Introduction To Heat Transfer

Suppose you are heating water in a kettle.

You want to boil the water for Maggie.

For boiling water, the heat gets transferred in steps from the kettle to water then to the surrounding.

First heat gets transferred to the kettle surface and then to the water inside the kettle and finally, it gets transferred to the surrounding.

This step by step procedure of transfer of heat takes place everywhere because heat can't get transfer suddenly from one body to another body.

Let's understand about different modes of heat transfer

Heat has a tendency to flow from a hotter body to a cooler body.

Heat transfer is the rate at which heat is transferred from one body to another.

The rate of heat transfer() can be expressed as,

There are three methods of heat transfer- Conduction, convection and radiation.

Let's understand them individually.

Conduction is the mode of heat transfer when two objects of different temperature are kept in contact.

Heat transfers from warmer body to cooler body until both reach the same temperature.

In conduction, the transfer of heat is due to the collision of molecules in the conducting medium.

If a metal rod is heated then heat transfer takes place gradually from one end to the other end.

In convection heat transfer takes place due to the motion of the hot fluid over the solid surface or within the fluid itself.

In convection, when fluid get heated then its density becomes less and it expands and rises over the cold fluid.

Exchange of fluid due to heat transfer within the fluid is called convective current.

Sea breeze and land breeze are due to the heating and cooling of sea water in day and night respectively, which causes convection.

Radiation is the method of heat transfer in which energy is transferred without any contact between source and body.

The body which has the temperature above zero Kelvin radiates energy in the form of radiation.

Radiation is the only method of heat transfer in which no medium is required.

Sun radiates energy in the form of radiation and requires no medium to transfer it from space to the earth.

Revision

Heat transfer is the rate at which heat is transferred from one body to another.

Conduction is the mode of heat transfer when two objects of different temperature are kept in contact.

In convection heat transfer takes place due to the motion of the hot fluid over the solid surface or within the fluid itself.

Radiation is the method of heat transfer in which energy is transferred without any contact source and body.

The End