Stainless Steel Coil Tube (Coiltube) — Ice Storage Pre-Cooling System Application
1. Product Overview
The Stainless Steel Coil Tube (盘管Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered seamless or welded stainless steel tube formed into continuous helical or spiral coil configurations. This product is specifically designed for ice storage spraying pre-cooling devices (Ice Storage Spraying Pre-cooling System), where it serves as the primary heat exchange and thermal energy storage/release medium. The coil tube functions as the core component within evaporator assemblies, facilitating efficient heat transfer between the refrigerant circuit and the ice storage medium, enabling peak-load shifting in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) applications.
Based on extensive research into the heat storage and release characteristics (蓄放冷特性) of coil tube-based ice storage systems, this product has been optimized for superior thermal performance, structural integrity, and long-term corrosion resistance under repeated freeze-thaw cycling conditions.
2. Material & Properties
2.1 Base Material
- Grade 304 (AISI 304 / UNS S30400): Austenitic stainless steel with excellent general corrosion resistance, suitable for most ice storage pre-cooling applications.
- Grade 316 (AISI 316 / UNS S31600): Enhanced austenitic stainless steel with superior chloride ion resistance, recommended for applications involving dehumidification agents or coastal environments.
- Grade 316L (UNS S31603): Low-carbon variant of 316L offering improved weldability and resistance to intergranular corrosion.
2.2 Key Physical and Thermal Properties
| Property | Grade 304 | Grade 316L |
|---|---|---|
| Density (kg/m³) | 8.00 | 8.03 |
| Thermal Conductivity at 20°C (W/m·K) | 16.3 | 14.6 |
| Specific Heat Capacity at 20°C (J/kg·K) | 500 | 500 |
| Coefficient of Thermal Expansion (10⁻⁶/K, 20–100°C) | 17.3 | 16.0 |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 |
| Tensile Strength (MPa, min.) | 520 | 485 |
| Yield Strength (MPa, min.) | 205 | 170 |
| Elongation (%) | ≥40 | ≥40 |
2.3 Surface Finish
- Inner Surface: Electropolished or passivated finish with surface roughness Ra ≤ 0.4 μm to minimize ice adhesion and fouling, ensuring efficient heat transfer and easy cleaning.
- Outer Surface: 2B (No. 4) finish or custom hairline finish for corrosion protection and aesthetic requirements.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ38.1 mm (custom sizes available) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch (Center-to-Center) | 10 mm – 50 mm (adjustable per design) |
| Coil Length (Per Section) | Up to 5,000 m continuous coil |
| Coil Diameter (Bundle OD) | Φ100 mm – Φ1,200 mm |
| Tube Configuration | Single-pass, double-pass, or multi-pass helical coil |
| End Connection | Flared, threaded (NPT/BSP), flanged, or welded stub ends |
| Design Pressure | Up to 2.5 MPa (ASME B31.3 compliant) |
| Design Temperature | −40°C to +120°C |
| Ice Storage Capacity (Typical) | 0.3 – 2.0 kWh per meter of coil (design-dependent) |
| Heat Transfer Coefficient (U-value) | 250 – 600 W/m²·K (system-dependent) |
| Freeze-Thaw Cycle Endurance | ≥10,000 cycles without degradation |
| Standard Reference | ASTM A269 / ASTM A312 / EN 10216-5 |
4. Manufacturing Process
4.1 Raw Material Preparation
High-purity stainless steel wire rod or strip is procured from certified mills, undergoing incoming inspection for chemical composition (via Optical Emission Spectrometry, OES) and mechanical properties in accordance with ASTM and EN standards.
4.2 Seamless Tube Production
- Piercing and Elongation: Steel billets are heated to 1,150–1,250°C and pierced to produce hollow tubes.
- Pilger Milling: Progressive rolling reduces wall thickness and achieves precise dimensional tolerances.
- Draw-Through (Cross-Piercing or Mannesmann Process): Final sizing and shape correction on precision drawing benches.
4.3 Coil Forming
- Coil Winding: Straight tubes are fed through precision forming dies on CNC-controlled coil winding machines at controlled tension to produce uniform helical geometry.
- Pitch Control: Automated systems maintain coil pitch accuracy within ±0.5 mm tolerance.
- End Fitting: Tube ends are flared, threaded, or prepared for welding connections.
4.4 Heat Treatment and Passivation
- Solution Annealing: Tubes are heated to 1,050–1,100°C followed by controlled air or water quenching to achieve full austenitic microstructure and maximum corrosion resistance.
- Stress Relief: Optional low-temperature treatment at 300–400°C to relieve residual stresses from forming operations.
- Acid Pickling and Passivation: Immersion in nitric/hydrofluoric acid solutions to remove oxide scale and establish a protective chromium oxide passive film.
4.5 Quality Inspection
- Hydrostatic Pressure Testing: 100% of coils tested at 1.5× design pressure for leak detection.
- Dimensional Verification: CMM (Coordinate Measuring Machine) or laser scanning for OD, wall thickness, pitch, and straightness.
- Non-Destructive Testing (NDT): Eddy current testing for surface and near-surface defects; ultrasonic testing (UT) for internal flaw detection.
- Visual Inspection: Surface quality, weld integrity, and end condition assessment.
5. Applications
5.1 Primary Application: Ice Storage Pre-Cooling Systems
The stainless steel coil tube is the principal heat exchanger element in ice storage spraying pre-cooling devices (盘管蓄冰式喷淋预冷装置). In this configuration, refrigerant flows through the coil tubes while a water-based ice slurry or direct ice formation occurs on the tube surfaces. The system operates in two modes:
- Ice Charging Mode (蓄冰): Refrigerant circulates through coils to freeze water into ice, storing thermal energy during off-peak hours.
- Ice Discharging Mode (放冷): Stored ice melts to absorb heat from process water or air streams during peak cooling demand periods.
5.2 Additional Applications
- Commercial Refrigeration: Display cases, walk-in coolers, and cold chain logistics systems.
- Food and Beverage Processing: Pasteurization, pasteurization heat exchangers, and sanitary-grade cooling systems (FDA compliant).
- Pharmaceutical Manufacturing: Process cooling and temperature-controlled equipment requiring hygienic-grade materials.
- Geothermal Systems: Closed-loop ground source heat exchangers where corrosion resistance is critical.
- Industrial Process Cooling: Chemical processing, semiconductor manufacturing, and cryogenic applications.
- Marine and Offshore: Seawater-cooled condensers and evaporators requiring 316L-grade corrosion resistance.
6. Quality Certifications and Standards Compliance
6.1 Material Certifications
- EN 10204 3.1 Certificate: Full mill certification with chemical analysis and mechanical test data for each heat lot.
- EN 10204 3.2 Certificate: Third-party verified certification available upon request.
6.2 Manufacturing Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO/TS 22163 (IRIS) — Railway Industry Quality Standard (for transit applications)
- ASME "S" Stamp — Pressure Vessel and Piping Components (where applicable)
- NACE MR0175 / ISO 15156 — Materials for H₂S-containing environments (for oil/gas sector applications)
6.3 Product Standards
- ASTM A269 — Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Heat-Transfer Applications
- ASTM A312 — Seamless, Welded, and Heavy-Walled Austenitic Stainless Steel Tubes for High-Temperature Service
- EN 10216-5 — Heat-Exchanger and Heat Transfer Tubes (Stainless Steel)
- JIS G3459 — Cold-Rolled Stainless Steel Tubes
- GB/T 12771 — Stainless Steel Seamless Tubes for Fluid Transport (Chinese National Standard)
6.4 Sanitary and Hygienic Compliance
- 3-A Sanitary Standards — For dairy and food processing applications
- FDA 21 CFR — Food contact material compliance
- EHEDG (European Hygienic Engineering Design Group) — Hygienic design guidelines
7. Unique Selling Points
- Superior Freeze-Thaw Durability: Engineered for ≥10,000 freeze-thaw cycles without material degradation, cracking, or loss of mechanical integrity — validated through accelerated cycling tests.
- Low Ice Adhesion Surface: Electropolished inner surfaces (Ra ≤ 0.4 μm) significantly reduce ice nucleation and adhesion, improving discharge efficiency and reducing system downtime for defrosting.
- High Thermal Efficiency: Optimized coil geometry and pitch design maximize the heat transfer area-to-volume ratio, achieving ice storage densities of up to 2.0 kWh/m of coil length.
- Extended Service Life: Austenitic stainless steel construction provides exceptional resistance to pitting, crevice corrosion, and general corrosion in aqueous environments, ensuring 20+ year operational lifespan.
- Custom Engineering Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil dimensions, materials, and configurations tailored to specific system designs and thermal performance requirements.
- Full Traceability: Each coil is individually traceable from raw material heat number through final inspection, ensuring complete quality chain documentation.
8. Technical Notes and Design Considerations
Important: When selecting stainless steel coil tubes for ice storage pre-cooling applications, engineers should consider the following factors:
- The coil pitch must be optimized to balance heat transfer efficiency against pressure drop through the tube bundle.
- Freeze-thaw cycling induces thermal stresses; proper expansion loop design or flexible connections are essential to prevent fatigue failure at tube supports.
- For applications involving glycol-water mixtures or other heat transfer fluids, material compatibility must be verified against the specific fluid chemistry.
- The minimum bend radius during installation should not be less than 5× the tube outer diameter to avoid work hardening and potential cracking.
9. Packaging and Delivery
- Coils are wound on steel or wooden reels and secured with stainless steel strapping bands.
- Each coil is wrapped in moisture-proof polyethylene film and packed in export-grade wooden cases or pallets.
- Standard coil weight per package: 500 – 2,000 kg (configurable).
- Delivery options: FOB (Free on Board), CIF (Cost, Insurance, and Freight), or EXW (Ex Works) per Incoterms 2020.
10. Manufacturer Information
Wenzhou Jixing Metal Materials Co., Ltd. is a specialized manufacturer of stainless steel tubes, pipes, and formed products with extensive expertise in heat exchanger and thermal management applications. The company maintains a vertically integrated production facility in Wenzhou, Zhejiang Province, China, encompassing raw material processing, seamless tube production, coil forming, surface treatment, and final inspection under one roof.