Stainless Steel Coil Tube (Coiltube) — Fan Coil Unit Heat Exchange Element

Product Overview

The Stainless Steel Coil Tube (Coiltube), product reference No. 1529, is a precision-engineered tubular heat exchanger component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coiled tube is specifically designed for integration into Fan Coil Units (FCU), where it serves as the primary heat transfer medium in air conditioning, HVAC (Heating, Ventilation, and Air Conditioning), and thermal management systems. The coil tube operates by facilitating convective and conductive heat exchange between a circulating working fluid (typically chilled water or hot water) and ambient air blown across the coil surface by a fan assembly.

The fundamental thermodynamic relationship governing the performance of this coil tube within a Fan Coil Unit is described by the Cooling and Heating Capacity Conversion Equation:

Q = m × Cp × (Tin − Tout) = h × A × ΔTlm

Where: Q = Heat transfer rate (W); m = Mass flow rate of fluid (kg/s); Cp = Specific heat capacity of fluid (J/kg·K); Tin, Tout = Inlet and outlet fluid temperatures (°C); h = Overall heat transfer coefficient (W/m²·K); A = Effective heat transfer surface area (m²); ΔTlm = Logarithmic Mean Temperature Difference (LMTD)

This equation underscores the critical importance of maximizing the effective heat transfer surface area (A) and maintaining a high overall heat transfer coefficient (h) — both of which are directly achieved through the optimized spiral geometry and high-conductivity stainless steel material of this product.

Material & Properties

The coil tube is fabricated from premium-grade austenitic stainless steel, selected for its superior combination of thermal conductivity, corrosion resistance, and mechanical integrity under cyclic thermal loading conditions.

Specifications

Parameter Specification
Product Reference No. 1529
Product Name Coiltube (Fan Coil Unit Heat Exchange Coil)
Tube Outer Diameter (OD) 9.52 mm / 12.7 mm / 15.88 mm (available options)
Tube Wall Thickness 0.5 mm – 1.0 mm (standard); up to 1.5 mm (heavy duty)
Coil Inner Diameter (ID) 200 mm – 1200 mm (customizable per unit design)
Coil Height (Row Depth) 200 mm – 1000 mm (configurable, typically 2 to 6 rows)
Tube Pitch (Horizontal) 15.0 mm – 25.4 mm
Tube Pitch (Vertical) 15.0 mm – 25.4 mm
Row Configuration 2-row, 3-row, 4-row, or custom multi-row arrangements
Fin Material (if finned variant) Aluminum (Al-Mg-Si alloy) or stainless steel fins
Fin Spacing 1.5 mm – 3.0 mm (typical)
Effective Heat Transfer Area Calculated per LMTD method; typically 15 – 200 m² per coil assembly
Design Pressure 1.0 – 1.6 MPa (standard); up to 4.0 MPa (high-pressure variant)
Hydrostatic Test Pressure 1.5× Design Pressure (minimum 2.4 MPa)
Working Fluid Chilled water (6–12°C), hot water (40–80°C), glycol-water mixtures
Flow Rate Capacity 0.5 – 50 L/min (dependent on coil dimensions)
Cooling Capacity Range 1.5 kW – 50 kW per unit (per ASHRAE standard test conditions)
Heating Capacity Range 2.0 kW – 60 kW per unit (per ASHRAE standard test conditions)
Connection Type Threaded ports, flanged connections, or soldered headers
Surface Treatment Passivation, electropolishing, or chemical cleaning
Compliance Standards ASTM A269, ASTM A312, EN 10216-5, GB/T 12771

Manufacturing Process

The production of the stainless steel coil tube follows a rigorously controlled multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and optimal thermal performance:

  1. Material Selection and Incoming Inspection: Cold-rolled stainless steel strip or seamless tube stock is procured from certified mills. Each batch undergoes spectrographic analysis (OES), mechanical testing, and visual inspection to verify compliance with ASTM A269/A312 chemical and mechanical requirements.
  2. Coil Forming (Tube Coiling): The straight tube is precision-formed into a helical spiral geometry using CNC-controlled coiling machinery. The forming process employs progressive bending with controlled curvature radii to prevent ovalization, wrinkling, or wall thinning. The maximum allowable ovality is limited to 5% of nominal OD.
  3. Heat Treatment (Solution Annealing): Post-forming annealing at 1050°C–1150°C followed by rapid water quenching eliminates residual stresses introduced during cold forming, restores full austenitic microstructure, and ensures maximum corrosion resistance and ductility.
  4. Pickling and Passivation: The coil is immersed in a nitric acid/hydrofluoric acid mixture to remove oxide scale and contaminants. Subsequent passivation with a 20–30% nitric acid solution establishes a protective chromium oxide film (Cr₂O₃) on the surface.
  5. Finning (if applicable): Aluminum or stainless steel fins are mechanically inserted or bonded to the coil tubes using specialized fin-tube bonding equipment. Fin engagement depth is controlled to ±0.05 mm to ensure consistent thermal contact resistance.
  6. Header Assembly: The coil ends are brazed or welded to stainless steel headers (manifolds) using silver-bearing filler metal (Ag-30, Cu-Ag) under inert atmosphere (argon shielding) to prevent oxidation at weld zones.
  7. Pressure Testing: Each completed coil assembly undergoes hydrostatic pressure testing at 1.5× design pressure for a minimum hold time of 30 minutes, with zero leakage tolerance. Pneumatic leak testing (helium or nitrogen) may be additionally performed for critical applications.
  8. Final Inspection and Documentation: Dimensional verification (laser scanning or CMM), surface finish measurement, material traceability documentation, and performance certification are completed prior to packaging.

Applications

The stainless steel coil tube is a critical component across a broad spectrum of thermal management and HVAC applications:

Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management systems and product certifications ensuring international market compliance:

Unique Selling Points