Computational fluid dynamics assessment of natural ventilation in three types of large-scale broiler poultry houses in Botswana

Abstract

Effects of house design, orientation, and regional location on the natural ventilation of commercial, large-scale broiler poultry houses in the North-eastern and South-eastern farming regions of Botswana were assessed at full scale through computational fluid dynamics (CFD) simulations using the OpenFOAM CFD code. Local air change effectiveness (ACE), ε_L was computed in a 0.25 m high animal occupation zone inside gable-, hoop-, and seesaw-roofed houses selected from three different farms per region. Observed airflow patterns and ε_L values did not show regional dependence, whereas both were influenced by house orientation and, to a lesser extent, house design. Local ACE values obtained from the North-eastern farms ranged from 0.62 to 0.75, while in the South-eastern region values ranged from 0.56 to 0.90, with hoop- and gable -roofed structures yielding better ε_L values than the seesaw-roofed structures from both regions. Simulations of theoretical perpendicular wind incidence (WI) angles for houses oriented to 140 and 135° reduced their ACE values by 18.75 % and 0.53 %, respectively, indicating that their current orientation was optimal and allowing them to experience high WI. Houses oriented to 100° and 105° exhibited moderate improvements in ε_L values of 5.84 % and 6.4 %, respectively, while houses oriented to 95° and 90° showed the greatest improvement in ε_L values of 19.9 % and 37.52 %, respectively. Thus, site-specific orientation of poultry houses to 120°-150° would be recommended as it would allow for higher WI angles and better ε_L in both geographical farming zones in Botswana. Furthermore, it may be concluded that design proposals to improve natural ventilation based on the hoop- and gable-roofed structures – supported by CFD simulations with experimental validation – is warranted.