I don't think using the evaporation of water will be very effective because compared to 200 watts or heat will be insignificant. Also if the water condenses again all of your benefit will be lost. If you wanted to do this a mister like they use in gardens to cool it down might be an option, but you will need to continuely replace your coolant as well, and I don't think it is going to be cost effective in the respect as well.