Oil refining indirect cooling
An example of indirect cooling is oil refining. The oil is heated to produce various types of oils, and these heated oils must be cooled for further processing. Heated oil passes on one side of a heat exchanger with cooling water on the other, while the heat passes from the oil into the water.The now heated cooling water passes over a cooling tower where a portion of the hot cooling water evaporates.
A cooling tower is a structure where the heated water cascades from the top over a series of splash plates to create small droplets into a basin. Evaporation removes the heat from the water and latent heat also removes a portion of the heat. Once the heat is removed, this now cooled water is recycled back to the process for additional heat removal.
As the cooling water evaporates it must be replaced with fresh water, but during evaporation contaminates remain behind in the water. Typical contaminates include calcium and magnesium, which are also known as hardness and can cause scale. Because this cooling water is exposed to the environment, it can also be contaminated with dirt or debris which cause deposits or biological material and can cause biofouling. This cooling water can also be corrosive to metal. Scales, deposits, and biological fouling can reduce heat transfer and flow, while corrosion can deteriorate equipment: these issues increase costs and reduce production.