ELECTRIC HEATING

                       ELECTRIC HEATING

 WHAT IS ELECTRIC HEATING?

ELECTRIC HEATING IS ANY PROCESS IN WHICH ELECTRICAL ENERGY IS CONVERTED INTO HEAT ENERGY. ELECTRIC HEATING WORKS ON THE PRINCIPLE OF 'JOULE HEATING' (AN ELECTRIC CURRENT THROUGH A RESISTOR CONVERTS ELECTRICAL ENERGY INTO HEAT ENERGY)

A SOLID MATERIAL WHICH AS RESISTANCE 'R' OHMS AND CURRENT FLOWING THROUGH IT'S AMPS FOR 't' SECONDS THEN THAT HEAT PRODUCED IN THE MATERIAL WILL BE IN JOULES.

APPLICATION OF ELECTRICAL HEATING

-GEYSERS

-ELECTRIC KETTLE

-ELECTRIC IRON

-ELECTRIC OVEN FOR BAKING PRODUCTS

-ROOM HEATER FOR HEATING THE BUILDING

INDUSTRIAL APPLICATION

-MELTING OF METALS

-ELECTRIC WELDING

-BAKING OF INSULATOR

-MAKING OF PLYWOOD

ADVANTAGES OF ELECTRICAL HEATING OVER OTHER METHOD OF HEATING

1. CLEAN AND ATMOSPHERE/ FREE FROM DUST

2. NO POLLUTION

3. NO FLUE GASES

4. RESPONSE QUICKLY

5. LOCALIZED APPLICATION

6. MOBILITY OF JOB

7. HIGHEST EFFICIENCY OF UTILIZATION

8. ACCURATE CONTROLLED TEMPERATURE CAN BE MADE EASILY

HOW HEAT IS TRANSFERRED/ TRANSFER OF HEAT

CONDUCTION

 THE PHENOMENON TAKES PLACE IN SOLID, LIQUID, AND GAS, HEAT TRANSFER IS PROPORTIONAL TO THE DIFFERENCE OF TEMPERATURES BETWEEN TWO FACES. NO ACTUAL MOTION OF MOLECULES. MOLECULE OF ONE SUBSTANCE IS HEATED AND TRANSFER HEAT TO ADJACENT ONE.

                                                   Q= KA (T1-T2)T/t

CONVECTION

THIS PHENOMENON TAKES PLACE IN LIQUID AND GAS. HEAT IS TRANSFERRED DUE TO ACTUAL MOTION OF MOLECULES DURING MIXING OF ONE PORTION OF FLUID WITH ANOTHER.

                                                      H=A(T1-T2)b

RADIATION

THIS PHENOMENON OS CONFINED TO SURFACES. RADIANT ENERGY EMITTED OR ABSORBED IS DEPENDENT ON THE NATURE OF THE SURFACE.

HOT BODY EMITS MORE HEAT

COLD BODY RECEIVES MORE HEAT

H= 5.72*104K{(t1/1000)4-(1000)4}

CLASSIFICATION OF ELECTRICAL HEATING

#POWER FREQUENCY HEATING

1. RESISTANCE HEATING

a. DIRECT RESISTANCE HEATING

b. INDIRECT RESISTANCE HEATING                              

2. ARC HEATING

a. DIRECT ARC HEATING

b. INDIRECT ARC HEATING

# HIGH-FREQUENCY HEATING

1. INDUCTION HEATING

a. DIRECT CORE TYPE

b. CORELESS TYPE

2. DIELECTRIC HEATING

3. INFRARED HEATING

CHARACTERISTICS OF HEATING ELEMENTS

- HIGH RESISTIVITY SO THAT SMALL LENGTH OF WIRE MAY BE SUFFICIENT TO PRODUCE REQUIRED AMOUNT OF HEAT.

- ABLE TO WITHSTAND HIGH TEMPERATURES WITHOUT DETERIORATION

- LOW-TEMPERATURE COEFFICIENT OF RESISTANCE SO THAT RESISTANCE MAY NOT CHANGE WITH VARY RESISTANCE.

#RESISTANCE HEATING

1. DIRECT RESISTANCE HEATING

. AS THE HEAT IS DEVELOPED IN THE CHARGE ITSELF, THIS BECOMES A VERY EFFICIENT PROCESS OF HEATING

2. INDIRECT RESISTANCE HEATING

IN THIS METHOD, HEAT IS TRANSFERRED TO THE CHARGE BY CONDUCTION, CONVECTION, OR RADIATION.

DIFFERENCE BETWEEN DIRECT HEATING AND INDIRECT HEATING

# DIRECT HEATING

1. ELECTRIC CURRENT IS PASSED THROUGH THE BODY(CHARGE) TO BE HEATED.

2. HIGH EFFICIENCY

3. MODE OF HEATING IS CONDUCTION

#INDIRECT HEATING

1. ELECTRIC CURRENT IS PASSED THROUGH HIGHLY RESISTIVE WIRE(HEATING ELEMENT) PLACED INSIDE AN OVEN.

2. MODE OF HEAT TRANSFER IS CONDUCTION/ CONVECTION/ RADIATION

# DIELECTRIC HEATING

1. IT IS ALSO CALLED HIGH-FREQUENCY CAPACITIVE HEATING

2. EMPLOYED FOR HEATING INSULATORS LIKE WOOD, PLASTIC, AND CERAMICS

3. DEHYDRATION OF FOOD

# INDUCTION HEATING

INDUCTION HEATING PROCESS MAKES USE OF CURRENTS INDUCED BY ELECTROMAGNETIC ACTION IN THE MATERIAL TO BE HEATED AND IT USES TRANSFORMER PRINCIPLE AND THE CONVERSION OF ELECTROMAGNETIC ENERGY INTO HEAT ENERGY TAKES PLACE IN THE MATERIAL.