Stainless Steel Coil Tube for Water-Cooled Surface Condensers
1. Product Overview
The Stainless Steel Coil Tube (product reference: JX-CT-1339) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product specifically designed for application in water-cooled surface condensers and heat exchanger assemblies. This coil tube is formed from high-grade austenitic stainless steel strip and is wound into a helical configuration that maximizes heat transfer surface area within a compact volumetric envelope.
The product is developed in alignment with advanced thermal-hydraulic research methodologies, including the Coil Surface Average Temperature Method (CSATM) for calculating wet-condition performance of surface condensers. This engineering approach ensures that the coil tube geometry is optimized for efficient latent and sensible heat exchange under both dry and condensing (wet) operating regimes.
Unique Selling Points
- Helical coil geometry provides superior heat transfer coefficients compared to straight-tube configurations, achieving up to 25–35% enhanced thermal performance due to induced secondary flow patterns and turbulence intensification.
- Corrosion-resistant austenitic stainless steel construction ensures long-term durability in aggressive water-cooling environments containing chlorides, sulfates, and dissolved oxygen.
- Manufactured to precise dimensional tolerances to ensure uniform heat transfer surface temperature distribution, as validated by the Coil Surface Average Temperature Method.
- Compact volumetric design reduces installation footprint while maintaining high thermal capacity.
2. Material & Properties
The coil tube is fabricated from austenitic stainless steel strips conforming to international standards. The primary material grades available include:
- SAE 304 / AISI 304 (UNS S30408): General-purpose austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Contains approximately 18% Chromium and 8% Nickel.
- SAE 316 / AISI 316 (UNS S31608): Enhanced corrosion resistance grade with 2–3% Molybdenum addition, suitable for environments with elevated chloride concentrations.
- SAE 316L (UNS S31603): Low-carbon variant of 316 grade with carbon content ≤0.03%, providing superior resistance to intergranular corrosion in welded assemblies.
Mechanical and Thermal Properties
| Property | SAE 304 | SAE 316 | SAE 316L |
|---|---|---|---|
| Density (kg/m³) | 8,000 | 8,000 | 8,000 |
| Thermal Conductivity (W/m·K) at 20°C | 16.3 | 14.6 | 14.6 |
| Specific Heat (kJ/kg·K) at 20°C | 500 | 500 | 500 |
| Young's Modulus (GPa) | 193 | 193 | 193 |
| Tensile Strength (MPa) | ≥515 | ≥515 | ≥485 |
| Yield Strength (MPa) | ≥205 | ≥205 | ≥170 |
| Elongation (%) | ≥40 | ≥40 | ≥40 |
| Maximum Service Temperature (°C) | 870 | 870 | 870 |
| Chromium Content (%) | 18.0–20.0 | 16.0–18.0 | 16.0–18.0 |
| Nickel Content (%) | 8.0–10.5 | 10.0–14.0 | 10.0–14.0 |
| Molybdenum Content (%) | — | 2.0–3.0 | 2.0–3.0 |
| Carbon Content (%) | ≤0.08 | ≤0.08 | ≤0.03 |
3. Specifications
| Parameter | Specification |
|---|---|
| Product Designation | JX-CT-1339 Series |
| Product Form | Helical Coil Tube (Continuous Spiral Winding) |
| Tube Outer Diameter (OD) | 6.0 mm – 25.4 mm (customizable) |
| Tube Wall Thickness | 0.3 mm – 1.0 mm |
| Coil Pitch (Center-to-Center Spacing) | 12.0 mm – 40.0 mm |
| Coil Outer Diameter | 50 mm – 500 mm |
| Coil Length (Developed) | Up to 10,000 mm (custom orders available) |
| Surface Finish | Mirror Polish (Ra ≤ 0.1 μm), Satin Finish (Ra ≤ 0.4 μm), or As-Rolled |
| Dimensional Tolerance (OD) | ±0.05 mm |
| Dimensional Tolerance (Pitch) | ±0.2 mm |
| Operating Pressure | Up to 1.6 MPa (design dependent) |
| Operating Temperature Range | −196°C to +400°C |
| Winding Direction | Clockwise (CW) or Counter-Clockwise (CCW) |
| End Forming | Open, Flanged, or Welded Closure |
4. Manufacturing Process
4.1 Raw Material Preparation
High-purity austenitic stainless steel strip is sourced from certified mills with full chemical composition verification. Incoming material undergoes visual inspection, dimensional measurement, and spectroscopic analysis (OES) to confirm grade compliance before entering production.
4.2 Cold Forming and Coil Winding
The coil tube is produced through a precision cold-forming process:
- Strip Feeding: Stainless steel strip is fed into a hydraulic or servo-controlled winding machine.
- Tube Formation: The flat strip is progressively rolled into a circular tube cross-section via a series of calibrated rollers (roll-forming process), achieving the target outer diameter and wall thickness without welding in the tube body.
- Helical Winding: The formed tube is wound onto a precision mandrel in a continuous helical pattern at a controlled pitch, using CNC-guided motion to maintain uniform spacing and concentricity.
- Welded Seam (if applicable): For seamless tube construction, the strip edges are overlapped and continuously welded using Laser Welding (LTW) or High-Frequency Induction Welding (HF), followed by internal and external finishing to smooth the weld bead.
4.3 Post-Forming Heat Treatment
Following winding, the coil tube undergoes solution annealing at 1050°C ± 25°C in a protective atmosphere (argon or vacuum), followed by rapid quenching. This process:
- Relieves residual stresses introduced during cold forming
- Restores full austenitic microstructure for optimal corrosion resistance
- Eliminates carbide precipitation at grain boundaries
4.4 Surface Treatment
Depending on application requirements, the coil tube receives one of the following surface treatments:
- Pickling and Passivation: Acid bath treatment (nitric/hydrofluoric acid blend) to remove oxide scale and form a protective chromium oxide passive layer.
- Mechanical Polishing: Rotary buffing or vibratory finishing to achieve mirror or satin surface finishes.
- Electrolytic Polishing: Electrochemical dissolution to achieve ultra-smooth surfaces (Ra ≤ 0.1 μm) with enhanced passive film integrity.
4.5 Quality Inspection
Each production lot undergoes comprehensive inspection including:
- Visual examination for surface defects, weld imperfections, and geometric irregularities
- Dimensional verification using coordinate measuring machines (CMM) and laser scanners
- Helium leak testing at 10⁻⁹ mbar·L/s sensitivity for pressure-retaining applications
- Hydrostatic pressure testing at 1.5× working pressure
- Chemical composition verification via X-Ray Fluorescence (XRF) spectrometry
- Hardness testing (Rockwell B scale) to confirm heat treatment effectiveness
5. Applications
The JX-CT-1339 Stainless Steel Coil Tube is engineered for demanding thermal management applications, with primary deployment in the following sectors:
5.1 Water-Cooled Surface Condensers
This is the primary design application. The coil tube serves as the core heat transfer element in surface condensers used in:
- Power generation plants (thermal and nuclear)
- Industrial refrigeration and air conditioning systems
- Chemical process cooling and condensation duties
5.2 Heat Exchanger Assemblies
The helical coil configuration provides compact, high-efficiency heat exchange in shell-and-coil, plate-and-coil, and custom heat exchanger designs operating under wet (condensing) conditions.
5.3 Additional Applications
- Pharmaceutical and biotechnology process cooling systems
- Food and beverage industry pasteurization and sterilization equipment
- Marine cooling systems (seawater service with 316/316L grade)
- Automotive and aerospace thermal management components
- Solar thermal energy collection systems
- Petroleum and natural gas processing
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems ensuring product conformance to international standards:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System Certification |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health and Safety Management |
| ASTM A213 / A269 | Standard Specification for Stainless Steel Tubing |
| ASME B31.3 | Process Piping Design Compliance |
| EN 10216-5 | European Standard for Stainless Steel Tubes for Heat Exchangers |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes |
| CE Marking | European Conformity for Pressure Equipment Directive (PED 2014/68/EU) |
| NSF/ANSI 61 | Drinking Water System Components Compliance (for potable water applications) |
| 3-A Sanitary Standards | Food Industry Hygienic Design Compliance |
Material Traceability
Each coil tube lot is accompanied by a full material traceability document including mill test certificates (MTC/EN 10204 Type 3.1), heat number identification, chemical analysis reports, mechanical test results, and heat treatment records, ensuring complete supply chain transparency and regulatory compliance.
7. Thermal Performance Characteristics
Based on research methodology utilizing the Coil Surface Average Temperature Method (CSATM), the thermal performance of this coil tube under wet condensing conditions can be characterized by the following design parameters:
- Overall Heat Transfer Coefficient (U): 800–1,500 W/m²·K (dependent on fluid velocities, coil geometry, and operating conditions)
- Heat Transfer Enhancement Factor: 1.25–1.35 relative to equivalent straight-tube configurations
- Pressure Drop: Optimized through pitch-to-diameter ratio selection to balance thermal performance against pumping power requirements
- Wet Condition Stability: Maintains uniform heat transfer coefficient distribution across the coil surface under condensing film conditions, as validated by the average temperature method
8. Ordering Information and Customization
Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil tube solutions. Customers may specify:
- Material grade (304, 316, 316L, or special alloys)
- Tube outer diameter and wall thickness
- Coil pitch and overall coil dimensions
- Surface finish requirements
- End forming and connection type
- Special coatings or additional surface treatments
- Custom heat treatment specifications
Minimum order quantities and lead times are available upon request. Technical consultation and thermal performance simulation services are provided to optimize coil tube design for specific application requirements.