There are two kinds of fluids in these exchangers and the cooling fluid is always air. Mechanism of these kinds of exchangers is like this:

Hot fluid enters from one side of the bundle that is been called Tube Bundle and on the way passing trough Tube Bundle gets cold by the air. In all kind of Air Coolers, air can enter to Tube Bundle in two different ways Force and Induced.

Entering air to the Tube Bundle exchanges heat with the moving fluid in the tubes. For increasing the rate of exchange the tubes in Tube Bundle have fins. These fins make the heat exchanging process much more effective. Small dimensions model of this exchanger is car's radiator.