Cleanroom HVAC and Air Handling Equipment

Recirculation Air Handling Unit

A high-volume return-air unit that recirculates filtered cleanroom air while handling sensible load and maintaining stable airflow.

High Recirculation Airflow
Low Fan Energy Path
Stable Sensible Cooling
Variable-Speed Air Volume

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Product Introduction

The recirculation air handling unit moves the high air volume needed for particle dilution without repeatedly conditioning the entire stream as outdoor air. Return air passes through accessible filters, a cooling or trim coil and direct-drive fans before returning to ceiling filters or supply distribution. Fresh conditioned air can enter upstream as a smaller measured quantity. Large coil face area and low-pressure-drop components reduce fan energy, while airflow control compensates for terminal filter loading and operating mode changes.

Key Features

Large filter and coil face areas keep pressure drop low across the high recirculation volume.

A small conditioned fresh-air connection can be mixed with the return stream without oversizing the outdoor-air unit.

Direct-drive fan arrays provide turndown and service redundancy for continuous production areas.

Sensible trim cooling removes room and fan heat without duplicating full latent treatment.

Customer Product Concerns

High cleanroom air-change rates magnify every unnecessary filter, coil and duct pressure loss in the recirculation path.

A small coil and filter bank create excessive fan energy at high recirculation volume.Expanded face area lowers component velocity and reduces pressure drop.

Terminal filter loading gradually reduces cleanroom air changes.Variable-speed fans maintain the scheduled airflow or duct static-pressure setpoint.

One large fan failure stops production airflow.A multi-fan array can continue at reduced capacity while one fan position is isolated.

Mixing humid outdoor air into the return stream destabilizes room moisture.A separate conditioned fresh-air connection introduces air at a controlled dew point.

Typical Applications

Large pharmaceutical cleanroomsSemiconductor clean productionMedical-device assembly hallsBattery manufacturing clean zonesHigh-air-change laboratories

Technical Parameters

The following ranges describe a high-volume cleanroom recirculation AHU casing.

Core Material	Polyurethane or high-density mineral-wool acoustic and thermal panel insulation
Panel Thickness	50–60 mm double-skin casing
Effective Width	1200–4200 mm nominal casing width
Maximum Length	Up to 9000 mm for filters, coil, fan array and mixing section
Steel Facing Thickness	0.6–1.0 mm galvanized or coated casing skins
Core Density	42–45 kg/m³ polyurethane or 80–110 kg/m³ mineral wool
Thermal Conductivity	0.022–0.040 W/(m·K) depending on panel core
Surface Finish	Powder-coated outer skin with smooth galvanized or coated inner skin
Joint Type	Gasketed low-leakage panel joints and bolted modular fan/coil sections
Customization	Available based on the intended application and operating environment.

Available Options

EC fan wall with N+1 fan positionChilled-water or refrigerant trim coilReturn prefilter or fine-filter bankTop, side or end return and supply connections

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