Transcript Electrical Heating

ELECTRICAL HEATING
ELECTRICAL HEATING: Electric heating is any process in which electrical
energy is converted to heat.
 An electric heater is an electrical device that converts
electric current to heat.
 The heating element inside every electric heater is an
electrical resistor, and works on the principle of Joule
heating: an electric current passing through a resistor
will convert that electrical energy into heat energy.
Application:1. Domestic purposes –
 • Hot plates for cooking
 • Room heaters
 • Immersion heaters for water heating
 • Electric irons
 • Electric toasters
 • Electric ovens for baking etc.
2. Industrial purposes –
 • Melting of metals
 • Moulding of glass
 • Heat treatment processes
 • Baking of insulators
 • Enamelling of copper wires etc.
Mathode of electrical heating: Direct resistance heating: in this mathod of heating,current is passed through the body to
be heated.
Mathod of direct resistance heating: Resistance welding.
 In electrod boiler for heating water.
 Salth bath fernace.
Indirect resistance heating
 in this mathod of heating current is passed through a high
resistance wire know as heating elament. In this mathod heat
produse is proportional to losses.
 Heat so developed is transferred to from heating element to the
body to be heated.
Mathod of indirect resistance heating: Room heater.
 Immersion water heater.
 Restance ovens.
 In matelic strip used in starter.
Introduction of induction
heating
 Induction heating is a process which is used to bond, harden
or soften metals or other conductive materials. For many
modern manufacturing processes, induction heating offers
an attractive combination of speed, consistency and control.
 Induction heating is a non-contact heating process. It uses
high frequency electricity to heat materials that are
electrically conductive. Since it is non-contact, the heating
process does not contaminate the material being heated. It is
also very efficient since the heat is actually generated inside
the workpiece. This can be contrasted with other heating
methods where heat is generated in flame or heating
element, which is then applied to the workpiece. For these
reasons Induction heating leads itself to some unique
applications in industry.
How Induction heating
works?
 It helps to have a basic
understanding of the
principles of electricity.
When an alternating
electrical current is
applied to the primary
of a transformer, an
alternating
magnetic
field is created. A source
of
high
frequency
electricity is used to
drive a large alternating
current through a coil.
This coil is known as
the work coil. See the
picture opposite.
 In a basic induction heating setup shown at right, a solid state RF power
supply sends an AC current through an inductor (often a copper coil),
and the part to be heated (the workpiece) is placed inside the inductor.
The inductor serves as the transformer primary and the part to be heated
becomes a short circuit secondary. When a metal part is placed within
the inductor and enters the magnetic field, circulating eddy currents are
induced within the part.
 The passage of current through this coil generates a very intense and
rapidly changing magnetic field in the space within the work coil. The
workpiece to be heated is placed within this intense alternating magnetic
field.
 Depending on the nature of the workpiece material, a number of things
happen...
Alternative industrial
heating method
 Flame heating
 Resistance heating
 Traditional ovens and furnaces
Advantages of
induction heating
 Cleanliness
 Maximize productivity
 Improved product quality
 Extended fixture life
 Environmentally sound
 Reduce energy consumption
Advantages
 Absence of flue gases.
 Ease of control.
 Better working conditions.
 Very high efficiency of utilization.
 Uniform heating.
 No limit to upper maximum temperature.
Dielectric heating: The heating of non-metallic materials,such as wood
,plastics or ceramics, use can be made of thr dielectric
loos.
 Supply frequency are used as 10-50MHz.
 Voltage needed me be as high as 20Kv.
 Overall efficiency of dielectrical heating is about 50%.
Dielectric heating diagram:-
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