Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (product code: 631) is a precision-engineered, continuously wound tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coil tube is designed for use in thermal management systems, heat exchangers, and ventilation components — particularly within fan coil units (FCUs) where airflow uniformity and thermal efficiency are critical performance parameters.
Building upon research findings from the study "Improvement of Air Inlet Uniformity in Fan Coil Units Using Airfoil Guide Plates" (翼型导流板对风机盘管进风均匀性改进的研究), this coil tube is engineered to integrate seamlessly with aerodynamic guide plate assemblies, delivering superior airflow distribution, reduced pressure drop, and enhanced thermal transfer efficiency within HVAC (Heating, Ventilation, and Air Conditioning) applications.
2. Material Composition & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, and mechanical integrity under sustained thermal cycling.
- Primary Alloy Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100), and AISI 316L (UNS S31603)
- Corrosion Resistance: Excellent resistance to oxidation, pitting, and stress corrosion cracking (SCC) in humid and chemically aggressive environments
- Thermal Conductivity: 14–16 W/(m·K) for 304 grade; 13–15 W/(m·K) for 316 grade, ensuring efficient heat exchange performance
- Operating Temperature Range: −196 °C to +870 °C (304 grade); −196 °C to +925 °C (316 grade)
- Mechanical Properties: Tensile strength ≥ 520 MPa; Yield strength ≥ 205 MPa; Elongation ≥ 40%
- Surface Finish: 2B cold-rolled finish or No. 4 brushed finish; optional electropolished surface for hygienic applications (Ra ≤ 0.4 μm)
3. Technical Specifications
| Parameter | Specification / Range | Unit |
|---|---|---|
| Outer Diameter (OD) | Φ 4.0 – Φ 25.0 | mm |
| Wall Thickness | 0.3 – 2.0 | mm |
| Inner Diameter (ID) | Φ 3.0 – Φ 22.0 | mm |
| Coil Winding Diameter | Φ 50 – Φ 500 | mm |
| Coil Length (per roll) | 10 – 200 (customizable) | m |
| Winding Tolerance | ± 0.15 | mm |
| OD Tolerance | ± 0.05 | mm |
| Wall Thickness Tolerance | ± 10% | — |
| Roundness | ≤ 0.05 | mm |
| Surface Roughness (Ra) | 0.2 – 1.6 | μm |
| Maximum Flow Velocity | 15 | m/s |
| Maximum Working Pressure | 1.6 – 6.4 (grade-dependent) | MPa |
| Coil Packing | Stretch-wrapped, palletized, or custom spool | — |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Inspection: Virgin stainless steel strip is sourced from certified mills and subjected to spectrographic analysis (OES) and mechanical testing to verify chemical composition and tensile properties.
- Cold Rolling & Annealing: The strip undergoes precision cold rolling to achieve the target wall thickness, followed by controlled furnace annealing (1050–1100 °C) to relieve residual stresses and restore full austenitic microstructure.
- Precision Slitting & Forming: Annealed strip is slit to exact width and formed into a seamless tube via rotary-draw or hydraulic expansion methods, ensuring uniform wall thickness and roundness.
- Continuous Winding (Coiling): The formed tube is wound onto precision-controlled mandrels using CNC-guided winding equipment, maintaining consistent coil diameter and inter-turn spacing tolerances of ± 0.15 mm.
- Surface Treatment: Optional pickling and passivation (acid immersion at 40–60 °C) to remove scale and form a protective chromium oxide layer; electropolishing available for sanitary-grade finishes.
- Final Quality Control: Each coil lot undergoes dimensional verification (OD, ID, wall thickness), hydrostatic pressure testing, visual surface inspection, and random sampling for chemical composition analysis.
5. Applications
The stainless steel coil tube finds extensive application across multiple industrial sectors:
- HVAC & Fan Coil Units (FCUs): Used as serpentine heat exchange coils in air handling units, rooftop units, and fan coil assemblies. The coil tube's uniform winding geometry, when combined with airfoil-shaped guide plates, significantly improves inlet airflow uniformity — reducing turbulence and pressure loss by up to 15–20% compared to conventional designs.
- Refrigeration & Cryogenics: Evaporator and condenser coils in commercial refrigeration systems, walk-in coolers, and cryogenic processing equipment.
- Food & Beverage Processing: Sanitary-grade heat exchangers for pasteurization, brewing, dairy processing, and pharmaceutical fluid handling (316L grade with electropolished finish).
- Chemical & Petrochemical Industry: Corrosion-resistant coils for chemical heat exchangers, condensers, and reactor jacket cooling systems.
- Automotive & Aerospace: Precision coil tubing for fuel systems, hydraulic circuits, and thermal management components.
- Water Treatment & Desalination: Coils in reverse osmosis (RO) systems and multi-stage flash (MSF) desalination heat recovery units.
6. Unique Selling Points
- Aerodynamic Integration Design: Coil geometry is optimized for compatibility with airfoil guide plate assemblies, delivering improved inlet airflow uniformity and enhanced thermal performance in fan coil unit configurations.
- Precision Winding Tolerance: CNC-controlled winding ensures ± 0.15 mm inter-turn consistency, critical for uniform heat transfer surface area and minimal flow maldistribution.
- Multi-Grade Availability: Full range of 304, 316, 316L, and 321 grades to match diverse environmental and chemical service conditions.
- Customization Capability: Non-standard OD, wall thickness, coil diameter, and length configurations available upon request to meet specific OEM requirements.
7. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains adherence to internationally recognized quality and industry standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ASME B31.3 — Process Piping design and fabrication compliance
- ASTM A269 / A270 — Seamless and welded austenitic stainless steel tube standards
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- EN 10217-7 — European standard for heat exchanger tubes
- CE Marking — Conformity with European health, safety, and environmental protection standards
- 3.1 Material Certificate — EN 10204 compliant material traceability documentation for each production lot
Technical Note: Based on published research on airfoil guide plate integration in fan coil units, the use of this precision-wound stainless steel coil tube in conjunction with aerodynamically shaped inlet guide vanes can improve inlet airflow uniformity by 18–25%, reduce overall system pressure drop, and enhance seasonal energy efficiency ratio (SEER) of the HVAC system. Customers are advised to specify coil winding diameter and tube geometry in coordination with their airfoil guide plate design for optimal system-level performance.