Environmental conditions within tunnel-ventilated and naturally ventilated dairy freestall facilities

摘要

Three pairs of naturally ventilated and tunnel-ventilated dairy barns were monitored during the summer of 2000 to compare the thermal environments developed by the two warm-season ventilation systems. Ambient air temperatures during midsummer were cooler than normal in both New York and Ohio, but both states had near-normal cooling seasons. Both ventilation systems performed well during these temperate summer conditions with indoor thermal conditions closely tracking those outdoors. Each of the tunnel-ventilated barns provided a slightly cooler interior environment than its naturally ventilated counterpart when outdoor conditions were potentially stressful (THI greater than 70). The average advantages in terms of reduced differentials between indoor and outdoor environments were -0.4 C and -0.4 for air temperature and THI, respectively, for the tunnel-ventilated barns. No difference existed between average air speeds within the cow spaces for the two summertime ventilation systems. Considerable spatial variation in air speed existed with both systems - at least a spread of 1 m/s in all barns. Airspeeds in the cow spaces were no less changeable with either system. Therefore, microclimate control should be an area of emphasis with both ventilationsystems. Improved designs are needed for tunnel ventilation to enable systems to maintain desired air velocities throughout the cow space and to better accommodate large barns.