Stainless Steel Planar Coil Tube (Coiltube) — Technical Product Specification

1. Product Overview

The Stainless Steel Planar Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. in the form of a continuous, flat-arranged coil configuration. Unlike conventional straight or helical coil tubing, the planar coil tube features a flattened geometry that optimizes the surface-to-volume ratio, thereby enhancing thermal transfer efficiency and hydraulic performance. This product is particularly suited for heat exchange applications where compact footprint and superior fluid dynamics are critical design parameters.

The planar coil geometry has been the subject of extensive experimental research, notably documented in the study "Experimental Study on the Hydraulic Characteristics of Planar Coil Tubes", which validated the unique pressure drop behavior, flow distribution uniformity, and Reynolds number dependencies specific to this configuration. The findings from such research have directly informed the design optimization and quality assurance protocols employed in the manufacturing of this product.

2. Material & Properties

The Coiltube is fabricated from high-grade austenitic stainless steel, with the following material specifications available:

• 304 Stainless Steel (UNS S30400): General-purpose grade with excellent corrosion resistance and formability. Chromium (Cr) content ≥ 18%, Nickel (Ni) content ≥ 8%.
• 316 Stainless Steel (UNS S31600): Enhanced corrosion resistance due to the addition of Molybdenum (Mo) 2–3%, suitable for aggressive chemical and marine environments.
• 321 Stainless Steel (UNS S32100): Titanium-stabilized grade with superior resistance to intergranular corrosion at elevated temperatures.
• 316L Stainless Steel (UNS S31603): Low-carbon variant of 316 with carbon content ≤ 0.03%, ideal for welded assemblies requiring high resistance to sensitization.

Mechanical Properties (Typical Values for 304/316 Grade)

• Tensile Strength: 515–720 MPa
• Yield Strength (0.2% Offset): 205–310 MPa
• Elongation at Break: ≥ 40%
• Hardness (Brinell): 140–210 HB
• Thermal Conductivity (at 20°C): 14.5–16.3 W/(m·K)
• Thermal Expansion Coefficient (20–100°C): 16–18 × 10⁻⁶ /°C

Hydraulic Performance Characteristics

Based on experimental research into planar coil tube hydraulics, the following performance characteristics are notable:

• Planar coil configurations exhibit a lower pressure drop compared to conventional helical coils of equivalent total length, owing to the reduced centrifugal acceleration forces on the fluid.
• The flow distribution across parallel planar coil channels demonstrates improved uniformity, with measured deviation typically below 5% at Reynolds numbers (Re) between 1,000 and 100,000.
• The friction factor in planar coils follows a modified Darcy-Weisbach relationship, with empirical corrections applied for the flattened cross-sectional geometry.
• Enhanced turbulent mixing at the coil bends contributes to a higher Nusselt number (Nu), improving convective heat transfer coefficients by 15–30% relative to straight tube baselines.

3. Specifications

Parameter	Specification / Range	Standard Reference
Outer Diameter (OD)	6 mm – 50.8 mm (¼" – 2")	ASTM A554 / A556
Wall Thickness	0.5 mm – 4.0 mm	ASTM A554
Coil Diameter	100 mm – 2,000 mm	Custom
Coil Length	1 m – 100 m (continuous)	Custom
Flattened Cross-Section Ratio	1.0 : 1.0 – 1.0 : 3.0	Custom
Surface Finish	2B, BA (Bright Annealed), No. 4 Brushed, Electropolished (Ra ≤ 0.4 μm)	ASTM A480
Operating Temperature Range	-196°C to +870°C	Material-dependent
Operating Pressure (Design)	Up to 4.0 MPa (580 PSI)	ASME B31.3
Welding Process	Orbital TIG (Tungsten Inert Gas), Pulse Arc Welding	ASME BPV Section VIII
End Condition	Plain, Beveled, Threaded, Flanged, Socket-Welded	Custom
Passivation Treatment	ASTM A967 (Nitric Acid or Citric Acid based)	ASTM A967
Packaging	Wooden crate / Export-grade pallet with desiccant	ISO 4180

4. Manufacturing Process

The production of the Stainless Steel Planar Coil Tube follows a rigorous, multi-stage process to ensure dimensional accuracy, metallurgical integrity, and hydraulic performance:

1. Raw Material Inspection: Incoming stainless steel strip or round bar is verified for chemical composition (via Optical Emission Spectroscopy, OES), mechanical properties, and surface condition in accordance with the purchase specification.
2. Coil Winding: The stainless steel tube is precisely wound into the planar coil geometry using CNC-controlled winding machines. Tension and curvature radii are monitored in real time to prevent ovalization or residual stress accumulation.
3. Flattening / Forming (if applicable): For planar coil variants requiring a flattened cross-section, the tube undergoes cold flattening through calibrated roller dies, maintaining wall thickness uniformity within ±5% tolerance.
4. Welding: Where continuous coil integrity requires joining, orbital TIG welding is employed with argon gas shielding (99.995% purity). Weld parameters are optimized to minimize Heat-Affected Zone (HAZ) sensitization.
5. Stress Relief Annealing: The formed coil is subjected to solution annealing at 1050–1150°C followed by controlled cooling to relieve residual stresses and restore full austenitic microstructure.
6. Pickling and Passivation: The coil undergoes acid pickling to remove oxide scale, followed by passivation treatment per ASTM A967 to establish a protective chromium oxide film.
7. Surface Finishing: Final surface treatment (brushing, polishing, or electropolishing) is applied to achieve the specified surface roughness (Ra) and aesthetic finish.
8. Non-Destructive Testing (NDT): Each coil lot undergoes visual inspection (VT), dye penetrant testing (PT) per ASTM E709, and hydrostatic pressure testing at 1.5× the design pressure for a minimum dwell time of 30 seconds.
9. Dimensional Verification: Coordinate Measuring Machine (CMM) or laser scanning is used to verify coil diameter, pitch accuracy, and overall geometry within specified tolerances.
10. Packaging and Dispatch: The finished product is wrapped in protective film, placed in export-grade wooden crates, and shipped with full documentation including Mill Test Certificates (MTC).

5. Applications

The Stainless Steel Planar Coil Tube is deployed across a wide range of industrial applications where compact heat exchange, corrosion resistance, and hydraulic efficiency are paramount:

• Air Conditioning and Refrigeration (HVAC): Evaporator and condenser coils for commercial and industrial refrigeration systems, where the planar geometry maximizes heat transfer area within a constrained envelope.
• Automotive Industry: Radiator cores, intercoolers, and oil coolers for passenger vehicles, commercial trucks, and heavy machinery.
• Heat Exchangers: Compact heat exchanger bundles in chemical processing plants, power generation facilities, and petrochemical refineries.
• Food and Beverage Processing: Pasteurization equipment, CIP (Clean-in-Place) systems, and beverage chiller coils where sanitary-grade stainless steel is mandatory.
• Pharmaceutical Equipment: Reactor cooling coils, distillation column condensers, and GMP-compliant processing equipment requiring electropolished surfaces.
• Marine and Offshore Engineering: Seawater heat exchangers, ballast water treatment systems, and offshore platform cooling circuits where 316/316L grades provide chloride resistance.
• Solar Thermal Systems: Concentrated solar power collectors and solar water heating systems leveraging the enhanced surface-to-volume ratio of planar coils.
• Industrial Process Heating and Cooling: Polymer extrusion barrel cooling, metalworking quenching systems, and chemical reactor temperature control loops.

6. Quality Certifications

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework backed by the following certifications and standards compliance:

• ISO 9001:2015 — Quality Management Systems certification, ensuring consistent product quality and continuous improvement.
• ISO 14001:2015 — Environmental Management Systems certification, demonstrating commitment to sustainable manufacturing practices.
• ISO 45001:2018 — Occupational Health and Safety Management Systems certification.
• ASME (American Society of Mechanical Engineers) — Fabrication in compliance with ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, where applicable.
• EN 10204 3.1 — Third-party inspection and testing certificates available upon request.
• ASTM / AISI Compliance — All materials conform to applicable ASTM International standards for chemical composition, mechanical properties, and dimensional tolerances.
• PED (Pressure Equipment Directive 2014/68/EU) — CE marking available for products intended for the European Economic Area (EEA) market.
• Mill Test Certificates (MTC / EN 10204 2.2/3.1) — Provided with every shipment, documenting heat numbers, chemical analysis, mechanical test results, and traceability.

7. Unique Selling Points

Planar Geometry Advantage: The flat-coil configuration provides a superior surface-to-volume ratio compared to conventional round coils, delivering 15–30% higher convective heat transfer coefficients (as validated by experimental hydraulic studies) while occupying a more compact installation footprint.

• Customizable Geometry: Coil diameter, pitch, length, and cross-sectional profile are fully customizable to meet specific application requirements, enabling optimized integration into existing systems.
• Full Traceability: Every coil is traceable from raw material mill certificate through final inspection, ensuring complete supply chain transparency.
• Multi-Grade Availability: Products are available in 304, 316, 316L, 321, and other specialty grades to address diverse corrosion and temperature requirements.
• Hydraulically Optimized Design: Informed by peer-reviewed experimental research on planar coil hydraulics, the product design minimizes pressure drop and maximizes flow uniformity across the coil length.
• Surface Quality: Electropolished finishes achieving Ra ≤ 0.4 μm are available for sanitary, pharmaceutical, and food-grade applications, reducing bacterial adhesion and facilitating CIP processes.
• Export-Grade Quality: With ISO 9001 certification and PED compliance, the product meets international standards for quality, safety, and regulatory acceptance.
• Competitive Lead Times: Leveraging advanced CNC winding and forming capabilities, the manufacturer offers reduced production lead times compared to traditional coil fabrication methods.

8. Technical Notes

When specifying or ordering the Stainless Steel Planar Coil Tube, customers should provide the following information to ensure optimal product selection:

1. Required tube outer diameter and wall thickness
2. Desired coil diameter and total coil length
3. Material grade (e.g., 304, 316L) and surface finish requirement
4. Operating conditions: fluid type, temperature range, and maximum operating pressure
5. Applicable standards or codes (e.g., ASME, EN, PED)
6. End connection type (plain, threaded, flanged, etc.)
7. Required certifications and documentation (MTC, EN 10204 3.1, etc.)

For detailed technical consultations, custom engineering support, or quotation requests, please contact Wenzhou Jixing Metal Materials Co., Ltd. directly.