Stainless Steel Coil Tube for Evaporative Condensing Condenser Systems

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 586) specializes in the manufacturing and supply of precision-engineered stainless steel coil tubes (Coil Tubes / Spirally Wound Heat Exchanger Tubes) designed specifically for evaporative condensing condenser systems in power station applications. These coil tubes serve as the core heat transfer elements within condensation units, facilitating efficient latent heat rejection from low-pressure steam to ambient air through evaporative cooling. The product line encompasses a comprehensive range of coil tube geometries, diameters, and material grades tailored to meet the demanding thermal-hydraulic and mechanical requirements of utility-scale power generation facilities.

The design philosophy governing these coil tubes is rooted in the principles outlined in the technical study of "Design of Heat Exchange Coil Tubes for Evaporative Condensing Condenser Systems in Power Stations", which emphasizes optimal balance between heat transfer efficiency, pressure drop minimization, corrosion resistance, and long-term structural integrity under cyclic thermal loading conditions.

Material & Properties

Coil tubes are manufactured from austenitic and duplex stainless steel grades selected for their exceptional combination of corrosion resistance, mechanical strength, and thermal stability. The primary material specifications include:

Property Type 316L Grade 2205 Grade 2507
Tensile Strength (MPa, min) 485 550 620
Yield Strength (MPa, min) 205 450 550
Thermal Conductivity (W/m·K at 20°C) 16.3 18.0 18.0
Thermal Expansion Coefficient (10⁻⁶/K) 17.2 14.0 13.0
Corrosion Resistance (Pitting, NaCl) Moderate High Very High
Maximum Service Temperature (°C) 450 350 300
PREN (Pitting Resistance Equivalent Number) 24–26 34–38 38–42

Specifications

The coil tubes are engineered according to international standards including ASTM A269 (Austenitic Stainless Steel Seamless Tubing), ASTM A312 (Welded Austenitic Stainless Steel Tubing), EN 10216-5, and ASME B31.3 (Process Piping). Key dimensional and performance specifications are detailed below:

Parameter Specification Range
Outer Diameter (OD) 12 mm – 114.3 mm (½" – 4½")
Wall Thickness 0.5 mm – 6.0 mm
Coil Diameter 150 mm – 1200 mm
Coil Length per Unit 5 m – 200 m (continuous)
Maximum Operating Pressure Up to 4.0 MPa (580 psi)
Operating Temperature Range −40°C to +450°C
Surface Finish Ra ≤ 0.8 μm (electropolished); Ra ≤ 1.6 μm (mechanical polished)
Heat Transfer Coefficient (Steam Condensation) 8,000 – 15,000 W/m²·K
Pressure Drop (Design) ≤ 50 kPa (typical for shell-side flow)
Coiling Method Hot coiling / Cold coiling / Precision cold-formed
Joint Type Continuous (seamless) / Orbital-welded (with 100% radiographic testing)

Manufacturing Process

The production of high-performance coil tubes follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical homogeneity, and surface integrity:

  1. Material Selection & Incoming Inspection: Raw stainless steel seamless or welded pipe stock is procured from certified mills and subjected to spectrographic analysis, mechanical property verification, and visual inspection per ASTM E1010 and ASTM E1086.
  2. Pipe Preparation: Raw tubing is cut to specified lengths, deburred, and cleaned. For welded tubes, the longitudinal seam is inspected via ultrasonic testing (UT) per ASTM E1647.
  3. Coiling Operation:
    • Hot Coiling: Tubes are heated to a controlled temperature range (600–900°C depending on grade) and coiled around precision mandrels using hydraulic forming equipment to achieve the target coil diameter without work-hardening.
    • Cold Coiling: Smaller diameter tubes (OD ≤ 50 mm) are cold-formed using multi-die progressive bending systems to ensure uniform curvature with minimal springback.
  4. Heat Treatment (where applicable): Solution annealing at 1050–1150°C followed by controlled cooling to relieve residual stresses and restore full austenitic microstructure. Duplex grades receive stabilization treatment at 900–1050°C.
  5. Surface Finishing: Electropolishing or mechanical polishing to achieve specified surface roughness, critical for minimizing fouling and maximizing convective heat transfer coefficients.
  6. Final Quality Control: Dimensional verification (OD, wall thickness, coil diameter tolerance ±1%), hydrostatic pressure testing (1.5× design pressure), radiographic inspection of welds (if applicable), and material certification per EN 10204 Type 3.1.

Applications

The primary application domain for these coil tubes is the evaporative condensing condenser system in thermal power stations, where they function as the heat exchange surface within the condensation unit. Additional applications include:

Design Considerations for Evaporative Condenser Systems

Based on the technical study of heat exchange coil design for power station evaporative condensers, the following engineering principles govern the coil tube configuration:

The coil tube geometry must be optimized to achieve maximum heat transfer surface area per unit volume while maintaining adequate air-side flow velocity for effective evaporative cooling. The spiral coil arrangement ensures uniform distribution of cooling water and promotes turbulent flow conditions, thereby enhancing the film coefficient on the water side. Critical design parameters include the coil pitch (typically 1.5–2.5× OD), the number of turns per bundle, and the orientation of the coil relative to the air flow direction to minimize aerodynamic resistance while maximizing wetted surface contact.

Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification systems:

Unique Selling Points