Several of our monitor farms are working to install fans to help with cow cooling. These tend to be the big (60” to 72” diameter) vertical fans – often with wind-directing vanes. Two points come to mind.
Firstly the aim is to generate a light breeze (2 m/sec, Force 2 Beaufort or, leaves rustle) across the backs of the cows. So the fans want to be situated where we want the cows to be (cubicles, feed barriers, collecting yard) and the fans directed so the wind blows down into the cows. When the wind hits the cows or the ground it will bounce back up so do not have the fans too high nor the downward angle too severe and try to ‘daisy-chain’ the fans to repeatedly push the air back down amongst the cows.
Secondly there is a daily cycle to heat stress; cows build up a heat load during the day and then try and rid them selves of the load in the evening. During the day fans will reduce the build up but in the cooler evenings the fans really help shift the heat load build up. Some farms will run the fans 24 hrs a day to maximise the night time reduction of heat load, some will tun them off from say 2am to 6am but avoid turning them off at 8pm just as the evening is cooling down as the cows still need to shed the day’s heat load.