Stainless Steel Coil Tube (Coiltube) — Calorimeter-Grade Heat Exchanger Product
Product Code: No. 252 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. and supplied in coiled configuration for downstream heat exchanger fabrication. This product is specifically designed and validated for use in calorimeter systems, refrigeration circuits, and high-performance thermal management applications where the working fluid includes refrigerants such as R134a (1,1,1,2-Tetrafluoroethane).
Based on extensive flow characteristic analysis and structural optimization research, the coil tube geometry has been refined to achieve superior heat transfer efficiency, minimal pressure drop, and enhanced resistance to flow-induced vibration under a wide range of operating conditions. The product represents a synthesis of metallurgical excellence and thermal-fluid dynamic engineering, making it a preferred choice for OEM manufacturers of refrigeration equipment, air conditioning systems, and industrial calorimetric instrumentation.
2. Material & Properties
2.1 Base Material
- Primary Grade: Austenitic Stainless Steel — AISI 304 (UNS S30400) and AISI 316 (UNS S31600)
- Alternative Grades: 316L (UNS S31603), 321 (UNS S32100), and 347 (UNS S34700) available upon specification
- Surface Condition: Bright Annealed (BA) or Pickled and Passivated (2B finish)
2.2 Key Physical and Mechanical Properties
| Property | Specification (AISI 304) | Specification (AISI 316) |
|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 |
| Elongation (%) | ≥ 40 | ≥ 40 |
| Thermal Conductivity at 20°C (W/m·K) | 16.3 | 14.6 |
| Density (kg/m³) | 8.00 | 8.03 |
| Corrosion Resistance (Pitting) | Good (general environments) | Excellent (chloride-rich environments) |
| Operating Temperature Range (°C) | −196 to +870 | −196 to +870 |
2.3 Metallurgical Features
- Full solution-annealed microstructure ensuring maximum ductility and fatigue resistance
- Low carbon content variants (304L, 316L) available to prevent intergranular sensitization during welding
- Non-magnetic or weakly magnetic in annealed condition (per ASTM A240)
- Excellent resistance to stress corrosion cracking (SCC) in dilute chloride solutions
3. Specifications
3.1 Dimensional Specifications
| Parameter | Range / Value | Tolerance |
|---|---|---|
| Outer Diameter (OD) | φ3.0 mm – φ25.4 mm | ±0.05 mm (OD < 10 mm); ±0.10 mm (OD ≥ 10 mm) |
| Wall Thickness | 0.3 mm – 1.5 mm | ±10% of nominal |
| Coil Inner Diameter (Coil ID) | φ100 mm – φ600 mm | ±5 mm |
| Coil Length per Spool | Up to 3,000 m (continuous) | — |
| Minimum Bend Radius | ≥ 3× OD | — |
| Surface Roughness (Ra) | ≤ 0.4 μm (electropolished); ≤ 0.8 μm (BA finish) | — |
| Pressure Rating (at 20°C) | Up to 4.0 MPa (depending on OD/WT) | Per ASME B31.3 |
3.2 Performance Specifications (R134a Flow Optimization)
| Performance Parameter | Target Value |
|---|---|
| Heat Transfer Coefficient Enhancement | Up to 30% improvement over baseline straight-tube geometry |
| Pressure Drop (per meter, R134a at 1.5 m/s) | ≤ 850 Pa/m (optimized coil pitch) |
| Flow Uniformity Index | ≥ 0.95 across multi-pass configurations |
| Vibration Threshold Frequency | ≥ 120 Hz (first natural frequency) |
| Reynolds Number Operating Range | Re = 2,000 – 50,000 (laminar to fully turbulent) |
4. Manufacturing Process
The coil tube is produced through an integrated, multi-stage manufacturing process designed to ensure dimensional precision, metallurgical integrity, and thermal performance optimization:
- Steel Coil Receiving and Inspection: Hot-rolled stainless steel strip is received from certified mills and subjected to incoming chemical analysis (per ASTM A276) and mechanical property verification.
- Cold Rolling: The strip is cold-rolled to precise thickness tolerances using controlled reduction ratios to achieve desired mechanical properties and surface finish.
- Welding (Seam Formation): Precision TIG (Tungsten Inert Gas) welding or laser welding is employed to form the longitudinal seam, producing a fully fused, watertight joint with minimal heat-affected zone (HAZ).
- Coiling (Continuous Forming): The welded tube is continuously formed into a coil using a multi-roller coiling machine with servo-controlled tension to prevent ovality and wrinkling.
- Heat Treatment (Annealing): Solution annealing at 1,050–1,150°C followed by controlled cooling (air or water quench) to restore full austenitic structure and relieve residual stresses.
- Pickling and Passivation: Immersion in a controlled nitric/hydrofluoric acid bath to remove oxide scale and form a protective chromium oxide passive layer.
- Dimensional Inspection: Each coil is verified for OD, wall thickness, ovality, and length using ultrasonic thickness gauges, laser OD scanners, and mechanical gauges.
- Pressure Testing: Hydrostatic or pneumatic pressure testing per ASME B31.3 at 1.5× the design pressure, held for a minimum of 30 seconds with zero leakage tolerance.
- Coil Structure Optimization Validation: Prototype coils are subjected to R134a flow characterization testing (pressure drop, heat transfer coefficient, flow visualization) to validate the optimized coil pitch, bend radius, and helical geometry parameters.
5. Applications
- Calorimetric Systems: Primary application — high-precision calorimeter coil tubes for refrigerant flow measurement and thermal energy quantification in HVAC/R research and industrial testing.
- Refrigeration Heat Exchangers: Evaporators, condensers, and subcoolers in commercial and industrial refrigeration systems using R134a, R404A, R410A, and other refrigerants.
- Air Conditioning Systems: Compact coil assemblies for chillers, heat pumps, and rooftop units.
- Process Engineering: Fluid-to-fluid heat exchangers in chemical processing, pharmaceutical manufacturing, and food & beverage pasteurization.
- Cryogenic Applications: Low-temperature service in liquid nitrogen (LN2) and liquid argon (LAr) handling systems.
- Marine and Offshore: Corrosion-resistant heat exchange coils in seawater cooling circuits (316L grade).
- Medical and Laboratory Equipment: Precision temperature control coils in analytical instruments and medical device manufacturing.
6. Quality Certifications & Standards Compliance
| Standard / Certification | Description |
|---|---|
| ASTM A269 / A270 | Standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel tubing |
| ASTM A240 | Standard specification for chromium and chromium-nickel stainless steel plate, sheet, and strip |
| EN 10216-5 | Non-alloy and alloy steel tubes for technical purposes — austenitic stainless steel |
| ISO 9001:2015 | Quality Management System certification for manufacturing operations |
| ISO 14001:2015 | Environmental Management System certification |
| ASME B31.3 | Process piping design and fabrication compliance |
| CE Marking (PED 2014/68/EU) | Pressure Equipment Directive compliance for EU market access |
| NACE MR0175 / ISO 15156 | Materials for use in H₂S-containing environments (where applicable) |
| Third-Party Inspection (TPI) | Available upon request — SGS, Bureau Veritas, or TÜV Rheinland |
7. Unique Selling Points
Flow-Optimized Coil Geometry: Unlike conventional coil tubes, this product line incorporates structurally optimized helical parameters — coil pitch, bend radius, and helix angle — derived from rigorous R134a flow characteristic analysis. The result is a demonstrably improved heat transfer-to-pressure-drop ratio, translating directly into energy efficiency gains in end-use systems.
- Continuous-Length Supply: Up to 3,000 meters per coil spool eliminates the need for field splicing, reducing leak points and installation labor.
- Full Traceability: Each coil is batch-traceable to the originating mill heat number, with complete chemical composition and mechanical test data provided.
- Custom Geometry Available: Coil pitch, OD, wall thickness, and coil inner diameter can be customized to match specific OEM heat exchanger design requirements.
- Corrosion Resistance: Inherent resistance to atmospheric, aqueous, and many chemical environments ensures long service life with minimal maintenance.
- Weldability: Excellent welding characteristics facilitate downstream fabrication into complex coil assemblies without degradation of mechanical or corrosion properties.
- Regulatory Compliance: Pre-certified to international standards, reducing time-to-market for OEM integrators operating in regulated industries.
8. Ordering Information
Customers are advised to specify the following parameters when placing orders:
- Stainless steel grade (e.g., 304, 316, 316L)
- Outer diameter (OD) and wall thickness (WT)
- Coil inner diameter (Coil ID)
- Required coil length
- Surface finish requirement (BA, 2B, electropolished, matte)
- Intended application and operating fluid (e.g., R134a, water, steam)
- Maximum operating pressure and temperature
- Applicable standards and required certifications
Wenzhou Jixing Metal Materials Co., Ltd. — Precision Stainless Steel Coil Tubes for Thermal Systems