| The thermal environmental quality and odor gases concentrations are critical to the health of livestock. The internal environmental condition is significant to the safety of livestock production and profit of livestock farmers. A good assessment of internal environmental conditions can reveal the drawbacks of the current ventilation system and contribute to the optimal design, then lower the risk of economic loss. Assessments on farrowing house and laying hen house and an optimal design were conducted using Computational Fluid Dynamic (CFD) technology in this research. It can not only provide an effective method for the numerical simulation of thermal environmental condition, but also provide a theory basis and useful guidance for the design of ventilation and cooling system in livestock facilities, even the structure of them.A typical farrowing house and caged laying hen house were selected to conduct the field experiments. Ansys Fluent14.0was applied and RNG k-ε turbulence model was chosen in this research, and after solving the governing equations, we get the simulated results of distribution for airflow, temperature, relative humidity. The simulated results show that:1) In the farrowing house, two airflow generated by the two wet pads were merged into one airflow. This airflow was droved from west to east by the exhausting fans which were equipped in the east wall. The air velocities close to inlets and outlets were all bigger than other places, especially the pig occupied zone (POZ). There were two big stagnant zones in the house. They were closed to the two side wall at the area5-10meter away from the west wall, caused by the airflow. The temperature increased along with the movement of air. The highest temperature was34℃occurred at the place closed to the outlets. In general, temperature above POZ was lower than that close to the POZ. Relative humidity distribution showed an inverse trend compared with temperature distribution. The highest RH was87.5%at the inlet. It can be concluded that this wet pad cooling system was not suitable for sows and piglets in the hot humid summertime. 2) In the laying hen house, similar with farrowing house, the air velocities near inlets and outlets were higher than other places. The velocity was very small at the place near cages. Because the two additional wet pads were equipped in the two side walls, there were two stagnant zones in the velocity contours. The area of stagnant zones showed a positive relation to the area of the wet pad equipped in the side wall. The temperature increased from27℃near inlets to32℃near outlets. The heat accumulation was significant in the stagnant zone closed to layers. It came to conclusion that this kind of wet pad cooling system can not suit all layers. Besides that, according to the drawbacks of current ventilation system, two improved designs were pointed out. The two pads in the side walls were removed from side walls and added to the west end wall in one case. In the other case, all pads including those in the west wall were removed and equipped separately at the middle of the two side walls. The simulated results of both improved cases show that the uniformity of airflow is best in these three cases, and the mean temperature in improved case2is the lowest in these three cases. |
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