Stainless Steel Coil Tube (Coiltube) — Ice Slurry Heat Exchange Application
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered helical or spiral-wound tubular component designed specifically for high-efficiency heat exchange applications involving ice slurry (Ice Slurry Secondary Refrigerant) systems. Ice slurry, a two-phase mixture of ice crystals suspended in a brine or aqueous solution, offers superior heat transfer performance compared to conventional single-phase refrigerants due to its high latent heat capacity and excellent thermal conductivity characteristics.
Through extensive experimental research on the heat transfer characteristics of ice slurry flowing within coiled tube geometries, it has been demonstrated that the helical configuration induces secondary flow patterns (Dean vortices) that significantly enhance convective heat transfer coefficients. This coil tube product leverages these fluid-dynamic advantages to deliver exceptional thermal performance in cold storage, industrial refrigeration, and energy-efficient cooling systems.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from high-grade austenitic stainless steel, with primary grades including:
- SUS304 / ASTM 304 — General-purpose corrosion-resistant grade with excellent formability
- SUS316L / ASTM 316L — Enhanced chloride resistance for marine and chemical environments
- SUS321 / ASTM 321 — Stabilized grade with superior high-temperature resistance
- SUS310S / ASTM 310S — Ultra-high temperature oxidation resistance for extreme conditions
2.2 Key Mechanical Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (UTS) | ≥ 520 MPa | ASTM A269 / GB/T 249 |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ASTM A269 / GB/T 249 |
| Elongation | ≥ 40% | ASTM A269 |
| Hardness (Rockwell B) | ≤ 95 HRB | ASTM A262 |
| Operating Temperature Range | −196°C to +870°C | — |
2.3 Corrosion Resistance
The austenitic stainless steel matrix provides outstanding resistance to:
- Brine and saltwater corrosion (critical for ice slurry applications using NaCl or CaCl₂ solutions)
- Atmospheric oxidation and rust formation
- Intergranular corrosion (particularly in 304L and 316L low-carbon grades)
- Pitting and crevice corrosion in chloride-containing environments
3. Technical Specifications
| Parameter | Specification Range | Unit |
|---|---|---|
| Outer Diameter (OD) | 6 – 114.3 | mm |
| Wall Thickness | 0.5 – 3.0 | mm | Coil Diameter (Center-to-Center) | 100 – 2000 | mm |
| Helical Pitch | 15 – 150 | mm |
| Tube Length (per coil) | 1 – 50 | m |
| Surface Finish | 2B / BA / No.4 / Mirror (Ra ≤ 0.4 μm) | — |
| End Preparation | Beveled / Flat / Threaded / Flanged | — |
| Welding Method | TIG (GTAW) / Orbital / Push-Back | — |
| Pressure Rating | Up to 1.6 MPa (standard); up to 6.4 MPa (custom) | MPa |
| Dimensional Tolerance | ±0.1 mm (OD); ±10% (wall thickness) | — |
| Ice Slurry Heat Transfer Enhancement | 1.5× – 3.0× vs. straight tube | Factor |
4. Manufacturing Process
4.1 Raw Material Preparation
Stainless steel strip or seamless tubing is sourced from certified mills with full traceability documentation. Incoming material undergoes spectroscopic analysis to verify chemical composition compliance with specified grades.
4.2 Coil Forming
Helical coil tubes are produced through one of the following methods:
- Continuous Coil Winding (CCW) — Seamless tubing is fed through precision CNC-guided forming heads that progressively bend the tube into a helical geometry with controlled pitch and radius.
- Segmented Coil Assembly — Pre-formed U-bends or S-bends are welded together to create multi-pass coil configurations for enhanced heat transfer surface area.
- Spool Winding — Straight tube sections are wound around mandrels to produce compact spiral configurations.
4.3 Welding
Where joints are required, Tungsten Inert Gas (TIG / GTAW) welding is employed with argon or helium shielding gas. Orbital welding automation ensures consistent weld bead geometry and penetration. Back-purging with inert gas prevents internal oxidation of the weld zone, maintaining metallurgical integrity critical for cryogenic and refrigeration service.
4.4 Surface Treatment & Finishing
- Pickling and Passivation — Removal of weld scale followed by passivation to restore the chromium oxide protective layer
- Precision Polishing — Electropolishing or mechanical polishing to achieve specified surface roughness (Ra values down to 0.2 μm)
- Internal Cleaning — Acid pickling or mechanical brushing to ensure contamination-free internal surfaces for food-grade and pharmaceutical applications
4.5 Quality Inspection
- Dimensional Verification — CMM (Coordinate Measuring Machine) inspection of coil geometry, OD, and wall thickness
- Weld Inspection — Visual inspection, dye penetrant testing (DPT), and radiographic testing (RT) for weld integrity
- Pressure Testing — Hydrostatic or pneumatic pressure testing at 1.5× working pressure
- Heat Transfer Performance Testing — Verification of thermal performance under ice slurry flow conditions
5. Applications
5.1 Ice Slurry Refrigeration Systems
The primary application domain for this coil tube is ice slurry secondary refrigeration. Ice slurry systems utilize a mixture of ice crystals (typically 5–25% by weight) in brine solutions as the heat transfer medium. The coil tube's helical geometry promotes turbulent flow and Dean vortex formation, dramatically improving heat transfer efficiency compared to conventional straight-tube heat exchangers. Experimental studies have confirmed heat transfer coefficient enhancements of 1.5 to 3.0 times relative to equivalent straight tubes under identical flow conditions.
5.2 Industrial Cold Storage
- Freezer and cold room evaporator coils
- Plate-finished evaporator assemblies
- Quick-freezing tunnel refrigeration systems
- Cryogenic storage systems (liquid nitrogen applications)
5.3 HVAC & Chiller Systems
- Chilled water coil heat exchangers
- Air handling unit (AHU) coil assemblies
- Process cooling in industrial manufacturing
- Central air conditioning condenser coils
5.4 Food & Beverage Industry
- Beer and wine cold conditioning coils
- Dairy product cooling and pasteurization systems
- Meat and poultry blast-freezing systems
- Pharmaceutical cold chain equipment
5.5 Marine & Offshore
- Ship refrigeration systems (316L grade for seawater resistance)
- Offshore platform cooling coils
- Marine air conditioning systems
6. Unique Selling Points
Enhanced Heat Transfer Performance: The helical coil geometry generates Dean secondary vortices that continuously disrupt the thermal boundary layer, resulting in significantly higher Nusselt numbers and heat transfer coefficients compared to straight tubes — a critical advantage for ice slurry systems where rapid, uniform heat extraction is essential.
Ice Slurry-Optimized Design: Unlike conventional coil tubes, this product is specifically engineered and validated for ice slurry flow conditions. The geometry accounts for the non-Newtonian rheological behavior of ice slurry mixtures, preventing ice crystal accumulation and maintaining consistent heat transfer throughout the operational cycle.
Superior Corrosion Resistance: The austenitic stainless steel construction ensures long-term durability in aggressive brine environments (NaCl, CaCl₂, MgCl₂ solutions) without degradation of mechanical or thermal properties.
Customizable Configurations: Full customization of coil diameter, pitch, tube OD, wall thickness, and end preparations to match specific system design requirements, enabling optimal integration into existing refrigeration and HVAC infrastructure.
Energy Efficiency: By achieving superior heat transfer performance, these coil tubes enable smaller heat exchanger surface areas, reduced refrigerant charges, and lower pumping power consumption — contributing to meaningful energy savings and reduced carbon footprint.
7. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| ASTM A269 / A270 | Standard specification for austenitic stainless steel seamless tubing |
| GB/T 12771 | Chinese national standard for stainless steel welded tubes |
| EN 10217-7 | European standard for stainless steel tubes for mechanical applications |
| JIS G3459 | Japanese Industrial Standard for austenitic stainless steel tubing |
| PED 2014/68/EU | Pressure Equipment Directive compliance (where applicable) |
| NSF / ANSI 61 | Drinking water system components certification (food-grade applications) |
| CE Marking | European Conformity for machinery and pressure equipment |
8. Technical Note on Ice Slurry Heat Transfer
Based on experimental research published in the field of ice slurry heat transfer within coiled tubes, the following key findings inform the design and application of this product:
- Heat Transfer Enhancement Mechanism: Ice slurry flow in helical coils benefits from a synergistic combination of Dean vortex-induced turbulence and the enhanced thermal conductivity of the ice-brine mixture, resulting in heat transfer coefficients that far exceed those of pure water or single-phase refrigerants in identical geometries.
- Optimal Ice Fraction: The heat transfer performance of ice slurry in coiled tubes peaks at an ice fraction (by mass) of approximately 10–20%, beyond which excessive viscosity increases pressure drop without proportional heat transfer gains.
- Reynolds Number Dependency: The coil tube geometry maintains turbulent flow conditions at lower flow velocities compared to straight tubes, enabling energy-efficient operation at reduced pumping power.
- Pressure Drop Consideration: While helical geometry increases pressure drop relative to straight tubes (due to centripetal acceleration effects), the net energy efficiency remains favorable when accounting for the reduced heat exchanger surface area and refrigerant charge required.
9. Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. offers full customization services for stainless steel coil tubes. Customers are advised to provide the following parameters for accurate quotation:
- Stainless steel grade (e.g., SUS304, SUS316L)
- Tube outer diameter and wall thickness
- Coil diameter and helical pitch
- Total tube length and number of passes
- Surface finish requirement
- End preparation type
- Operating pressure and temperature conditions
- Applicable ice slurry concentration and flow rate
- Applicable industry standards and certifications required