Stainless Steel Coil Tube (Coiltube) for Cooling & Dehumidification Applications — Wenzhou Jixing Metal Materials Co., Ltd.
Product Catalog No.: 1310 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. (温州吉兴金属材料有限公司) | Classification: Literature & Technical Reference Series
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed specifically for use in air-conditioning, refrigeration, and industrial thermal management systems. This product is supplied in continuous coiled form, enabling seamless integration into heat exchanger assemblies, evaporator coils, condenser units, and dehumidification systems.
The coil tube is engineered to withstand prolonged exposure to corrosive environments, high-temperature differentials, and mechanical fatigue while maintaining dimensional accuracy and thermal conductivity. Its coiled geometry facilitates efficient heat transfer through optimized flow dynamics and compact spatial arrangement, making it a critical component in cooling and dehumidification coil thermal performance calculations.
The technical foundation of this product is informed by rigorous thermal hydraulic analysis, including the methodology outlined in Thermal Calculation of Cooling and Dehumidification Coils (《冷却除湿盘管的热工计算》), which provides the engineering framework for evaluating coil efficiency, airflow resistance, and moisture removal capacity under varying operating conditions.
2. Material Composition & Properties
2.1 Base Material Grades
The coil tube is manufactured from high-quality austenitic and duplex stainless steel grades, selected to balance corrosion resistance, mechanical strength, and thermal performance:
- AISI 304 (UNS S30408): The most widely used grade for general cooling and HVAC applications, offering excellent corrosion resistance and formability.
- AISI 316 (UNS S31608): Enhanced molybdenum content provides superior resistance to chlorides, making it ideal for coastal, marine, and chemical processing environments.
- AISI 316L (UNS S31603): Low-carbon variant suitable for welded assemblies requiring resistance to intergranular corrosion.
- AISI 321 (UNS S32100): Titanium-stabilized grade for high-temperature applications up to 900°C (1652°F).
- Duplex 2205 (UNS S31803): For demanding applications requiring high yield strength and resistance to stress corrosion cracking.
2.2 Mechanical Properties
| Property | Grade 304 | Grade 316 | Grade 316L | Duplex 2205 |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 485 | ≥ 550 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 170 | ≥ 450 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 45 | ≥ 25 |
| Thermal Conductivity (W/m·K @ 20°C) | 16.3 | 14.6 | 14.6 | 16.3 |
| Operating Temperature Range (°C) | −196 to 870 | −196 to 870 | −196 to 870 | −50 to 300 |
2.3 Chemical Composition (wt%)
| C | Si | Mn | P | S | Cr | Ni | N |
|---|---|---|---|---|---|---|---|
| ≤ 0.08 | ≤ 1.00 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | 18.00–20.00 | 8.00–10.50 | ≤ 0.10 |
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (1/8" – 1") |
| Wall Thickness (WT) | 0.3 mm – 2.0 mm (tolerance ±10%) |
| Coil Inner Diameter (Coil ID) | 200 mm – 600 mm |
| Tubular Length per Coil | Up to 500 m (continuous) |
| Surface Finish | Bright Annealed & Pickled (B&P), No. 4 Brushed, Mirror Polish (Ra ≤ 0.4 μm) |
| End Condition | Plain cut, Beveled, Flanged, or Threaded (upon request) |
| Dimensional Tolerance | OD: ±0.05 mm; WT: ±0.03 mm; Straightness: ≤ 0.5 mm/m |
| Helix Pitch | Customizable: 6 mm – 30 mm |
| Helix Diameter | Customizable: 10 mm – 100 mm |
| Packaging | Wooden pallet with moisture-proof wrapping; alternative bulk packaging available |
4. Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow adhering to international quality standards:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis to verify chemical composition compliance with ASTM and EN specifications.
- Slitting & Straightening: The strip is slit to precise width dimensions and straightened to eliminate residual curvature, ensuring uniform tube formation.
- Tube Forming (Seamless or Welded):
- Seamless Process: Strip is wound onto a mandrel and rolled into a tubular form, followed by resistance welding of the longitudinal seam.
- Welded Process: Edge-welding (ERW) or orbital TIG welding is employed to create a continuous tube with a fully fused seam.
- Heat Treatment (Annealing): Tubes are annealed at 1050°C–1150°C in a protective atmosphere (argon or vacuum) to relieve residual stresses, restore full solution-annealed microstructure, and achieve desired mechanical properties.
- Pickling & Passivation: Surface scale and oxide layers are removed via pickling acid baths (mixed HNO₃/HF), followed by passivation to restore the protective chromium oxide film (Cr₂O₃) for optimal corrosion resistance.
- Precision Coiling: The finished tube is coiled using numerically controlled coiling equipment to maintain consistent helix geometry, minimizing springback and ensuring dimensional repeatability.
- Final Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification (OD, WT, coil ID), hydrostatic pressure testing (typically at 1.5× working pressure), and optional eddy current or ultrasonic flaw detection.
5. Applications
5.1 Primary Application Domains
- Air Conditioning & HVAC Systems: Evaporator and condenser coils for commercial and industrial air conditioning units, chiller systems, and heat pump assemblies. The coiled geometry maximizes heat transfer surface area within compact footprints.
- Dehumidification Systems: Critical component in industrial dehumidifiers, precision air handling units, and pharmaceutical cleanroom HVAC systems where moisture control is essential.
- Refrigeration Equipment: Freezer coils, cold storage unit evaporators, and refrigeration compressor discharge line tubing.
- Food & Beverage Processing: Pasteurization heat exchangers, milk cooling coils, and food-grade refrigeration systems (316L grade for food contact compliance).
- Pharmaceutical & Medical Equipment: Sterilizable heat exchange coils in bioreactors, cleanroom air filtration systems, and medical gas delivery apparatus.
- Marine & Offshore Applications: Seawater cooling coils, marine air conditioning systems, and offshore platform HVAC units (316/Duplex 2205 grades for chloride resistance).
- Industrial Process Cooling: Chemical processing heat exchangers, polymer cooling lines, and industrial waste heat recovery systems.
- Solar Thermal Systems: Absorber tubes in evacuated tube solar collectors and solar water heating systems.
5.2 Thermal Performance Context
Based on the thermal calculation methodology for cooling and dehumidification coils, the coil tube's performance is characterized by the following parameters:
- Overall Heat Transfer Coefficient (U-value): Typically 25–60 W/m²·K depending on tube material, fluid type, and flow velocity.
- Heat Transfer Rate (Q): Q = U × A × ΔTlm, where ΔTlm is the log-mean temperature difference.
- Pressure Drop (ΔP): Calculated using the Darcy-Weisbach equation; optimized tube geometry minimizes ΔP while maximizing heat transfer.
- Dehumidification Capacity: Determined by the enthalpy difference between inlet and outlet air streams, with coil tube surface temperature below the dew point of the process air.
- Fin-to-Tube Efficiency (ηf): When fins are attached, the overall surface efficiency is calculated using the fin efficiency correlation for annular fins.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and adheres to the following international standards and certifications:
| Standard / Certification | Scope of Application |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing operations |
| ISO 14001:2015 | Environmental Management System certification |
| ASTM A213 / A269 | Standard specification for austenitic stainless steel seamless and welded tubing |
| ASTM A778 | Standard specification for cold-rolled austenitic stainless steel tube |
| EN 10216-5 | Seamless stainless steel tubes for general purposes |
| JIS G3446 | Stainless steel seamless tubes for general purposes (Japanese Industrial Standard) |
| GB/T 14976 / GB/T 13296 | Chinese national standards for stainless steel seamless tubes |
| ASME B31.3 / B31.9 | Pressure piping code compliance for process and refrigeration piping |
| NSF/ANSI 61 | Drinking water system components certification (for food-grade applications) |
| CE Marking | European Conformity marking for products sold within the European Economic Area |
7. Unique Selling Points
- Precision Coiled Geometry: Numerically controlled coiling ensures consistent helix pitch and diameter, enabling direct integration into heat exchanger assemblies without secondary forming operations, reducing fabrication costs by up to 30%.
- Multi-Grade Availability: Comprehensive material selection from 304 to Duplex 2205 addresses diverse corrosion environments and mechanical requirements within a single supply chain.
- Thermal Optimization: Product specifications are validated against established cooling and dehumidification coil thermal calculation methodologies, ensuring predictable and documented heat transfer performance.
- Customization Capability: Flexible customization of OD, wall thickness, coil diameter, helix pitch, surface finish, and end conditions to meet specific OEM and project requirements.
- Full Traceability: Every coil is accompanied by a mill test certificate (MTC) with heat number, chemical composition, mechanical test results, and dimensional verification data.
- Weld-Ready Surface Finish: Bright annealed and pickled surfaces eliminate the need for pre-welding cleaning, ensuring high-quality orbital or TIG weld joints in downstream assembly.
8. Ordering & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support for coil tube selection, including thermal performance modeling, material selection guidance, and application-specific engineering consultation. Custom quotations and sample coils are available upon request. Minimum order quantities (MOQ) vary by grade and specification; standard lead times are 15–25 business days for stocked grades and 30–45 business days for custom specifications.
Technical Note: For cooling and dehumidification coil applications, the selection of coil tube OD and wall thickness should be optimized in conjunction with fin spacing, tube pitch (staggered or in-line arrangement), and refrigerant-side flow velocity. The thermal calculation methodology referenced in this product literature should be used as a design guide, with actual performance validated through system-level testing under representative operating conditions.