The chemical process industry, petroleum refining, utilities, and many other industries, use large quantities of water for cooling.
There is an increased emphasis being placed upon the re-use of cooling water by means of cooling towers. The cooling effect is obtained by the evaporation of a small fraction of water and heat exchange with the air passing through the cooling tower. The problems encountered in cooling systems are not usually with the equipment, but with the water. As the water evaporates, the dissolved solids concentrate. These impurities in water cause scale and corrosion in the heat exchange equipment.