Assessing ventilation design of dairy buildings equipped with automated milking systems using computational fluid dynamics

Abstract

• CFD models were developed and validated for two full-scale AMS dairy barns. • Baffles reduced pen temperature by 4.25 % and more than doubled airflow. • Supply fans showed no airflow benefit at cow resting height (0.5 m). • AMS units placed along the side wall did not block airflow (preferred layout). • Air inlets with baffles improved airflow more efficiently than supply fans. Automated milking systems (AMS) are increasingly used in dairy production to address labor shortages while supporting cow health and milk production. However, their integration into barn layouts can restrict airflow and increase the risk of heat stress in lactating cows. In this study, we developed and validated computational fluid dynamics (CFD) models for two full-scale AMS barns to evaluate airflow and temperature distribution under different ventilation designs. Farm 1, a tunnel-ventilated barn, housed 218 lactating cows and six milking robots, while Farm 2, a cross-ventilated barn, accommodated 424 lactating cows and eight robots. The model geometry incorporated standing and lying cows, AMS units, ventilation and circulation fans, air inlets, stalls, feed alleys, and baffles. A mesh convergence test was conducted, with the final number of elements ranging from 16.7 to 21.4 million and y + values below 300. In Farm 1, replacing supply fans with an air inlet had no significant impact on temperature or airflow distribution at either cow resting or standing heights, indicating limited benefit from using supply fans, especially considering their energy consumption. Meanwhile, adding baffles reduced temperatures in the commitment pen by up to 4.25 % and increased air velocity at 0.5 m from 0.33 ± 0.2 to 0.77 ± 0.3 m s −1 (p = 0.005). In Farm 2, AMS units were placed along the side wall, and as expected, their removal had no measurable effect on temperature (≤0.2 °C difference, p > 0.05) or air velocity (≤0.08 m s −1 difference, p > 0.05). This highlights the importance of strategically placing AMS units, even in retrofitted barns, to prevent blocking airflow. Although supply fans improved airflow at 1.5 m, they provided no benefit at 0.5 m, where air velocity remained low (0.98 ± 0.1 m s −1 ), comparable to or even lower than other treatments, further suggesting their limited effectiveness, particularly at cow resting height.