Abstract
The effective ventilation rates and the mixing factors in a mechanical ventilated dairy barn were measured and evaluated by using a water vapor balance method. Farther, the methods of estimating these parameters were discussed. The results were summarized as follows;
(1) The effective ventilation rates were approximately equal to the exhaust air volumes of fans at the time of low ventilation rate when the only two fans were moved. They showed two patterns of values, higher and lower than the exhaust air volumes of fans, at the time of high ventilation rate when the five fans were moved simultaneously. During the grazing time, the effective ventilation rates were lower than the exhaust air volumes of fans. From these results, it was suggested that the short-circuiting air ways occurred in the air space of the dairy barn at the time of high ventilation rate and at the grazing time.
(2) The mixing factors obtained from the effective ventilation rates and the exhaust air volumes of fans were from 0.6 to 1.3 in time and from 0.5 to 1.8 in space. The range of these values was wider than that of the values which Barber et al. (1984) obtained in the scale model experiments.
(3) The mixing factors based on the water vapor balance agreed approximately with those based on the sensible heat balance.
(4) Through these results and discussions, it was confirmed that the effective ventilation rates and mixing factor in livestock barns could be evaluated by the water vapor balance method.
