Is Boiler Heat Exchanger:Facts And Comparative Analysis


This article answers the question- Is boiler heat exchanger?  The answer is yes. Heat exchangers as their name suggests are the devices that are used to transfer heat between the fluids.

Boiler will add heat to the working fluid and convert it into its gaseous state. This is exactly what a heat exchanger does- transfers heat. In this article we shall study about boilers in detail and find answers to various questions regarding it.

What is a boiler?

The name itself suggests that it boils the liquid and convert it into its gaseous state. A notable feature of boiler is that the temperature of the fluid remains the same and only the phase changes.

This is an example of adding latent heat to the system, in which the temperature does not change even when the heat is added. Boilers find their applications in power plants. Let us study more about boilers in detail.

is boiler heat exchanger
Image: A movable (mobile) boiler

Image credits: I, Sir IwanKociol parowy lokomobilowy typ Ln2 skansen kopalniatg 20070627CC BY-SA 3.0

Does boiler have a heat exchanger?

The main component of boiler is the heat exchanger. Without heat exchanger the transfer of heat cannot take place. We can say that boiler is itself a type of heat exchanger.

The working fluid that is liquid in this case is passed through this heat exchanger, another fluid with higher temperature also flows from other side of heat exchanger. Heat is transferred from the hotter liquid to the working liquid. The phase of the liquid changes into gaseous after absorbing the heat. The temperature of the hotter liquid comes down whereas the temperature of the working fluid remains the same (Note: working fluid here refers to the fluid that changes its phase)

Do all boilers have heat exchangers?

Yes. The heat exchanger is an essential component in any boiler. The number of heat exchangers inside the boiler can vary but boiler should have at least one heat exchanger.

The main function of boiler that is, to transfer heat to change the phase of fluid, is carried out by heat exchanger present inside the boiler. Without heat exchanger the heat transfer won’t be taking place.

Boiler vs heat exchanger

Boiler and heat exchanger are not exactly same. Their meanings are inter connected. Let us find out how they differ from each other and how they are similar to each other.

The table below shows the comparison between a boiler and a heat exchanger-

BoilerHeat Exchanger
Heat is added in the systemHeat can be added or extracted
Only phase transformation takes placePhase transformation is not compulsory
Temperature does not changeTemperature changes in most cases
All boilers are heat exchangersAll heat exchangers are not boilers
Table: Boiler vs Heat Exchanger

Applications of boiler

Boilers are used in industry for various applications. Some of the applications of boilers are mentioned in the section given below

  1. Operating room sterilization – Clean steam is produced by the boilers. This type of steam can be used for killing the bacteria and germs. Hence boilers find its application in hospitals as well.
  2. Equipment sterilization– As discussed in the above section, steam can be used to clean equipment also. The germs and bacteria on the surface of the equipment are killed which makes the equipment sterile.
  3. Production of clean steam– Clean steam is produced by boilers. No additives are required to change the phase of liquid.
  4. Providing heat for the building- Boilers are used in the buildings to heat up the buildings when its too cold outside. This generally happens in the areas where snowfall is a regular thing.
  5. Humidification for emergency rooms– Emergency rooms use boilers for humidification. The steam produced by the boiler increases the humidity inside the emergency room.
  6. Industrial laundry– Industrial laundry uses a boiler to heat the water and convert it into steam.
  7. Food preparation- When the food needs to be prepared in bulk, a boiler is used to heat up the contents of the food. This makes the food making process faster. Conventional gas flame will take a lot of time to heat up the contents to the required temperature. The boiler can also evenly heat the food items whereas gas flame will heat up the surface more as compared to the middle section.

Types of boilers

There are many types of boilers used in the industry. The type application defines the type of boiler that is to be used. Some applications require immense amount of heat and large size of boilers whereas some applications require only a small amount of heat and small sized boilers.

The different types of boilers used in the industry are given in the section below-

  1. Gas boilers– As the name suggests, a gas boiler burns gas to increase its kinetic energy. This can be used to create superheated steam or run turbines to generate electricity.
  2. Oil boilers- Likewise, oil boilers are types of boilers that burn oils for their applications.
  3. Husk fired boilers- In fired boilers, hot gases pass from a fire through tubes through a container of water which is sealed.
  4. Water tube boilers– As the name suggests, water is passed through tubes that are heated by fire. Many bathroom geysers use this type of boilers.
  5. Electric boilers– Electric boilers as their name suggests are those type of boilers in which heating is done by electricity. 
  6. High efficiency boilers- The high efficiency boilers have a better efficiency as they prevent escaping heat and bring it back to the heating space. This process is called condensing.
  7. Waste heat boilers– Waste heat refers to the rejected heat from any industrial process. Usually this heat is discarded and is not used. Waste heat boilers use this waste heat to perform.
  8. Biomass boilers- As the name suggests, Biomass boilers use naturally occurring non-fossil fuels as source of heat. These sources have high calorific value hence give out immense heat that can then be used in boilers.

Does temperature of working fluid change in Boiler?

One of the notable characteristics of boiler is that it does not change the temperature of working fluid (Here working fluid refers to the fluid whose phase transformation is taking place.

This is so because boiler only provides the latent heat of vaporisation which is only responsible for phase transformation and not increase in temperature. The phase transformation takes place at the same temperature, only the phase of the working fluid changes as we add heat to the system.

Conclusion

In this article we discussed about different types of boilers and drew a line between heat exchangers and boilers. They both are often considered as same things. But heat exchanger holds a broader meaning and boiler is just one small application of heat exchanger. Hence this confusion should be avoided.

Abhishek

I, Abhishek Khambhata, have pursued Btech in Mechanical Engineering. Throughout four years of my engineering, I have designed and flown unmanned aerial vehicles. My forte is fluid mechanics and thermal engineering. My fourth year project was based on performance enhancement of unmanned aerial vehicles using solar technology. I would like to connect with like minded people.

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