Double Skin Air Handling Unit 

Introduction

A Double Skin Air Handling Unit (AHU) is a modular device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. The "double skin" refers to its construction with inner and outer panels separated by an insulating material, providing superior thermal and acoustic performance compared to single-skin units.

Types of Double Skin Air Handling Unit 

• Standard AHUs: For general comfort conditioning.
• Hygienic/Hospital AHUs: Designed for critical environments with stringent air quality requirements (e.g., hospitals, cleanrooms), often featuring smooth internal surfaces, HEPA filters, and specialized coatings.
• Fresh Air AHUs (FAHUs): Primarily handle outdoor air to provide ventilation.
• Heat Recovery AHUs: Incorporate heat exchangers (e.g., plate heat exchangers, heat wheels) to recover energy from exhaust air.
• Modular AHUs: Assembled from pre-fabricated sections.
• Custom-Built AHUs: Designed for specific project requirements.

Applications of Double Skin Air Handling Unit

• Applications: Commercial buildings (offices, shopping malls), hospitals and healthcare facilities, pharmaceutical manufacturing, cleanrooms, data centers, hotels, educational institutions, industrial facilities.
• Modular Construction: Allows for flexible configurations and easier transport/installation.
• Energy Efficiency: EC (Electronically Commutated) motors for fans, variable frequency drives (VFDs) for precise airflow control, heat recovery wheels/plates, advanced filtration systems (e.g., HEPA, activated carbon).
• Thermal and Acoustic Insulation: Double skin construction with materials like rock wool, fiberglass, or PU foam.
• Integrated Controls: Building Management System (BMS) integration for centralized monitoring and control, demand-controlled ventilation.
• Humidification/Dehumidification Systems: Steam humidifiers, desiccant wheels.
• UVGI (Ultraviolet Germicidal Irradiation) Lamps: For air disinfection in critical applications.
• Fan Technology: Backward-curved centrifugal fans, plug fans, often with direct drives.

Material Selection of Double Skin Air Handling Unit 

• Outer Casing: Galvanized steel, pre-painted galvanized steel (PPGI), aluminum, or stainless steel for corrosion resistance and durability.
• Inner Casing: Galvanized steel, stainless steel (especially for hygienic applications), or aluminum, selected for corrosion resistance, ease of cleaning, and non-shedding properties.
• Insulation: Rock wool, mineral wool, fiberglass, or polyurethane (PU) foam, chosen for thermal and acoustic insulation properties, fire resistance, and moisture resistance. Density and R-value are key.
• Structural Frame: Aluminum profiles or galvanized steel angles for rigidity and support.
• Coils (Heating/Cooling): Copper tubes with aluminum fins are common due to excellent heat transfer properties. Stainless steel or coated coils for corrosive environments.
• Fans: Galvanized steel, aluminum, or specialized alloys.
• Filters: Filter media varies (fiberglass, synthetic media, activated carbon, HEPA filter media) depending on the required filtration efficiency. Frames are typically cardboard, galvanized steel, or plastic.
• Drain Pans: Stainless steel (especially 304 or 316) for corrosion resistance and hygiene