Cooling towers exchange the heat contained in the circulating water by spreading out the water over a large surface area and bringing air into contact with the surface of the water. The volume of water passed over the cooling tower is always much greater than the amount of evaporation that occurs, which is typically about 1.6 percent of the circulating flow. So, the opportunity for impurities to build up is reduced because the water has a constant washing affect. Fouling of the heat exchange surface does not significantly reduce the surface area of the water until it is severe.
DHD Cooling Ltd.