Jet momentum criteria for inlet control to reduce wind effects on the air distribution in a side-wall-inlet ventilation system.

A problem in a livestock building ventilated in the system with wall inlet at two sides is wind effects to the indoor air flow patterns. The in-proper inlet jet penetration profiles may cause draught at occupied zone and unnecessary stress of animals. The wind effects on such a system can be reduced by applying windbreak to the inlets from design point of view. However, a remain issue is if the effect could be reduced by regulating inlet opening and how to perform the control operation. The hypothesis of this study is that the unbalance of the incoming air flows from the two side wall, which caused by wind effects, can be overcome by adjusting the inlet openings to maintain the balance of the jet momentum of the both incoming air jets. If that is true, inlet jet momentum criteria should be able to applied in a control system to maintain the similar inlet jets from both side walls. A 1/10 scale model of a livestock building with both-side wall inlet was used in the investigation in laboratory conditions. In the experiments, the model was placed at a wind board with simulated wind speed of 0- 3. 5 mis across the model. Different ventilation rates, inlet openings and operating pressures were applied. The experimental results great supported the above hypothesis. It is concluded that if the jet momentum ratio is maintained to unity under the wind condition the jet penetration depths from two sides will be balanced. The jet momentum criteria can be applied to control side wall inlets to reduce wind effect on the indoor air distribution.