Stainless Steel Condensate-Free Coil Tube for HVAC Systems
Product Overview
The Stainless Steel Condensate-Free Coil Tube is a precision-engineered heat exchange component designed for high-efficiency air conditioning and ventilation systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product addresses a critical challenge in HVAC engineering — the formation of condensate on coil surfaces — which can lead to microbial growth, indoor air quality degradation, and system performance deterioration. The design and performance characteristics of this coil tube have been validated through rigorous experimental research, including comprehensive performance studies in controlled hospital environments such as SARS isolation wards, where hygienic integrity and thermal efficiency are paramount.
This coil tube is specifically engineered to operate below the dew point temperature of ambient air without producing condensate, leveraging advanced stainless steel surface treatments and optimized fin-and-tube geometry. The product is classified under the Coil Tube (盘管) product line and is suitable for integration into fresh air air conditioning systems (新风空调系统) requiring high standards of cleanliness and reliability.
Material & Properties
Base Material Composition
- Tube Material: Austenitic Stainless Steel (奥氏体不锈钢), conforming to AISI 304 / ASTM A213 TP304 or AISI 316 / ASTM A213 TP316L specifications
- Fin Material: Stainless Steel (SUS 304/316) or Aluminum (Al-Mg1) bonded to stainless steel tube via diffusion bonding process
- Protective Coating (Optional): Titanium Dioxide (TiO₂) photocatalytic coating or hydrophilic fluoropolymer coating for enhanced condensate prevention
Key Material Properties
- Corrosion Resistance: Excellent resistance to chloride-induced pitting and intergranular corrosion, suitable for humid and chemically aggressive environments
- Thermal Conductivity: 16.3 W/(m·K) (AISI 304) / 14.6 W/(m·K) (AISI 316L)
- Surface Roughness (Ra): ≤ 0.4 μm for internal tube surfaces to minimize flow resistance
- Hydrophilicity / Hydrophobicity: Surface-treated to manage condensate nucleation; condensate-free design eliminates liquid water accumulation
- Temperature Resistance: Operational range from −40°C to +250°C
- Hygienic Performance: Non-porous surface prevents bacterial adhesion and biofilm formation
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Category | Coil Tube (盘管) | — |
| Tube Outer Diameter (OD) | 7.94 mm / 9.53 mm / 12.70 mm (⅜" / ⅜" / ½") | ASTM A213 |
| Tube Wall Thickness | 0.50 mm – 1.00 mm | ASME B36.19M |
| Tube Length (Coiled) | 5 m – 50 m (customizable) | — |
| Coil Winding Diameter | 100 mm – 500 mm | — |
| Fin Pitch | 1.5 mm – 3.0 mm (adjustable) | — |
| Fin Thickness | 0.10 mm – 0.25 mm | — |
| Fin Height | 8 mm – 15 mm | — |
| Number of Rows | 1 – 6 rows (configurable) | — |
| Tube Layout | In-line or staggered arrangement | — |
| Maximum Operating Pressure | 1.6 MPa – 2.5 MPa | ASME BPV Section I |
| Refrigerant Compatibility | R-410A, R-134a, R-32, Water (CHW/HW) | — |
| Heat Transfer Efficiency | ≥ 85% of theoretical maximum (condensate-free mode) | ASHRAE Standard 34 |
| Pressure Drop (Air Side) | ≤ 150 Pa at nominal face velocity (2.5 m/s) | — |
| Condensate Formation | None at operating temperatures ≥ 5°C below dew point | Experimental Validation |
| Surface Treatment | Electropolished / Passivated / TiO₂ Coated (optional) | ASTM A967 |
Manufacturing Process
1. Tube Forming & Precision Rolling
Stainless steel coil stock (SUS 304/316) is precision-rolled into seamless tubes using cold-rolling technology to achieve uniform wall thickness and tight dimensional tolerances (±0.05 mm). The internal surface is electropolished to achieve a mirror finish (Ra ≤ 0.4 μm), reducing flow resistance and preventing particulate accumulation.
2. Fin-Tube Bonding
Fin stock (stainless steel or aluminum) is bonded to the tube surface using one of the following methods:
- Diffusion Bonding: Applied for stainless steel fin configurations, ensuring metallurgical bonding without flux contamination.
- Expanding Process: Hydraulic or mechanical expansion creates a tight mechanical interference fit between fin and tube, supplemented by brazing at critical joints.
3. Coil Winding
The finned tube assembly is wound into a helical coil using CNC-controlled winding machinery. Winding tension is precisely controlled to prevent tube deformation and ensure uniform coil geometry. The coil is then secured with stainless steel support rings at specified intervals.
4. Surface Treatment & Condensate-Free Coating
To achieve condensate-free performance, the coil surface undergoes specialized treatment:
- Hydrophobic Coating: A nanoscale fluoropolymer or silicone-based coating is applied via plasma-assisted deposition, increasing the water contact angle to >110° to prevent condensate nucleation.
- Hydrophilic Coating (Alternative): A TiO₂ photocatalytic coating promotes rapid condensate drainage and self-cleaning properties under UV exposure.
- Passivation: Chemical passivation per ASTM A967 forms a chromium oxide layer enhancing corrosion resistance.
5. Pressure Testing & Quality Inspection
Each coil tube unit undergoes hydrostatic pressure testing at 1.5× the maximum operating pressure for a minimum of 30 minutes to verify structural integrity. Non-destructive testing (NDT) including dye penetrant inspection and helium leak detection ensures zero-defect output.
6. Assembly & End Fitting Installation
Header tubes, U-bends, and connection fittings are welded using orbital TIG (Tungsten Inert Gas) welding with internal gas shielding to maintain internal cleanliness. All welds are inspected via radiographic testing (RT) or ultrasonic testing (UT).
Applications
Primary Applications
- Hospital & Medical Facilities: Ventilation systems in operating theaters, isolation wards (including infectious disease wards such as SARS, COVID-19 facilities), and intensive care units (ICU) where hygienic air quality is critical.
- Pharmaceutical Manufacturing: Cleanroom HVAC systems (ISO Class 5–8) requiring non-shedding, corrosion-resistant heat exchange components.
- Semiconductor & Electronics Manufacturing: Precision temperature and humidity control in fabrication facilities (fabs).
- Food & Beverage Processing: Cooling and dehumidification systems in hygienic processing environments.
- Commercial Fresh Air Systems: Dedicated Outdoor Air Systems (DOAS) and energy recovery ventilation (ERV) units.
- Marine & Offshore Platforms: HVAC systems exposed to high-salinity, high-humidity environments.
Performance in Hospital Ventilation Systems
Experimental research conducted on SARS ward ventilation systems demonstrated that the condensate-free coil tube integrated with fresh air air conditioning systems achieved the following performance outcomes:
- Elimination of condensate water accumulation on coil surfaces, preventing microbial growth (bacteria, mold, and Legionella)
- Maintenance of indoor relative humidity (RH) within the optimal 40–60% range
- Improved air change rate efficiency with reduced pressure drop compared to conventional coil tubes
- Extended service intervals due to reduced fouling and corrosion
- Compliance with hospital-grade air quality standards (ASHRAE 170, EN 13779)
Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| CE Marking | Compliance with European Machinery and Pressure Equipment Directives |
| ASME BPV Code Section I | Boiler and Pressure Vessel Code compliance for pressure-bearing components |
| ASTM A213 | Standard specification for austenitic stainless steel seamless, cold-rolled or drawn tubing |
| EN 10216-5 | European standard for seamless stainless steel tubes for general purposes |
| GB/T 14976 | Chinese national standard for seamless stainless steel tubes for cold-rolling |
| UL Listed (Applicable) | Underwriters Laboratories safety certification for HVAC components |
| RoHS Compliant | Restriction of Hazardous Substances compliance for all materials |
Unique Selling Points
1. Condensate-Free Operation: Unlike conventional coil tubes that produce condensate when operating below dew point, this product eliminates liquid water formation entirely through advanced surface engineering, preventing microbial proliferation and maintaining superior indoor air quality.
2. Hospital-Grade Hygienic Design: Validated through experimental research in high-infection-risk environments (SARS wards), the product meets the most stringent requirements for medical facility ventilation systems.
3. Superior Corrosion Resistance: Full stainless steel construction (tube and fin) provides unmatched durability in humid, chemically aggressive, and saline environments, with a service life exceeding 20 years without degradation.
4. Enhanced Energy Efficiency: The condensate-free design eliminates the latent heat load associated with condensate evaporation in downstream air handling, reducing overall system energy consumption by an estimated 8–15%.
5. Reduced Maintenance Burden: The non-porous, corrosion-resistant surface resists fouling, scaling, and biological growth, significantly extending cleaning intervals and reducing lifecycle maintenance costs.
6. Customizable Configuration: Available in multiple tube diameters, fin pitches, row configurations, and coil geometries to suit specific system design requirements and space constraints.
7. Environmental Sustainability: RoHS compliant, fully recyclable stainless steel construction, and energy-saving performance contribute to reduced environmental impact throughout the product lifecycle.
Technical Notes
Design Considerations: When integrating this condensate-free coil tube into a fresh air air conditioning system, engineers should account for the modified heat transfer characteristics. The absence of condensate film changes the dominant heat transfer mechanism from condensation (high h) to sensible heat transfer (lower h), requiring careful sizing to ensure adequate cooling/dehumidification capacity. Computational Fluid Dynamics (CFD) modeling is recommended for system-level performance verification.
Material Selection Guidance: For applications involving chlorinated water or high-chloride environments (e.g., coastal facilities, swimming pools), AISI 316L with molybdenum (Mo) content of ≥ 2.0% is recommended over AISI 304 to ensure long-term resistance to pitting and crevice corrosion.
Traceability: Each production batch is accompanied by a Material Test Report (MTR) per EN 10204 3.1, including chemical composition analysis (via optical emission spectroscopy), mechanical property verification, and dimensional inspection records.