Stainless Steel Coil Tube (Coiltube) — Ice Storage Heat Exchange Application

Product Overview

The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for use in ice storage thermal energy systems within regional centralized air conditioning chiller stations. This product is supplied in coil form, enabling efficient storage, transportation, and on-site deployment for large-scale district cooling infrastructure projects. The Coiltube serves as the primary heat transfer medium in ice storage chillers, facilitating the phase-change thermal storage process where water is frozen into ice during off-peak hours and subsequently melted during peak demand periods to deliver cooling capacity.

This product is engineered to meet the rigorous demands of long-duration thermal cycling, low-temperature operation (typically down to −5°C to −10°C), and continuous exposure to water-based heat transfer fluids, ensuring exceptional corrosion resistance, mechanical durability, and thermal efficiency throughout its operational lifecycle.

Material & Properties

Base Material Composition

The Coiltube is fabricated from austenitic stainless steel grades conforming to international standards, with the following primary grades offered:

Mechanical Properties

Property 304 Grade 316L Grade 321 Grade
Tensile Strength (MPa) ≥ 520 ≥ 485 ≥ 515
Yield Strength (0.2% Proof Stress, MPa) ≥ 205 ≥ 170 ≥ 190
Elongation at Break (%) ≥ 40 ≥ 40 ≥ 40
Density (g/cm³) 7.93 7.98 7.93
Thermal Conductivity (W/m·K, at 100°C) 16.3 14.6 16.3
Operating Temperature Range (°C) −196 to +870 −196 to +870 −196 to +900
Surface Roughness (Ra, μm) ≤ 0.8 (Pickled & Passivated) ≤ 0.8 (Pickled & Passivated) ≤ 0.8 (Pickled & Passivated)

Chemical Composition (Maximum, wt%)

Element 304 316L 321
C (Carbon) ≤ 0.08 ≤ 0.03 ≤ 0.08
Si (Silicon) ≤ 0.75 ≤ 0.75 ≤ 0.75
Mn (Manganese) ≤ 2.00 ≤ 2.00 ≤ 2.00
P (Phosphorus) ≤ 0.045 ≤ 0.045 ≤ 0.045
S (Sulfur) ≤ 0.030 ≤ 0.030 ≤ 0.030
Cr (Chromium) 18.00–20.00 16.00–18.00 17.00–19.00
Ni (Nickel) 8.00–10.00 10.00–14.00 9.00–13.00
Mo (Molybdenum) — 2.00–3.00 —
Ti (Titanium) — — 5×C to 0.70

Specifications

Parameter Specification
Outer Diameter (OD) 12.7 mm – 50.8 mm (1/2" – 2")
Wall Thickness (WT) 0.8 mm – 3.0 mm (customizable)
OD Tolerance ±0.10 mm
Wall Thickness Tolerance ±10% of nominal
Coil Diameter (CD) 400 mm – 1200 mm
Coil Length (per bundle) 50 m – 500 m (configurable)
Bend Radius (minimum) ≥ 3× OD
Surface Finish Pickled and Passivated (2B finish) or Polished (Ra ≤ 0.4 μm)
End Form Plain end, flanged, threaded, or U-bend (as specified)
Delivery Form Coiled on wooden reel with protective end caps
Standards Referenced ASTM A269, ASTM A270, GB/T 14976, EN 10216-5, JIS G3459
Test Pressure 1.5× working pressure (hydrostatic test)
Design Pressure (typical) 1.0 – 2.5 MPa
Design Temperature (typical) −10°C to +120°C

Manufacturing Process

The production of the Coiltube follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:

  1. Raw Material Selection & Inspection — Virgin stainless steel strip or seamless tube stock is procured from certified mills. Incoming material undergoes spectroscopic analysis (OES), mechanical property verification, and visual inspection for surface defects.
  2. Coiling & Straightening — Seamless tubes are straightened to within ±0.3 mm/m straightness tolerance, then coiled to the specified coil diameter using computer-controlled coiling equipment to ensure uniform bend radii and prevent kinking or ovality.
  3. Forming & Bending — Precision bending stations form the tubes into the required coil configuration. CNC-controlled bending ensures consistent minimum bend radius compliance (≥3×OD), preventing wall thinning, cracking, or ovality exceeding 5%.
  4. Welding (where applicable) — For U-bend configurations or end connections, automated orbital welding (TIG) is employed with helium back-purging to maintain internal oxide-free conditions. Weld parameters are monitored in real-time via process control systems.
  5. Pickling & Passivation — All coils undergo acid pickling (nitric/hydrofluoric acid blend) to remove oxide scale, followed by passivation treatment to establish a protective chromium oxide film (≥10% Cr₂O₃ content on surface).
  6. Hydrostatic Pressure Testing — Each coil undergoes 100% hydrostatic pressure testing at 1.5× the design working pressure, with automated leak detection and data logging for traceability.
  7. Dimensional Inspection & Non-Destructive Testing (NDT) — Ultrasonic testing (UT) for wall thickness verification, eddy current testing for surface defect detection, and visual inspection in accordance with ASTM E1417.
  8. Packaging & Labeling — Coils are wrapped in moisture-barrier film, secured on wooden reels with steel strapping, and labeled with unique batch identification, material certificate reference, and shipping documentation.

Applications

The Coiltube is purpose-engineered for the following primary applications:

Unique Selling Points

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains the following quality management certifications and product compliance standards:

Technical Notes for Ice Storage Applications

In regional centralized air conditioning chiller station ice storage systems, the Coilt