In a perfect world, a “Big Ass Fan” is the way to go –
http://www.bigassfans.com/application/agricultural/equine/
In the real world, Air King Industrial makes very powerful, high quality, durable fans. You would probably only need a 14" fan on low - wouldn’t recommend the 12", b/c I don’t think it has a sealed motor. I have the 20" floor fan, which we mounted up on the wall; and it will blow you away on high. It’s way more fan than I needed. Yes, the Air King Industrial costs more than a Wal-Mart box fan; but not only is the quality and durability a million times better; they are a lot safer. The smallest size will be fine and cost less, but check the pricing, because sometimes a larger size in on sale and less expensive. You can’t go wrong with one of the black, powder coated models w/ the sealed bearings / motor.
Here’s a comparison of the options -
http://www.airkinglimited.com/compare/IndustrialComparison.pdf
http://www.airkinglimited.com/pages/industrial/floor2.html
Here is the fan I have
http://www.amazon.com/Air-King-20-Inch-Pivoting-9220/dp/B0007Q3RHK/ref=cm_cr_pr_product_top
I also have 2 of these fans from Northern tool - and they are less expensive - though I get free shipping w/ Amazon Prime.
http://www.northerntool.com/shop/tools/product_754509_754509
They would also probably work fine for you, but I do not expect them to last as long as the Air King, because they are not powder coated, and we live where rust is a problem. Additionally, while they say it moves 4550 cfm of air vs. 3670 cfm for the Air King. The Air King seems to be about twice as powerful, so I am skeptical about their specs. The Air King also has a more powerful motor - 1/6 hp for Air King vs. 1/8 hp for the Q standard. The Q Standard from Northern tool also claims a safety shutoff if it overheats, and although I don’t see it mentioned I KNOW ours came with brackets to mount them on the wall. WARNING - there is a review that says it does NOT have a sealed motor, so they may have changed something. Call Northern Tool before you order this to verify that it has a sealed motor – you definitely want a sealed motor!
Good Luck!