BPXG-1 High-Efficiency Ice Coil Tube Thermal Storage System — Stainless Steel Coil Tube
1. Product Overview
The BPXG-1 High-Efficiency Ice Coil Tube Thermal Storage System (BPXG-1 Efficient Ice Storage Coil Tube Accumulator) is a specialized stainless steel coil tube product engineered for thermal energy storage applications in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents a cutting-edge solution in the field of off-peak energy storage and demand-side management.
The BPXG-1 system utilizes stainless steel coil tubes as the primary heat exchange medium within an ice thermal storage tank. The coil tubes are designed to circulate chilled water or brine solution through a controlled environment, enabling the formation and storage of ice during off-peak electricity hours, followed by controlled ice melting to provide cooling capacity during peak demand periods. This technology significantly reduces peak electrical loads, optimizes energy consumption patterns, and delivers substantial economic and environmental benefits.
The coil tube assembly is the critical component governing heat transfer efficiency, structural integrity, and long-term reliability of the entire thermal storage system. Wenzhou Jixing Metal Materials Co., Ltd. applies rigorous metallurgical standards and precision manufacturing processes to ensure each coil tube meets the demanding operational requirements of ice storage applications.
2. Material & Properties
2.1 Base Material Specification
The BPXG-1 coil tube is fabricated from high-quality austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity under cryogenic and low-temperature operating conditions.
- Primary Alloy Grade: AISI 304 (UNS S30400) / SUS304 — the standard-grade austenitic stainless steel offering excellent general corrosion resistance, weldability, and formability.
- Alternative Grade: AISI 316L (UNS S31603) / SUS316L — a low-carbon variant with added molybdenum (Mo) content for enhanced resistance to pitting and crevice corrosion in aggressive chemical environments.
- Surface Treatment: Passivated and polished finish to ensure maximum surface cleanliness and corrosion protection.
2.2 Key Physical and Mechanical Properties
| Property | Specification (AISI 304) | Specification (AISI 316L) |
|---|---|---|
| Carbon (C) Max | 0.08% | 0.03% |
| Chromium (Cr) | 18.0–20.0% | 16.0–18.0% |
| Nickel (Ni) | 8.0–10.5% | 10.0–14.0% |
| Molybdenum (Mo) | — | 2.0–3.0% |
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 485 MPa |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (A50mm) | ≥ 40% | ≥ 45% |
| Density | 7.93 g/cm³ | 8.00 g/cm³ |
| Thermal Conductivity (at 20°C) | 16.3 W/(m·K) | 14.5 W/(m·K) |
| Operating Temperature Range | −196°C to +870°C | −196°C to +870°C |
2.3 Performance Characteristics in Ice Storage Applications
- Corrosion Resistance: The austenitic microstructure provides outstanding resistance to frost corrosion, brine solution attack, and ice-salt induced degradation, ensuring service life exceeding 25 years under normal operating conditions.
- Cryogenic Performance: The material retains full ductility and mechanical strength at sub-zero temperatures (down to −40°C), eliminating the risk of brittle fracture during ice formation and melting cycles.
- Thermal Conductivity: Optimized thermal conductivity facilitates rapid heat transfer between the circulating fluid and the ice slurry, maximizing the charge/discharge efficiency of the thermal storage system.
- Hygienic Surface: The smooth, non-reactive stainless steel surface prevents biofilm formation and contamination, ensuring water quality compliance for potable water-adjacent applications.
3. Specifications
| Parameter | Specification |
|---|---|
| Product Model | BPXG-1 |
| Product Category | Stainless Steel Coil Tube for Ice Thermal Storage |
| Material Grade | AISI 304 / SUS304 (Standard) or AISI 316L / SUS316L (Enhanced) |
| Outer Diameter (OD) | φ12 mm – φ51 mm (customizable per project requirements) |
| Wall Thickness | 0.8 mm – 2.0 mm (selected based on pressure rating and thermal load) |
| Coil Pitch | 15 mm – 40 mm (optimized for heat transfer efficiency) |
| Coil Length | Up to 200 m per continuous coil assembly |
| Operating Pressure | 0.4 MPa – 1.6 MPa (design pressure) |
| Test Pressure | 1.5× design pressure (hydrostatic test) |
| Working Temperature | −40°C to +20°C (ice storage operating range) |
| Cooling Medium | Chilled water (2–7°C) or ethylene glycol brine solution |
| Heat Transfer Efficiency | ≥ 85% effective heat transfer coefficient relative to theoretical maximum |
| Ice Storage Capacity | Configurable: 50 kWh – 50,000 kWh per system (depending on tank volume) |
| Manufacturing Standard | GB/T 14976-2012, ASTM A312/A312M, EN 10216-5 |
| Welding Standard | GB/T 12467, AWS D10.6 (Stainless Steel Welding Code) |
| Surface Finish | Industrial pickled and passivated (Ra ≤ 0.8 μm) or mirror polished (Ra ≤ 0.4 μm) |
| End Connections | Flanged (PN16), threaded (NPT/BSP), or welded (butt-weld) per customer specification |
| Expected Service Life | ≥ 25 years (under normal operating and maintenance conditions) |
4. Manufacturing Process
4.1 Material Procurement and Incoming Inspection
Raw stainless steel pipe stock is sourced from certified mills with full mill test certificates (MTC) conforming to EN 10204 Type 3.1. Each incoming batch undergoes rigorous inspection including:
- Spectroscopic chemical composition verification (OES — Optical Emission Spectroscopy)
- Visual surface inspection for defects, inclusions, and surface irregularities
- Dimensional verification using calibrated gauging equipment
- Mechanical property spot testing (tensile, hardness)
4.2 Coil Forming and Bending
The straight stainless steel pipe sections are fed into precision CNC (Computer Numerical Control) coil forming machinery. The forming process employs:
- Multi-roller forming: Progressive bending through a series of adjustable rollers to achieve uniform coil geometry with consistent pitch and radius.
- Controlled forming speed: Optimized feed rate to prevent work-hardening, material thinning, or geometric distortion during the bending process.
- In-line monitoring: Real-time measurement of coil diameter, pitch uniformity, and ovality using laser scanning systems.
4.3 Welding and Assembly
Coil tube assemblies requiring multiple pipe sections are joined using:
- TIG Welding (GTAW — Gas Tungsten Arc Welding): Primary welding method for seamless, high-integrity joints using argon (Ar) shielding gas.
- Pulse TIG welding: Applied for thin-wall sections to minimize heat input and prevent warping or grain growth.
- Internal purge gas: Nitrogen (N₂) or argon back-purging to prevent internal oxidation and maintain joint integrity.
- Weld quality assurance: 100% visual inspection, with selective radiographic testing (RT) or dye penetrant testing (PT) for critical joints.
4.4 Surface Treatment and Passivation
Post-welding, all coil assemblies undergo:
- Pickling: Immersion in a hydrochloric acid (HCl) and nitric acid (HNO₃) mixture to remove weld discoloration, oxide scale, and surface contaminants.
- Passivation: Treatment with nitric acid or citric acid solution to restore the natural chromium oxide (Cr₂O₃) protective layer on the surface.
- Final polishing (optional): Mechanical or electrolytic polishing to achieve specified surface roughness values.
4.5 Testing and Quality Assurance
- Hydrostatic pressure test: Each coil assembly is pressure-tested at 1.5× the design pressure for a minimum of 30 minutes with no leakage or permanent deformation permitted.
- Dimensional verification: Final measurement of coil outer diameter, pitch, total length, and end connection dimensions.
- Non-destructive testing (NDT): Magnetic particle inspection (MT) or eddy current testing (ET) on weld seams and critical areas.
- Corrosion resistance testing: Salt spray testing (ASTM B117) for minimum 96 hours with no pitting or red rust formation.
5. Applications
5.1 Primary Application Domains
- Commercial Building HVAC Systems: Shopping malls, office complexes, hotels, and hospitals where ice thermal storage enables peak load shifting and reduced electricity costs.
- Industrial Process Cooling: Chemical processing, pharmaceutical manufacturing, food and beverage production requiring stable, reliable cooling capacity with redundancy.
- Data Center Cooling: High-density server room cooling systems where thermal storage provides backup cooling capacity and load management.
- Supermarket and Cold Chain Applications: Large-scale refrigeration systems for retail and logistics requiring temperature-controlled storage.
- Municipal Energy Storage: District cooling systems and urban energy management infrastructure.
5.2 System Integration Configuration
The BPXG-1 coil tube is installed within a cylindrical or rectangular thermal storage tank, typically constructed from carbon steel with internal epoxy or stainless steel lining. The coil tubes are arranged in a helical configuration to maximize surface area-to-volume ratio, enabling efficient heat exchange between the circulating coolant and the water/ice medium within the tank.
Typical system configurations include:
- Single-coil system: One continuous coil tube for tanks up to 50 m³.
- Multi-coil parallel system: Multiple coil assemblies operating in parallel for tanks exceeding 50 m³, enabling modular capacity scaling.
- Hybrid coil-baffle system: Combination of coil tubes with internal baffles for enhanced flow distribution and uniform ice formation.
6. Quality Certifications and Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control. |
| ISO 14001:2015 | Environmental Management System certification demonstrating sustainable manufacturing practices. |
| CE Marking (EU) | European Conformity marking for compliance with relevant EU directives including Pressure Equipment Directive (PED 2014/68/EU). |
| GB/T 14976-2012 | Chinese national standard for seamless stainless steel tubes for general engineering purposes. |
| ASTM A312/A312M | American standard specification for austenitic stainless steel seamless, welded, and heavily cold-worked wrought austenitic stainless steel tubing. |
| EN 10216-5 | European standard for welded stainless steel tubes for pressure purposes — technical delivery conditions. |
| TSG 21-2016 | Chinese safety technical regulation for fixed pressure vessels (applicable to thermal storage tanks). |
| NACE MR0175/ISO 15156 | Resistant materials for H₂S-containing environments in oil and gas industry (where applicable). |
7. Unique Selling Points
- Superior Thermal Efficiency: The optimized coil geometry and high-grade stainless steel material achieve heat transfer coefficients exceeding 85% of theoretical maximum, outperforming conventional ice storage solutions by 15–20%.
- Exceptional Durability: AISI 304/316L stainless steel provides resistance to frost corrosion, brine attack, and thermal cycling fatigue, ensuring 25+ years of reliable service without degradation.
- Cryogenic Reliability: Full mechanical integrity maintained