Have you ever wondered why is heat such an interesting form of energy? This heat energy keeps us warm during the colder months. It helps us to prepare hot and delicious meals. However, its applications are not just limited to these. We must understand the properties of both heat and heat transfer since they are the key to several fields of science. Thermodynamics is one such field which only deals with the heat flow in a particular system, which refers to the heat transfer in that system. Did you know that even nuclear energy makes use of the heat which is created by the atoms for generating electricity? We can hence infer that heat is quite an important form of energy in our day to day life. This means that we must take a closer look at it and learn more about what is heat transfer.
The transfer of heat is a phenomenon that occurs from one object to the other. This generally happens from the object that is hot to the cold object. The process of heat transfer occurs through three different means which are mentioned as follows.
Let us define the conduction of heat.
According to the definition of heat conduction, it refers to the method of transfer of heat within the body or from one body to another. The heat transfer occurs because the molecules tend to vibrate at their mean positions. However, for the heat transfer to occur, the bodies through which it occurs have to be in close contact with one another. Also, we must remember that in heat conduction, there is no movement of matter occurring when the heat gets transferred from one object to the other.
The heat transfer or thermal conductivity tends to occur generally in the solids wherein the molecules in the structure are tightly held together by strong intermolecular forces of attraction. Hence, they only tend to vibrate at their mean positions when they receive the heat energy and then they tend to pass this energy to their surrounding molecules through vibrations.
Now that we learnt what is thermal conduction, let us learn what is convection.
Convection refers to the method of heat transfer that occurs usually in the liquid and gaseous states. According to this method, the transfer of heat energy takes place when there is an actual motion of the matter from one place in the body to another. Have you noticed that when you boil water, you would see bubbles and currents getting developed?
This is a great example if we want to understand what is heat convection. However, have you wondered why does this happen? Well, you notice the currents and bubbles while boiling water because the hot water at the bottom of the vessel become lighter and tend to move upwards. This forces the dense and colder water at the top move downwards to get heated up.
Radiation is the third type of heat transfer method. It is a process of heat transfer which does not need any sorts of medium and can easily be used for the transfer of heat in a vacuum. The process of heat transfer through radiation makes use of the electromagnetic waves that tend to transfer the heat from one place to another. A great example of the radiation process is sunlight. Both heat and light from the sun reach the Earth through the process of radiation.
Did you know about this amazing fact that the process of radiation is the most potent form of transfer of heat? This is the reason why we feel warm whenever we sit near the fire during winters without actually touching the wood that is burning. We feel this warmth and heat only because of radiation.
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Q1. What is Heat Exchange?
Ans. Heat transfer or heat exchange refers to the discipline of thermal engineering which involves the use, the generation, the exchange and the conversion of the heat energy between several systems. We can classify heat exchange into different mechanisms like conduction, convection, radiation and the transfer of the heat energy due to the phase changes. Many engineers also tend to consider the transfer of the mass of varying chemical elements, be it hot or cold, for achieving the heat exchange. All these heat exchange mechanisms often have varying characteristics but tend to occur simultaneously in a given system.
Q2. What are the Three Types of Heat Transfer?
Ans. The three types of heat transfer are thermal conduction, thermal convection and thermal radiation, all of which are defined as follows.
If we talk about the thermal conduction definition, it refers to the direct exchange of the kinetic energy of the molecules between two different systems. When one object is at a different temperature from the other in its surroundings, heat tends to flow so that both the body and the surrounding reaches the same temperature to a point of thermal equilibrium. This heat transfer occurs from the region of higher temperature to the region of lower temperature.
Thermal convection happens when the liquid or gas tends to carry the heat energy with the flow of the matter in that liquid.
Thermal radiation is a process of heat transfer which occurs through any transparent medium (either solid, liquid, or gas) or a vacuum. This transfer of heat through radiation occurs through the photons present in the electromagnetic waves that are governed by the same kind of laws.