Airflow and contaminants in a swine barn with recirculation assisted slot inlets
The airflow pattern and contaminant distribution under non-isothermal turbulent flow conditions in a swine growing/finishing building were investigated experimentally and numerically. In the test facility, the ventilation system consisted of discontinuous ceiling inlets with recirculation assisted slots. Air speed, dust and ammonia concentration at selected locations in the-building were measured during the winter ventilation season in a cold climate. The corresponding temperature distribution at one cross section within the air space also was measured. Experimentally it was found that both the ventilation rate and the recirculation rate had a limited effect on the dust concentration. The ventilation rate had a significant effect on the ammonia concentration in the air space, while the recirculation rate did not affect the ammonia concentration. The FLUENT computer code was used to simulate the air flow pattern and ammonia concentration in the swine building. The numerical simulation model used was the k-$\varepsilon$ turbulence model which includes a buoyancy term. The predicted airflow pattern indicated that the flow structure in such a ventilated swine barn is a three-dimensional flow. The three-dimensional flow structure and the contaminant concentration and temperature at the human breathing line were highly affected by the combined behavior of ceiling inlet jets and recirculation slot jets. The presence of pigs in the swine building had three effects: the air stream near the pigs was deflected; the air speed above the pigs was increased; and the ammonia concentration in the air space was decreased. Both experimental and numerical results showed that temperature and ammonia concentration were uniformly distributed across most of the air space in a building ventilated with discontinuous ceiling inlets and recirculation slots. Numerical results also indicated that the heat generated by animals affected the airflow pattern. Increasing the heat load at the floor resulted in increased air speed, temperature, contamination level, turbulence kinetic energy, dissipation rate and effective viscosity along the breathing line. The placement of the ceiling inlet and the recirculation duct affected airflow patterns, but had only a slight effect on the distribution of temperature and ammonia concentration along the human breathing line. Increasing the flow rate of cleaned recirculation airflow resulted in lower ammonia contaminant level along the human breathing line. However, higher flow rates of cleaned recirculation air means there will be higher fan operation and air cleaning costs. The optimum ratio of ventilation rate to the cleaned recirculation air rate appeared to be approximately 1:4.
DegreeDoctor of Philosophy (Ph.D.)
DepartmentAgricultural and Bioresource Engineering
ProgramAgricultural and Bioresource Engineering
CommitteeBergstrom, Donald J.; Barber, Ernest M. (Ernie)
Copyright DateFebruary 1997
heating and ventilation