Overview
Composite rectangular air ducts are engineered for modern HVAC systems, offering superior airflow management in constrained spaces. Their rectangular shape maximizes efficiency in vertical or horizontal installations, commonly replacing round ducts in commercial buildings. The composite construction often includes an inner layer for smooth airflow, insulation for thermal control, and an outer protective shell. These ducts are prefabricated to standardized dimensions, reducing on-site labor. They comply with international ventilation standards (e.g., SMACNA, DW/144), ensuring compatibility with most HVAC systems. Their modular design allows for easy integration with fire dampers and diffusers.
Structure and Working Principle
The duct typically comprises three layers: a rigid inner liner (often galvanized steel), middle insulation (fiberglass or foam), and an outer protective coating (aluminum or PVC). This sandwich structure dampens noise while preventing thermal bridging. Airflow follows the Venturi effect, with the rectangular cross-section minimizing turbulence at corners compared to sharp-angled designs. Internal seams are lock-formed or welded to reduce leakage, maintaining static pressure efficiency. Gaskets or mastic sealants are applied at joints during assembly.
Key Features
1. **Customizable Dimensions**: Available in widths from 100mm to 2000mm, with aspect ratios up to 1:4. 2. **Fire Resistance**: Some variants include intumescent coatings for fire-rated applications (up to 2 hours). 3. **Modularity**: Flanged connections allow quick assembly without specialized tools. Optional features include antimicrobial liners for healthcare facilities or acoustic linings for noise-sensitive environments. The ducts' rigidity permits spans up to 3 meters without additional supports, reducing installation costs.
Application Areas
Widely used in: - **Data Centers**: For precise cooling airflow management. - **Hospitals**: With airtight seals to maintain pressure differentials. - **Manufacturing Plants**: Where chemical-resistant coatings are added. They excel in retrofitting projects due to their space-efficient profile. In high-rise buildings, composite ducts are preferred for vertical shafts where weight savings versus pure steel ducts matter. Some designs integrate cable trays or plumbing within the duct structure.
Maintenance and Precautions
Routine inspections should check for: - Sealant degradation at joints. - Insulation moisture absorption (indicated by sagging). - External corrosion in coastal areas. Cleaning requires specialized brushes to avoid damaging inner liners. Avoid high-pressure washing unless the duct is rated for it. For repairs, use manufacturer-approved patches to maintain fire ratings. Always isolate ducts from electrical conduits to prevent galvanic corrosion.
B2B Procurement Guide
1. **Specifications**: Request ASTM E84 flame-spread ratings and leakage test reports. 2. **MOQs**: Standard orders start at 50 linear meters; custom sizes may require 100+ meters. 3. **Lead Times**: 4–6 weeks for coated specialty orders. Top manufacturers include Lindab, Unifrax, and local fabricators with EN 1507 certification. Consider FOB terms for international shipments—ducts are typically packed in 3-meter crates. Request samples for on-site airflow testing before bulk purchases.
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