As fate and transport of air emissions from animal housing systems is of increasing concern, dispersion models have become commonly used tools to estimate the downwind concentrations of pollutants at certain locations...As fate and transport of air emissions from animal housing systems is of increasing concern, dispersion models have become commonly used tools to estimate the downwind concentrations of pollutants at certain locations surrounding the animal production farms. In application of Gaussian dispersion model for downwind concentration predictions of animal housing emissions, unknown plume rise (△h) and plume shape of the horizontally emitted plumes from animal housing systems have been vital weak points challenging the accuracy of the model predictions. This paper reports an inverse AERMOD modeling study to derive the plum rises of PM10 emissions from mechanically ventilated egg production houses based upon field measurements of PM10 emission rate, downwind concentrations, and meteorological conditions. In total, 87 hourly plume rises were found for 20 days (five days per season for four seasons, from fall 2008 to summer 2009). The mean plume rises for fall 2008, winter 2008, spring 2009 and summer 2009 were 16.2 m (SE = 11.2 m), 7.9 m (SE = 9.5 m), 16.5 m (SE = 12.4 m), and 14.3 m (SE = 10.0 m), respectively. The relationships between plume rises and various factors were tested. While the diurnal patterns of the plume rises were not consistent among different selective days, they generally followed the diurnal patterns of house ventilation rates. Plume rise for weekends were significantly higher than those for weekdays in fall. Multiple linear regression showed a significant positive relationship (p = 0.0134) between wind speed and the plume rises. Ambient relative humidity and total volume flow were also found to be slightly (p = 0.171 and 0.217, respectively) related to the plume rises.展开更多
Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models...Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models may be challenged due to the unknown plume rise and plume shape. This paper reports a combination of theoretical and field study of the plum rise and shape of air flow from a ventilation fan commonly used in mechanically ventilated animal houses. The theoretical modeling of the plume shape was conducted using a commercial Computational Fluid Dynamics (CFD) package named FloEFD;the field measurements of the plume field was conducted using five 3D ultrasonic anemometers to simultaneously measure the air flow in the plume at various locations (four heights and five downwind distances). The TECPLOT package was used to visualize the plume flow field based upon anemometer measurements. While the plume shapes were found to be left-shifted by the CFD model and TECPLOT visualization, the magnitudes of the 3D wind velocities from field measurement were found to be significantly larger than those from CFD model. The plume field measurements indicated that the plume of a 0.6 m (24-inch) ventilation fan had a depth about 9 m, a width about ±6 m, and a rise (lifting) beyond the highest measurement point, 4.88 m (16 ft).展开更多
文摘As fate and transport of air emissions from animal housing systems is of increasing concern, dispersion models have become commonly used tools to estimate the downwind concentrations of pollutants at certain locations surrounding the animal production farms. In application of Gaussian dispersion model for downwind concentration predictions of animal housing emissions, unknown plume rise (△h) and plume shape of the horizontally emitted plumes from animal housing systems have been vital weak points challenging the accuracy of the model predictions. This paper reports an inverse AERMOD modeling study to derive the plum rises of PM10 emissions from mechanically ventilated egg production houses based upon field measurements of PM10 emission rate, downwind concentrations, and meteorological conditions. In total, 87 hourly plume rises were found for 20 days (five days per season for four seasons, from fall 2008 to summer 2009). The mean plume rises for fall 2008, winter 2008, spring 2009 and summer 2009 were 16.2 m (SE = 11.2 m), 7.9 m (SE = 9.5 m), 16.5 m (SE = 12.4 m), and 14.3 m (SE = 10.0 m), respectively. The relationships between plume rises and various factors were tested. While the diurnal patterns of the plume rises were not consistent among different selective days, they generally followed the diurnal patterns of house ventilation rates. Plume rise for weekends were significantly higher than those for weekdays in fall. Multiple linear regression showed a significant positive relationship (p = 0.0134) between wind speed and the plume rises. Ambient relative humidity and total volume flow were also found to be slightly (p = 0.171 and 0.217, respectively) related to the plume rises.
文摘Various dispersion models have been developed to simulate the fate and transport of air emissions from animal housing systems to meet the increasing need for knowledge in this area. However, the accuracy of the models may be challenged due to the unknown plume rise and plume shape. This paper reports a combination of theoretical and field study of the plum rise and shape of air flow from a ventilation fan commonly used in mechanically ventilated animal houses. The theoretical modeling of the plume shape was conducted using a commercial Computational Fluid Dynamics (CFD) package named FloEFD;the field measurements of the plume field was conducted using five 3D ultrasonic anemometers to simultaneously measure the air flow in the plume at various locations (four heights and five downwind distances). The TECPLOT package was used to visualize the plume flow field based upon anemometer measurements. While the plume shapes were found to be left-shifted by the CFD model and TECPLOT visualization, the magnitudes of the 3D wind velocities from field measurement were found to be significantly larger than those from CFD model. The plume field measurements indicated that the plume of a 0.6 m (24-inch) ventilation fan had a depth about 9 m, a width about ±6 m, and a rise (lifting) beyond the highest measurement point, 4.88 m (16 ft).
