The cooling effect of a tower is based on the Latent Heat of Vapourisation. The latent heat of vapourisation is the amount of energy required to convert 1g of water to water vapour at the same temperature. An example is your kettle. When it boiling the water will remain at 100C unti all the water is converted to vapour. The amount of energy required heat 1g of water by 1C is 1 Joule but the amount of energy required to convert 1g of water to vapour is 540 Joules. In a cooling tower the higher energy water molecules are converted to water vapour by absorbing energy from surrounding molecules. The molecules that "donate" this energy are then depleted of energy and are therefore colder. If you go and do a serach under the heading of cooling towers you will find a lot of info on this process.
And also how the heat transfer takes place in a radiator witha fan strapped to it