Emission effects of three different ventilation control strategies—A scale model study

The objectives of this paper are to determine the effects of varying the ventilation rates on ammonia emission using three different control strategies: constant inlet opening area, constant inlet air velocity and constant inlet air jet momentum. In addition, methods for estimation of air exchange rates between the headspace and the room are investigated. The work is based on scale model experiments in three different floor configurations. The model was made to scale 1:12.5 of a sub-section of a pig house with double rows of pens. Ventilation air was supplied through adjustable slats at two sides beneath the ceiling spanning the whole width of the model. Ammonia water was added in the scale model bottom to serve as a reservoir providing measurable gas emission. In addition to no-floor, two types of slatted floor were investigated with opening area 33.3% and 16.7%. The effect on the emission of increasing the ventilation rate is seen to greatly depend on the control strategy. The highest emission rate was found for constant inlet opening. The emission was reduced considerably when the inlet opening was adjusted to maintain constant inlet velocity, and when the inlet opening was adjusted to maintain constant momentum the emission was nearly independent of ventilation rate. The maximum emission was found with no slatted floor and the minimum emission was found for the slatted floor with the lower opening area.