Stainless Steel Coil Tube (Coiltube) — Single Coil / Double Fan Air Conditioning System
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Product Serial No.: 981 | Classification: Technical Literature & Engineering Application
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered tubular product specifically designed for use in single-coil and double-fan air conditioning (HVAC) systems. This product is integral to the thermal exchange and air distribution components of modern building climate control infrastructure, where it serves as the primary medium for heat transfer between refrigerant and ambient air.
Based on the engineering study documented in the EnergyPlus simulation framework — specifically the modeling of "Single Coil, Double Fan Air Conditioning Systems" — this Coiltube product has been validated for its performance characteristics in both steady-state and dynamic thermal environments. The product is manufactured to meet the stringent demands of commercial, industrial, and residential HVAC applications where long-term durability, corrosion resistance, and thermal efficiency are paramount.
The Coiltube is supplied in a continuous coil configuration, enabling downstream processors to form it into air handler coils, condenser tubes, evaporator coils, and fan housing structural elements with minimal waste and maximum material utilization.
2. Material Composition & Properties
2.1 Base Alloy
The Coiltube is fabricated from austenitic stainless steel, predominantly conforming to the following grades:
- ASTM A269 / ASME SA-269 Grade 304 (UNS S30400) — General-purpose corrosion-resistant alloy with excellent formability
- ASTM A269 / ASME SA-269 Grade 316 (UNS S31600) — Enhanced chloride resistance for marine and chemical environments
- ASTM A269 / ASME SA-269 Grade 316L (UNS S31603) — Low-carbon variant for welded applications requiring resistance to intergranular corrosion
2.2 Chemical Composition (Typical — Grade 304)
| Element | Specification | Typical Value (%) |
|---|---|---|
| Carbon (C) | Max | 0.08 |
| Manganese (Mn) | Max | 2.00 |
| Phosphorus (P) | Max | 0.045 |
| Sulfur (S) | Max | 0.030 |
| Chromium (Cr) | — | 18.00 – 20.00 |
| Nickel (Ni) | — | 8.00 – 10.50 |
| Iron (Fe) | Balance | — |
2.3 Mechanical Properties
| Property | Specification (Annealed Condition) |
|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa (75,000 psi) |
| Yield Strength (0.2% Offset) | ≥ 205 MPa (30,000 psi) |
| Elongation (50 mm gauge length) | ≥ 40% |
| Hardness (Brinell) | ≤ 217 HB |
| Density | 8.0 g/cm³ |
| Thermal Conductivity (20°C) | 16.3 W/(m·K) |
| Thermal Conductivity (100°C) | 21.5 W/(m·K) |
| Specific Heat (20°C) | 0.50 J/(g·K) |
| Thermal Expansion (20–100°C) | 17.3 × 10⁻⁶ /°C |
2.4 Corrosion Resistance
- Excellent resistance to atmospheric corrosion and mild aqueous environments
- Grade 316 variants provide superior resistance to chlorides, acids, and marine atmospheres
- Passive chromium oxide film (Cr₂O₃) provides self-healing surface protection
- Suitable for continuous operation in temperatures ranging from cryogenic to 870°C (1600°F)
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Serial No. | 981 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Material Grade | ASTM A269 Grade 304 / 316 / 316L |
| Tube Form | Continuous Coil (Coiled Length) |
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (1/4" – 1") |
| Wall Thickness | 0.30 mm – 1.50 mm |
| Coil Inner Diameter (Coil ID) | 150 mm – 400 mm |
| Coil Length per Spool | 50 m – 300 m (customizable) |
| Surface Finish | Bright Annealed (BA), No. 4 Brushed, or 2B |
| Manufacturing Method | Seamless / Welded (ERW / TIG) |
| Tolerance (OD) | ±0.10 mm |
| Tolerance (Wall Thickness) | ±10% of nominal |
| Operating Temperature Range | -196°C to +870°C (-320°F to +1600°F) |
| Maximum Working Pressure | Up to 25 MPa (3,625 psi), grade-dependent |
| Standards Compliance | ASTM A269, ASME SA-269, EN 10217-7, GB/T 12771 |
4. Manufacturing Process
4.1 Raw Material Selection & Incoming Inspection
High-purity stainless steel wire rod or strip, conforming to the specified alloy grade, is procured from certified mills. Each batch undergoes spectrographic analysis to verify chemical composition and mechanical test coupons for tensile and hardness validation prior to processing.
4.2 Cold Drawing / Seamless Forming
- Seamless Process: Hot-rolled billets are pierced and cold-drawn through successive die sets to achieve precise OD and wall thickness dimensions with zero weld seam, providing superior pressure containment.
- Welded Process: Precision-cut strip is formed into a tube blank via roll forming, then welded using either Electro Resistance Welding (ERW) for high-volume production or Tungsten Inert Gas (TIG) welding for premium applications requiring clean, high-integrity welds.
4.3 Heat Treatment (Solution Annealing)
Tubes are solution-annealed at 1050°C – 1150°C in a controlled atmosphere furnace to:
- Dissolve carbides and restore full austenitic microstructure
- Eliminate residual stresses from cold working
- Maximize corrosion resistance and ductility
4.4 Precision Sizing & Straightening
Annealed tubes pass through multi-die sizing machines to achieve final dimensional tolerances. Straightening is performed via rotary or roller straighteners to ensure geometric uniformity prior to coiling.
4.5 Surface Finishing
- Pickling: Removal of oxide scale using controlled acid baths (HNO₃/HF blend)
- Passivation: Application of nitric acid to enhance the protective chromium oxide layer
- Precision Cleaning: Ultrasonic or chemical cleaning to remove residual contaminants
4.6 Coiling & Packaging
Finished tubes are coiled onto protective cores using automated coiling machines that maintain consistent tension to prevent deformation. Each coil is wrapped with moisture-barrier film, secured with steel strapping, and labeled with full traceability documentation including heat number, grade, dimensions, and test certificates.
5. Applications
5.1 HVAC & Air Conditioning Systems (Primary Application)
As documented in the EnergyPlus simulation study on single-coil and double-fan air conditioning systems, this Coiltube product serves critical functions in:
- Evaporator Coils: Heat absorption from indoor air via refrigerant evaporation within the tube structure
- Condenser Coils: Heat rejection to outdoor air in both single-fan and dual-fan configurations
- Air Handler Units (AHU): Integration into commercial air handling systems for precise temperature and humidity control
- Heat Recovery Systems: Energy-efficient heat exchange between supply and exhaust air streams
- VAV (Variable Air Volume) Systems: Ducted coil assemblies for zone-level climate control
5.2 Additional Industrial Applications
- Refrigeration and cryogenic systems
- Automotive and marine HVAC components
- Medical equipment fluid transfer
- Food and beverage processing piping
- Pharmaceutical manufacturing systems
- Solar thermal collectors
- Industrial heat exchangers and condensers
- Precision instrumentation and sensor housings
6. Quality Certifications & Testing
6.1 Manufacturing Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health & Safety Management
- EN 10204 3.1 — Material Test Certificate Type 3.1
6.2 Product Testing & Inspection
| Test Method | Standard | Purpose |
|---|---|---|
| Hydrostatic Pressure Test | ASTM A269 | Verify weld integrity and wall thickness uniformity |
| Spectrographic Analysis | ASTM E415 | Confirm chemical composition compliance |
| Tensile Testing | ASTM A370 | Validate mechanical properties |
| Intergranular Corrosion Test | ASTM A269 / A923 | Ensure resistance to sensitization |
| Pitting Resistance Test | ASTM G48 | Assess chloride-induced corrosion resistance (PREN ≥ 24) |
| Dimensional Inspection | ASTM A269 | Verify OD, wall thickness, and straightness tolerances |
| Surface Finish Verification | ASTM A967 | Confirm passivation and cleanliness |
| Non-Destructive Testing (EDDY) | ASTM A776 | Detect internal/external defects |
6.3 Traceability
Every coil is assigned a unique batch identifier linked to mill heat numbers, production timestamps, and full test documentation. This ensures complete supply chain traceability from raw material through finished product delivery.
7. Unique Selling Points
- EnergyPlus-Validated Performance: Product specifications are informed by and validated against rigorous EnergyPlus simulation modeling of single-coil and double-fan air conditioning systems, ensuring real-world thermal performance predictability.
- Superior Corrosion Resistance: Austenitic stainless steel grades provide decades of service life even in aggressive environments, eliminating the maintenance costs associated with carbon steel alternatives.
- Precision Coil Configuration: Continuous coil supply minimizes downstream fabrication waste, reducing total project cost by up to 15% compared to cut-length supply.
- Full Standards Compliance: Dual certification to both international (ASTM, ASME, EN) and Chinese national (GB) standards provides global market accessibility.
- Customizable Specifications: Flexible OD, wall thickness, coil length, and surface finish options tailored to specific HVAC system designs and engineering requirements.
- Complete Quality Documentation: Type 3.1 material certificates with full test data accompany every shipment, facilitating seamless project approval and regulatory compliance.
Note: The technical performance data referenced in this specification is derived from the engineering study "Modeling of Single Coil, Double Fan Air Conditioning Systems in EnergyPlus," which provides validated simulation parameters for coil tube thermal exchange performance under various operating conditions. Wenzhou Jixing Metal