Stainless Steel Coil Tube — Industrial Heat Transfer Application Series
Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous tubular product formed into helical or serpentine configurations, designed specifically for high-efficiency thermal exchange applications. This product series is engineered to meet the demanding requirements of water-cooled surface coolers (水冷式表冷器), where convective and evaporative heat transfer under both dry and wet operating conditions demands superior thermal conductivity, corrosion resistance, and structural integrity over extended service cycles.
Coil tubes represent a critical component in the design of evaporative cooling systems, chiller coils, and condensing surfaces. Their continuous helical geometry maximizes surface-area-to-volume ratios, enabling enhanced heat dissipation while minimizing pressure drop across the flow path. The product knowledge base draws upon rigorous academic research, including studies on the average surface temperature method (平均温度法) for calculating wet-condition performance of surface coolers, ensuring that every design parameter is validated against established thermodynamic principles.
Material & Properties
Stainless steel coil tubes are fabricated from austenitic stainless steel grades selected for optimal balance of mechanical strength, thermal performance, and resistance to chemical degradation in humid and corrosive environments.
- Primary Alloy Grade: AISI 304 / 304L (UNS S30400 / S30403) — Chromium-Nickel austenitic stainless steel offering excellent general corrosion resistance and formability.
- Alternative Grades: AISI 316 / 316L (UNS S31600 / S31603) — Molybdenum-enhanced grade for applications involving chloride-containing media or aggressive chemical environments.
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C, providing reliable heat transfer performance under both dry and wet conditions.
- Operating Temperature Range: −196°C to +870°C (depending on grade), accommodating cryogenic to elevated-temperature industrial processes.
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and intergranular corrosion due to chromium oxide passive film formation (minimum 18% Cr content).
- Mechanical Properties: Tensile strength ≥ 515 MPa (304 annealed); yield strength ≥ 205 MPa; elongation ≥ 40%.
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A269 / GB/T 12771 |
| Wall Thickness | 0.3 mm – 3.0 mm | ASTM A269 |
| Coil Pitch (Helical Spacing) | 10 mm – 150 mm (customizable) | ISO 11901 |
| Coil Diameter (Bundled) | 50 mm – 600 mm | Manufacturer Specification |
| Tube Length (Uncoiled) | 3 m – 120 m (continuous) | — |
| Surface Finish | Mirror polished (Ra ≤ 0.4 μm), satin (Ra 0.8–1.6 μm), or industrial (Ra ≤ 3.2 μm) | ASTM A270 |
| End Forming | Plain, flared, threaded, or welded to headers | ASME B31.9 |
| Tolerance (OD) | ±0.05 mm to ±0.15 mm | ISO 1307 |
| Material Certification | EN 10204 3.1 / 3.2 Material Test Certificate | EN 10204 |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a multi-stage process ensuring dimensional accuracy, metallurgical integrity, and surface quality suitable for demanding heat transfer applications:
- Material Selection & Incoming Inspection: Stainless steel strip or seamless pipe stock is verified against mill test certificates (MTC) for chemical composition (per ASTM A240 / EN 10088-2) and mechanical properties.
- Coil Forming (Bending): Cold-rolled stainless steel strip is precisely formed into tubular shape using high-precision roll-forming or hydraulic bending equipment. The coil geometry (pitch, diameter, number of turns) is controlled by CNC-guided forming machines to maintain uniformity throughout the length.
- Welding (for welded coil tubes): Longitudinal seam welding is performed using Automatic Optical Flash Butt Welding (AOFBW) or TIG welding, followed by inline weld inspection via ultrasonic or eddy current testing.
- Heat Treatment (Annealing): Solution annealing at 1050–1150°C followed by rapid water quenching to dissolve carbide precipitates, restore full austenitic microstructure, and ensure maximum corrosion resistance and ductility.
- Pickling & Passivation: Chemical pickling removes oxide scale and discoloration; subsequent passivation treatment with nitric or citric acid regenerates the protective chromium oxide passive film on the surface.
- Surface Finishing: Mechanical polishing, electrolytic polishing, or electropolishing is applied to achieve the required surface roughness (Ra value), which directly impacts convective heat transfer coefficients and fouling resistance in surface cooler applications.
- Dimensional Inspection & Testing: Final quality assurance includes hydrostatic pressure testing (typically 3–6× working pressure), dimensional verification, visual inspection, and optional endoscopic examination of internal surfaces.
Applications
Stainless steel coil tubes from this product series find extensive application across multiple industrial sectors where reliable thermal management and corrosion resistance are paramount:
- Water-Cooled Surface Coolers (水冷式表冷器): Primary application domain — coil tubes serve as the heat exchange medium in evaporative cooling coils, where air passes over the coil surface and heat is transferred to circulating chilled water. The average surface temperature method enables accurate performance prediction under wet (condensing) conditions, ensuring optimal coil design.
- Commercial & Industrial HVAC Systems: Chilled water coils, condenser coils, and air handling unit (AHU) heat exchangers requiring resistance to condensate corrosion.
- Refrigeration & Cryogenic Systems: Evaporator coils operating at sub-zero temperatures where austenitic stainless steel maintains ductility and structural integrity.
- Food & Pharmaceutical Processing: Heat exchangers in pasteurization, sterilization, and cooling systems where sanitary-grade surfaces (Ra ≤ 0.4 μm) prevent microbial adhesion.
- Chemical & Petrochemical Industries: Condensers, reboilers, and cooling coils handling corrosive process fluids (chlorides, acids, organic solvents) where 316L grade provides enhanced resistance.
- Power Generation: Economizer tubes and feedwater preheaters in boiler systems.
- Marine & Offshore Applications: Seawater-cooled heat exchangers requiring resistance to chloride-induced pitting and crevice corrosion.
Thermal Performance & Design Considerations
Research into water-cooled surface cooler performance — specifically the methodology of using average coil surface temperature to calculate wet-condition heat transfer — underscores the critical role of coil tube geometry and material properties in system efficiency:
- Enhanced Surface Area: The helical coil configuration provides significantly greater heat transfer area per unit volume compared to straight-tube arrangements, improving the overall heat transfer coefficient (U-value).
- Wet Condition Performance: Under condensing conditions, the coil surface average temperature governs the driving force for latent heat transfer. Stainless steel's thermal conductivity and surface finish directly influence condensation film thickness and heat transfer rates.
- Pressure Drop Optimization: Smooth internal surfaces (electropolished) reduce frictional pressure losses, improving pump efficiency and system energy consumption.
- Anti-Fouling Characteristics: Mirror-polished stainless steel surfaces minimize biofouling and scale adhesion, maintaining long-term thermal performance without frequent chemical cleaning.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications ensuring compliance with international standards:
- ISO 9001:2015 — Quality Management System certification for consistent manufacturing quality and process control.
- ISO 14001:2015 — Environmental Management System certification for sustainable and responsible production practices.
- EN 10204 3.1 / 3.2 — Material Test Certificates (MTC) documenting chemical composition and mechanical test results for each production batch.
- ASTM / ASME Compliance — Products manufactured in accordance with ASTM A269 (stainless steel welded tubing), ASTM A270 (stainless steel seamless tubing), and ASME B31.9 (pressure piping — fuel gas, oxygen, and other fluids).
- GB/T 12771 — Chinese national standard for seamless stainless steel tubes for fluid conveyance.
- Third-Party Inspection: Available upon request — SGS, Bureau Veritas, or TÜV verification for critical applications.
- Hydrostatic Testing: 100% inline hydrostatic pressure testing at 3–6× maximum working pressure with recorded test data.
- Non-Destructive Testing (NDT): Ultrasonic testing (UT), eddy current testing (ECT), and radiographic testing (RT) available for weld integrity verification.
Unique Selling Points
Academic-Validated Design: Product specifications are informed by peer-reviewed research into surface cooler thermal performance, ensuring that coil tube dimensions, surface treatments, and material selections are optimized for real-world heat transfer conditions — both dry and wet.
- Precision Coil Geometry: CNC-controlled forming ensures uniform pitch and diameter tolerances (±0.5 mm), guaranteeing consistent flow distribution and heat transfer performance across the entire coil assembly.
- Customizable Configurations: Coil pitch, diameter, tube OD, wall thickness, and surface finish are fully customizable to match specific thermal load requirements and equipment constraints.
- Corrosion-Resistant Longevity: Austenitic stainless steel construction provides service life exceeding 25 years in most industrial environments without degradation of thermal performance.
- Sanitary-Grade Available: Electropolished surfaces meeting 3-A / EHEDG standards for food and pharmaceutical applications, eliminating dead legs and microbial harborage points.
- Full Traceability: Each coil tube batch is traceable from raw material mill certificate through manufacturing, testing, and final delivery, ensuring complete supply chain transparency.