Refrigeration & Air Conditioning
Prepared By :
• The electrical energy is utilized by
converting it into one form or other for
getting suitable output from it.
• The utilization electrical energy for the
refrigeration and air conditioning is fast
replacing the old methods.
WHAT IS REFRIGERATION &
AIR CONDITIONING ?
• The process of reducing the temperature of a body
from the general level of temperature of
surroundings is called refrigeration.
• Air-conditioning means control of
temperature,humidity,purity and movement of air.
• The working conditions and comfort for human
beings is improved by air-conditioning.
• The temperature is brought down during summer
and increased during winter without causing any
• This is the machine by which the
temperature of substances is lowered by
storing them in this machine.
• A refrigerator works on
the principle of cooling
caused by evaporation.
• when we dip our finger
in petrol or spirit,and
the finger is taken out
cooling is felt. This is
because when petrol or
spirit evaporates it
draws heat from the
finger thus cooling it.
• The refrigerant is generally a gas which
circulated through different stages to extract
the heat from the substances.
• The various refrigerants used are carbon
and methyl chloride etc.
VAPOUR COMPRESSION CYCLE
• The main purpose of vapour
compression cycle is to
remove heat from the
refrigerant by putting it into a
stage for reuse.
• The various stages are
• The vapour compression refrigeration cycle is
employed for the following purposes
– Domestic refrigerator,
– Water cooler,
– Air conditioner,
– Ice plant,
– cold storage etc.
• The actual lay out of domestic refrigerator
is shown in figure below.
ELECTRICAL CIRCUIT OF
• The main parts of the electrical
circuit are shown in figure
• The various parts are
1. motor compressor unit
2. starting relay
4. overload protector
5. cabinet light
6. drier assembly.
MOTOR COMPERESSOR UNIT
• The motor is a single phase capacitor start
• The actual capacity of the motor depends
upon the size of the refrigerator.
• But generally the horsepower of motors
varies from 7/32 H.P. to 1/8 H.P.
• Mostly the motor and compressor are in one
unit and is known a sealed unit.
• The motor is operated
by this relay which is
also called motor
• It essentially consists
of a plunger on which
a coil is wound .
• The figure below
• A thermostatic
switch is used on all
controlled, and it is
• The construction of a
thermostat used in a
refrigerator is shown
in figure below:
• This is a thermal device which opens the
circuit of the motor when overloaded and
is called overload protector.
• The figure below shows the enlarged view
of a overload protector.
• This circuit contains a lamp and a switch.
• The switch is called door switch and so
installed that when the door is closed,the
bulb remains off.
• When the door is opened, the bulb remains
• This assembly is not employed on all the
• This is a high resistance wire passing
around the drier to remove the moisture
from the refrigerator.
• This is connected across the supply by the
• The room air conditioner is used to condition the
air of a particular space occupied by the human
beings i.e. office, room etc.
• It has automatic operation to control and maintain
the humidity of air.
• There are two parts divided by a partition with a
small opening at the top as
• The complete operation of
an air conditioner can be
studied under these sub
1.vapour compression cycle
• The figure below shows a
room air conditioner
• The electrical energy is utilised by converting it into
one form or the other form for getting suitable
output from it.
• The utilization of electrical energy for the
refrigeration and air conditioning is fast replacing
the old methods.
• Refrigeration and Air Conditioning has become a
necessity in every sphere of human utility and