Summary
Using the dimensionless concentration of virtual air-contaminant as an index of air-distribution in the pig housings, the ventilation characteristics of three rooms in the housing with different air-inlet were compared by the numerical calculation method introducing the terms of volume porosity and surface permeability mentioned in the former report (part 1). Examined numerically air inlets of the room were the porous diffusion ceiling ~)orous inlet) and slotted inlet positioned on the gable wall (slotted inlet D and side wall (slotted inlet II), respectively. The decay mode and slope of the concentration of air-contaminant varied depending on the type of air inlet and each location in a room. The diffusing ceiling inlet gave the unidirectional fiow which resulted to the effective displacement ventilation in the room. The slotted inlet gave the main jet flow along the ceiling and substantial circulating flow in the room, which resulted to mix and dilute the inside air with outside iresh air, and the decay slope of the concentration widely varied with different locations in the room. Index of ventilation efficiency was introduced using the decay time ratio of virtual contaminant concentration.HomePage
The diffusing inlet showed rather uniform values of the index ranging 1 to 1.9, average being 1.32. The slotted inlet I gave the index values between 0.9 to 1.4, average being 1.09. The ventilation efficiency couldn't be estimated in the case of slotted inlet II, because the dimensionless concentration did not decrease to 1/10 of the initial value within a get time period (240 sec.).Keywords: livestock housing, air distribution, air change efficiency, numerical simulation, diffusing ceiling inlet, slotted inlet