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Monday, August 5, 2013

PPT On Electric Heating

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Electric Heating Presentation Transcript:
1.Power Distribution & Utilization

2.Contents to be Covered
Introduction
Modes of Transfer of Heat
Classification of Electric Heating Methods
Resistance Heating
Arc Furnaces
Induction Heating
Dielectric Heating

3.Introduction:
Heating is required for domestic purposes as well as industrial purposes.
Industrial applications include
Melting of Metals
Hardening
Tempering
Case Hardening
Drying
Melting

4.Main Advantages of Electric Heating
Economy
Cleanliness
Absence of Flue Gases
Ease of Control
Automatic Protection
Upper Limit of Protection
Special Heating Requirement
High Efficiency of Utilization
Better Working Conditions
Safety

5.Modes of Transfer of Heat
Conduction
Convection
Radiation

6.Conduction:
In this mode of transfer of heat, one molecule of the substance gets heated and transfer the heat to the adjacent and so on.
Rate of conduction of heat along a substance depends upon temperature gradient.
Q=kA/t(T1-T2)T

7.Convection is the movement of molecules within fluids (i.e. liquids, gases).
It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.

8.Radiation:
Radiation is a process in which energetic particles or energy or waves travel through a medium or space.

9.Conduction:
In this mode of transfer of heat, one molecule of the substance gets heated and transfer the heat to the adjacent and so on.
Rate of conduction of heat along a substance depends upon temperature gradient.
Q=kA/t(T1-T2)T

10.Convection is the movement of molecules within fluids (i.e. liquids, gases).
It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids.

11. Radiation is a process in which energetic particles or energy or waves travel through a medium or space.

12.Classification of Electric Heating:
It can be classified as:
Direct Resistance Heating
Indirect Resistance Heating
Infra-red or Radiant Heating
Arc Heating
Direct Induction Heating
Indirect Induction Heating
Dielectric Heating

13.Resistance Heating:
It is based upon the I2R effect.
Has wide applications in heat treatment of metals, drying, baking of potteries, stoving of enamelled ware and domestic cooking.
Temperature upto 1000 celsuis can be obtained in ovens.
Two common methods of resistance heating are
Direct Resistance Heating
Indirect Resistance Heating

14.Direct Resistance Heating:
It is accomplished by the dissipation of an electric current in a material.
Material to be melted is placed inside a furnace with electrodes in the walls.
Alternating or direct electric current is then passed between the electrodes through the material.
Resistance losses are dissipated as heat, causing the material to melt.

15.Advantages:
High efficiency.
It gives uniform heat and high temperature.
Application:
It is mainly used in salt bath furnace and water heaters.

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