CFD simulation of influence of air supply location on airflow and temperature in stacked-cage hen house with tunnel ventilation

The environment in hen house is critical to the production performance of laying hens. Tunnel ventilation which combines cooling pad and exhausted fans is commonly adopted in hen house in summer. The air motion is driven by exhaust fans on the gable wall. After cooled down by the wet pad, the air takes away the heat produced by hens, and then goes out through the exhaust fans. In this study, the effects of the air supply location were studied to identify its influence on the airflow, temperature and its distribution based on computational fluid dynamics (CFD) simulations. The hen house measured in this study was a breeding house with five columns fours stacked layer cages. The length of the hen house was 105 m and the width was 15 m, the height of the gable wall was 6 m and of the roof was 7 m, the distance between the gable wall and first cage was 7.5 m. The number of hens was 28 717. The air supply locations investigated in this study were differed by the inlet area in the side and gable wall, the distance between sidewall inlet and gable wall inlet, the distance between the inlet and first hen cage. The simulation model was validated by field experiment, in which speed and temperature in the breeding hen house in 18 points in the aisles were measured. The relative difference between measured and simulated results of temperature was 0.1%, and of speed was 9.5%, illustrating that the model was reasonable to simulate the environment in the hen house. The simulation results showed that without flaps behind the inlet, the increase of the distance between the air supply location and the cage could significantly increase the average wind speed inside the caged-hen occupied zone (CZ) near the air inlet zone (within 17.5 m from the first cage). The maximum increase amplitude was 0.54 m/s in this study. With flaps behind the air inlet, the air supply location had no significant effect on the average speed in CZ in the cage. Meanwhile, with the increased distance between the air supply location and the cage, the uniformity of airflow distribution in CZ nearby the inlet increased, the temperature in CZ decreased and its distribution tended to be more uniformity. However, the influence range of the air supply location on the environment in CZ was limited. In this study, the influence range in CZ of the air supply location on air speed was within 27 m from the first cage, on airflow distribution uniformity was within 45 m from the first cage, on temperature distribution was within 18 m from the first cage. This study showed that in the design of air supply location in hen house in summer, the gable wall should be utilized as much as possible. The overlap between the inlet and the hen cage should also be avoided, to guarantee that the inlet airflow could be fully developed before entering the CZ. This design was beneficial to reduce the weakly ventilated zone and vortex in CZ, and can guide the design of air supply location in hen houses.