DISTRIBUTION PROPERTIES OF DUST CONCENTRATION IN AN ENCLOSED MODEL LAYER HOUSE

摘要

Scale model experiments were performed to evaluate how the dust distribution properties are affected by differences in the ventilation system in relation to outlet position and incoming jet direction. The house used was an enclosed layer house with slot inlets and dampers on the ceiling. Distribution properties were expressed by three different ventilation efficiencies; the space averaged value of concentration (SAVC), which refers to exhausting efficiency; the average diffusion radius of contaminant dispersion (ADRCD), which evaluates the contaminant diffusion; and dimensionless concentration (DC(X)), which is related to local exchange rate of air. It was found that SAVC was significantly (1%) affected by outlet location for aerodynamic particle diameters less than 2 µm. The outlet at the highest position provided better exhausting efficiency with an SAVC of 0.73. The effect of aerodynamic particle diameters on SAVC was significant (0.5%). As the aerodynamic particle diameter increased, SAVC tended to increase accordingly. Experimental factors were not found to have an effect on ADRCD which was, on the average, 2 m. However, the effect of aerodynamic particle diameters on ADRCD showed a significant difference (0.5%). The ADRCD was found to be small when the aerodynamic particle diameter was large. It was also observed that the high concentration regions of DC(X) corresponded to stagnant region of airflow.