Presentationon

HEAT TRANSFER submitted by: Aaditya soni b.tech(mechanical)

HEAT

It is the form of energy that could be transfer from one system to another.

Heat is never contained in a body.Associated with the motion of molecules.

.Heat transfer is the exchange of thermal

energy between physical systems.Temperature difference is its driving force.Always occur from higher temperature region

to lower temperature region.

Heat transfer

CONDUCTIONCONVECTIONRADIATION

Modes of heat transfer

Transfer of heat through direct contact.Without any appreciable motion of

molecules.Heat flows as a result of temperature

gradient.From high temperature region to low

temperature region.

CONDUCTION

Through lattice vibration.By the transport of free electron.

Modes of heat transfer by conduction

STEADY STATE CONDUCTIONTRANSIENT CONDUCTIONRELATIVISTIC CONDUCTIONQUANTUM CONDUCTION

Types of CONDUCTION

Some materials conduct heat better than others.Materials that transfer heat well are called

conductors.Metals are usually good conductors.Wood, paper and plastic are not.Materials that stop the transfer of heat are called

insulators (styrofoam, wool, fiberglass).

CONDUCTORS AND INSULATORS

ConductionThe molecules do

not have to be the same substance.

1. When you heat a metal pan at the bottom, the heat travels to the other end.

As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat, since it’s a metal heat will also by the transport of electron within the boundary of metal pan.

Example OF CONDUCTION

Example 2

The metal conducts heat from the cup of warm water to the cup of cool water.

Your Coke becomes cold because the heat from the soda transfers into the ice, not the other way around.

Example 3

Convection

• Heat transfer by convection is the transfer of heat through the fluid (liquids and gases) movement of currents.

Types of CONVECTION

NATURAL CONVECTIONFORCED CONVECTION

Natural Convection

• Warm fluids rise, cool down, sink, and then are warmed again.

Forced convection

When the convection is accomplish with the help of forced air or fan then it is known as forced convection

The radiator warms the room by warming theair around it. Then the warm air transfers heat

to the rest of the room through convection.

As air above the road warms up, it rises and is replaced bycooler air, forming a convection current.

RadiationHeat transfer by radiation is the transfer of heat

through electromagnetic waves. In the bandwidth of between 0.1 to 100 micro meter.

Radiation

• There is no direct contact between the substances.

No need of material or medium to propagate.

Example

This picture illustrates all three type of heat transfer.Can you identify them all?

Conduction

Radiation

Convection

In nuclear power stationsFast dissipation of heat in engines(Fins)Heat transfer through composite wallsArchitecture.Heat exchangers.Cooling techniques.

APPLICATIONS OF HEAT TRANSFER

ReferencesJP HOLLMAN (HEAT TRANSFER)TECHMAXIIN

Thank you folks!

ANY QUESTIONS?