Industrial Usage
See also: Cooling towerIndustrial cooling towers may use river water, coastal water (seawater) or well water as their source of fresh cooling water. The large mechanical induced-draft or forced-draft cooling towers in industrial plants continuously circulate cooling water through heat exchangers and other equipment where the water absorbs heat. That heat is then rejected to the atmosphere by the partial evaporation of the water in cooling towers where upflowing air is contacted with the circulating downflow of water. The loss of evaporated water into the air exhausted to the atmosphere is replaced by "make-up" fresh river water or fresh cooling water. Since the evaporation of pure water is replaced by make-up water containing carbonates and other dissolved salts, a portion of the circulating water is also continuously discarded as "blowdown" water to prevent the excessive build-up of salts in the circulating water.
On very large rivers, but more often at coastal and estuarine sites, "direct cooled" systems are often used instead. These industrial plants do not use cooling towers and the atmosphere as a heat sink but put the waste heat to the river or coastal water instead. These OTC systems thus rely upon a good supply of river water or seawater for their cooling needs. The warmed water is returned directly to the aquatic environment, often at temperatures above the ambient receiving water. Thermal pollution of rivers, estuaries and coastal waters is a consideration when siting such plants.
High grade industrial water (produced by reverse osmosis) and potable water is sometimes used in industrial plants requiring high-purity cooling water.
Some nuclear reactors use heavy water as cooling. Heavy water is employed in nuclear reactors because it is a weaker neutron absorber. This allows for the use of less enriched fuel. For the main cooling system, normal water is preferably employed through the use of a heat exchanger as heavy water is much more expensive. Reactors that use other materials for moderation (graphite) may also use normal water for cooling.
Read more about this topic: Water Cooling
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