Stainless Steel Coil Tube for Ice Slurry Heat Exchange Applications
Product Overview
The Stainless Steel Coil Tube (also known as Coiltube or Coil Pipe) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed specifically for high-efficiency heat exchange systems, particularly those involving ice slurry (Ice Slurry) refrigeration technologies. This product represents a critical component in secondary refrigeration loops, district cooling networks, and industrial heat transfer applications where compact geometry, superior thermal performance, and corrosion resistance are paramount.
Unlike conventional straight pipe configurations, coil tubes leverage their helical geometry to dramatically increase the surface-area-to-volume ratio, thereby enhancing convective heat transfer coefficients. The inherent curvature of the coil tube induces secondary flow patterns (Dean Vortices) within the fluid stream, which disrupt the thermal boundary layer and significantly improve heat exchange efficiency compared to equivalent straight-pipe systems.
Material & Properties
Base Material Grades
Wenzhou Jixing Metal Materials Co., Ltd. offers coil tubes fabricated from a range of austenitic and duplex stainless steel grades, selected to meet the demanding requirements of cryogenic and refrigeration environments:
- AISI 304 (UNS S30408) — General-purpose austenitic stainless steel offering excellent corrosion resistance in most atmospheric and industrial environments. Suitable for ice slurry systems operating at temperatures above −196 °C.
- AISI 316L (UNS S31603) — Low-carbon austenitic grade with added molybdenum (2.0–3.0%), providing superior resistance to chloride-induced pitting and crevice corrosion. Preferred for coastal and chemical-processing applications.
- AISI 321 (UNS S32100) — Titanium-stabilized austenitic steel with enhanced resistance to intergranular corrosion, suitable for elevated-temperature preheating sections.
- AISI 316Ti (UNS S31635) — Titanium-stabilized variant of 316L, combining chloride resistance with improved mechanical strength at cryogenic temperatures.
- Super Duplex 2205 (UNS S31803) — For applications requiring high mechanical strength combined with excellent resistance to chloride stress corrosion cracking (ClSCC) and erosion-corrosion.
Key Mechanical Properties (AISI 304 — Representative Values)
- Tensile Strength (Rm): ≥ 520 MPa
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A50): ≥ 40%
- Hardness (HB): ≤ 210
- Density: 7.93 g/cm³
- Thermal Conductivity (at 20 °C): 16.3 W/(m·K)
- Thermal Expansion Coefficient (100–500 °C): 17.2 × 10⁻⁶ /K
- Cryogenic Ductility: Maintains excellent toughness down to −196 °C (LNG temperature)
Corrosion Resistance Characteristics
The passive chromium oxide film (Cr₂O₃) formed on the surface of these stainless steel coil tubes provides robust protection against:
- Atmospheric corrosion (industrial and marine)
- Chemical attack from glycol-based ice slurry fluids (ethylene glycol, propylene glycol)
- Chloride pitting (particularly in 316L and 2205 grades)
- Intergranular corrosion following welding operations
- Erosion-corrosion from high-velocity slurry flow
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Material Grades | 304, 304L, 316, 316L, 321, 316Ti, 2205 |
| Outer Diameter (OD) | Φ6 mm – Φ50 mm (custom sizes available) |
| Wall Thickness | 0.3 mm – 3.0 mm |
| Coil Diameter (Bundle OD) | 100 mm – 1500 mm |
| Coil Pitch (Turn-to-Turn Spacing) | 1.5 mm – 15 mm (adjustable per design requirement) |
| Length per Coil | 5 m – 100 m (continuous or segmented) |
| Surface Finish | Pickled & Passivated (2B), Polished (Ra ≤ 0.4 μm), or Mirror (Ra ≤ 0.1 μm) |
| Operating Temperature Range | −196 °C to +450 °C |
| Maximum Operating Pressure | Up to 6.3 MPa (PN63) depending on geometry |
| Applicable Standards | ASTM A213/A269, EN 10216-5, GB/T 12771, JIS G3459 |
| Manufacturing Tolerance | OD: ±0.1 mm; Wall: ±10%; Straightness: ≤ 1 mm/m |
| Packaging | Wooden crate or export-standard steel frame; moisture-proof wrapping |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous multi-stage manufacturing workflow:
-
Raw Material Selection and Inspection
Hot-rolled stainless steel strip or seamless tube blanks are sourced from certified mills. Incoming materials undergo spectroscopic analysis (PMI — Positive Material Identification), mechanical property testing, and visual inspection to ensure compliance with specified chemical composition and grade requirements. -
Pipe Forming
Seamless tubes are produced via the automatic piercing and multi-stand rolling process, or welded tubes are manufactured through the Electric Resistance Welding (ERW) or Automatic Submerged Arc Welding (ASAW) methods, depending on the application requirements and wall thickness. -
Heat Treatment (Solution Annealing)
The formed tubes undergo solution annealing at 1010–1150 °C followed by rapid water quenching. This process dissolves carbide precipitates, restores full austenitic microstructure, and ensures optimal corrosion resistance and mechanical properties. -
Precision Coiling (Helical Forming)
The straight tubes are fed through a computer-controlled coil forming machine that applies controlled bending forces to create the helical geometry. Critical process parameters include:- Bending radius (minimum bend radius ≥ 3D to prevent ovalization)
- Coil pitch accuracy (±0.5 mm tolerance)
- Residual stress minimization through controlled spring-back compensation
-
Pickling and Passivation
After coiling, the tubes are subjected to pickling (acid bath treatment with mixed HNO₃/HF solution) to remove oxidation scale and heat-tint. Subsequent passivation with dilute nitric acid (5–10% HNO₃) re-establishes the protective chromium oxide passive film on the surface. -
Quality Control and Testing
Comprehensive inspection protocols include:- Dimensional measurement (OD, wall thickness, coil diameter, pitch)
- Helium or pneumatic pressure testing (leak tightness verification)
- Acid immersion testing (ASTM A967) for passivation verification
- Visual and dye penetrant inspection of weld seams (where applicable)
- Ultrasonic thickness measurement
-
Final Packaging and Dispatch
Finished coil tubes are individually wrapped in moisture-barrier film, placed in export-grade wooden crates with cushioning material, and prepared for international shipment.
Applications
Primary Application: Ice Slurry Heat Exchange Systems
The coil tube geometry is particularly advantageous in ice slurry (slush ice) heat exchange systems. Ice slurry — a mixture of ice crystals suspended in a brine or glycol solution — operates at temperatures between −5 °C and −15 °C, providing a high latent heat transport medium with excellent subcooling capacity. The key advantages of coil tubes in this application include:
- Enhanced Heat Transfer Coefficient: The Dean number (De) associated with helical flow increases the turbulent heat transfer coefficient by 20–40% compared to equivalent straight tubes.
- Compact Design: High surface-area-to-volume ratio enables compact heat exchanger cores suitable for space-constrained installations.
- Reduced Fouling: The secondary Dean vortices promote continuous fluid mixing, reducing the deposition of ice crystals on the tube walls and maintaining stable heat transfer performance over time.
- Cryogenic Compatibility: Austenitic stainless steels retain their ductility and strength at cryogenic temperatures, preventing brittle fracture during thermal cycling.
Additional Applications
- District Cooling Systems: Secondary loop piping for centralized chilled water distribution networks.
- Process Cooling: Heat exchanger cores in pharmaceutical, food and beverage, and chemical processing industries.
- Building Energy Storage: Ice thermal energy storage (TES) systems for peak-load shifting in commercial buildings.
- LNG (Liquefied Natural Gas) Systems: Cryogenic heat exchange components operating at −162 °C.
- Marine Refrigeration: Shipboard refrigeration systems requiring corrosion-resistant, compact heat exchangers.
- Medical and Laboratory Equipment: Ultra-low temperature storage and cryogenic sample handling systems.
- Solar Thermal Systems: Heat collector coils in solar water heating installations.
Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and product certifications to ensure international market acceptance:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing quality.
- ISO 14001:2015 — Environmental Management System certification.
- EN 10204 3.1 — Inspection and Test Certificate issued by an authorized inspection body.
- CE Marking — European Conformity for products meeting applicable EU directives.
- PED (Pressure Equipment Directive 2014/68/EU) — Compliance for pressure-containing components where applicable.
- Mill Test Reports (MTR) — Full chemical composition and mechanical property documentation for every heat lot.
- Material Traceability — Complete heat-number traceability from raw material mill through final product delivery.
Unique Selling Points
- Ice Slurry Optimization: Products are specifically engineered and validated for ice slurry heat exchange applications, with coil geometry parameters (pitch, diameter, tube dimensions) optimized through experimental studies on ice slurry heat transfer characteristics.
- Cryogenic Reliability: Full mechanical property retention from ambient temperature down to −196 °C, ensuring safe operation in extreme cold environments without risk of brittle fracture.
- Custom Geometric Engineering: Flexible coil diameter, pitch, and tube dimension customization to match specific heat exchanger design requirements.
- Multi-Grade Availability: Comprehensive material grade portfolio (304 through 2205) allowing selection based on corrosion environment, mechanical requirements, and budget constraints.
- Compact Thermal Performance: Superior heat transfer efficiency per unit volume compared to straight-tube alternatives, enabling smaller equipment footprints and reduced installation costs.
- Long Service Life: Exceptional resistance to corrosion, erosion, and thermal fatigue in aggressive refrigeration media, minimizing maintenance intervals and lifecycle costs.
- Export-Ready Quality: Full international standard compliance with complete documentation, enabling seamless integration into global supply chains.
Academic Reference Context
This product specification is informed by experimental research documented in the study "Experimental Investigation on Ice Slurry Heat Transfer Characteristics in Coil Tubes" (《盘管内冰浆换热特性试验研究》), which examined the influence of coil geometry parameters (coil diameter, tube outer diameter, pitch) on the heat transfer performance of ice slurry flowing through helical stainless steel tubes. Key findings include that increasing the coil diameter-to-tube-diameter ratio enhances the heat transfer coefficient up to a critical point, beyond which diminishing returns occur. These research insights directly inform the geometric optimization of Wenzhou Jixing's coil tube product line for ice slurry applications.
Conclusion
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. represents a technically advanced solution for ice slurry and general refrigeration heat exchange applications. Combining precision manufacturing, materials engineering expertise, and research-driven geometric optimization, this product delivers superior thermal performance, exceptional durability, and full compliance with international quality standards. It is an ideal choice for engineers and designers seeking reliable, high-efficiency heat exchange components in demanding cryogenic and refrigeration environments.