Cooling towers can be either open or closed-loop, while condensing towers can only be closedloop. Open cooling towers are also necessarily wet towers. An open cooling tower directly sprays the process water into atmospheric air where some of it evaporates, cooling the remaining water, which is collected in a basin at the bottom of the tower. In a closed tower, the process liquid and air are always separated by a heat exchange barrier. Open cooling towers have fewer parts and are therefore less expensive; however, they may only be used to cool liquid water.