Heat Transfer Designs

Introduction :

Heat transfer:- There are three modes of heat transfer for different form of substance we have different method of transfer of heat. Like for solids mode of transfer of heat is conduction. Conduction is a process of heat transfer in solids. In this process, heat is transferred from particles to particles of the solid, without the actual movement of the particles.

 

We can see the simple experiment for this

1. Put drops of wax at regular intervals on an iron rod( or any other metal).
2. Heat one end of the rod over a candle flame.
3. Repeat the procedure using a plastic rod.

Observation and Conclusions for Heat Transfer

Observation:

1. With the metal rod:- the drop nearest to the flame melts first, one by one all the drops melts, and the end of the rod opposite to the flame begins to feel warm to the touch.
2. With plastic rod :- the end closer to the flame begins to melt while the wax drops remain unaffected. Also, the rod does not feel warm to the touch.

Conclusion:

1. Certain material for example allows heat to pass through them while certain material does not.
2. The heat is transferred from particles to particles themselves moving. This is inferred from the fact that the entire rod does not get heated at once. The wax drops melt one by one gradually. This mode of heat transfer is called conduction.

Heat Transfer by Convection

Convection:- convection is the transfer of heat through a body by the hot particles themselves moving from place and place.
Transfer of heat by convection takes place in liquid and gases only. It does not occur in solids because the particles in solids are not free to move about.
One example when a beaker of water containing a crystal of potassium permanganate is heated over a low flame, an upward current of colored water is seen rising from the point where heat is applied. This colored stream reaches the top, spreads out and circulates down the sides of the beaker.
These were the some points related to heat transfer. Knowledge of this much is very important.