We have a lot of the "silliest" answers here, from people who have no datacenter or AC experience. You put up a bounty, you get stupid spammers and beggars.
Before qualifying any answer as silly or stupid, I think we need to know some additional considerations such as the amount of money he is willing to spend.
If we take into account the kind of unit he is considering to buy, that
sounds more like a kind of garage project, in the line of DIY and low cost solutions.
In the company where I work, we recently did an investment in a cooling solution. The company spent a bit more than 50,000 euros (about 80,000 USD) in a solution based on in-row equipment from APC, like the one linked below. This was a very small datacenter with a power consumption much lower than 40,000 W
http://www.apc.com/products/family/index.cfm?id=379So, if someone is willing to spend an amount in the range of 3000~4000 USD, maybe the silly solutions are those intended for real datacenters. May be, if he had a budget in the range of 100,000 USD he would be addressing his doubts to a professional cooling consultant. May be he would be ordering and paying a whole study and a project instead of being offering 0.25 BTC (about 180 USD) looking for ideas into a community of unknown people.
This.
I am looking for low cost, DIY solutions. This will be built out in space not originally intended for Crypto mining. I want to keep expenses to a minimum.....no need to spend all the profit on cooling the damn things.