Heat exchangers are devices that are specifically designed to be able to efficiently transfer heat from one fluid to another through a solid surface. This heat transfer takes one of two forms namely dissipation of heat or absorption. These two fluids should never come into contact with each other. They are found in everyday applications that include furnaces, air conditioning systems, domestic hot water systems, pool heaters, radiant floor heating, ground water systems, refrigerators and boilers.
Other applications of them include petroleum refineries, sewage treatment, space heating, power plants, natural gas processing, chemical plants and petrochemical plants. They are also known to be energy savers as they recover wasted heat and make it useful again. They come in different types and these are distinguished based on which direction the liquid will be flowing. This will include cross flow, parallel flow and counter-current heat exchangers. Parallel flow heat exchangers are designed in a way that all the fluids will be flowing on the same direction by entering and exiting the exchanger side by side.
The cross flow models are designed in a way that the fluid paths are running perpendicular to each other. The counter-current models are designed in a way that the fluid paths are flowing in opposite directions where one exists where the other is entering. They are more effective compared to the others. Heat exchangers are not classified according to their fluid direction only. They can also be classified according to their composition. Some of them are made of several tubes while others have hot plates that have room for the flow of liquid between them.
A Shell and tube exchanger is designed with several tubes which are divided into two sets where one contains the liquid for cooling or heating and the other contains the liquid that triggers the exchange. This type of exchanger should be well designed especially the diameter of the tube and the thickness of the wall in order to allow optimum heat exchange. A plate exchanger has thin plates that are joined together with small spaces between them. These exchangers have large surface areas.
Regenerative heat exchanger is another type of exchanger and this works when a fluid is passed on the two sides of the exchanger. This fluid can get very hot and this will mean that the exiting fluid will be used for warming the incoming fluid which will maintain a near constant temperature. Another type of exchanger is the Adiabatic wheel heat exchanger where an intermediate fluid is used for storing heat and is then transferred to the exchangers opposite side. This exchanger has a large wheel that has threads for rotating through the fluids to transfer heat.
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