Computational Fluid Dynamics Modeling of Ventilation and Hen Environment in Cage-Free Egg Facility

SIMPLE SUMMARY: The goal of this study was to model and evaluate indoor environment for commercial poultry barns to help builders and egg producers accommodate current transitions to cage-free facilities. By modeling, a one-eighth section of a typical cage-free hen house with 2365 individual hens at full-scale, environmental conditions were assessed in terms of important parameters such as temperature, air speed, and static pressure difference. The simulated ventilation rate for the hen house was set at a desirable cold weather ventilation rate at freezing outside conditions. Contours of interior airflow, temperature, and pressure suggested the indoor conditions were maintained within comfortable ranges, especially important as documented at the bird level. Our findings demonstrated computational fluid dynamics (CFD) modeling is a powerful tool to assess a ventilation system and its impact on the indoor environment for comfort, particularly within the animal-occupied zone of livestock housing. ABSTRACT: Poultry facilities are going through an evolution in design due to growing demands for cage-free eggs and egg products without unified guidelines to accommodate these transitions. The goal of this study was to help builders and egg producers assess current ventilation design within cage-free production facilities for conditions that impact hen comfort and welfare. The method of evaluation was simulation of the indoor environment of a hen house via computational fluid dynamics (CFD) modeling with individual hens modeled at a typical stocking density. This paper describes the development of a three-dimensional model of a commercial floor-raised cage-free hen house that is cross-ventilated to document current environmental conditions. A one-eighth section of the barn was modeled at full-scale using existing ventilation schemes with each bird represented by a hen-shaped, heated, solid body. A conventional top-wall inlet, side-wall exhaust (TISE) ventilation configuration was modeled for this study. The simulated ventilation rate for the hen house was approximately 3 m(3)/h (1.77 ft(3)/min) per hen resulting in 7092 m(3)/h (4174 ft(3)/min) for the 2365 birds, which falls at the higher end of the desired cold weather (0 °C) ventilation range. Contours of airflow, temperature, and pressure were generated to visualize results. Three two-dimensional planes were created at representative cross-sections to evaluate the contours inside and outside the barn. Five animal-occupied zones within each of the model planes were evaluated for practical hen comfort attributes. The simulation output suggested the TISE standard ventilation system could limit air speed to a comfortable average of 0.26 m/s (51 ft/min) and the temperature could be maintained between 18 and 24 °C on average at the bird level. Additionally, the indoor static pressure difference was very uniform averaging −25 Pascal (0.1 inches of water), which falls in the normal range for a floor-raised hen house with negative-pressure ventilation during cold weather conditions. Findings confirmed that CFD modeling can be a powerful tool for studying ventilation system performance at the bird level, particularly when individual animals are modeled, to assure a comfortable indoor environment for animal welfare in poultry facilities.