Numerical study on the convective heat transfer of fattening pig in groups in a mechanical ventilated pig house

It is recognized that increasing the local air speed in the animal occupied zone (AOZ) is one of the effective approaches to decrease the heat stress of pigs. To predict the effects of the air speed in an AOZ, knowledge of the relationship between convective heat loss and air speed is essential. In this study, the convective heat losses from pig models were modelled through numerical simulation under semi-practical conditions. The convective heat transfer coefficients of pigs in groups were tested at different inlet speeds. Virtual pig bodies (pig models) corresponding to three different body weights, i.e., 30 kg, 50 kg, and 80 kg, were generated and used in the investigation. Two wall inlet styles, a conventional inlet with an upward guiding plate and a modified inlet that supplied downward airflow directly onto the pigs, were compared to estimate the effect of ventilation system on the convective heat loss of pigs. The results showed that convective heat transfer coefficients of pigs in a group were strongly correlated with the inlet air speeds as well as the reference air speed in the AOZ (the average air speed in AOZ was selected as reference air speed in this study). The weight of the pig models showed no significant effect on the convective heat transfer coefficient. The convective heat transfer coefficient of the pigs in pens with the downward inlet was averagely 60.4% higher than those with the upward inlet.