Ventilation Considerations for Indoor Environmental Quality for a Control Center

This paper presents design considerations of ventilation and indoor environmental quality(IEQ) for a control center. Raised access floors are extensively used to provide flexibilitiesfor control cables and wires required by a control center. Underfloor air distribution system(UFAD) is more practice and economical than an overhead mixing system. It improvesindoor ventilation effectiveness due to the air stratification of thermal plume, and it provides abetter indoor environment for the equipment and occupied people. From the analyses andcalculations for a control center, when the load density is less than 40 btuh/s.f., and the throwheight of the floor panel diffuser is less than 4, the ventilation effectiveness is up to 1.2,similar to the displacement ventilation. When the load density is between 40 and 60 btuh /s.f,and the throw height of the floor panel diffuser is between 4 and 6, the stratification ofthermal plume is still generated, the ventilation effectiveness is approximately 1.1. When theload density is over 60 btuh/s.f., the throw height of the floor panel diffuser is over 6.Without the air stratified layer, the ventilation effectiveness is 1.0, equal to perfect mixing airdistribution. In the high supply airflow rate situation, ventilation airflow for providing anacceptable IAQ around people should be maintained at least 10% of supply air, in order toprovide at least 5 cfm fresh air for people who can obtain nearby.