Stainless Steel Coil Tube (Coiltube) — Partial-Freezing Ice Storage System
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered heat exchange component designed for partial-freezing ice storage cooling systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1104), this coil tube integrates advanced partial-freezing technology with air-charging ice melting mechanisms to achieve superior thermal performance, energy efficiency, and operational reliability in district cooling, commercial refrigeration, and peak-load shifting applications.
Unlike conventional fully-freezing ice storage systems, the partial-freezing coil tube design maintains a controlled ice layer on the outer surface of the tubes while preserving a liquid coolant core, thereby minimizing thermal resistance degradation and enabling rapid ice melting cycles through the proprietary air-charging defrosting method. This approach significantly enhances the system's coefficient of performance (COP) and extends the service life of the coil assembly.
Material & Properties
Base Material
- Primary Alloy: Austenitic Stainless Steel, conforming to ASTM A269 / ASTM A213 / EN 10216-5 / GB/T 12771 standards
- Preferred Grades: SUS304 (AISI 304, 1.4301), SUS316L (AISI 316L, 1.4404) for enhanced corrosion resistance in brine or glycol-based environments
- Surface Finish: Pickled and Passivated (P&P) or Electropolished to a surface roughness of Ra ≤ 0.8 μm
Mechanical & Thermal Properties
- Tensile Strength: ≥ 520 MPa (SUS304), ≥ 550 MPa (SUS316L)
- Yield Strength: ≥ 205 MPa (SUS304)
- Elongation: ≥ 40% (SUS304), ≥ 35% (SUS316L)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (SUS304)
- Corrosion Resistance: Excellent resistance to chloride-induced pitting (SUS316L), suitable for long-term immersion in calcium chloride (CaCl₂) or ethylene glycol (EG) brine solutions
- Operating Temperature Range: −40°C to +120°C
- Operating Pressure: Up to 1.6 MPa (design pressure), tested to 2.4 MPa (hydrostatic test)
Specifications
| Parameter | Specification |
|---|---|
| Product Model | Coiltube Series (Ref. No. 1104) |
| Tube Outer Diameter (OD) | φ12 mm, φ14 mm, φ16 mm, φ19 mm, φ22 mm (customizable) |
| Tube Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Pitch (Center-to-Center Spacing) | 25 mm – 50 mm (adjustable per thermal load) |
| Coil Diameter | φ300 mm – φ2000 mm |
| Coil Length / Effective Heat Transfer Area | Up to 200 m per coil; total heat transfer area configurable |
| Maximum Ice Layer Thickness | ≤ 6 mm (partial-freezing controlled) |
| Ice Melting Method | Air-Charging Defrost (injected air bubble nucleation) |
| Refrigerant / Brine Media | Calcium Chloride (CaCl₂) brine, Ethylene Glycol (EG), Propylene Glycol (PG) |
| Connection Type | Welded (TIG / Argon Arc), Flanged, or Threaded End Fittings |
| Surface Treatment | Passivation, optional PTFE or ceramic anti-icing coating |
| Compliance Standards | ASTM A269, GB/T 12771, EN 10216-5, ISO 15499 |
Manufacturing Process
1. Raw Material Inspection
Each stainless steel coil tube blank is subjected to spectroscopic analysis (OES) to verify chemical composition, ensuring compliance with the specified grade requirements. Incoming material must pass ultrasonic flaw detection (UT) and visual surface inspection per ASTM A999.
2. Precision Cutting & Deburring
Coil tube lengths are cut to precise dimensions using cold-shear or laser-cutting technology, followed by mechanical deburring to eliminate burrs and sharp edges that could obstruct fluid flow or compromise welding integrity.
3. Coil Winding & Forming
Individual tubes are wound onto precision-mandrel coil forms using CNC-controlled winding machinery to maintain uniform pitch and concentricity. The winding process is performed under controlled tension to prevent ovalization or residual stress accumulation.
4. TIG Welding (Tungsten Inert Gas)
U-bend connections, header integrations, and end fittings are welded using TIG (GTAW) welding under continuous argon (Ar) shielding. Internal purge gas is employed to prevent internal oxidation. Weld beads are ground smooth and inspected per ASME Section IX qualification standards.
5. Hydrostatic Pressure Testing
Each completed coil assembly undergoes hydrostatic testing at 1.5× the maximum design pressure for a minimum dwell time of 30 minutes to verify structural integrity and weld soundness. Leak detection is performed using soap-bubble or electronic pressure-decay methods.
6. Pickling & Passivation
Post-welding pickling removes heat-affected zone (HAZ) oxide scales using a nitric-hydrofluoric acid (HNO₃/HF) blend, followed by passivation to restore the chromium oxide protective layer. This ensures long-term corrosion resistance in aggressive brine environments.
7. Surface Coating (Optional)
An anti-icing nano-coating (PTFE-based or ceramic composite) may be applied to the outer tube surface to reduce ice adhesion force, facilitating faster and more complete ice release during the air-charging defrost cycle.
Manufacturing Process Flow
- Raw Material Receiving & Spectroscopic Verification
- Coil Tube Cutting & End Preparation
- CNC Coil Winding on Precision Mandrel
- Header Fabrication & U-Bend Forming
- TIG Welding with Internal Argon Purge
- Hydrostatic Pressure Testing
- Pickling & Passivation Treatment
- Optional Anti-Icing Surface Coating
- Final Dimensional Inspection & Non-Destructive Testing (NDT)
- Packaging & Dispatch
Applications
Primary Application Domains
- Ice Storage District Cooling Systems: The coil tube serves as the core heat exchanger in ice storage tanks, enabling thermal energy storage during off-peak electricity periods and discharge during peak cooling demand, thereby reducing peak electrical load by 30%–50%.
- Commercial Building HVAC: Integrated into chiller-plant systems for large commercial complexes, shopping malls, and office towers requiring high-capacity, energy-efficient cooling.
- Process Cooling in Food & Beverage Industry: Used in cold storage, beverage pasteurization, and dairy processing where rapid temperature reduction and precise thermal control are critical.
- Pharmaceutical & Biotechnology: Applied in cold-chain storage, vaccine refrigeration, and bioreactor temperature management where corrosion resistance and sanitary-grade surfaces are mandatory.
- Industrial Refrigeration: Deployed in ammonia-based or CO₂-based refrigeration systems requiring durable heat exchange components.
- Peak-Load Shifting & Grid Stabilization: Supports utility-scale demand-side management programs by shifting electrical consumption from peak to off-peak hours.
Air-Charging Ice Melting Mechanism
The partial-freezing coil tube employs a proprietary air-charging defrost technology validated through experimental research (as documented in the study "Experimental Investigation of Air-Charging Ice Melting in Partial-Freezing Ice Coil Tubes"). During the discharge cycle, controlled air bubbles are injected into the coolant flow, creating nucleation sites that disrupt the ice layer adhesion. This method reduces ice melting time by up to 40% compared to conventional hot-water or brine defrost methods, while maintaining the partial-freezing ice layer thickness within a thermally optimal range (≤ 6 mm), preventing excessive thermal resistance buildup.
Quality Certifications & Standards Compliance
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Machinery and Pressure Equipment Directive (PED 2014/68/EU)
- TUV Certification — Product safety and quality verification
- Material Certifications: EN 10204 Type 3.1 / Type 3.2 mill certificates for each batch
- Welding Certification: ASME Section IX qualified welders; welding procedure specifications (WPS) and qualified welding procedures (PQR) available
- NDT Compliance: Dye Penetrant Testing (PT) per ASTM E709; Ultrasonic Testing (UT) per ASTM E164
Unique Selling Points
- Partial-Freezing Design Superiority: Maintains a controlled, thin ice layer (≤ 6 mm) that avoids the thermal resistance penalty of full-freezing systems, delivering 25%–35% higher cooling capacity per unit volume compared to traditional fully-frozen ice storage coils.
- Air-Charging Rapid Defrost: Proprietary air-injection ice melting technology achieves rapid, uniform ice release without thermal shock to the tube walls, extending coil service life beyond 20 years.
- Premium Material Selection: SUS304/SUS316L austenitic stainless steel provides exceptional resistance to chloride pitting, stress corrosion cracking (SCC), and galvanic corrosion in brine environments, eliminating the need for sacrificial anode protection.
- Full Traceability: Each coil tube carries a unique heat number and batch identifier, enabling complete material traceability from mill certificate to final installation.
- Custom Engineering: Flexible configuration options for tube diameter, wall thickness, coil pitch, and heat transfer area to meet specific thermal load calculations and system integration requirements.
- Energy Efficiency Contribution: Enables peak-load shifting and demand response programs, contributing to measurable reductions in operational energy costs and carbon footprint for end-users.
Technical Support & Documentation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical documentation including dimensional drawings (AutoCAD/DWG), material test reports, weld inspection reports, and installation/maintenance manuals. Engineering consultation services are available for system-level thermal design integration. All products are backed by a minimum 2-year manufacturing warranty with optional extended service agreements.