Stainless Steel Spiral Coil Tube — Coiltube Series

1. Product Overview

The Stainless Steel Spiral Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered heat transfer component manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed for high-efficiency thermal energy storage and release systems, leveraging the geometric advantages of a helical/spiral configuration to maximize the surface-area-to-volume ratio within a compact envelope. The Coiltube series is particularly suited for applications involving latent and sensible heat storage devices, where rapid and uniform heat exchange is critical to system performance.

Based on extensive experimental research into spiral coil heat storage device heat release characteristics, this product line incorporates validated design parameters that ensure optimal convective heat transfer coefficients, minimal thermal resistance, and long-term structural integrity under cyclic thermal loading conditions.

2. Material & Properties

The Coiltube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal conductivity, and mechanical durability.

2.1 Base Materials

2.2 Key Material Properties

Property 304 316L 321
Tensile Strength (MPa) ≥ 515 ≥ 485 ≥ 515
Yield Strength (MPa) ≥ 205 ≥ 170 ≥ 205
Elongation (%) ≥ 40 ≥ 35 ≥ 40
Thermal Conductivity (W/m·K, at 20 °C) 16.3 14.6 16.3
Operating Temperature Range (°C) −196 to 870 −196 to 870 −196 to 900
Crystal Structure Austenitic (FCC) Austenitic (FCC) Austenitic (FCC)

3. Specifications

Parameter Specification
Outer Diameter (OD) Φ 6 mm – Φ 25 mm (customizable)
Wall Thickness 0.5 mm – 2.0 mm
Coil Pitch (Helix Spacing) 8 mm – 30 mm
Coil Diameter Φ 50 mm – Φ 500 mm
Tube Length (Developed) Up to 200 m per coil assembly
Surface Finish BA (Bright Annealed), 2B, or custom Ra ≤ 0.8 μm
End Preparation Plain, threaded (BSP/NPT), or flanged
Pressure Rating Up to 2.5 MPa (design-dependent)
Tolerance on OD ± 0.1 mm
Applicable Standards ASTM A213/A269, EN 10217-7, GB/T 12771

4. Manufacturing Process

4.1 Process Flow

  1. Material Selection & Inspection: Raw stainless steel pipe material is sourced from certified mills and subjected to spectroscopic analysis (PMI) and hydrostatic testing to confirm chemical composition and structural soundness.
  2. Precision Pipe Forming: Seamless or welded pipes are cold-drawn to achieve exact OD and wall thickness tolerances. The cold-drawing process also enhances surface finish and mechanical properties through work hardening.
  3. Spiral Coil Winding: Pipes are wound onto precision CNC-controlled mandrels using computerized winding machines. The winding parameters (pitch, tension, diameter) are controlled to ± 0.5% accuracy, ensuring uniform helical geometry critical for consistent heat transfer performance.
  4. Welding & Joining: Inlet/outlet manifolds and inter-coil connections are fabricated using orbital TIG (Tungsten Inert Gas) welding or laser welding, producing fully penetration welds with minimal heat-affected zone (HAZ).
  5. Heat Treatment & Stress Relief: Where required, coils undergo solution annealing (1010–1150 °C followed by rapid quench) to restore full austenitic microstructure and relieve residual stresses from forming operations.
  6. Surface Treatment: Optional passivation (nitric acid or citric acid based) and pickling treatments remove surface contaminants and restore chromium oxide passive layer for maximum corrosion resistance.
  7. Final Quality Assurance: Each coil assembly undergoes dimensional verification (CMM or laser scanning), pressure testing, and visual/NDT inspection (dye penetrant or eddy current) prior to packaging and shipment.

4.2 Design Optimization

Research into spiral coil heat storage device heat release experiments has demonstrated that the helical geometry promotes secondary flow patterns (Dean vortices) within the tube, enhancing turbulent mixing and increasing the convective heat transfer coefficient by 30–60% compared to straight-tube configurations at equivalent Reynolds numbers. The Coiltube series incorporates this validated design philosophy, with coil pitch and diameter ratios optimized for specific thermal duty requirements.

5. Applications

6. Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring traceability and compliance with international standards:

7. Unique Selling Points

Research-Validated Performance: Design parameters are derived from and validated against experimental heat release data from spiral coil thermal storage systems, ensuring predictable and optimized thermal performance in real-world operating conditions.