Stainless Steel Coil Tube for Ice Thermal Storage Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered cold-formed coil tube specifically designed for integration into Ice Thermal Storage Systems (Ice Thermal Energy Storage Systems). These coil tubes serve as the primary heat exchange elements within ice storage tanks, facilitating the efficient transfer of thermal energy between the refrigerant loop and the stored ice mass. The product is engineered to withstand the demanding cyclic thermal and hydraulic conditions inherent in ice thermal storage applications, ensuring long-term structural integrity and thermal performance.
The coil tube geometry—characterized by its continuous helical winding configuration—provides a significantly higher surface-area-to-volume ratio compared to conventional straight-pipe heat exchangers, enabling superior heat exchange efficiency within the constrained spatial envelope of an ice storage tank.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, mechanical strength, and thermal conductivity. The primary material grades employed are as follows:
- SUS304 (AISI 304) — Standard austenitic stainless steel with 18% Chromium (Cr) and 8% Nickel (Ni) composition, offering excellent general corrosion resistance and weldability.
- SUS316L (AISI 316L) — Low-carbon austenitic stainless steel with added Molybdenum (Mo, 2–3%), providing enhanced resistance to chlorides and pitting corrosion, particularly suited for applications involving brine-based heat transfer fluids.
- SUS321 (AISI 321) — Titanium-stabilized austenitic stainless steel, offering superior resistance to intergranular corrosion and elevated-temperature scaling.
Key Material Properties (SUS304 Reference Values)
- Thermal Conductivity (at 20°C): 16.3 W/(m·K)
- Specific Heat Capacity (at 20°C): 500 J/(kg·K)
- Yield Strength (σ0.2): ≥ 205 MPa
- Tensile Strength (Rm): 520–750 MPa
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Excellent resistance to atmospheric, freshwater, and mild chemical environments
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Material Grade | SUS304 / SUS316L / SUS321 (customizable) |
| Outer Diameter (OD) | Ø12 mm – Ø48 mm (customizable) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Pitch (Winding Spacing) | 15 mm – 60 mm (adjustable per thermal design) |
| Coil Diameter | 300 mm – 1500 mm (per tank configuration) |
| Tube Length per Coil | 5 m – 200 m (continuous) |
| Surface Finish | 2B (Cold Rolled) / BA (Bright Annealed) / No.4 Brushed |
| Connection Type | Threaded (BSP/NPT), Flanged, or Soldered End Fittings |
| Design Pressure | 0.6 MPa – 2.5 MPa (per ASME/EN standards) |
| Design Temperature | −25°C to +120°C |
| Heat Transfer Fluid | Water, Ethylene Glycol (EG) Brine, Propylene Glycol (PG) Brine, Calcium Chloride (CaCl₂) Brine |
| Applicable Standards | GB/T 14976, ASTM A269, EN 10217, ASME B31.9 |
| Minimum Order Quantity | 500 meters |
Manufacturing Process
The production of high-quality stainless steel coil tubes for ice thermal storage systems follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical soundness, and long-term service reliability:
- Material Selection & Incoming Inspection — Certified stainless steel strip (coil) is sourced from approved mills and subjected to spectroscopic analysis (OES) for chemical composition verification, along with visual inspection for surface defects.
- Precision Slitting — The stainless steel coil is slit to the required strip width using high-precision slitting lines, ensuring edge quality and dimensional tolerance within ±0.1 mm.
- Hydroforming / Cold-Bending Coiling — The flat strip is fed through a CNC-controlled coiling machine that forms the tube into the specified helical geometry. The process employs progressive die sets and tension-controlled feeding to maintain consistent coil pitch, tube roundness, and wall thickness throughout the entire length.
- Welding (if applicable) — For welded coil tube variants, the longitudinal seam is welded using TIG (Tungsten Inert Gas) Welding under controlled argon shielding. Weld parameters are optimized to minimize heat input and prevent sensitization of the austenitic microstructure.
- Solid-State Coiling (Seamless) — For seamless coil tubes, the process employs a hydroforming technique where the tube blank is formed under high internal hydraulic pressure (up to 20 MPa) within a precision mandrel, producing a continuous helical tube without any weld seam.
- Surface Treatment & Passivation — The finished coil tube undergoes chemical passivation (nitric acid or citric acid bath) to remove scale and restore the protective chromium oxide layer. Surface finishing (2B, BA, or brushed) is applied as specified.
- Quality Control & Testing — Each batch undergoes hydrostatic pressure testing (1.5× design pressure, held for 30 minutes), dimensional inspection (OD, wall thickness, coil pitch), and visual examination. Random samples are subjected to intergranular corrosion testing (ASTM A262 Practice E).
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd are primarily deployed in the following engineering domains:
- Ice Thermal Storage Systems — The primary application. Coil tubes are installed within ice storage tanks to facilitate the freezing and melting cycles of ice, enabling peak-shaving (load shifting) of electrical demand in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) systems. The helical coil geometry maximizes heat exchange area within the confined tank volume.
- Cold Storage & Refrigeration — Used as evaporator coil elements in industrial refrigeration systems, cold rooms, and frozen food processing facilities where corrosion resistance and hygienic surface quality are critical.
- Process Cooling Systems — Employed in chemical processing, pharmaceutical manufacturing, and food and beverage industries for closed-loop cooling circuits requiring sanitary-grade piping.
- Geothermal & Heat Pump Systems — Utilized as ground-coupled heat exchanger coils in closed-loop geothermal systems, where the stainless steel construction resists degradation from geothermal fluids containing dissolved minerals.
- Building Energy Management — Integrated into district cooling networks and large-scale commercial buildings to provide thermal buffering and improve overall system energy efficiency.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing, inspection, and supply chain processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- EN 10204 3.1 — Material Test Certificate (MTC) issued by authorized technical personnel for each production batch, confirming chemical composition, mechanical properties, and test results.
- ASME B31.9 — Compliance with the Pressure Piping Code for Refrigeration Systems, ensuring safe design and fabrication under pressure.
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes, governing dimensions, tolerances, and technical requirements.
- ASTM A269 — Standard specification for seamless austenitic stainless steel tube, covering chemical composition, mechanical properties, and hydrostatic testing.
- CE Marking — Conformity with applicable European directives for products intended for use in the European Economic Area (EEA).
Unique Selling Points
- Optimized Helical Geometry for Maximum Heat Exchange — The precisely controlled coil pitch and uniform winding geometry ensure maximum heat transfer surface area within the ice storage tank, achieving thermal efficiency gains of 20–35% compared to conventional straight-pipe configurations.
- Superior Corrosion Resistance in Brine Environments — SUS316L grade coil tubes with Molybdenum-enhanced microstructure provide outstanding resistance to chloride-induced pitting and crevice corrosion, critical for long-term service in CaCl₂ or ethylene glycol brine solutions.
- Seamless Hydroformed Construction — Available in seamless hydroformed variants that eliminate the weld seam entirely, removing the primary failure point in welded coil tubes and extending service life to 25+ years under cyclic thermal loading.
- Full Traceability & Batch Documentation — Every coil tube batch is accompanied by a complete EN 10204 3.1 material test certificate with full chemical analysis, mechanical test data, and heat number traceability back to the original mill.
- Customization Capability — Wenzhou Jixing Metal Materials Co., Ltd offers fully customizable coil tube configurations including OD, wall thickness, coil pitch, coil diameter, surface finish, and end fittings to match specific thermal design requirements and tank geometries.
- Experience in Ice Thermal Storage Applications — Deep technical expertise derived from extensive involvement in ice thermal storage system projects, including direct participation in construction technology standardization, ensuring practical engineering know-how is embedded in product design.
Technical Notes & Installation Guidelines
Thermal Cycling Consideration: Ice thermal storage systems subject coil tubes to repeated freeze-thaw cycles (typically 1–4 cycles per day). The stainless steel material must be selected to accommodate the volumetric expansion of ice (≈9%) and the associated mechanical stresses at the tube-tube and tube-tank interfaces. SUS304 and SUS316L grades provide adequate ductility for this application.
Installation Clearance: Adequate flow channel spacing (coil pitch) must be maintained to ensure uniform heat transfer fluid distribution and prevent localized ice bridging between adjacent coil turns. A minimum coil pitch of 15 mm is recommended for water-based heat transfer fluids; 20–30 mm is advised for glycol brine systems.
Hydrostatic Testing: All coil tubes must be pressure-tested at 1.5× the maximum design pressure for a minimum hold time of 30 minutes prior to installation. Post-installation, a system-wide hydrostatic test at 1.25× design pressure is required per ASME B31.9 Section 344.
Product Catalog Reference No.: 967 | Classification: Technical Literature & Learning Resources | Supplier: Wenzhou Jixing Metal Materials Co., Ltd