Stainless Steel Coil Tube (U-Shaped Coiled Heat Exchanger Tube)

Product Overview

The Stainless Steel Coil Tube, catalogued as Product No. 1161 by Wenzhou Jixing Metal Materials Co., Ltd., is a specialized coiled tubular product engineered for underground U-shaped heat exchanger systems. This product is designed and manufactured to meet the rigorous demands of geothermal energy exchange, district heating networks, and subterranean thermal management applications. The coil tube is formed into a continuous helical or serpentine configuration, enabling compact installation within boreholes or trench systems while maximizing heat transfer surface area per unit volume.

Grounded in the principles of Cylindrical Source Theory (CST), the performance characteristics of this U-shaped coil heat exchanger tube have been validated through rigorous numerical simulation and analytical modeling. The cylindrical source theory provides a foundational mathematical framework for predicting thermal response in buried pipe configurations, ensuring that the coil geometry, wall thickness, and material selection are optimized for efficient heat exchange in subsurface environments.

Material and Properties

The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical integrity, and thermal stability across a wide range of operating temperatures.

Specifications

Parameter Specification
Product Name Stainless Steel Coil Tube (U-Shaped Coiled Heat Exchanger Tube)
Catalog Number 1161
Manufacturer Wenzhou Jixing Metal Materials Co., Ltd.
Outer Diameter (OD) 12 mm – 50 mm (customizable upon request)
Wall Thickness 0.5 mm – 3.0 mm (tolerance ±10%)
Coil Diameter 0.3 m – 3.0 m (configurable per installation geometry)
Coil Length (per spool) 10 m – 500 m (continuous or segmented)
Material Grade AISI 304 / 316 / 316L / 2205 Duplex
Surface Finish 2B (cold rolled and annealed), No. 4 brushed, or polished (Ra ≤ 0.4 μm)
End Configuration Plain cut, beveled, or pre-welded fittings (flange, thread, socket)
U-Bend Radius ≥ 3 × OD (minimum bend radius to prevent wall thinning or buckling)
Design Pressure Up to 1.6 MPa (standard); up to 4.0 MPa (thick-wall configuration)
Standards Compliance ASTM A269, ASTM A213, EN 10217-7, GB/T 12771
Coating / Insulation Optional: HDPE (High-Density Polyethylene) wrap, PEX (Cross-linked Polyethylene) jacket, or mineral wool thermal insulation sleeve

Manufacturing Process

The production of the stainless steel coil tube follows a meticulously controlled multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical quality, and mechanical reliability:

  1. Raw Material Selection: Virgin stainless steel strip or tube blanks are sourced from certified mills, accompanied by mill test certificates (MTC) verifying chemical composition and mechanical properties in accordance with ASTM or EN standards.
  2. Tube Forming: Seamless tubes are produced via the Piercing and Pilger Mill process or the Tube and Pipe (TP) extrusion method. For welded coil tube, precision cold-drawn strip is roll-formed into a tubular cross-section and joined by TIG (Tungsten Inert Gas) welding with a nitrogen back-purge to prevent internal oxidation.
  3. Cold Drawing and Sizing: Tubes undergo multiple passes through calibrated dies to achieve the target outer diameter and wall thickness with tight tolerances (±0.05 mm for OD, ±10% for wall thickness).
  4. Coiling / U-Bend Formation: The straight tube is fed through a precision coiling machine equipped with multi-roller bending heads and servo-controlled feed mechanisms. The U-bend radius is maintained at a minimum of 3 × OD to prevent localized wall thinning, ovality, or plastic deformation. The coiling process is performed at controlled speed to minimize strain hardening.
  5. Stress Relief Annealing: Post-coiling, the tube assembly may undergo a controlled stress relief anneal at 450–550°C followed by air cooling, to relieve residual bending stresses and restore full austenitic microstructure without sensitization (chromium carbide precipitation).
  6. Surface Treatment: Depending on the application, tubes may receive pickling and passivation (acid bath treatment with nitric/hydrofluoric acid mixture) to remove scale and establish a robust passive chromium oxide film. Polishing grades (Ra ≤ 0.4 μm) are achieved through mechanical or electropolishing processes.
  7. Quality Inspection: Every production batch undergoes Eddy Current Testing (ECT), Hydrostatic Pressure Testing (at 1.5 × design pressure for 30 seconds minimum), Visual Inspection, and Dimensional Verification using laser micrometry and ultrasonic wall thickness gauging.
  8. Packaging and Shipping: Coiled tubes are wound onto protective wooden or steel spools, wrapped in moisture-proof polyethylene film, and secured with steel strapping. Each coil is labeled with a unique heat traceability number, material grade, dimensions, and test results.

Applications

The U-shaped stainless steel coil tube is purpose-engineered for a broad spectrum of thermal and fluid transport applications, with particular emphasis on subsurface heat exchange systems:

Quality Certifications and Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that every coil tube product meets international standards and regulatory requirements:

Unique Selling Points

Note: All specifications listed herein are representative and subject to final confirmation based on project-specific requirements. Wenzhou Jixing Metal Materials Co., Ltd. reserves the right to modify product specifications with prior notice. For detailed engineering drawings, simulation data, and material certifications, please contact the technical sales department with your specific application parameters.