Stainless Steel Coil Tube (Coiltube) — Ice Storage Heat Exchange Coil System
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered heat exchange component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 315). This product is specifically designed for ice-storage air conditioning systems, serving as the core thermal transfer element in coil-type ice storage (Ice Storage Air Conditioning) technologies. The coil tube facilitates efficient latent heat exchange during both the ice-making (charging) and ice-melting (discharging) cycles, enabling peak-load shifting and energy optimization in commercial and industrial HVAC applications.
Unlike conventional direct-expansion or water-cooled systems, the coil tube in ice storage configurations operates under alternating thermal loads, cycling between sub-zero brine temperatures (typically −5°C to −15°C) and moderate melting-phase temperatures (0°C to 5°C). This demands exceptional material integrity, corrosion resistance, and mechanical fatigue tolerance — all of which are addressed through the use of high-grade austenitic stainless steel.
Material & Properties
The coil tube is fabricated from austenitic stainless steel, predominantly conforming to the following grades:
- SUS304 / AISI 304: The standard grade offering excellent general corrosion resistance, formability, and weldability. Suitable for most brine-based ice storage applications.
- SUS316 / AISI 316: Enhanced with molybdenum (2–3% Mo) for superior resistance to chloride-induced pitting and crevice corrosion, recommended for coastal or high-chloride brine environments.
- SUS316L / AISI 316L: Low-carbon variant with improved resistance to intergranular corrosion post-welding, ideal for applications requiring extensive welding of coil assemblies.
Key Material Properties:
- Operating temperature range: −196°C to +400°C
- Non-magnetic (austenitic structure)
- Low thermal conductivity relative to carbon steel, contributing to reduced heat ingress losses in ice storage tanks
- High resistance to stress corrosion cracking (SCC) in brine solutions
- Long service life exceeding 25 years under normal operating conditions
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product No. | 315 |
| Material Grade | SUS304 / SUS316 / SUS316L (per customer requirement) |
| Outer Diameter (OD) | Φ8 mm – Φ38 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Length | 5 m – 200 m (per coil assembly) |
| Surface Finish | No. 2B / BA (Bright Annealed) / Electropolished |
| Winding Pitch | 1.5× OD – 3.0× OD (adjustable per thermal design) |
| Tolerance (OD) | ±0.1 mm |
| Tolerance (Wall Thickness) | ±10% |
| Operating Pressure | Up to 1.6 MPa (232 psi) |
| Test Pressure | 2.4 MPa (348 psi) — hydrostatic test |
| End Treatment | Plain cut / Threaded / Flanged / Brazed fitting |
| Standard References | ASTM A269 / ASTM A270 / GB/T 12771 / JIS G3459 |
Manufacturing Process
The production of stainless steel coil tubes for ice storage applications follows a rigorous multi-stage manufacturing workflow:
- Strip Sourcing & Inspection: Cold-rolled stainless steel strip is procured from certified mills and subjected to incoming quality checks including chemical composition analysis (per ASTM E415), mechanical property verification, and surface defect screening.
- Pipe Forming (Cold Roll / Roll Forming): The flat strip is precisely formed into a seamless tube through a series of progressive forming rolls. This process maintains dimensional accuracy and minimizes work hardening, ensuring uniform wall thickness throughout the coil length.
- Coil Winding: The formed tube is wound into a helical coil configuration using CNC-controlled winding equipment. Winding pitch, diameter, and total coil volume are programmable to meet specific thermal load requirements of the ice storage system.
- Heat Treatment (if applicable): For thicker-wall tubes, solution annealing (1050–1150°C followed by rapid quench) may be performed to restore full austenitic structure and eliminate residual stresses introduced during forming.
- Surface Finishing: Tubes may undergo mechanical polishing, chemical pickling, or electropolishing to achieve the required surface roughness (Ra ≤ 0.8 μm for electropolished finish), which minimizes biofilm formation and reduces hydraulic resistance.
- End Processing & Fitting: Coil ends are cut, deburred, and fitted with threaded or brazed connections suitable for integration into the ice storage tank piping manifold.
- Quality Testing: Each coil assembly undergoes hydrostatic pressure testing, dimensional inspection (OD, wall thickness, coil diameter, pitch uniformity), and visual examination for surface defects.
Applications
The stainless steel coil tube is integral to the following engineering domains:
- Ice Storage Air Conditioning Systems: Primary heat exchange element in latent heat thermal energy storage (LTES) tanks, enabling off-peak ice production and peak-demand cooling delivery. Applicable in commercial buildings, hospitals, data centers, and industrial facilities.
- Brine-to-Water Heat Exchangers: Serves as the secondary circuit in plate-and-coil hybrid heat exchangers for chilled water production.
- Supermarket & Cold Chain Refrigeration: Used in evaporator coil assemblies for refrigerated display cases and walk-in coolers operating with glycol or brine secondary refrigerants.
- Process Cooling in Food & Beverage Industry: Compliant with sanitary standards (FDA, 3-A), suitable for milk cooling, beer pasteurization heat recovery, and pharmaceutical cold storage.
- Geothermal & Heat Pump Systems: Employed as ground-loop coil elements in closed-loop geothermal heat exchange installations.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and product certification portfolio:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- GB/T 12771 — Chinese national standard for welded and seamless stainless steel tubes for general application.
- ASTM A269 / A270 — American standards for seamless and welded austenitic stainless steel tubing.
- CE Marking — Conformity with European health, safety, and environmental protection standards for products sold within the European Economic Area.
- Food-Grade Compliance — Materials certified for contact with food and beverages (EU 1935/2004, FDA 21 CFR compliance).
Unique Selling Points
- Specialized Ice Storage Engineering: Coil geometry and material selection are optimized specifically for the cyclic thermal loading unique to ice-storage HVAC systems, outperforming generic coil tubes in longevity and efficiency.
- Full Material Traceability: Every coil tube batch is accompanied by mill certificates (EN 10204 Type 3.1) documenting chemical composition, mechanical properties, and heat treatment records.
- Customizable Coil Configurations: CNC winding capability allows bespoke coil diameters, pitches, and lengths tailored to specific thermal storage tank geometries and system design parameters.
- Corrosion-Resistant in Brine Environments: SUS316/316L grades provide proven resistance to calcium chloride (CaCl₂) and ethylene glycol (EG) brine solutions used in ice storage systems.
- Energy Efficiency Contribution: The low thermal conductivity of austenitic stainless steel reduces parasitic heat gains through the tank wall, improving overall system COP (Coefficient of Performance) by an estimated 5–12% compared to carbon steel alternatives.
- Sustainable Lifecycle: Stainless steel is 100% recyclable with no degradation of material properties, supporting circular economy objectives and reducing lifecycle carbon footprint.
Technical Note: For ice storage applications operating with calcium chloride brine solutions at concentrations exceeding 15%, it is strongly recommended to specify SUS316L grade material and apply a minimum wall thickness of 1.0 mm to ensure long-term resistance against localized corrosion and hydrogen-induced stress cracking under cyclic thermal loading conditions.