Abstract
The application of naturally ventilated pig buildings (NVPBs) with outdoor exercise yards is on the rise mainly due to animal welfare considerations, while the issue of emissions from the buildings to the surrounding environment is important. Since air pollutants are mainly transported by airflow, the knowledge on the airflow characteristics downwind the building is required. The objective of this research was to investigate airflow properties downwind of a NVPB with a roofed outdoor exercise yard for roof slopes of 5°, 15°, and 25°. Air velocities downwind a 1:50 scaled NVPB model were measured using a Laser Doppler Anemometer in a large boundary layer wind tunnel. A region with reduced mean air velocities was found along the downwind side of the building with a distance up to 0.5 m (i.e., 3.8 times building height), in which the emission concentration might be high. Additional air pollutant treatment technologies applied in this region might contribute to emission mitigation effectively. Furthermore, a wake zone with air recirculation was observed in this area. A smaller roof slope (i.e., 5° slope) resulted in a higher and shorter wake zone and thus a shorter air pollutant dispersion distance.
Highlights
Natural ventilation systems have the advantages of low capital investment, energy saving [1], and absence of noise [2] compared with mechanical ventilation systems
The objectives of this study were to investigate mean and turbulent characteristics of airflows downwind of a naturally ventilated pig buildings (NVPBs) with an outdoor exercise yard covered with roofs with different roof slopes, to predict air pollutant distribution and dispersion properties, and to provide valuable experimental data for computational fluid dynamics (CFD) validation
Mean air velocity and air turbulence downwind a 1:50 scaled model of a naturally ventilated pig building with a totally roofed outdoor exercise yard with different roof slopes were measured in a large boundary layer wind tunnel to investigate downwind airflow characteristics and the related air pollutant transport and dispersion properties
Summary
Natural ventilation systems have the advantages of low capital investment, energy saving [1], and absence of noise [2] compared with mechanical ventilation systems. Sci. 2020, 10, 4931 and South Africa [3,4] This housing system provides pigs larger living areas, enables the separation of lying and excretion areas, and allows pigs to exhibit natural behaviours [5]. It provides pigs access to an outdoor exercise area, enables pigs to mainly excrete outdoors, and results in improved indoor air quality [6], animal welfare [3], and meat quality [7] compared with a conventional housing system
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