have you ever wondered how the
refrigerators in your home work
refrigerators which have become an
integral part of every household work
based on some simple and interesting
scientific principles
[Music]
beginning with the basic refrigerator
model this video will elaborate on the
operation of modern refrigerators along
with the secrets behind their high
energy efficiency
the basic principle of refrigerators is
simple simply pass a colder liquid
continuously around the object to be
cooled
let's see how this continuous cold
liquid flow is achieved inside a
refrigerator
a simple device called a throttling
device is the most crucial component of
refrigerators here a capillary tube is
used as throttling device a cold liquid
is produced using the throttling
phenomenon for effective throttling at
the inlet the refrigerant should be at a
liquid state under high pressure
the throttling device is an obstruction
to the flow so a huge pressure drop
occurs when the liquid flows through it
as the pressure drops the boiling point
of the liquid comes down thus the
refrigerant liquid evaporates the energy
required for such evaporation comes from
the refrigerant so its temperature drops
if you check the temperature across the
throttling device you will notice this
drop
please note that only a portion of the
refrigerant is evaporated here this is
one important property of the
refrigeration fluid it should be able to
change the phase while varying the
pressure under normal temperatures
the next phase is simple just pass this
cold liquid over the body which is to be
cooled
during the heat absorption process the
refrigerant further evaporates and
transforms into pure vapor
since there is phase change during this
process the refrigerant temperature does
not increase this heat exchanger is
called the evaporator
with the help of clever airflow
circulation inside the refrigerator
using an evaporator fan one can maintain
different temperature levels
so we have produced the required
refrigeration effect if we can take this
low pressure refrigerant to the state
before throttling that is high pressure
liquid we will be able to repeat this
process
so the first step is to raise the
pressure
a compressor is used for this purpose
the compressor will raise the pressure
back to its initial value
you can see that a reciprocating type
compressor is used here
however since it is compressing gas
along with pressure the temperature will
also increase this is unavoidable
now the refrigerant is high pressure
vapor to convert it to a liquid stage we
introduce another heat exchanger this
heat exchanger is fitted outside of the
refrigerator thus it will liberate heat
to its surroundings vapor will be
converted to liquid and temperature will
reach a normal level this heat exchanger
is known as a condenser
now the refrigerant is back to its
initial state so it can be fed to the
throttling device again
just by repeating this cycle over and
over we will be able to achieve a
continuous cooling effect this cycle is
more specifically called the vapor
compression cycle
refrigerator performance can be
evaluated using a term called
coefficient of performance
performance is output divided by input
so the coefficient of performance can be
easily defined as follows
this is the most basic refrigerator
possible ever this refrigerator will
work well in theory however
in practice it will face many issues
let's see what these issues are and how
to overcome them
one major issue is the frost developed
in the freezer compartment
the circulated air has moisture content
inside it so when the air comes in
contact with the cold evaporator coil
they will condense and form a frost
around the coil
such ice coating prevents further heat
transfer and the refrigerator becomes
inefficient over time
one great way to solve this issue is to
remove frost occasionally with the help
of a heating rod
this is why you can see a pan and water
condensate at the bottom of your
refrigerator
moreover in modern refrigerators you
won't be able to see the condenser fins
at the back of the refrigerator instead
they use a compact condenser arrangement
this compact arrangement is assisted by
a cooling fan and the same heat
rejection purpose is achieved here the
hot air expelled by the fan can be used
to effectively evaporate the water
condensate formed during the frosting
the improved refrigerator looks like
this
an interesting temperature distribution
in different parts of the refrigerator
is illustrated here
the temperature drop across the
capillary tube is also clearly depicted
here
you can see two refrigerant lines
outside the refrigerators one takes the
cold liquid from the capillary tube to
the evaporator coil and the other the
exit vapor line from the evaporator
however if you check your home
refrigerator you can see only one line
on the outside
why is this the case
the most crucial part of the
refrigerator is the capillary tube which
need not be a spring-like device it can
be a long straight tube as shown
temperature variation in the new
straight capillary tube is depicted here
you see only one line on your home
refrigerator because this straight
capillary tube runs inside the
evaporator exit coil
this simple technique has major
advantages
we know that during the heat absorption
process at evaporator the refrigerant
temperature does not rise only its phase
changes
this means that if we allow the
capillary tube to come into contact with
the evaporator exit line this will bring
down the capillary tube refrigerant
temperature by a great degree
this in effect will lead to greater
temperature drops in the capillary tube
thus creating a better refrigeration
effect
on the other hand the evaporator exit
coil absorbs heat this will ensure that
the refrigerant in the evaporator exit
line has transformed into pure vapor
this is good for compressors which are
designed to handle only pure vapor
a filter dryer is used to remove any
moisture contents in the refrigerant
which might become trapped in the
compressor operation
let us now explore the most recent
innovation in refrigerators which has
transformed modern refrigerators
digital inverter compressors
a compressor is the heart of any
refrigerator and is the device that
gives life to the whole system
you might have noticed that the
compressors in old refrigerators will
either be on or off this is a single
speed technology when the inside
temperature of the refrigerator reaches
an optimum level the compressor will be
turned off when the temperature goes
above a certain limit the compressors
will be turned on
so you can see that the temperature
control inside the refrigerator is not
smooth moreover such abrupt speed
variation of the compressors will lead
to durability issue to the compressor
components
with the help of digital inverter
compressor a variable compressor speed
is possible
thus a smooth and efficient evaporator
temperature control can be achieved here
here the ac power is converted to dc
using a controller the controller then
supplies electric power in variable
frequency to accurately control the
motor speed
the most common motor used in this
technology is a bldc digital inverter
compressor consumes at least 40 percent
less energy compared to the single speed
compressors
we hope this video gives you a clear
insight of the working of a modern
refrigerator we request your support at
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