Evaluation of Positive Pressure Air Distribution Systems for Diary Housing

摘要

Heat stress is a major concern for dairy farmers across the United States. During the summer months especially, the stress brought on by excessive heat can cause lactating cows to produce less milk and can also adversely affect an animal's health. Inparticular, dairy cows often experience acute heat stress due to the high temperatures and high relative humidity in crowded holding pens. To mitigate the problem, many dairies have been using arrays of large-diameter fans to circulate the air in the lounging area. These fans, however, tend to merely recirculate the hot and humid air inside the holding pen, and air speed they generate is generally not high enough to alleviate heat stress. The present study examines the efficacy of using positive pressure tubes to entrain fresh air from outside the holding pen and blow uniform impinging jets at an optimum speed to achieve desired convective cooling effects. We developed a prototypical poly-tube cooling system so that we could examine the flow patterns of the air jets and thereby achieve enhanced heat transfer coefficients within the target area. Using computational fluid dynamics followed by experimental verifications, we evaluated an array of air jets that directly impinge on targeted animals.