Estimation of tunnel fan operating conditions for a laying hen house based on the ventilation resistance characteristics

Tunnel-ventilated laying houses need adequate ventilation rates to abate heat stress in hot climates. However, due to the underestimation of the ventilation resistance caused by the caged-hen occupied zone (COZ), the differential static pressure (DSP) of fans determined empirically is lower than the actual value, resulting in insufficient ventilation rate in the laying house. In this study, field measurements of the ventilation rate and DSP were conducted with various operating fans in a commercial layer house. A ventilation resistance curve was developed according to the results of computational fluid dynamics (CFD) simulations on the DSP distribution. The ventilation rate was estimated by the number of operating fans, resistance curve and fan performance curve. When the number of operating fans increased from 16 to 24, the fan ventilation rate decreased by 24.56 %, and the fan DSP increased from 41.6 to 67.7 Pa. The resistance caused by COZ contributed more than 60 % to the fan DSP. The DSP distribution near the fan was not uniform. The measured fans and fan DSP measuring point were in the low DSP area, resulting in the predicted ventilation rate being lower than the measured ventilation rate. The error of ventilation rate predicted by the in situ fan performance curve (E 3.47 %–6.51 %; RMSE 8.7) was higher than that predicted by the designed fan performance curve (E 0.77 %–4.72 %; RMSE 4.49). This study provides a methodological basis for accurately developing the ventilation resistance curve of the tunnel ventilated laying house.