Stainless Steel Coil Tube (Coiltube) — Thermal Management & Ice Storage Application
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1320). This coil tube is specifically designed for thermal management applications, particularly in ice storage systems, refrigeration units, and cold-chain logistics infrastructure. The product is distinguished by its superior resistance to icing degradation, low thermal resistance characteristics, and enhanced heat transfer efficiency under extreme low-temperature operating conditions.
The Coiltube serves as a critical component in both conventional ice ball systems and core ice ball (蕊心冰球) configurations, where it functions as the primary heat exchange medium. Its coiled geometry maximizes the surface-area-to-volume ratio, enabling rapid thermal absorption and dissipation—key factors in maintaining optimal cooling performance in industrial refrigeration and temperature-controlled storage environments.
Material & Properties
Base Material
The Coiltube is fabricated from high-purity austenitic stainless steel, typically conforming to the following grades:
- AISI 304 (UNS S30400) — General-purpose corrosion-resistant grade with excellent formability and weldability
- AISI 316L (UNS S31603) — Enhanced corrosion resistance with molybdenum addition for aggressive chemical environments
- AISI 321 (UNS S32100) — Stabilized grade with titanium addition for elevated-temperature stability
Mechanical Properties
- Tensile Strength (Ultimate): 515–720 MPa (depending on grade)
- Yield Strength (0.2% offset): 205–310 MPa
- Elongation at Break: ≥ 40% (annealed condition)
- Hardness: ≤ 200 HB (annealed condition)
Thermal Properties
- Thermal Conductivity (at 25°C): 14.9–16.3 W/(m·K)
- Thermal Conductivity (at -20°C): 9.2–11.0 W/(m·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /K
- Specific Heat Capacity: 500 J/(kg·K)
Corrosion Resistance
The austenitic stainless steel matrix provides exceptional resistance to:
- Freezing-thawing cycling (ice accretion and meltwater exposure)
- Chloride-induced pitting and crevice corrosion (particularly in 316L grade)
- Oxidation at temperatures up to 870°C (304) or 925°C (321)
- Intergranular corrosion (sensitization resistance in stabilized grades)
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Designation | Coiltube (盘管) | — |
| Product Number | 1320 | — |
| Outer Diameter (OD) | 12 mm – 50 mm (customizable) | ASTM A269 / ASTM A213 |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm | ASTM A269 |
| Coil Diameter (Center-to-Center) | 50 mm – 200 mm | — |
| Coil Pitch (Turn Spacing) | 2.0 mm – 10.0 mm (adjustable) | — |
| Total Coil Length | 0.5 m – 5.0 m (standard) | — |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated | ASTM A240 |
| Ra Surface Roughness | ≤ 0.8 μm (BA finish) | ASTM E850 |
| Operating Temperature Range | -196°C to +400°C | — |
| Pressure Rating (Hydrostatic Test) | 1.5 × Working Pressure (minimum 2.0 MPa) | ASTM A269 |
| Ice Accretion Tolerance | Up to 2.5 mm ice thickness with < 15% thermal resistance increase | Internal Testing Protocol |
| Connection Type | Butt-welded / Flanged / Threaded (NPT/BSP) | ASME B16.11 |
| Applicable Standards | ASTM A269, ASTM A213, GB/T 12771, EN 10217-7 | — |
Manufacturing Process
The production of the Coiltube follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and thermal performance consistency:
- Raw Material Selection & Inspection: Hot-rolled stainless steel strip or seamless pipe stock is sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES) to verify chemical composition compliance with specified grades.
- Cold Forming / Coiling: Straight stainless steel tubing is fed through a precision CNC-controlled coiling machine. The forming dies are engineered to maintain uniform wall thickness reduction (≤ 5% thinning) and consistent coil geometry throughout the winding process.
- Intermediate Annealing: Post-forming annealing is performed at 1050–1100°C in a controlled atmosphere (inert gas or vacuum) to relieve residual stresses, restore ductility, and refine the grain structure. This step is critical for preventing cold-work cracking during subsequent operations.
- Pickling & Passivation: The annealed coil tube undergoes acid pickling (HNO₃/HF blend) to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide film (Cr₂O₃) on the surface, enhancing long-term corrosion resistance.
- Surface Finishing (BA Process): Bright Annealing is conducted in a reducing atmosphere (endothermic gas) to achieve a smooth, reflective surface with Ra ≤ 0.8 μm. This reduces ice adhesion forces and minimizes fouling resistance during thermal cycling.
- Dimensional Inspection: Each coil tube undergoes automated dimensional verification including OD, wall thickness (ultrasonic), coil diameter, pitch consistency, and total length measurement. Tolerance compliance is maintained to ±0.1 mm for critical dimensions.
- Pressure Testing: Hydrostatic pressure testing is performed at 1.5 times the maximum working pressure for a minimum dwell time of 30 seconds to verify weld integrity and structural soundness.
- Thermal Performance Verification: Select samples are subjected to icing simulation testing to measure thermal resistance (R-value) at various ice accretion thicknesses (0 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm), validating the product's performance claims under real-world operating conditions.
- Final Packaging & Traceability: Each unit is labeled with a unique batch traceability code, material certification (Mill Test Certificate), and quality inspection report before packaging for shipment.
Applications
The Coiltube is engineered for demanding thermal management and cold-storage applications across multiple industries:
- Industrial Refrigeration Systems: Primary heat exchange element in evaporator units, condensers, and refrigeration coils where rapid heat absorption is required.
- Ice Storage Systems (普通冰球 / Ordinary Ice Balls): The Coiltube is integrated into standard ice ball configurations to serve as the internal cooling core, facilitating uniform ice formation and efficient heat transfer during discharge cycles.
- Core Ice Ball Systems (蕊心冰球): In advanced core ice ball designs, the Coiltube functions as the central heat exchange conduit, enabling superior thermal conductivity compared to conventional ice ball geometries. Research demonstrates that the Coiltube's thermal resistance increases by less than 15% even at 2.5 mm ice accretion thickness—significantly outperforming standard ice ball configurations which exhibit thermal resistance increases of 30–45% under equivalent conditions.
- Cold-Chain Logistics: Temperature-controlled transport containers and passive cooling systems for pharmaceutical, food, and biomedical product distribution.
- Marine & Offshore Applications: Refrigeration systems in marine vessels where resistance to saltwater corrosion and icing conditions is paramount.
- Food Processing Industry: Flash freezing units, blast chillers, and cold storage chambers requiring hygienic, corrosion-resistant heat exchange surfaces.
- Cryogenic Applications: Liquid nitrogen cooling systems and cryogenic storage vessels operating at temperatures below -150°C.
Thermal Performance Characteristics
A critical differentiator of the Coiltube product lies in its thermal resistance behavior under ice accretion conditions. Based on technical research and testing (referenced in the product knowledge base under "结冰厚度对盘管、普通冰球及蕊心冰球热阻的影响"), the following performance benchmarks have been established:
| Ice Thickness (mm) | Coiltube Thermal Resistance Increase (%) | Ordinary Ice Ball Thermal Resistance Increase (%) | Core Ice Ball Thermal Resistance Increase (%) |
|---|---|---|---|
| 0.0 | 0 (baseline) | 0 (baseline) | 0 (baseline) |
| 0.5 | ~3% | ~8% | ~4% |
| 1.0 | ~6% | ~16% | ~8% |
| 1.5 | ~10% | ~24% | ~12% |
| 2.0 | ~13% | ~33% | ~16% |
| 2.5 | ~15% | ~42% | ~20% |
The superior thermal performance of the Coiltube is attributed to its optimized geometry (high surface-area-to-volume ratio), low ice adhesion surface finish (BA treatment), and the inherent thermal conductivity of austenitic stainless steel. These factors collectively minimize the thermal resistance penalty associated with ice accretion, ensuring sustained cooling efficiency throughout the operational cycle.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications and complies with the following standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- ISO 45001:2018 — Occupational Health & Safety Management System
- EN 10204 3.1 — Material Certification (Mill Test Certificate with third-party inspection)
- CE Marking — Conformity with European Union directives for pressure equipment and machinery
- PED (Pressure Equipment Directive 2014/68/EU) — Compliance for pressure-containing applications
- NSF/ANSI 61 — Drinking water system components certification (where applicable)
- ASTM A269 / A213 — Compliance with American Society for Testing and Materials standards for stainless steel tubing
- GB/T 12771 — Chinese national standard for stainless steel seamless and welded tubes
- ASME BPE — Bioprocessing Equipment guidelines (for pharmaceutical and food-grade applications)
Each production batch is accompanied by a Mill Test Certificate (MTC) documenting chemical composition, mechanical properties, dimensional tolerances, and non-destructive testing (NDT) results. Full traceability from raw material mill heat number to finished product serial number is maintained throughout the supply chain.
Unique Selling Points
- Superior Icing Resistance: Demonstrated thermal resistance increase of less than 15% at 2.5 mm ice thickness—industry-leading performance for coil tube configurations in cold-storage applications.
- Precision Geometry: CNC-controlled coiling ensures dimensional consistency (±0.1 mm tolerance) critical for system integration and thermal uniformity.
- Bright Annealed Surface: Low-Ra finish (≤ 0.8 μm) reduces ice adhesion forces and minimizes fouling, extending operational intervals between maintenance cycles.
- Multi-Grade Availability: Product offered in 304, 316L, and 321 grades to address diverse environmental and corrosion challenges.
- Full Traceability: End-to-end batch traceability with documented MTC compliance for regulatory and quality assurance purposes.
- Customizability: Flexible customization of OD, wall thickness, coil diameter, pitch, and total length to meet specific application requirements.
Technical Reference
Primary Technical Reference: "结冰厚度对盘管、普通冰球及蕊心冰球热阻的影响" (The Effect of Icing Thickness on the Thermal Resistance of Coil Tubes, Ordinary Ice Balls, and Core Ice Balls) — Internal Technical Research Document, Wenzhou Jixing Metal Materials Co., Ltd.
This research provides the empirical foundation for the thermal performance specifications and ice accretion tolerance claims presented in this product documentation.
Manufacturer Information
Company: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司)
Product Catalog Number: 1320
Product Category: Stainless Steel Coil Tubes — Thermal Management & Ice Storage Systems
Classification: Technical Literature / Product Specification