Air Motion and Thermal Environment in Pig Housing Facilities with Diffuse Inlet: PhD Thesis Defended in public at the Danish Institute of Agricultural Sciences Research Centre Bygholm (131206)

A ventilation system with ambient air supply through diffuse ceiling used in pig production facilities is presented. The climatic conditions were examined both experimentally and numerically in an full scale experimental room and the inlet boundary conditions of the diffuse inlet were examined in a wind tunnel model. In the full scale experiments the focus has been on the correlation between variations in ambient climatic conditions and changes in environmental condition in the occupational zone. It was found that the environmental conditions in the occupational zone were independent on changes in ambient temperature and air exchange rate. The effect of housing equipment on environmental conditions has been examined both experimental and numerically and it was found that impervious housing equipment has a significant effect on the climatic conditions close to the wall in the occupational zone.

The wind tunnel experiments show that the diffuse material works as a heat exchanger and preheats the inlet air if the temperature in the room is higher than the inlet air. The result of the experiment is that the heat exchanging function of the inlet boundary surface is dependent on flow velocity and radiative conditions in the room. The experiments show that a wall boundary condition of no-slip does not apply at the surface of the diffuse material, since there can be some penetration depth of the boundary layer into the porous material.

The preheating effect is significant to the correct estimation of thermal comfort in terms of the operative temperature of the occupational zone. A model of the boundary condition of the diffuse inlet is necessary because the inlet is a conglomeration of an inlet and a wall boundary condition. Two methods of modelling can be chosen, a model based on the determination of radiative and convective material properties of the diffuse material, or a model based on empirical determination of the inlet surface temperature. The latter is chosen because it gives a better understanding of the physical interactions between the room climate conditions and the inlet flow velocity and temperature. A linear approach has been taken to develop a model of the surface temperature from experimental data of the independent parameters of flow through the diffuse material and flow and radiation properties in the occupational room.