Heat Exchanger is equipment for heat transfer. It is rightly said that for efficient heat transfer from one medium to another medium heat exchanger is best to use. Because there are two different medium for transformation of heat both medium are separated by solid walls and they cannot mix each other but they can contact each other directly. Refrigeration, air-condition, power plants, natural gas processing, space heating are the areas for using heat exchanger.
Types of Heat Exchanger
According to flow arrangement heat exchanger is classified into two main class e.g. counter flow heat exchanger and parallel flow heat exchanger. When two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side this arrangement is called parallel fluid. When the fluids enter the exchanger from opposite ends is called counter flow heat exchanger. The counter flow design is more efficient because more heat is transfer through medium due to average temperature difference. Heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger for more efficiency. For increasing performance the addition of fins in one or both direction, it increase surface area and channel fluid flow.
Choosing the right heat exchanger (HX) requires some knowledge of the different heat exchanger types, as well as the environment where the unit must operate. Typically in the manufacturing industry, several differing types of heat exchangers are used for just the one process or system to derive the final product. There are many types of heat exchanger discussed below.
Shell and tube heat exchanger:
In this type a series of tubes is arranged. This set of tube is known as tube bundle. One fluid is passes through the one set of tube and other fluid either heated or cooled passes over the tubes for heat transfer by absorbing or providing heat. This type is used for high pressure application.
Plate heat exchanger:
This type consists of separated plates which are multiple and thin. Due to arrangement of plate the surface area is increased for heat transfer for fluid flow. It is mostly used in heating and ventilation and air conditioning (HVAC) application.
Adiabatic wheel heat exchanger:
A fourth type of heat exchanger uses an intermediate fluid or solid store to hold heat, which is then moved to the other side of the heat exchanger to be released. Two examples of this are adiabatic wheels, which consist of a large wheel with fine threads rotating through the hot and cold fluids, and fluid heat exchangers.
Spiral heat exchangers:
It consist of a helical tube configuration. There is a pair of flat surface in the form of coiled for counter flow arrangement. It has a long curves=d path for fluid ports are connected tangentially to outer arm of the coil.
To select an appropriate heat exchanger, the system designers (or equipment vendors) would firstly consider the design limitations for each heat exchanger type. Heat exchangers are most often selected via computer programs, either by system designers, or equipment vendors. Though cost is often the primary criterion, several other selection criteria are important such as thermal range, pressure limit, thermal performance and fluid flow capacity etc.
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