Stainless Steel Coil Tube (Coiltube) — High-Density Direct Evaporation Air Conditioning Ice Storage Application
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for high-density direct evaporation coil-type air conditioning ice storage systems. This product represents a critical component in advanced thermal energy storage (TES) technology, where the coil tube functions as the primary heat exchange element facilitating the phase-change process between liquid water and ice.
Unlike conventional refrigeration piping, these coil tubes are engineered to operate under sustained low-temperature conditions while maintaining structural integrity and thermal conductivity. The coiled geometry maximizes the heat transfer surface area within a compact volumetric footprint, enabling high-density ice storage configurations that are essential for peak-shaving and load-management applications in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems.
Wenzhou Jixing Metal Materials Co., Ltd applies advanced metallurgical science and precision forming technology to produce coil tubes that meet the stringent requirements of ice-storage refrigeration systems, ensuring long service life, minimal corrosion resistance degradation, and consistent thermal performance across thousands of freeze-thaw cycles.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from high-purity austenitic stainless steel conforming to international standards. The primary material grades include:
- ASTM A269 / ASME SA-269 — Seamless stainless steel tubing for heat exchangers
- ASTM A554 / ASME SA-554 — Stainless steel tubing for heat exchangers
- EN 10216-5 — European standard for austenitic stainless steel tubes
- Grade 304 (UNS S30408) — General-purpose austenitic stainless steel with excellent corrosion resistance
- Grade 316 (UNS S31608) — Enhanced molybdenum-bearing grade for aggressive chemical environments
2.2 Mechanical Properties
- Tensile Strength: ≥ 520 MPa (Grade 304) / ≥ 515 MPa (Grade 316)
- Yield Strength (0.2% offset): ≥ 205 MPa
- Elongation: ≥ 40% (minimum)
- Impact Strength: Retains ductility at cryogenic temperatures (down to −196°C / −320°F)
- Hardness: ≤ 217 HB (Rockwell B ≤ 95)
2.3 Thermal Properties
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (Grade 304)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Specific Heat Capacity: 500 J/(kg·K) at 20°C
- Operating Temperature Range: −196°C to +800°C
2.4 Chemical & Corrosion Resistance
- Chromium Content: ≥ 18.0% (Grade 304) / ≥ 16.0% (Grade 316)
- Nickel Content: ≥ 8.0% (Grade 304) / ≥ 10.0% (Grade 316)
- Molybdenum Content: ≤ 0.08% (Grade 304) / 2.0–3.0% (Grade 316)
- Carbon Content: ≤ 0.08% (Grade 304) / ≤ 0.08% (Grade 316)
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, fresh water, ice-slurry mixtures, and mild brine solutions
3. Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Catalog No. | 1055 |
| Material Grade | SUS 304 / SUS 316 / Custom Grades Available |
| Outer Diameter (OD) | 6.0 mm – 32.0 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.5 mm (customizable) |
| Coil Pitch (Spacing) | 10 mm – 50 mm (configurable per thermal design) |
| Tube Length per Coil | 3 m – 30 m (adjustable) |
| Surface Finish | No. 4 Brushed / Mirror Polish / Matte / Passivated |
| End Preparation | Plain / Beveled / Flanged / Threaded (per drawing) |
| Tolerance on OD | ±0.1 mm (standard) / ±0.05 mm (precision) |
| Tolerance on Wall Thickness | ±10% of nominal |
| Standards Compliance | ASTM A269, ASTM A554, EN 10216-5, GB/T 14976 |
| Minimum Order Quantity | 1,000 meters (negotiable) |
| Delivery Condition | Coiled on wooden spools / Palletized |
4. Manufacturing Process
4.1 Raw Material Selection and Inspection
High-quality stainless steel wire rod or seamless tube stock is sourced from certified mills and subjected to rigorous incoming inspection, including spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition and hardness testing to confirm mechanical properties conform to the specified grade requirements.
4.2 Seamless Tube Forming
The coil tube is produced through the following sequential manufacturing stages:
- Piercing & Heading: Billet heating and piercing to produce seamless tube blanks
- Pilger Drawing / Mannesmann Process: Cold or warm forming to reduce wall thickness and achieve precise OD dimensions
- Pipe Milling / Tube Milling: Multi-pass rolling to achieve final dimensions with tight tolerances
- Heat Treatment (Annealing): Solution annealing at 1050–1100°C followed by controlled cooling to relieve residual stresses and restore full austenitic microstructure
- Pickling & Passivation: Acid immersion to remove oxide scale and establish a protective chromium oxide passivation layer
4.3 Coiling & Heat Exchange Configuration
The straightened tube is precision-coiled using CNC (Computer Numerical Control) coiling machines to achieve exact coil pitch, helix diameter, and total length specifications. The coiling process is performed under controlled tension to prevent kinking, ovalization, or residual stress concentration at the coil transitions.
4.4 Quality Control and Testing
- Hydrostatic Testing: Each coil tube undergoes pressure testing at 1.5× the maximum operating pressure to verify weld integrity and structural soundness
- Dimensional Inspection: CMM (Coordinate Measuring Machine) verification of OD, wall thickness, coil pitch, and overall geometry
- Surface Inspection: Visual and eddy current testing to detect surface defects, cracks, or inclusions
- Corrosion Testing: Salt spray testing (ASTM B117) for minimum 1,000 hours without significant corrosion for Grade 316 applications
- Intergranular Corrosion Testing: ASTM A262 Practice No. 1E verification for weld stability
5. Applications
5.1 High-Density Direct Evaporation Ice Storage Systems
The primary application of this coil tube is in high-density direct evaporation coil-type air conditioning ice storage devices. In these systems, the stainless steel coil tube serves as the refrigerant flow path through which the phase-change medium (water) is frozen. The coil's geometry and material properties enable:
- Efficient heat transfer between the refrigerant and the ice-forming medium
- Uniform ice formation around the coil surface, minimizing thermal bridging
- Resistance to ice-expansion stresses during repeated freeze-thaw cycles
- Compact system design enabling higher storage density (kWh/m³) compared to traditional tank-based ice storage
5.2 Additional Applications
- Commercial Refrigeration: Ice makers, refrigerated display cases, and cold storage facilities
- Food & Beverage Industry: Heat exchangers for pasteurization, brewing, and dairy processing
- Pharmaceutical & Biotech: Cryogenic equipment and ultra-pure water systems
- Marine & Offshore: Seawater heat exchangers and ship refrigeration systems
- Chemical Processing: Corrosive fluid transfer and heat exchange in aggressive environments
- Building Energy Management: Peak-load shifting and demand-side management in commercial HVAC systems
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains the following quality management and product certifications:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- CE Marking — Conformity with European safety directives
- EN 10204 3.1 — Material test certificate compliance
- NADCAP — National Aerospace and Defense Contractors Accreditation Program (for aerospace-grade applications)
All production batches are accompanied by mill test certificates (MTC) detailing chemical composition, mechanical properties, and heat treatment records, traceable to the original heat number for full supply chain transparency.
7. Unique Selling Points
- Superior Cryogenic Performance: Maintains full mechanical integrity and toughness at ice-storage operating temperatures (−5°C to −15°C), avoiding brittle fracture risks associated with carbon steel alternatives
- High Corrosion Resistance: Eliminates internal scaling and biofilm formation, ensuring long-term thermal efficiency and hygienic operation in potable water and ice-contact applications
- Precision Coiling Geometry: CNC-controlled coiling ensures uniform heat transfer coefficients across the entire coil length, preventing hot spots or ice-thickness variations
- Extended Service Life: Designed for 20+ years of operation with minimal degradation, significantly reducing lifecycle costs compared to galvanized or copper alternatives
- Customization Capability: Full flexibility in OD, wall thickness, coil pitch, and surface finish to match specific thermal design requirements and system integration constraints
- Sustainability: Stainless steel is 100% recyclable with no loss of material properties, supporting circular economy and green building certification goals (LEED, BREEAM)
Technical Note: The application of stainless steel coil tubes in high-density direct evaporation ice storage systems represents a convergence of advanced metallurgy and thermal engineering. The austenitic microstructure's inherent resistance to cryogenic embrittlement, combined with the precise coiling geometry optimized for maximum heat transfer area density, makes this product an ideal solution for next-generation thermal energy storage architectures. Wenzhou Jixing Metal Materials Co., Ltd leverages decades of expertise in stainless steel tube manufacturing to deliver products that meet the most demanding performance specifications in the HVAC and refrigeration industry.