Slotted-inlet ventilation (SIV) systems are commonly used in animal confinement buildings. The slot inlets (diffusers are long and narrow and designed such that incoming fresh air issues into the enclosures as a wall (ceiling) jet. Air mixing and distribution patterns for isothermal cases are influenced primarily by the jet momentum at the diffuser and by the size of the confining space. A control criterion is required to maintain suitable airflow patterns. The main objective of this study was to determine a criterion for establishing similar (isothermal) airflow patterns independent of the enclosure size. Wall jet pack velocities, wall jet penetration distances, static pressure, and wall shear stress distributions along the ceiling were measured in two geometrically similar enclosure models. As measures of wall jet flow pattern similarity, the diffuser Reynolds number (Re = Uih/v) and the diffuser jet momentum number (J = Ui to the power 2h/[LH]) were found inappropriate. A criterion representative of the ratio of jet momentum at the diffuser to the momentum deficit due to the length of the inside walls, denoted here as the jet momentum ratio (RM = Ui to the power 2h/[L+H]), was derived and found to be the appropriate similarity criterion.

KEYWORDS: walls, air flow, slot diffusers, ventilation, jets, farm animal housing, animal housing, outdoor air, supply air, diffusers, air inlets, ceilings, distribution, isothermal, speed, static pressure, walls, measuring, Reynolds numbers, calculating.