling, and long-term reliability in corrosive environments. The product is backed by internationally recognized quality certifications and supported by comprehensive customization options to address the specific requirements of each application.