Stainless Steel Dry Coil Tube for Clean Air Conditioning Systems
Product Code: No. 248 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Dry Coil Tube (also referred to as Dry Coil Heat Exchanger Coil) is a precision-engineered coiled heat exchange component specifically designed for dry-coil air conditioning systems integrated with bypass valve controls. This product serves as the core thermal exchange element in clean air conditioning architectures, where latent heat removal and precise temperature-humidity control are critical requirements.
In a typical dry coil system, the coil tube operates by circulating chilled water through the coiled tubing while air passes over the tube surface. The air is cooled to its dew point, and moisture condenses on the coil surface. The condensate is then drained, while the cooled air is reheated to the desired supply temperature using a separate reheat mechanism. The bypass valve regulates the flow of chilled water through the coil, enabling precise modulation of cooling capacity and maintaining stable indoor conditions.
Wenzhou Jixing Metal Materials Co., Ltd. manufactures these coil tubes to meet the rigorous demands of pharmaceutical, semiconductor, hospital, and other cleanroom environments where contamination control and energy efficiency are paramount.
2. Material & Properties
The coil tubes are fabricated from high-purity austenitic stainless steel, selected for its superior corrosion resistance, thermal conductivity, mechanical strength, and hygienic surface finish.
- Primary Alloy Grades:
- AISI 304 (UNS S30408): Standard austenitic stainless steel containing approximately 18% Chromium (Cr) and 8% Nickel (Ni). Offers excellent general corrosion resistance and weldability. Suitable for most HVAC applications.
- AISI 316 (UNS S31608): Enhanced austenitic stainless steel with 2–3% Molybdenum (Mo) addition. Provides superior resistance to chloride-induced pitting and crevice corrosion. Recommended for coastal environments, high-humidity cleanrooms, and pharmaceutical applications.
- AISI 316L (UNS S31603): Low-carbon variant of 316 with Carbon (C) content ≤ 0.03%. Ideal for welded assemblies requiring resistance to intergranular corrosion. Preferred for pharmaceutical and biotechnology cleanrooms.
- Surface Finish: Electro-polished (EP) or mechanical polished to achieve a surface roughness of Ra ≤ 0.4 μm, ensuring minimal microbial adhesion and ease of sanitization.
- Hygienic Compliance: All materials comply with FDA 21 CFR 178.3010 and EU 1935/2004 food-contact regulations, ensuring non-toxic, non-reactive properties suitable for cleanroom environments.
Key Physical and Mechanical Properties
| Property | ASTM 304 | ASTM 316 | ASTM 316L |
|---|---|---|---|
| Density (g/cm³) | 7.93 | 8.00 | 8.00 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 | 14.6 |
| Specific Heat at 100°C (kJ/kg·K) | 0.50 | 0.50 | 0.50 |
| Modulus of Elasticity (GPa) | 193 | 193 | 193 |
| Yield Strength (MPa, min.) | 205 | 205 | 170 |
| Tensile Strength (MPa, min.) | 515 | 515 | 485 |
| Maximum Service Temperature (°C) | 870 | 870 | 870 |
| Chromium Content (%) | 18–20 | 16–18 | 16–18 |
| Nickel Content (%) | 8–10.5 | 10–14 | 10–14 |
| Molybdenum Content (%) | — | 2–3 | 2–3 |
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Tube Outer Diameter (OD) | 6.35 mm (1/4"), 9.53 mm (3/8"), 12.70 mm (1/2"), 15.88 mm (5/8"), 19.05 mm (3/4"), 22.23 mm (7/8"), 25.40 mm (1") |
| Tube Wall Thickness | 0.5 mm – 1.5 mm (customizable) |
| Coil Pitch (Center-to-Center Spacing) | 12 mm – 30 mm (typical range for HVAC applications) |
| Number of Rows | 2 to 12 rows (configurable based on thermal load) |
| Coil Diameter | 150 mm – 1200 mm (standard); custom sizes available |
| Coil Length | Up to 6,000 mm (standard); longer lengths available upon request |
| Fin Type | Aluminum (Al 1100) or Stainless Steel (SS 304/316) corrugated fins |
| Fin Density | 8 FPI – 16 FPI (Fins Per Inch) |
| Operating Pressure | Up to 1.6 MPa (232 psi) standard; up to 4.0 MPa for high-pressure applications |
| Chilled Water Temperature Range | 2°C – 12°C (35.6°F – 53.6°F) |
| Airflow Velocity Across Coil | 1.5 m/s – 4.0 m/s (standard); up to 6.0 m/s for high-performance units |
| Refrigerant / Fluid Compatibility | Chilled water, glycol-water mixtures (up to 50% propylene glycol), compatible with standard HVAC refrigerants |
| Condensate Drainage | Integrated condensate drain pan with slope ≥ 1% for gravity drainage; compatible with active condensate pumping systems |
| Bypass Valve Integration | Compatible with electrically actuated 2-way or 3-way bypass control valves for precise flow modulation |
| Surface Roughness | Ra ≤ 0.4 μm (electro-polished); Ra ≤ 0.8 μm (mechanically polished) |
| Welding Process | TIG (Tungsten Inert Gas) welding with Argon (Ar) shielding; internal purge to prevent oxidation |
| Corrosion Resistance | PASS 1-4 (ASTM A967); ASTM A967 passivation treatment applied post-fabrication |
| Weight (Approximate) | Dependent on configuration; typically 5 kg – 80 kg per coil assembly |
4. Manufacturing Process
The production of stainless steel dry coil tubes follows a rigorous, multi-stage manufacturing process designed to ensure dimensional accuracy, thermal performance, and hygienic integrity:
- Raw Material Selection and Inspection: Stainless steel tubes (ASTM A269 / ASME B36.19M) are procured from certified mills. Each batch undergoes spectrographic analysis (OES – Optical Emission Spectroscopy) to verify chemical composition and mechanical property testing (tensile, hardness) to confirm compliance with specified grades.
- Tube Cutting and Deburring: Precision laser or mechanical cutting to required coil lengths. End deburring and chamfering to eliminate burrs that could obstruct flow or cause particle contamination.
- Coil Forming: Cold bending of stainless steel tubes using CNC-controlled coiling machines to achieve precise coil diameter, pitch, and number of turns. The forming process maintains the metallurgical integrity of the austenitic microstructure without inducing cold-work embrittlement.
- Fin Application: Corrugated aluminum or stainless steel fins are mechanically bonded or mechanically crimped onto the coil tubes at specified fin density. Fin-to-tube bonding integrity is verified through pull-off testing to ensure thermal contact resistance is minimized.
- Header and Port Fabrication: Inlet and outlet headers are fabricated from seamless stainless steel tubing. TIG welding with argon gas shielding (minimum 99.99% purity) is employed, with internal argon purge to prevent internal oxidation and discoloration.
- Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5 times the maximum design pressure (typically 2.4 MPa for standard configurations) for a minimum of 30 minutes. Zero leakage is required for acceptance.
- Passivation Treatment: Post-fabrication passivation per ASTM A967 using nitric acid or citric acid solutions. This process removes free iron contamination from the surface and enhances the passive chromium oxide film, improving long-term corrosion resistance.
- Surface Finishing: Electro-polishing (EP) is applied to achieve a smooth, hygienic surface finish with Ra ≤ 0.4 μm. EP also removes surface defects, embedded particles, and free iron, creating a uniform, corrosion-resistant passive layer.
- Final Inspection and Documentation: Visual inspection, dimensional verification, and leak testing. Each unit is assigned a unique serial number with full traceability documentation including material certificates, test reports, and quality records.
5. Applications
The Stainless Steel Dry Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. is engineered for demanding environments where precision climate control, contamination prevention, and energy efficiency are non-negotiable:
- Pharmaceutical Manufacturing: Cleanroom HVAC systems (ISO 14644 Class 1–8) where precise temperature and humidity control is essential for product quality and regulatory compliance (FDA, EMA, GMP).
- Semiconductor and Electronics Fabrication: Ultra-clean environments requiring sub-micron particle control, with dry coil systems providing stable thermal conditions without introducing moisture into the process area.
- Hospital and Medical Facilities: Operating theaters, intensive care units (ICU), and isolation wards where infection control and stable environmental conditions are critical.
- Food and Beverage Processing: Cleanroom areas in food production facilities where hygienic cooling is required without compromising product safety.
- Biotechnology and Laboratory Environments: BSL-2 through BSL-4 laboratories requiring precise environmental control for biosafety and experimental integrity.
- Data Centers: Server rooms and data halls where dry coil systems provide efficient heat removal while maintaining strict humidity limits to protect sensitive electronic equipment.
- Energy Efficiency Optimization: Integration with bypass valve control systems enables variable refrigerant flow, reducing compressor cycling and lowering overall energy consumption by 15–30% compared to conventional DX (Direct Expansion) systems.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and adheres to international standards governing materials, fabrication, and performance:
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management Systems – ensures consistent product quality and customer satisfaction through documented processes. |
| ISO 14001:2015 | Environmental Management Systems – demonstrates commitment to sustainable manufacturing practices. |
| ISO 45001:2018 | Occupational Health and Safety Management Systems – ensures workplace safety and employee welfare. |
| ASME B36.19M | Standard for welded and seamless wrought stainless steel pipe dimensions and tolerances. |
| ASTM A269 | Standard specification for austenitic stainless steel seamless, cold-drawn or cold-rolled tubing. |