Stainless Steel Coil Tube (盘管) — Spray Cooling Heat & Mass Transfer Enhanced Series
1. Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed for high-efficiency heat exchange applications. This product line incorporates advanced surface geometry and material selection optimized for spray cooling (Spray Cooling) environments, where convective heat and mass transfer (Heat and Mass Transfer) between the tube surface and impinging liquid jets are maximized through carefully controlled surface roughness, coil curvature, and hydraulic configuration.
Based on experimental research into the thermal-hydraulic performance of coil tube surfaces under spray cooling conditions, this product achieves superior thermal efficiency compared to conventional straight-tube heat exchangers. The coiled geometry inherently promotes turbulence enhancement, boundary layer disruption, and uniform heat distribution across the tube perimeter, making it an ideal solution for demanding industrial cooling, refrigeration, and thermal management systems.
2. Material & Properties
2.1 Base Material Composition
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, with the following primary material options:
- 304 (UNS S30400): Carbon equivalent ≤ 0.08%, Chromium 18–20%, Nickel 8–10.5%, Manganese ≤ 2.0%. Excellent general corrosion resistance and formability.
- 316 (UNS S31600): Carbon equivalent ≤ 0.08%, Chromium 16–18%, Nickel 10–14%, Molybdenum 2–3%. Superior pitting and crevice corrosion resistance due to molybdenum addition.
- 316L (UNS S31603): Low-carbon variant of 316 (Carbon ≤ 0.03%), ideal for welded assemblies requiring maximum intergranular corrosion resistance.
- 321 (UNS S32100): Titanium-stabilized grade (Ti ≥ 5×C), suitable for elevated temperature applications up to 870°C.
- 310S (UNS S31008): High-temperature grade with Chromium 19–25% and Nickel 24–30%, offering exceptional oxidation resistance up to 1150°C.
2.2 Key Physical & Thermal Properties (304 Grade Reference)
- Density: 7.93 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Specific Heat Capacity: 500 J/(kg·K)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Electrical Resistivity: 72 × 10⁻⁶ Ω·m
- Magnetic Susceptibility: Non-magnetic (paramagnetic) in annealed condition
2.3 Mechanical Properties (Annealed Condition)
- Tensile Strength (UTS): ≥ 520 MPa
- Yield Strength (0.2% Offset): ≥ 205 MPa
- Elongation: ≥ 40%
- Hardness: ≤ 217 HB (Brinell)
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6 mm – Φ50.8 mm (1/4" – 2") | ASTM A213 / EN 10216-5 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / GB/T 14976 |
| Bend Radius (Minimum) | 3D – 10D (D = Outer Diameter) | ASME B31.3 |
| Coil Diameter | Φ100 mm – Φ2000 mm | Custom / Project-Specific |
| Coil Length | 5 m – 500 m (per coil) | Custom / Project-Specific |
| Surface Finish | Mill finish / Pickle & Polish / Electropolished (Ra ≤ 0.4 μm) | ASTM A967 / GB/T 8890 |
| Dimensional Tolerance | ±0.05 mm (OD), ±0.05 mm (Wall Thickness) | ASTM A213 Class 1 |
| Operating Temperature Range | −196°C to +870°C (grade-dependent) | ASME BPV Code |
| Maximum Operating Pressure | Up to 40 MPa (design-dependent) | ASME B31.3 / EN 13480 |
| End Form | Plain cut / Beveled / Threaded / Flanged / Weld-prepared | ASTM A907 |
| Delivery Condition | Coiled / Spooled / Bundled | ISO 15480 |
| Heat Treatment | Solution Annealing (1010–1150°C, water quench) | ASTM A213 |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Procurement: High-purity stainless steel seamless tubes or ERW (Electric Resistance Welded) tubes are sourced from certified mill suppliers, with full chemical and mechanical property verification prior to acceptance.
- Dimensional Verification & Inspection: Incoming tubes undergo ultrasonic testing (UT) per ASTM E1650, dimensional gauging, and visual inspection for surface defects.
- Coiling / Forming Operation: Straight tubes are precisely formed into the desired coil geometry using CNC-controlled coiling machines. The forming process maintains dimensional accuracy (±0.1 mm) and avoids material strain hardening or wall thinning. Multi-station bending with progressive die sets ensures uniform curvature without ovality exceeding 2%.
- Surface Preparation (for Spray Cooling Applications): Tubes intended for spray cooling heat exchange undergo controlled surface texturing or micro-roughness engineering to enhance nucleate boiling and droplet impingement heat transfer coefficients. Surface roughness parameters (Ra, Rz) are calibrated to optimize the balance between frictional pressure drop and thermal performance.
- Heat Treatment: Solution annealing is performed in a controlled atmosphere furnace (1010–1150°C) followed by rapid quenching to restore full austenitic microstructure, eliminate residual stresses from forming, and achieve maximum corrosion resistance.
- Pickling & Passivation: Chemical pickling removes oxide scale and contamination, followed by passivation treatment (nitric acid or citric acid immersion) to establish a stable chromium oxide passive film (ASTM A967).
- Final Inspection & Testing: Includes hydrostatic pressure testing (ASTM A213), dimensional verification, surface finish measurement, and optional eddy current testing (ECT) for internal defect detection.
- Packaging & Dispatch: Coils are wrapped in protective film, placed on wooden pallets or steel racks, and labeled with full traceability documentation.
4.2 Spray Cooling Optimization Features
Building upon experimental research into spray cooling heat and mass transfer characteristics on coil tube surfaces, the following design enhancements are incorporated:
- Optimized Coil Pitch: Spiral pitch is engineered to ensure uniform spray coverage and minimize shadowing effects between adjacent turns, promoting consistent heat flux distribution.
- Surface Micro-Structuring: Controlled surface roughness (Ra 0.8–3.2 μm) enhances droplet breakup and increases effective heat transfer area without excessive hydraulic penalty.
- Boundary Layer Disruption: The inherent curvature of the coil promotes secondary flow patterns (Dean vortices) that continuously renew the thermal boundary layer, significantly enhancing convective heat transfer coefficients (h) by 20–40% over straight tubes.
- Mass Transfer Enhancement: Improved vapor-liquid interaction at the coil surface facilitates efficient evaporation cooling, critical for high-heat-flux applications exceeding 100 kW/m².
5. Applications
5.1 Primary Application Domains
- Industrial Refrigeration & Air Conditioning: Evaporator and condenser coil assemblies for commercial refrigeration systems, chiller units, and heat pump systems where spray cooling provides compact, high-capacity heat rejection.
- Power Generation: Steam generator coils, condenser tubes, and economizer sections in combined cycle power plants and nuclear power facilities.
- Petrochemical & Process Industries: Heat exchanger coils in distillation columns, reactor cooling systems, and cryogenic process equipment handling aggressive chemical media.
- Food & Beverage Processing: Pasteurization coils, CIP (Clean-in-Place) compatible heat exchange systems, and hygienic fluid heating/cooling circuits (FDA/3-A Sanitary compliant).
- Pharmaceutical Manufacturing: High-purity process cooling, reactor jacket coils, and sterilization systems requiring electropolished surfaces (Ra ≤ 0.25 μm).
- Automotive & Aerospace: Engine cooling manifolds, fuel cooling coils, hydraulic system heat exchangers, and thermal management in electric vehicle battery cooling systems.
- Electronics Cooling: Immersion cooling loops and spray cooling manifolds for high-power computing, semiconductor fabrication equipment, and data center thermal management.
- Medical Equipment: MRI superconducting magnet cooling circuits, CT scanner heat exchangers, and dialysis machine thermal regulation systems.
5.2 Spray Cooling-Specific Applications
- High-flux electronic component cooling (heat fluxes > 200 kW/m²)
- Nuclear fuel element cooling systems
- Gas turbine blade internal cooling passages
- Compact heat exchangers for space-constrained installations
- Waste heat recovery systems with evaporative cooling
6. Quality Certifications & Standards Compliance
6.1 Product Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- CE Marking — European Conformity (PED 2014/68/EU for pressure equipment)
- TÜV / DNV — Third-party inspection and certification for offshore and marine applications
- EN 10204 — Type 3.1 Mill Test Certificates (MTC) with full chemical and mechanical data
- NACE MR0175 / ISO 15156 — Compliance for sour service environments (H₂S-containing media)
6.2 Applicable Standards
| Standard | Scope |
|---|---|
| ASTM A213 | Seamless Austenitic Stainless Steel Tubes for High-Temperature Service |
| ASTM A269 | Welded Austenitic Stainless Steel Tubing for Chemical and General Applications |
| ASTM A967 | Pickling and Passivating Stainless Steel Parts |
| EN 10216-5 | Non-Alloy and Alloy Steel Tubes for Heat Exchangers and Heat Generators |
| GB/T 14976 | Stainless Steel Seamless Tubes for Fluid Transport (Chinese National Standard) |
| ASME B31.3 | Process Piping Design Code |
| ASME BPV Section I | Boiler and Pressure Vessel Code |
| ISO 4320 | Stainless Steel Tubes for Heat Exchangers and Heat Generators |
6.3 Testing & Quality Assurance
- Hydrostatic Testing: All coils tested at 1.5× working pressure for minimum 30 seconds per ASTM A213
- Ultrasonic Testing (UT): Full-length inspection per ASTM E1650 for internal discontinuities
- Eddy Current Testing (ECT): Per ASTM E797 for surface and near-surface defect detection
- Spectroscopic Analysis: Optical Emission Spectroscopy (OES) for chemical composition verification
- Hardness Testing: Rockwell B / Vickers hardness per ASTM E18 / E92
- Intergranular Corrosion Testing: ASTM A262 Practice E (for stabilized and low-carbon grades)
- Heat Transfer Performance Verification: Bench testing of spray cooling efficiency against design specifications
7. Unique Selling Points
Research-Backed Thermal Performance: This coil tube product line is uniquely informed