Dynamic transport of livestock generated VOC-odor in a ventilated airspace with mixing heterogeneity

This research proposes a multiple airflow regions gamma model to simulate airflow pattern in a ventilated airspace with mixing heterogeneity based on residence time distribution and gamma distribution statistics. We select p-cresol, toluene and p-xylene, three intensive odor causing volatile organic compounds (VOC-odor) found in swine housing, to account different mixing behaviors. By fitting the VOC-odor concentration profile calculated from VOC-odor transport model with three-parameter gamma distribution, we can characterize the extent of mixing and predict mixing heterogeneity in a ventilated livestock housing. A typical swine housing with a mechanical ventilation system in southern Taiwan was selected for model simulation. Results demonstrate that the mean residence time of p-cresol, toluene and p-xylene are 44.45±0.91, 267.30±58.90 and 332.38±129.83 h, whereas mean mixing factor are 0.20±0.05, 0.81±0.17, and 0.81±0.19, respectively, corresponding to a ventilation rate of 0.075±0.025 m3 s−1 pig−1 within manure moisture content of 70±10%. This research gives additional physical information to characterize mixing behavior temporally and spatially with mean residence time and mixing factor, respectively, in a ventilated airspace with mixing heterogeneity. The robustness of multiple airflow regions gamma model can offer designers to reconsider the efficiency of ventilation systems through different mixing flow patterns in place of complete mixing hypothesis.