Assessment of optimal airflow baffle locations and angles in mechanically-ventilated dairy houses using computational fluid dynamics

Abstract

Baffles are often installed in mechanically cross-ventilated barns to combat heat stress by enhancing the cooling effect produced by the barn’s design. How effectively these baffles operate during warm weather often depends on where each baffle is located and at what angle it is set. Currently, their location and orientation are determined primarily according to the personal experience of the contractor in charge of installing the barn’s ventilation system. This study seeks to quantify the extent to which the location and orientation may affect the efficiency of the installed baffles. Computational fluid dynamics was used to create a three-dimensional model of a typical low-profile, cross-ventilated dairy barn. Differences were evaluated using both heat transfer and heat stress index (the Equivalent Temperature Index for Cattle - EITC). The results obtained from the tested scenarios indicated that installing the baffles above the animal occupied zone (AOZ) could indeed increase the air velocity (from less than 0.5 m s−1 to around 3 m s−1 once baffles were in place), and could also greatly increase (by 21.1%–50.9%) the amount of heat removed, while reducing the EITC by ~6 °C. In comparisons between the most commonly used scenario (in which baffles were installed vertically in the middle of the AOZ), and the other with-baffle-scenarios, the rate at which heat was removed from the cows varied by −3.0% to 2.6%, with the maximum difference being 172.4W. However, these scenario produced no significant improvement comparing with the commonly used one. The results obtained should provide a more reliable reference for engineers engaged in designing large-scale dairy barns.