Computational modelling of thermal and humidity gradients for a naturally ventilated poultry house

Natural ventilation represents a strong tool for ameliorating climate and air quality in poultry houses if the benefits of weather conditions can be maximised. To that end, this investigation analyses the impact of natural ventilation on the dynamics of the internal climate of a poultry house focussing on the role played by the outside climatic parameters except wind direction. Experimental data with prevailing North-East wind direction was considered to identify seven periods with at least 4 h of stable wind direction. Three of these periods were chosen as typical examples and used to validate a 3D computational fluid dynamics (CFD) model, to integrate the main elements determining the internal climate: animal heat and water vapour generation, radiative heat transfer, and ventilation. The three periods under analysis allowed us to deduce, from the experimental and simulated data, the influence of all the other external climatic variables (i.e. temperature, absolute humidity, solar radiation and wind velocity) that affected the internal climate. The accuracy of the CFD model at evaluating each of the three periods reached a RMSE of 1.3 °C, 1.2 °C and 0.5 °C for internal temperature and a RMSE of 0.9 g [H₂O] kg⁻¹ [dry air], 0.6 g [H₂O] kg⁻¹ [dry air] and 0.2 g [H₂O] kg⁻¹ [dry air] for internal absolute humidity, respectively. Then, the predictions of the 3D CFD model were analysed, using air residence-time concept to estimate ventilation rates, and also to investigate sensible and latent heat exchanges.