Development and Validation of 3-D CFD Models to Simulate Airflow and Ammonia Distribution in a High-Rise Hog Building during Summer and Winter Conditions

Swine confinement buildings typically store manure in deep pits or use flush systems that generate liquid manure. This liquid is of great concern to hog producers because of its’ potential environmental impacts, odors and effects on human and animal health. An alternative system, the High-Rise ™ Hog Building (HRHB) attempts to address these issues by drying and partially composting hog manure in situ. However its ability to maintain optimal air quality throughout the animal space is unclear. In this study, 3-dimensional isothermal CFD models were developed to simulate the airflow patterns and ammonia distribution within a commercial High-Rise™ Hog Building (HRHB) during high ventilation rate (summer) and low ventilation rate (winter) operating conditions using FLUENT ® , a computational fluid dynamics program. The models were validated by measuring ammonia concentrations at 8 positions and two elevations on at least 2 different occasions within an HRHB building after finished hogs were removed. The CFD model predicted ammonia concentrations were not significantly different than the measured median 4-hour ammonia concentrations under both summer and winter conditions. This indicated that CFD modeling could be an effective way to evaluate air quality and ventilation across the 3-D space of a HRHB. A simulation using the initial and boundary conditions determined when hogs were present showed that in winter some ammonia from the manure storage area flows into the pig space which may affect animal health. According to the simulation, under winter conditions, ammonia concentrations within the pig space as high as 29 ppm were predicted at a height of 1.2 m (4 feet). Pens furthest from the exhaust fans exhibited the greatest ammonia concentrations. Under summer operating conditions, ammonia concentrations in the pig area were more evenly distributed and predicted to be below 1.5 ppm throughout the hog area and well below levels that are considered to adversely affect animal health. These ammonia concentrations are similar to the ranges previously observed in conventional deep pit buildings.

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