Airflow characteristics in a pig house with partial pit ventilation system: an experimental chamber study

Abstract. A partial pit ventilation system (PPV) has been proved capable to significantly improve indoor air quality and reduce ammonia emission if combined with an air purification system in field studies. The removal efficiency of PPV is very much airflow pattern dependent but research on detailed airflow characteristics in a room with this ventilation system is still missing. In this study, experiments were performed to investigate the influences of two types of air inlet, three types of floor and four levels of ventilation rate on airflow air velocities, turbulence intensities and airflow patterns near the floor region and air exchange rate between room and pit spaces. Results show that higher ventilation rate induced higher near-floor air velocity and higher air exchange rate in the pit. Much higher air velocities and lower turbulence intensities occurred in ventilation system with wall jet inlet (system-W) than in the one with diffusion ceiling inlet (system-C). A big dominant return flow was found in system-W, while small turbulent flows were in system-C. Increasing the floor opening ratio enhanced the air exchange rate between room and pit spaces. Results for ammonia emission from a field study regarding PPV together with different air inlets can be comprehensively explained by using the results of this study.