Abstract
Optimizing airflow patterns is important for energy conservation in cleanrooms. The airflow patterns are strongly influenced by air supply and return configurations. This study experimentally compares five airflow types: downflow, filter unit upflow, fan filter unit upflow, displacement ventilation, and ceiling supply and return. In the downflow type, air is introduced through ceiling fan filter units and returned through perforated raised floor panels. In the filter unit upflow type, air is supplied through perforated raised floor panels and returned through perforated ceiling panels. In the fan filter unit upflow type, air is supplied by underfloor fan filter units and returned through perforated ceiling panels. The experiments involve three different indoor heat loads, and the number of air changes per hour varies from 17 to 106. As there are few particles larger than 5 μm, no significant differences are identified in the experiments for particles of this size. However, for particles larger than 0.3 μm at1.1 m above the floor, the concentrations of particles are consistently lower in the upflow and ceiling supply and return types compared to the downflow type under all experimental conditions. Furthermore, the fan filter unit upflow type has the lowest concentration.
