A heat exchanger is a piece of equipment that continually transfers heat from one medium to another in order to carry process energy.
The natural laws of physics always allow the driving energy in a system to flow until equilibrium is reached. As long as there is a temperature difference, heat leaves the hottest fluid and will be transferred to the colder fluid. A heat exchanger is a piece of machinery designed solely for the transfer of heat energy between two mediums, it is therefor necessary that it has large contact surface areas of material separating each medium.
The theory of heat transfer from one media to another, or from one fluid to another, is determined by several basic rules:
• Heat will always be transferred from a hot product to a cold product.
• There must always be a temperature difference between the products.
• The heat lost by the hot product is equal to the amount of heat gained by the cold product, except for energy losses to the surrounding area.
About Heat Exchangers
Heat exchangers are devices used to transfer heat from one fluid to another while preventing the two from mixing. Heat exchanger manufacturers can make three main types: shell and tube heat exchangers, air-cooled heat exchangers and plate heat exchangers. Generally, a metal wall partition, acting as a conductor, is between the two fluids. A hot solution flowing on one side of the barrier transfers its heat to a cooler solution flowing on the other side. Thermal energy only flows from the hotter to the cooler in an attempt to reach equilibrium. The surface area of a heat exchanger affects its speed and efficiency: the larger a heat exchanger’s surface area, the faster and more efficient the heat transfer.
About Shell and Tube Type Heat Exchangers
Shell and tube type heat exchanger consist of a bundle of parallel sanitary tubes with the ends expanded in tube sheets. The bundle is contained in a cylindrical shell. Connections are such that the tubes can contain either the product or the media, depending upon the application. The major limitation is that they cannot be used to regenerate, but they can transfer a large amount of heat due to the large surface area.