A heat exchanger is a device used to transfer heat between two fluids, which can be liquid or gas, and this temperature exchange takes place without the need to mix them. The heat exchanger places two fluids next to each other without merging to transfer heat from the higher temperature fluid to the lower temperature fluid.
Heat exchangers can be used in central heating installations, air conditioners, swimming pools, chemical industries, and various other industries
The most important and widely used types of heat exchangers are:
• Shell and tube heat exchanger
• Plate heat exchanger
• Air-cooled heat exchanger
In the following, we will explain how each heat exchanger works, but before that, it should be mentioned that when choosing a heat exchanger, calculate and determine the capacity and heat level, type of exchanger, dimensions, material, working pressure, and fluid pressure drop. Passage through the coil or heat exchanger plates must be considered. Damatajhiz.com/en is a good reference for more information in this field.
Shell and tube heat exchanger
As mentioned earlier, we intend to use a heat exchanger to transfer heat between two fluids without direct contact between them. The shell and tube heat exchanger, as its name implies, consists of a large shell in which several tubes are placed. The first fluid passes through the shell and the second fluid flows through the tubes. In this way, the wall of the pipes will have two duties:
- First, as a barrier, they prevent the two fluids from combining.
- The second function of pipe walls is to transfer heat from hot fluid to colder fluid, and therefore their material must be as thermally conductive as possible.
Inside the shell of heat exchangers are parts called baffles to make the movement of fluid inside the shell uneven and heterogeneous. In this way, they increase the contact surface of the fluid inside the shell with the pipes containing the second fluid and thus increase the heat exchanging.
According to the shape, the fluid first enters from the inlet of the shell and then is guided by the baffles to the outlet of the shell. Similarly, the second fluid enters from the inlet of the pipes and passes through the pipes that pass through the shell so that it has the most contact with the fluid inside the shell. Fluid in the pipelines exits from the outlet after exchanging heat with the second fluid.
The design and construction of shell and tube heat exchangers are simpler than other types and in addition, they can withstand high pressure and temperature. That is why the use of shell and tube heat exchangers is very common in the industry.
In summary, the advantages of shell and tube converters are:
• In small volumes, they create a large surface for heat transfer.
• Can be used for a wide range of materials.
• They have a simpler design and manufacturing process.
• Easy to clean.
Plate heat exchanger
The structure and function of the plate heat exchanger are completely different from the type of shell and tube. This different structure and material make the plate heat exchanger not be able to withstand high pressure as much as the shell and tube type. But on the other hand, this structure allows more heat exchange, and this option causes them to show good efficiency in smaller volumes and dimensions, and as a result, their use in industry increases.
A plate heat exchanger consists of a large number of plates that are heat conductors and are placed in parallel. The system of this heat exchanger, like the type of shell and pipe, has two separate inlets and two outlets for each of the fluids, and as shown in the figure below, the path of each of these fluids is connected to the heat exchange plates one by one.
In this way, each plate contains a fluid, while inside the two adjacent plates, the second fluid flows at different temperatures, and these two fluids exchange heat through the wall of the plates without merging.
One of the types of heat exchangers that are especially used in most industries is cassette heat exchangers. Cassette plate heat exchangers, unlike welding types, are made of separate plates with sealing washers between them. It is taken and connected with screws.
Air-cooled heat exchanger
As the name implies, the air-cooled heat exchanger uses the air blown by the fans to reduce the temperature of the fluid inside the pipes (coils).
A very common and widely used example of air-cooled heat exchangers is the car radiator.
During the cooling process, the fluid enters the system pipes through the inlet. Twisted tubes with their curvature increase the joint surface with the blown air and accompany the fluid to the outlet of the system. Simultaneously with the passage of fluid through pipes, cool air is blown towards the pipes by the fans and thus the heat caused by the hot fluid is expelled.
It should be noted that air-cooled heat exchangers are a suitable alternative for projects that, given location and weather conditions, is not suitable to use cooling tower. Problems such as limited water resources or water pollution and its negative impact on the environment can be an obstacle to the use of cooling towers in some projects.
Finally, the types of air-cooled heat exchangers can be divided into 3 categories:
1. V-type air-cooled heat exchanger
2. Vertical air-cooled heat exchanger
3. Horizontal air-cooled heat exchanger
Do not forget that before buying and ordering an air-cooled heat exchanger, it is necessary to evaluate and design the plans related to the project and its location according to the usable environment and your needs.
In this regard, you can contact the experienced experts of the Damatajhiz collection, and receive the necessary specialized advice in 3 languages: Persian, English, and Arabic, or also you can obtain the necessary information by referring to the reference site of Damatajhiz.