The effect of supply air systems on the efficiency of a ventilated ceiling

The ventilated ceiling is a flexible solution for kitchen ventilation where heat loads are relatively low and aesthetics are a concern. The efficiency of the exhaust system should be specially emphasized with the ventilated ceiling systems where the exhaust is located at the ceiling level. The contaminant removal efficiency of the total system must be guaranteed and impurities spreading throughout the kitchen should be prevented. The supply air distribution strategy has a remarkable influence on the pollutant removal effectiveness. The flush-out effect of the supply air reduces the containment removal efficiency by circulating pollutants of the induced convection flow back to the occupied zone. The conducted laboratory measurements of a ventilated ceiling demonstrate that the capture and containment efficiency can be 85–93% using the concept of a low velocity ceiling supply and centralized capture jet and as high as 98% with the displacement system at the floor level. Using the ceiling supply and capture jet concept, the contaminant removal efficiency of 85% is reached by increasing the airflow rate 20% compared with the theoretical plume equation.