Stainless Steel Helical Coil Tube — Product Technical Specification

Product Name: Stainless Steel Coil Tube (Helical Coil Tube / Coiltube)

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd

Product Code / Reference No.: 305

Classification: Literature-Based Engineering Reference Product

1. Product Overview

The Stainless Steel Helical Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular component formed into a continuous helical geometry, designed for high-efficiency heat exchange applications. This product leverages the inherent advantages of stainless steel — including superior corrosion resistance, mechanical strength, and thermal conductivity — combined with the enhanced heat transfer characteristics of a helical configuration. The coiled geometry significantly increases the surface area-to-volume ratio, promoting turbulent flow within the tube and thereby improving convective heat transfer coefficients compared to straight-tube alternatives.

The Coiltube product line is particularly relevant in the field of underwater thermal management systems, where it serves as the core heat transfer element in submerged heat exchangers. Research conducted on GA-XGBoost (Genetic Algorithm-Extreme Gradient Boosting) hybrid machine learning models has demonstrated that the heat transfer performance of underwater helical coil tube heat exchangers can be accurately predicted and optimized, validating the engineering reliability and design flexibility of this product.

2. Material & Properties

2.1 Base Material Grades

2.2 Mechanical Properties (Typical — AISI 316L)

Property Unit Typical Value
Tensile Strength (Ultimate) MPa ≥ 515
Yield Strength (0.2% Offset) MPa ≥ 205
Elongation (at Break) % ≥ 40
Hardness (Rockwell B) HRB ≤ 95
Density g/cm³ 8.00

2.3 Thermal Properties

Property Unit Typical Value (AISI 316L)
Thermal Conductivity (at 20°C) W/(m·K) 16.3
Thermal Conductivity (at 100°C) W/(m·K) 18.5
Specific Heat Capacity J/(kg·K) 500
Thermal Expansion Coefficient (20–100°C) ×10⁻⁶ /K 17.3

2.4 Corrosion Resistance

3. Specifications

3.1 Geometric Dimensions

Parameter Symbol Range / Options
Outer Diameter (OD) D₀ 6 mm – 50 mm
Wall Thickness t 0.5 mm – 3.0 mm
Helix Coil Diameter (Mean) Dc 50 mm – 500 mm
Helix Pitch P 10 mm – 100 mm
Coil Length (Total Tube Length) L 0.5 m – 50 m (custom)
Number of Turns N 1 – 500+
Curvature Ratio (Dc/D₀) λ ≥ 5 (recommended ≥ 8 for optimal stress distribution)

3.2 Applicable Standards

3.3 Surface Finish Options

Finish Type Ra (μm) Application
Pickled & Passivated 0.4 – 1.6 General industrial heat exchange
Mechanical Polish 0.1 – 0.4 Food-grade, pharmaceutical
Electropolished 0.05 – 0.2 Bio-pharmaceutical, ultra-high purity
Shot Peened (Internal) 1.6 – 3.2 Enhanced fatigue resistance, flow turbulence

4. Manufacturing Process

4.1 Process Flow

  1. Raw Material Procurement: Selection of certified stainless steel seamless or welded tube stock from approved mills, with full material traceability (MTC — Material Test Certificate per EN 10204 Type 3.1).
  2. Incoming Inspection: Verification of chemical composition (via OES — Optical Emission Spectroscopy), mechanical properties, and dimensional tolerances.
  3. Coil Forming (Helical Winding): Precision CNC-controlled coiling using a rotary mandrel system. The tube is wound onto a helical former with controlled bend radius to prevent ovalization (eccentricity ≤ 2% of OD). The curvature ratio (λ = Dc/D₀) is maintained at or above the minimum threshold to avoid excessive residual bending stresses.
  4. Heat Treatment (if required): Solution annealing at 1050–1150°C followed by rapid water quenching to restore full austenitic structure, eliminate work-hardening from coiling, and maximize corrosion resistance.
  5. Pickling & Passivation: Immersion in nitric acid/hydrofluoric acid solution to remove oxide scale and contaminants, followed by passivation treatment to establish a stable chromium oxide passive film (Cr₂O₃).
  6. Surface Finishing: Mechanical polishing, electropolishing, or shot peening as specified by the end application.
  7. Quality Inspection: Dimensional verification (OD, wall thickness, coil diameter, pitch), visual inspection, eddy current testing (ECT) for wall thickness mapping, and hydrostatic pressure testing (typically at 1.5× working pressure).
  8. Packaging & Shipping: Protective wrapping, moisture barrier packaging, and secure crating for export or domestic delivery.

4.2 Key Manufacturing Considerations

5. Applications

5.1 Primary Application Domains

5.2 Performance Optimization — GA-XGBoost Modeling Insight

Recent research on underwater helical coil tube heat exchangers has employed a Genetic Algorithm (GA) – Extreme Gradient Boosting (XGBoost) hybrid model for heat transfer performance prediction. This approach optimizes the feature selection and hyperparameter tuning of the XGBoost regressor using a genetic algorithm, achieving prediction accuracy (R²) exceeding 0.95 for heat transfer rate estimation. Key influencing parameters identified include:

  • Helix coil diameter (Dc) and curvature ratio (λ)
  • Flow velocity and Reynolds number (Re)
  • Fluid properties (thermal conductivity, viscosity, specific heat)
  • Inlet/outlet temperature differential (ΔT)
  • Tube length and number of turns (N)

This data-driven optimization methodology provides engineering teams with a powerful tool for preliminary design sizing and performance benchmarking of Coiltube-based heat exchanger systems, reducing reliance on iterative CFD (Computational Fluid Dynamics) simulations during the early design phase.

6. Quality Certifications & Compliance

6.1 Manufacturing Certifications

6.2 Product-Specific Certifications