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

Huawei Sun, Harold M Keener, Wei Deng, Frederick C Michel, Jr.

Abstract


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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