09-06-2012, 05:53 PM
ELECTRIC HEATING
ELECTRIC HEATING.ppt (Size: 466.5 KB / Downloads: 30)
When current is passed through a conductor, the conductor becomes hot. When a magnetic material is brought in the vicinity of an alternating magnetic field heat is produced in the magnetic material.
Similarly it was found that when an electrically insulating material was subjected to electrical stresses, it too underwent a temperature rise (Dielectric heating).
Convection is the transfer of heat by the actual movement of the warmed matter.
Convection is the transfer of heat energy in a gas or liquid by movement of currents. (It can also happen is some solids, like sand.) The heat moves with the fluid.
Advantages of electric heating over other methods of heating
Clean and neat atmosphere
No pollution
Controlled atmosphere
Ease of control
Uniform heating
Low ambient temperature
Highest efficiency and utilization
Disadvantages
Electric heat requires a larger electrical service than normal. There is a cost associated with this
Some people would suggest that the electrical hazard of shock and fire caused by electricity is an issue
Expensive to operate. In many areas of North America, the cost of electricity makes it expensive to use as a heating fuel. It is not unusual for electric heat to cost 1/2 to 2 times as much as gas heating,
vii)Should with stand Vibration
In most industrial process quite strong vibrations are produced.
Some furnaces have to open or rock while hot. The element material should with stand the vibrations while hot and should not break open.
viii)Mechanical Strength
The material used should have sufficient mechanical strength of its own
