I would imagion where your live in Arizona it gets pretty hot in spring and summer so yours would vary to mine in Wyoming. I get by with a swamp cooler running it non stop while the steers are inside the room. When it is really hot, I keep them in during most of the day putting them in during the morning hours and letting them out at dusk when it starts to cool down. I them them out all night and they get a few hours of day lite between morning and dusk hours. If it gets really hot where you are at, a swamp cooler might not work and you would need a refrigerated room. When the steers are in the room, I would leave the cooling units always running as it always pushes fresh air into the room. Then let them out during the night time and a few hours on sun light is good for them. I don't think fan blade size matters much as long as it blows cool to keep the room cool and moves the air around enough, it is more of the temp inside of the room than a breeze blowing on the steers. Hope this helps.