Stainless Steel Coil Tube for Shell-and-Coil Heat Exchangers

Product Overview

The Stainless Steel Coil Tube (Model No. 785) is a precision-engineered continuous coil tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Specifically designed for integration into shell-and-coil heat exchanger assemblies, this product serves as the core heat transfer element in dual-medium (fluorocarbon refrigerant and water) high energy efficiency thermal exchange systems. The coil tube is formed into a helical or spiral geometry that maximizes the surface-to-volume ratio within a compact shell enclosure, thereby achieving superior thermal performance in industrial and commercial HVAC, refrigeration, and process engineering applications.

This product line has been extensively studied and validated through engineering literature, particularly in the context of dual-fluorine-water (R-series refrigerant and H₂O) high energy efficiency shell-and-coil heat exchangers. The design philosophy emphasizes maximizing heat transfer coefficients while minimizing pressure drop across the coil circuit, resulting in coefficient of performance (COP) improvements over conventional finned-tube alternatives.

Material & Properties

Base Material

Mechanical Properties

Thermal Properties

Corrosion Resistance

The austenitic stainless steel matrix provides exceptional resistance to pitting, crevice corrosion, and intergranular corrosion. SUS316L grade offers additional molybdenum (Mo 2.0–3.0%) content for enhanced chloride resistance in marine or chemical processing environments. The passivated oxide layer (Cr₂O₃) self-heals under oxidizing conditions, ensuring long-term structural integrity.

Specifications

Parameter Specification Unit Standard / Reference
Product Code 785 — Internal Catalog
Outer Diameter (OD) 6.35 / 8.00 / 9.53 / 12.70 mm ASTM A213
Wall Thickness 0.50 – 1.50 mm GB/T 14976
Coil Pitch (Helical Spacing) 15 – 40 mm Design Specification
Coil Diameter (Mean) 50 – 300 mm Design Specification
Tube Length (Developed) 3,000 – 12,000 mm Custom Order
Surface Finish Ra ≤ 0.8 μm (polished) / Ra ≤ 1.6 μm (pickled) μm GB/T 1031
End Condition Beveled / Plain / Threaded (per customer drawing) — Customer Specification
Working Pressure (Design) Up to 2.5 MPa EN 12828 / GB/T 151
Hydrostatic Test Pressure 1.5 × Design Pressure MPa ASME BPVC VIII
Refrigerant Compatibility R22, R404A, R407C, R134a, R32, R410A — ASHRAE 34
Water Side Compatibility Chilled water (5–15 °C), Cooling water (30–45 °C) °C Design Specification
Packaging Wooden crate with moisture-proof wrapping — ISO 4180

Manufacturing Process

  1. Raw Material Inspection: Incoming stainless steel seamless or welded tube stock is verified for chemical composition (via Optical Emission Spectrometry, OES), mechanical properties, and dimensional conformity per ASTM A213/A213M. Mill test certificates (MTC, EN 10204 Type 3.1) are reviewed prior to processing.
  2. Cutting & Deburring: Tube stock is cut to required developed length using precision sawing or laser cutting. Entry and exit burrs are removed to prevent flow turbulence and ensure clean welding interfaces.
  3. Straightening & Calibration: The tube is passed through a multi-roller straightening machine to achieve dimensional straightness within ±0.5 mm/m tolerance.
  4. Coil Forming (Cold Bending): The straightened tube is fed through a CNC-controlled coil forming machine that imparts the helical geometry. The forming parameters (pitch, coil diameter, bend radius) are programmatically controlled to ensure geometric accuracy. Minimum bend radius is maintained at ≥ 3 × OD to prevent wall thinning or ovality exceeding 5%.
  5. Stress Relief Annealing: Formed coils undergo a controlled heat treatment cycle (typically 1050 °C for SUS304, 1100 °C for SUS316L, air-cooled or furnace-cooled) to relieve residual stresses introduced during cold forming and restore full austenitic microstructure.
  6. Surface Treatment: Pickling and passivation treatment (HNO₃/HF acid bath) removes scale and contaminant films, establishing a stable chromium oxide passive layer. Optional electropolishing (Ra ≤ 0.4 μm) is available for hygienic or high-flow applications.
  7. Welding & Brazing: End connections are prepared for welding to header plates or distributor tubes. TIG (GTAW) welding is preferred for stainless steel to maintain corrosion resistance in the heat-affected zone (HAZ), using matching filler wire (ER308L or ER316L).
  8. Quality Inspection: Each coil undergoes dimensional verification (OD, wall thickness, pitch uniformity, total length), leak testing (helium mass spectrometry or pressure decay method per ASME BPVC Section VIII), and visual inspection of weld joints.
  9. Final Assembly & Packaging: Qualified coils are bundled, wrapped in moisture-proof material, and secured in export-grade wooden crates with desiccant packets for shipment.

Applications

Primary Application: Shell-and-Coil Heat Exchanger Systems

The coil tube is the primary heat transfer element in shell-and-coil heat exchanger configurations. In the dual-fluorine-water high energy efficiency architecture, the refrigerant flows through the coil tube (tubeside) while water circulates through the shell (shellside), or vice versa. The helical geometry induces secondary flow patterns (Dean vortices) that enhance turbulent mixing, resulting in heat transfer coefficients 15–30% higher than straight-tube equivalents at equivalent flow velocities.

Specific End-Use Sectors

Quality Certifications & Compliance

Manufacturing Certifications

Product Standards & Compliance

Testing & Documentation

Unique Selling Points

1. Superior Thermal Performance: The helical coil geometry generates Dean secondary flows that continuously disrupt the thermal boundary layer, yielding heat transfer coefficients up to 30% higher than straight-tube designs at equivalent Reynolds numbers. This translates directly into smaller heat exchanger footprints and lower capital expenditure (CAPEX).

2. Dual-Medium Optimization: Engineered specifically for dual-fluorine-water (refrigerant/water) applications, the coil tube dimensions and pitch are optimized to balance refrigerant-side nucleate boiling heat transfer with water-side convective cooling, achieving overall COP improvements of 8–15% over conventional configurations.

3. Corrosion-Resistant Longevity: The austenitic stainless steel construction (SUS304/SUS316L) provides a design life exceeding 25 years in aggressive environments, eliminating the need for cathodic protection or corrosion inhibitors required by carbon steel alternatives.

4. Precision CNC Manufacturing: Computer-numerically controlled coil forming ensures geometric consistency across production batches, with pitch uniformity within ±0.5 mm and ovality controlled to ≤ 3%, guaranteeing predictable hydraulic performance.

5. Full Traceability & Certification: End-to-end material traceability from mill heat number to finished product, supported by comprehensive EN 10204 Type 3.1 documentation and third-party inspection options, ensuring compliance with global regulatory requirements.

6. Custom Engineering Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil tube configurations — including non-standard ODs, wall thicknesses, pitch, coil diameter, and end preparations — tailored to specific heat exchanger design requirements through collaborative engineering with OEM partners.