Stainless Steel Coil Tube — Fan Coil Unit (FCU) Heat Exchanger Tube
Product Overview
The Stainless Steel Coil Tube (盘管, Coil Tube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular component designed primarily for use in Fan Coil Units (FCUs) and related HVAC (Heating, Ventilation, and Air Conditioning) systems. These coil tubes serve as the core heat exchange medium within air-handling equipment, facilitating efficient thermal transfer between the circulating refrigerant or hot water and the ambient air stream.
As a critical component in commercial and residential climate control systems, the coil tube must withstand cyclic thermal stress, resist corrosion from condensation and humid environments, and maintain dimensional accuracy over extended operational life. The product catalog entry (No. 1511) reflects Wenzhou Jixing's specialization in providing high-grade stainless steel tubing solutions tailored to the demanding requirements of the HVAC and refrigeration industries.
Material & Properties
The coil tubes are fabricated from austenitic stainless steel grades, with the primary material specification being AISI 304 (UNS S30400) and AISI 316 (UNS S31600), selected for their superior corrosion resistance, thermal conductivity, and mechanical integrity under variable flow conditions.
- Austenitic Stainless Steel (奥氏体不锈钢): Provides excellent resistance to pitting and crevice corrosion, essential for environments where condensate accumulation occurs within FCU heat exchangers.
- Chromium Content (Cr ≥ 18%): Ensures passive oxide layer formation, providing long-term protection against oxidation and chemical attack.
- Nickel Content (Ni ≥ 8%): Stabilizes the austenitic microstructure, enhancing ductility and forming capability during coil winding operations.
- Molybdenum (Mo, in 316 grade): Further improves resistance to chlorides and aggressive cooling water additives.
Key mechanical properties include a minimum tensile strength of 515 MPa, yield strength of 205 MPa, and elongation of at least 40%, ensuring the tube maintains structural integrity during coil winding and operational pressure cycles.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管, Coil Tube) |
| Catalog No. | 1511 |
| Material Grade | AISI 304 / AISI 316 / Custom Grades |
| Tube Outer Diameter (OD) | Φ6.35 mm – Φ12.70 mm (1/4" – 1/2") |
| Wall Thickness | 0.50 mm – 1.20 mm |
| Coil Diameter | Φ50 mm – Φ200 mm (configurable) |
| Coil Length | Up to 3,000 mm (continuous coil) |
| Surface Finish | BA (Bright Annealed) / No. 4 Brushed / Mirror |
| Operating Pressure | Up to 1.6 MPa (232 psi) |
| Operating Temperature | −40 °C to +200 °C |
| Heat Transfer Efficiency | Optimized for total heat, sensible heat, and latent heat exchange |
| Standard | ASTM A269 / ASTM A213 / EN 10217 / GB/T 13296 |
Manufacturing Process
The production of high-quality stainless steel coil tubes follows a rigorous multi-stage manufacturing protocol to ensure dimensional precision, surface integrity, and consistent mechanical performance:
- Hot Rolling & Annealing: The initial steel strip or rod is hot-rolled to approximate dimensions and subsequently annealed to relieve residual stresses and refine grain structure.
- Cold Drawing / Seamless Tube Formation: Precision cold drawing through calibrated dies produces tubes with tight dimensional tolerances (±0.05 mm on OD) and uniform wall thickness.
- Intermediate Annealing: Periodic annealing cycles during drawing prevent work hardening and maintain formability for subsequent coil winding operations.
- Coil Winding (盘管成型): The straight tube is wound into precise spiral configurations using CNC-controlled winding machines, maintaining consistent pitch and diameter to optimize heat exchange surface area.
- Final Annealing & Pickling: Post-winding annealing eliminates springback stresses; chemical pickling and passivation remove surface oxides and establish the protective chromium oxide layer.
- Pressure Testing & Inspection: Each coil tube undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure, with visual and dimensional inspection per applicable standards.
Applications
The stainless steel coil tubes produced by Wenzhou Jixing Metal Materials are integral components across multiple industrial and commercial sectors:
- Fan Coil Units (FCUs): Primary application — the coil tube forms the heat exchange core where variable water flow rates modulate total cooling capacity (全热冷量), sensible heat capacity (显热冷量), and latent heat capacity (潜热冷量). The study referenced in the product documentation ("The Effect of Variable Water Flow on Total, Sensible, and Latent Cooling Capacity of Fan Coil Units") underscores the critical relationship between water flow rate, tube geometry, and thermal performance.
- Air Handling Units (AHUs): Used in commercial HVAC systems for precise temperature and humidity control.
- Chilled Water Systems: Serves as the heat transfer element in secondary chilled water loops.
- Refrigeration & Cold Storage: Utilized in evaporator and condenser assemblies where corrosion resistance is paramount.
- Industrial Process Cooling: Applied in chemical processing, pharmaceutical manufacturing, and food & beverage industries requiring sanitary-grade heat exchange.
- Marine & Coastal Environments: AISI 316 grade coil tubes provide enhanced chloride resistance for HVAC installations in humid or salt-laden atmospheres.
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd adheres to internationally recognized quality management and product standards to ensure consistent product performance:
- ISO 9001:2015 — Quality Management System certification ensuring systematic process control from raw material sourcing through final delivery.
- ISO 14001 — Environmental Management System, demonstrating commitment to sustainable manufacturing practices.
- CE Marking — Compliance with European health, safety, and environmental protection standards for export to EEA markets.
- ASTM A269 / A213 — Conformance to American Society for Testing and Materials specifications for austenitic stainless steel seamless and welded tubing.
- GB/T 13296 — Compliance with Chinese national standards for seamless stainless steel tubes.
- EN 10217 — European standard for welded and seamless cold-drawn stainless steel tubes.
Unique Selling Point: The coil tube design is specifically engineered to accommodate variable water flow conditions within fan coil unit applications. Research demonstrates that the geometric configuration of the coil — including tube diameter, wall thickness, coil pitch, and overall surface area — directly influences the proportion of sensible heat to latent heat removal as water flow varies. Wenzhou Jixing's precision manufacturing capability ensures that each coil tube delivers predictable and optimal thermal performance across the full range of operating flow rates, maximizing energy efficiency and occupant comfort in HVAC systems.