Heat exchangers are devices that system operators use to transfer heat from one fluid to another. In most cases, industries normally apply these heat exchangers in cooling engines to avoid system overheating that may lead to breakage. The heat exchanger deals with the energy transfer heat flow, which involves different modes of heat transfer like;
1. Radiation;- The transfer of heat energy where electromagnetic waves from a heated object are emitted on the outside surface.
2. Conduction;- The transfer of heat energy within materials or objects that are in contact, where temperatures are said to be the average kinetic energy of the molecules on heated objects.
3. Convection;- The transfer of heat energy between fluids such as water or air through a motion way.
How do heat exchangers work?
The heat exchanger works by flaming all gases which are natural, thus making a line of heated gas jests that goes upward over the flowing water through the pipes or channels. The water inside the pipe absorbs the heat energy thus becomes hot where the gas jet gets cold while the water gets hot.
Mechanical industries use various types of heat exchangers to perform various functions like cooling or heating machines, thus enabling them to work more efficiently, which is why heat exchangers are necessary for most of their applications. Below are some of the most common types of heat exchangers and how they are beneficial to industries.
1. Plate heat exchangers
Plate heat exchangers are types of heat exchangers which are designed with many corrugated and thin plate bundles where every pair gives a way-like channel to enhance the flowing of various substances. It can enable two fluids to flow in different areas since the pairs are attached by welding machines or bolts systems.
Due to the designation of the plate heat exchangers, industrial operators use them in the following operations.
Industrial applications of plate heat exchangers
i) Used in chemical processing.
ii) Used in opening loop water through the closed-loop.
iii) Used in heating systems.
iv) Used in systems under low temperatures.
Advantages of a plate heat exchanger in the mechanical industry
i) Plate heat exchanger is simple and easy to maintain; hence can last for a long time.
ii) Plate heat exchanger has many different gaskets and plates to enhance the transfer of heat in two or more fluids.
iii) Plate heat exchangers give a higher efficiency in the transfer of heat.
iv) Plate heat exchangers provide the recovery of heat in various substances.
v) the number of the plates to be installed the cost of the plate heat exchanger.
Disadvantages of plate heat exchangers
i) When using a plate heat exchanger, additional pump power is needed because of the narrow channel, which drops the pressure flow more severely.
ii) Plate heat exchangers throw away heat to the surrounding environment, thus reducing its efficiency and effectiveness.
iii) Plate heat exchangers can lead to system leakage due to high compression of the gaskets.
iv) It does not allow a good transfer of heat energy on two fluids that contain high differential temperatures.
2. Shell and tube heat exchangers
Shell and tube heat exchanger is the most commonly used type of heat exchanger by various mechanical industries. They are designed using a series of parallel tubes which are closed in a sealed cylinder, which contains pressure. The fluids flow separately in such a way that one flows around the sealed cylinder while the other one flows in a small tube.
Industrial applications of shell and tube heat exchangers
i) Used in cooling oil.
ii) Used in industrial painting operations.
iii) Used in preheating applications.
iv) Used to recover vapor systems.
v) Used in an oil refinery.
vi) Used in the recovery of boiler blow-down heat.
Advantages of shell and tube heat exchangers
i) Shell and tube heat exchangers have got a long service life as compared to other heat exchanger types.
ii) One doesn’t need to clean shell and tube heat exchangers, as in other types of heat exchangers, due to their internal reliability.
iii) Shell and tube heat exchangers enhance the regulation of power by adding the length, diameter, and various sections in the channel.
Disadvantages of shell and tube heat exchangers
i) Shell and tube heat exchangers increase the loss of energy in the channel; hence is not efficient.
ii) Shell and tube heat exchangers are vulnerable, especially at the outer part, because of the use of the electrical pipes which make them.
iii) Shell and tube heat exchangers have big dimensions of four meters in length with a weight of 120-150 kilograms; hence can not fit in the facility area.
3. Double pipe heat exchangers
In a double pipe heat exchanger, there are two or more cylinder pipes that allow the fluids to flow separately between and around or outside the pipes. The two pipes, which are straight, always form a U to ensure the effectiveness of heat transfer. The fluids flow smoothly without mixing as in other heat exchanger types.
Industrial applications of double pipe heat exchangers
i) Used to heat and cool machines or engines in engineering operations.
ii) Used in systems that contain high temperatures and pressures, such as compressors and boilers.
iii) Used in treating sewage.
iv) Used petroleum refinery.
Advantages of double pipe heat exchangers
i) Double pipe heat exchangers provide flexibility since they allow any removal or addition of parts.
ii) System operators can use double pipe heat exchangers in high temperatures and pressures.
iii) Double pipe heat exchangers have the best heat transfer despite their small footprints that require less or no maintenance cost and space.
iv) The sourcing and the repair of double pipe heat exchangers are easier than other heat exchanger types due to their high popularity and standardization.
Disadvantages of double pipe heat exchangers
i) Double pipe heat exchanger causes leakage when you pair them with many units.
ii) Double heat exchangers are restricted to lower heat as compared to big designs.
iii) It is an inefficient heat transfer mode, especially when there is space and budget for shell and tube heat exchangers.
iv) The cleaning of a double pipe heat exchanger is hard since one has to disassemble the whole system.
4. Air cooled heat exchanger
An air-cooled heat exchanger works by allowing the flow of hot fluids in a finned tube where the environmental air goes through the tube, thus cooling the process fluid leading to the discharge of the hot air in the atmosphere.
Industrial applications of air-cooled heat exchangers
i) Used in various engines.
ii) Used in refinery and chemical plants.
iii) Used in power plants.
iv) Used in cooling industrial water.
Advantages of air-cooled heat exchangers
i) Air-cooled heat exchangers do not use water during the cooling process.
Disadvantages of air-cooled heat exchangers
i) Air-cooled heat exchangers require a high cost of manufacturing.
ii) The area of air-cooled heat exchanger installation should be spacious.
iii) The fans cause environmental noise pollution.
Other types of heat exchanger devices which mechanical industries use in various applications include compact condensers, evaporators, and diabatic wheels.
Heat exchanger devices are made using different materials such as metals, composites, and plastics. Industrial operators should consider the heat outputs, fluids types, costs, and size of the heat exchanger before deciding on which one to use for various applications.