Thermo Acoustic refrigeration is a phenomenon that uses high intensity sound waves in a pressurized gas tube to pump heat from one place to other to produce refrigeration effect. This system completely eliminates the need for lubricants and results in 40% less energy consumption.

1. THERMO ACOUSTIC REFRIGERATION
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Presented by
K.PAVAN KUMAR
MECHANICAL DEPT
VIGNAN ENGG COLLEGE
HYDERABAD.

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CONTENTS
• ABSTRACT
• INTRODUCTION
• BASICS OF REFRIGERATION
• DISADVANTAGES OF CONVENTIONAL REFRIGERATOR
• BASICS OF THERMO ACOUSTIC REFRIGERATION
• COMPONENTS
• HOW IT WORKS
• MERITS OF TAR
• DEMERITS OF TAR
• IMPROVEMENTS MADE
• APPLICATIONS
• CONCLUSION

3. ABSTRACT
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Thermo acoustic refrigeration (TAR) is a phenomenon
that uses high intensity sound waves in a pressurized gas tube to
pump heat from one place to other to produce refrigeration effect.
This system completely eliminates the need for
lubricants and results in 40% less energy consumption.

4. INTRODUCTION
 Thermo acoustic devices take advantage of sound waves
reverberating within them to convert a temperature differential into
mechanical energy or mechanical energy into a temperature
differential.
 Thermo acoustic devices perform best with inert gases.
 They do not produce the harmful environmental effects such as
global warming or stratospheric ozone depletion.
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Leading Researcher
United Technologies Corporation
Professor of Acoustics,
The Pennsylvania State
University.
He invented the thermo acoustic
refrigerator in the year 1992 and
that TAR was used in the space
shuttle Discovery(STS-42).
Steven L. Garrett

6. BASICS OF REFRIGERATION
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• In refrigeration heat is not created, it is converted and transferred.

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• The compressor is the heart of the system. It compresses the low pressure
refrigerant vapour into high pressure refrigerant vapour.
• The condenser removes heat from the refrigerant, it changes state into high
pressure liquid.
• Metering devices are small thin copper tubes (thermal expansion devices).
It regulates the amount of refrigerant going into the evaporator.
• The evaporator absorbs the heat in the system, the low pressure liquid
changes into low pressure gas.
• The low pressure vapour pulled into the compressor and the cycle starts
over….

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 Uses harmful refrigerants like ammonia, CFC’s and HFC’s
 Refrigerants if leaked causes the depletion in the ozone layers.
 Refrigerants are costly.
 The moving parts like the compressors require lubrication.
 Leakage of refrigerant may result in adverse human health
effects including cancers, immune system deficits, and
respiratory effects.
DISADVANTAGES OF CONVENTIONAL REFRIGERATOR

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BASICS OF THERMO ACOUSTIC REFRIGERATION
• Thermo acoustics combines the branches of acoustics and thermodynamics
together to move heat by using sound.
• While acoustics is primarily concerned with the macroscopic effects of sound
transfer like coupled pressure and motion oscillations, thermo acoustics
focuses on the microscopic temperature oscillations that accompany these
pressure changes.
• Thermo acoustics takes advantage of these pressure oscillations to move heat
on a macroscopic level.
• This results in a large temperature difference between the hot and cold sides
of the device and causes refrigeration.

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THERMO ACOUSTIC REFRIGERATOR

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COMPONENTS
RESONANCE TUBE:
The purpose of the resonance
tube in a TAR is to contain the
working fluid and to cause it to
have a desired natural frequency.

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ACOUSTIC LOUD SPEAKER:
• A loudspeaker is an electro acoustic
transducer that produces sound in
response to an electrical audio signal
input.
• It was invented in the mid 1820’s by
the scientist Johann Philipp Reis.
• It is powered by electricity.
• The magnet or the coil in the speaker
vibrates to produce the waves of
required frequency.

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REGENERATOR STACK:
• The most important piece of a thermo acoustic device is the stack.
• The stack consists of a large number of closely spaced surfaces that are
aligned parallel to the resonator tube.
• In a usual resonator tube, heat transfer occurs between the walls of cylinder
and the gas.
• However, since the vast majority of the molecules are far from the walls of
the chamber, the gas particles cannot exchange heat with the wall and just
oscillate in place, causing no net temperature difference.
• The purpose of the stack is to provide a medium where the walls are close
enough so that each time a packet of gas moves, the temperature differential
is transferred to the wall of the stack.

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• Most stacks consist of
honeycombed plastic spacers
that do not conduct heat
throughout the stack but rather
absorb heat locally.
• With this property, the stack
can temporarily absorb the heat
transferred by the sound waves.

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HEAT EXCHANGER:
• Heat exchangers are devices used to
transfer heat energy from one fluid to
another.
• The media maybe separated by a solid
wall, so that they never mix.
• They are widely used in space heating,
refrigeration, air conditioning, power
plants, chemical plants.

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HOW IT WORKS?
• Acoustic or sound waves can be utilized to produce cooling.
• The principle can be imagined as a loud speaker creating high amplitude
sound waves that can compress refrigerant allowing heat absorption.
• The pressure variations in the acoustic wave are accompanied by
temperature variations due to compressions and expansions of the gas.
• For a single medium, the average temperature at a certain location does not
change. When a second medium is present in the form of a solid wall, heat is
exchanged with the wall.
• An expanded gas parcel will take heat from the wall, while a compressed
parcel will reject heat to the wall.

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Experimental Setup

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MERITS OF TAR
• No moving parts for the process, so very reliable and a long life span.
• Environmentally friendly working medium (air, noble gas).
• Use of simple materials with no special requirements, which are commercially
available in large quantities and therefore relatively cheap.
• The technology could represent a major breakthrough using a variety of
refrigerants, and save up to 40% in energy.
• Thermo acoustic refrigeration works best with inert gases such as helium and
argon, which are harmless, nonflammable, nontoxic, non-ozone depleting or
global warming and is judged inexpensive to manufacture.

19. DEMERITS OF TAR
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• Thermo acoustic refrigeration is currently less efficient than the
traditional refrigerators.
• Lack of suppliers producing customized components.
• Lack of interest and funding from the industry due to their
concentration on developing alternative gases to CFCs.

20. IMPROVEMENTS MADE
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To overcome the drawbacks, some improvements were
made:
• In order to improve the efficiency, regenerators are used. The
function of a regenerator is to store thermal energy during part
of the cycle and return it later. This component can increase the
thermodynamic efficiency to impressive levels.
• Increasing the level of temperature gradient setup thereby
providing more refrigeration effect.

21. APPLICATIONS OF TAR
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• Liquefaction of natural gas.
• Chip cooling.
• Electronic equipment cooling on naval ships.
• Electricity from sunlight.
• Upgrading industrial waste heat.

22. CONCLUSION
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• Thermo acoustic engines and refrigerators were already being
considered a few years ago for specialized applications.
• Their simplicity, lack of lubrication and sliding seals, and their use
of environmentally harmless working fluids were adequate
compensation for their lower efficiencies.
• In future let us hope these thermo acoustic devices which promise
to improve everyone’s standard of living while helping to protect
the planet might soon take over other costly, less durable and
polluting engines and pumps.

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