Stainless Steel Spiral Coil Tube for Air-Cooled Heat Exchangers

Product Overview

The Stainless Steel Spiral Coil Tube (Model: JX-CT Series) is a precision-engineered coiled tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. specifically designed for air-cooled heat exchanger applications. The spiral coil geometry provides a significantly increased heat transfer surface area within a compact volumetric envelope, making it an optimal solution for high-efficiency thermal management systems. Through systematic analysis of coil parameters—including coil diameter, pitch, tube outer diameter, and wall thickness—the product has been optimized to achieve an excellent balance between heat transfer performance and pressure drop characteristics.

Unlike conventional straight-tube heat exchangers, the spiral coil configuration induces secondary flow patterns (Dean vortices) within the tube, which enhance turbulent mixing and substantially improve the convective heat transfer coefficient. This unique flow characteristic allows the JX-CT Series to deliver superior thermal performance while maintaining acceptable pressure drop levels across the full range of operating conditions.

Material & Properties

Base Materials

Mechanical Properties (AISI 304, Annealed Condition)

Physical & Thermal Properties

Corrosion Resistance

Specifications

Parameter Specification / Range Standard Reference
Tube Outer Diameter (OD) 6.35 mm – 38.10 mm (¼" – 1½") ASTM A269 / A213
Wall Thickness 0.50 mm – 3.00 mm (0.020" – 0.118") ASTM A269 / A213
Coil Mean Diameter (CMD) 100 mm – 1,200 mm (4" – 48") Customer-specific design
Coil Pitch 15 mm – 150 mm (0.59" – 5.91") Optimized per application
Coil Length (Developed) 1 m – 500 m (3.3 ft – 1,640 ft) Custom fabrication
Number of Turns 5 – 2,000 turns Per heat transfer requirement
Surface Finish Pickled & Passivated (Ra ≤ 0.8 μm) or Electropolished (Ra ≤ 0.4 μm) ASTM A380
End Configuration Plain ends, beveled ends, or pre-fitted with flanges / threaded couplings ASME B16.5 / B1.20.1
Tolerance on OD ±0.05 mm (±0.002") ASTM A269
Tolerance on Wall Thickness ±10% of nominal ASTM A269
Maximum Design Pressure Up to 40 MPa (5,800 psi) ASME BPVC Section VIII
Maximum Operating Temperature Up to 600°C (1,112°F) continuous Material-dependent
Heat Transfer Coefficient Enhancement 1.5× – 3.5× over straight tube (depending on Dean number) Empirical correlation validated
Pressure Drop Ratio (Coil / Straight) 1.2× – 2.0× (optimized trade-off) CFD-validated

Manufacturing Process

Process Flow

  1. Raw Material Procurement & Inspection — Certifiable stainless steel bar stock or seamless tube from approved mills, verified via Positive Material Identification (PMI) and spectroscopic analysis
  2. Cold Drawing — Seamless tube is cold-drawn to precise outer diameter and wall thickness tolerances using tungsten carbide dies and polymer-coated plugs
  3. Solution Annealing — Tubes are solution annealed at 1,050–1,150°C followed by controlled water quench to achieve full austenitic structure and maximum corrosion resistance
  4. Pickling & Passivation — Removal of surface oxide scale via citric acid or nitric-hydrofluoric acid pickling, followed by passivation to form a uniform chromium oxide film (ASTM A380)
  5. Spiral Coiling — Precision CNC-controlled coiling machine forms the tube into the specified spiral geometry with controlled coil diameter, pitch, and turn-to-turn consistency. The coiling process is performed in a single continuous operation to avoid stress concentrations at joints
  6. Stress Relief (if required) — Low-temperature stress relief at 300–400°C to eliminate residual stresses introduced during coiling, without compromising the corrosion-resistant passive film
  7. End Finishing & Fitting — Tube ends are prepared with bevels, threads, or flange welds per customer specification
  8. Quality Inspection — Comprehensive inspection including dimensional measurement, hydrostatic pressure testing, visual examination, and non-destructive testing (NDT) as applicable
  9. Packaging & Shipping — Coils are protected with VCI (Vapor Corrosion Inhibitor) paper wrapping, wooden crating, and moisture-absorbing desiccants for export-grade packaging

Key Manufacturing Advantages

Applications

Primary Application Domains

Performance Optimization Insight

Based on systematic parametric analysis of air-cooled heat exchanger spiral coil configurations, the following design guidelines have been established:

  • The Dean number (De = Re × √(d/D)) is the primary dimensionless parameter governing secondary flow intensity. Optimal De range for enhanced heat transfer: 100–500.
  • Coil diameter to tube diameter ratio (D/d) of 20–60 provides the best compromise between heat transfer enhancement and pressure drop penalty.
  • Increasing coil pitch beyond 4× tube OD yields diminishing returns in heat transfer while linearly increasing coil length and material cost.
  • For air-side heat transfer, the coil arrangement (in-line vs. staggered) and bundle density significantly impact the overall heat duty capacity.

Quality Certifications & Standards Compliance

Manufacturing Certifications

Product Standards & Codes

Testing & Inspection Protocols

Unique Selling Points