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Application and History of Cooling Towers

9/30/2013 12:45:03 PM | by Anonymous

Chemicals: Cooling Tower

Cooling towers are devices that are used to remove heat. They transfer processed heat that is unwanted to our surrounding atmosphere. Cooling towers can use the evaporation process of water to get rid of unwanted heat to cool the fluids. If the cooling tower is the dry cooling type which is closed circuit, then it will use only air to cool the fluids. Cooling towers can come in many shapes and sizes. The larger types of cooling towers can reach up to heights of 200 meters.
History of cooling towers


Cooling towers were originated from the development and invention of condensers that were built for steam engines in the 19th century. Condensers used cool water to condense the steam that was produced by the steam engine’s pistons or turbines. This reduced the back pressure of the engine which lead to a reduction in steal and fuel consumption. The water is also re used which increased the power of the steam engines. The downside is that while costs are saved on fuel, the costs to obtain a sufficient amount of water exceeded that. It was more of a problem for land based machines as sea machines did not face this issue.


After further development, other systems began to form by adapting to the environment. Areas with more land used cooling ponds; Areas with a limited supply of water took advantage of municipal water sources while urban areas which lacked space used cooling towers.


The cooling towers were usually placed on building or rooftops that were either utilizing natural airflow or supplied with air through fans. The larger sized cooling towers were built in around the 1920s for usage in a coal fired electrical power station.


Applications


Many industries such as petrochemical, oil refineries, thermal power stations and chemical plants use cooling towers for many of their operations. There are induced draft and natural draft cooling towers and their classifications are based on the type of air induction into the tower. The larger types of towers that may reach heights of up to 200 meters are often utilized in nuclear power plants. Some big chemical and industrial plants also use such towers. In most industries, however, the cooling towers are much smaller and there are also units to release heat from the building’s air conditioning equipment.

 

Heat transfer methods


There are three types of cooling towers and they are based on the type of heat transfer used in the cooling towers. The three types of cooling towers are: dry cooling towers which operate by heat transfer that divides the cooling fluid from the air. The air goes into a tube into an air heat exchanger. Dry cooling towers cool 100% using air and evaporation is not used. The next type of cooling tower would be open circuit cooling towers or wet cooling towers. These types of towers use evaporative cooling methods. The cooling fluid and the evaporated fluid is usually the same. The last type of towers are known as closed circuit cooling towers or fluid cooling towers, they are a hybrid of the evaporation system and air induced systems. In this system, the cooling fluid is put through some tubes where by clean water is sprayed and there are also fans to apply a draft for further cooling. This method is the best as it is able to cool effectively but also ensures that the working fluid is not exposed to any contamination.


If the air is fairly dry, the warm fluids can be cooled to a lower temperature than the surrounding air. The surrounding air is put through a flow of water and this evaporates the air. As energy is required to evaporate the water, the temperature is thus reduced.


To improve cooling performance, something called a fill is used to widen the surface area and the duration of contact between the water flow and air flow. A splash fill is used to cause splashing by intercepting the flow of water. A film fill is usually made out of PVC and it contains the flowing water. All of these methods can be used to increase the duration of contact between the gases and fluids, while also increasing surface area to improve a transfer of heat.

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