Introduction to Heat Transfer
On an Indian hot summer day, I took a glass of chilled orange juice to take few sips, but soon realised that it started getting warm amazingly fast. This drove my attention towards the heat transfer lessons I took during my online classes (P.S: It was a Pandemic Times).
After taking a deep dive into the discovery of heat transfer, I found that Newton is the first person to analyse the transfer of heat in 1701. Newton’s cooling law provides the first heat transfer formulation and is the formal basis of convective heat transfer. The key step in the application of the concept of heat transfer occurred with the publication of the “basic law of heat transfer” by Nusselt in 1915.
What is Heat Transfer?
Transfer of heat from one point to another point or from one bulk to another bulk due to driving force from higher potential region to lower potential region is known as heat transfer.
For an example of, the cold drink like coca cola becomes cold because the heat from soda transfers into the ice and not the other way around.
Heat transfer is further broken down to three modes as follows:
1) Conduction
2) Convection
3) Radiation
Conduction
So let’s split the word Conduction as “Conduct” and “Ions” which means conduction is the process by which heat is transmitted by collision of neighboring atoms and molecules. In conduction, particles are not allowed to leave its mean position that is static. But it is allowed to oscillate and vibrate being at the same mean position. Conduction always requires a conducting medium. Though the occurrence of conduction varies from medium to medium, i.e it occurs more easily in solid medium than liquid medium than gaseous medium.
For an example, consider you are cooking in an iron pot, placed over a stove top. At the same time, you leave a spoon into the pot while the stove is on. Here, your spoon will quickly turn hot taking the heat conducted from the iron pot.
Convection
Looking at the second mode of heat transfer that is Convection, it is the transfer of heat due to bulk movement of molecules within fluids i.e gases and liquids. Here in convection, the particles do not have any fixed mean position, rather they are free to move. Convection occurs more easily in gases and liquids as the molecules are less dense.
So let’s consider you’re boiling the water, here heat will be transferred from the fire to the bottom layer of your utensil. Water will soon start heating up and it’s density will be decreased. Due to this few water molecules will become lighter and bubbles would be formed. As bubbles start advancing upwards, the upper layered molecules of the water which is cold will be brought down. This whole process is known as convection.
Radiation
The third mode of heat transfer is Radiation. It is the emission and propagation of energy in the form of waves, rays or particles. The unique property of radiation from the other two modes is that it does not require any medium for heat transfer i.e. it is only the heat transfer mode which occurs in vacuum.
The simplest example is the radiation of heat from the sun through empty space to the earth. Here the heat transfer takes place through vacuum i.e. without any medium.
To conclude on the topic, as this is just an intro, I’ll soon be publishing each mode of heat transfer in detail. I hope you would like to deep dive further into modes of heat transfer with me :)
