Abstract
In generally ventilation design are considered under completely mixed condition of contaminants in a whole room. However contaminants in a room are not always uniformly distributed and it is necessary to introduce the concept of ventilation efficiency into the ventilation design. From the viewpoint of energy conservation, the necessity for minimizing the ventilation rate with the indoor contaminant concentration level controlled under the restriction value is high. In this paper, the values of the normalized concentration in an occupied zone (Cn) in an office space are calculated by CFD simulation techniques for several different ventilation systems and the minimum ventilation rate, which maintained the averaged concentration in an occupied zone under the regulated values, are analyzed using Cn indices. Furthermore, energy consumption and CO_2 emission associated with the change in ventilation rate are analyzed. In this analysis, for most ventilation systems, the Cn is around 1.0, but it changes greatly depending on the supply inlet velocity and temperature for the large circulation flow system. In the case in which applied Cn index, the energy consumption decreased about 9.8% compared with the case in which assume perfect mixed condition in this analytical conditions.
