Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (catalog reference No. 1611) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled tubular product designed for demanding industrial and HVAC (Heating, Ventilation, and Air Conditioning) applications. This product is specifically engineered to meet the thermal performance requirements of Fan Coil Units (FCU), where integrated cooling and heating capacity expressions are critical for system efficiency.
Coil tubes serve as the primary heat exchange medium in fan coil unit assemblies, facilitating the transfer of thermal energy between refrigerant or water circuits and ambient air. The coiled geometry maximizes surface area within a compact footprint, enabling superior thermal exchange efficiency compared to straight-tube configurations. This product line is classified under the Literature Study (文献学习) category, reflecting its foundation in established thermodynamic principles and empirical performance data as documented in industry research on cooling and heating capacity expressions.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from austenitic stainless steel, conforming to recognized international standards. The primary grade utilized is AISI 304 (UNS S30400), with AISI 316 (UNS S31600) available for corrosion-critical environments.
2.2 Key Material Properties
- Corrosion Resistance: Excellent resistance to atmospheric, chemical, and waterborne corrosion due to the minimum 18% Chromium (Cr) and 8% Nickel (Ni) composition in AISI 304 grade.
- Thermal Conductivity: Approximately 16.3 W/(m·K) at 20°C, providing efficient heat transfer performance.
- Mechanical Strength: Yield strength of ≥205 MPa and tensile strength of ≥515 MPa ensure structural integrity under cyclic thermal loading.
- Non-magnetic: Austenitic microstructure ensures non-magnetic properties, suitable for electromagnetic compatibility-sensitive installations.
- Hygienic Surface: Low surface roughness (Ra ≤ 0.8 μm) facilitates fluid flow with minimal fouling and supports sanitary applications.
- Weldability: Excellent formability and weldability without pre-heating or post-weld annealing requirements for thin-wall configurations.
2.3 Alloy Composition (AISI 304 — Typical)
| Element | Symbol | Content (wt%) |
|---|---|---|
| Chromium | Cr | 18.0 – 20.0 |
| Nickel | Ni | 8.0 – 10.5 |
| Carbon | C | ≤ 0.08 |
| Manganese | Mn | ≤ 2.0 |
| Silicon | Si | ≤ 1.0 |
| Phosphorus | P | ≤ 0.045 |
| Sulfur | S | ≤ 0.030 |
| Iron | Fe | Balance |
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Catalog No. | 1611 | Wenzhou Jixing Internal Classification |
| Material Grade | AISI 304 / AISI 316 | ASTM A213 / ASTM A269 |
| Outer Diameter (OD) | 6.35 mm – 25.4 mm (1/4" – 1") | EN 10217-7 / ASME B36.19M |
| Wall Thickness | 0.5 mm – 2.0 mm | ASTM A269 |
| Coil Diameter | 100 mm – 500 mm | Custom per application |
| Tube Length (per coil) | 3 m – 50 m (continuous coil) | — |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated | ASTM A478 |
| Maximum Operating Temperature | 870°C (AISI 304) / 870°C (AISI 316) | ASTM A213 |
| Maximum Operating Pressure | Up to 2.5 MPa (design-dependent) | ASME BPV Code Section VIII |
| Tolerance on OD | ±0.15 mm | EN 10217-7 |
| Tolerance on Wall Thickness | ±10% (nominal) | ASTM A269 |
| End Condition | Plain ends / Flared ends (available) | — |
| Coating | None (bare) / Optional passivation layer | ASTM A967 |
| Packaging | Wooden crate / Pallet with moisture barrier | ISO 4180 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection: High-purity stainless steel strip or seamless tube blanks are procured from certified mills with full chemical and mechanical traceability.
- Coiling (Tube Bending): Precision CNC-controlled coiling machines form straight tube sections into the required helical coil geometry. The bending process employs multi-roller forming with controlled feed rates to prevent ovality, wrinkling, or thinning of the tube wall.
- Heat Treatment: Post-forming solution annealing at 1050°C – 1150°C followed by rapid quenching restores full austenitic microstructure, eliminates residual stresses, and ensures maximum corrosion resistance.
- Pickling and Passivation: The coil is subjected to acid pickling (nitric/hydrofluoric acid blend) to remove scale and oxidation, followed by passivation to establish a protective chromium oxide film (minimum 100 Å thickness).
- Quality Inspection: Each coil undergoes dimensional verification, visual inspection, and optional pressure testing (hydrostatic at 1.5× working pressure for 30 seconds minimum).
- Packaging and Dispatch: Finished coils are wrapped in protective film, bundled, and secured on pallets or wooden crates for shipment.
4.2 Quality Control Measures
- 100% visual inspection for surface defects, deformations, and weld integrity
- Random sampling for chemical composition verification via Optical Emission Spectroscopy (OES)
- Dimensional measurement at intervals of every 5 meters of tube length
- Corrosion resistance testing per ASTM A967 (passivation verification)
- Pressure testing per ASME BPV Code requirements for pressure-bearing applications
5. Applications
5.1 Primary Applications
- Fan Coil Units (FCU): The principal application domain. Coil tubes serve as heat exchange elements in FCU assemblies where integrated cooling and heating capacity expressions govern system design. The coil configuration optimizes airflow-thermal interaction, achieving superior heat transfer coefficients (U-values) in both cooling and heating modes.
- HVAC Heat Exchangers: Chilled water and hot water distribution systems in commercial and residential buildings.
- Refrigeration Systems: Evaporator and condenser coils in industrial refrigeration and cold storage facilities.
- Process Cooling/Heating: Heat exchange in chemical processing, pharmaceutical manufacturing, and food processing industries.
- Automotive Radiators: Compact coil configurations for vehicle thermal management systems.
5.2 Performance in Fan Coil Unit Systems
In fan coil unit applications, the coil tube geometry directly influences the integrated cooling and heating capacity expression — a composite thermodynamic function that accounts for:
- Convective heat transfer coefficient between air and tube surface
- Conductive resistance through the tube wall
- Internal fluid-side heat transfer coefficient
- Effective surface area accounting for coil pitch and tube count
- Fin-to-tube contact resistance (when fins are applied)
The stainless steel coil tube product is engineered to minimize each resistance term, thereby maximizing the overall heat transfer capacity per unit volume — a critical parameter in compact FCU designs.
6. Quality Certifications
| Certification / Standard | Description | Applicability |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Manufacturing process assurance |
| ISO 14001:2015 | Environmental Management System | Sustainable manufacturing practices |
| EN 10204 3.1 | Inspection Certificate | Material certification per batch |
| CE Marking | European Conformity | EU market compliance |
| ASTM A213 / A269 | Material Specification Compliance | Chemical and mechanical property verification |
| ASME BPV Code | Boiler and Pressure Vessel Code | Pressure-bearing application suitability |
| RoHS Compliance | Restriction of Hazardous Substances | Environmental and health safety |
7. Unique Selling Points
- Superior Corrosion Durability: Austenitic stainless steel construction provides a service life exceeding 25 years in aggressive environments, significantly outperforming carbon steel alternatives.
- Thermal Efficiency Optimization: Precision coil geometry engineered for maximum heat exchange surface area-to-volume ratio, directly improving FCU system COP (Coefficient of Performance).
- Hygienic Design: Smooth, non-porous surface finish resists biofilm formation and supports easy cleaning, ideal for pharmaceutical and food-grade HVAC applications.
- Full Traceability: Every coil batch is traceable to raw material mill certificates, ensuring complete supply chain transparency.
- Customization Capability: Flexible dimensional configurations (OD, wall thickness, coil diameter, pitch) tailored to specific FCU design requirements and thermal load calculations.
- Compliance-Ready: Pre-certified to international standards, reducing qualification time for OEM integrators and project engineers.
Technical Note: The design and performance validation of this coil tube product are informed by the integrated cooling and heating capacity expression methodology applied to fan coil unit systems, ensuring that thermal performance predictions align with real-world operational conditions across the full range of design temperatures and airflow rates.