Thermoacoustic Refrigeration

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Thermoacoustic Refrigeration

• By
• P Naga Vishnu
• P Shanmukha Reddy

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Introduction

• Thermoacoustics combines the branches of
  acoustics and thermodynamics together to move
  heat using sound.
• Acoustics is primarily concerned with the
  macroscopic effects of sound transfer like
  coupled pressure and motion oscillations.
• Thermoacoustics focuses on the microscopic
  temperature oscillations that accompany these
  pressure changes.

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Basic Principle

• Thermoacoustics is based on the principle that
  sound waves are pressure waves and they propagate
  causing compressions and rarefactions in the
  medium.

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• In the region of compression the pressure is
  high, and in the region of rarefaction the
  pressure is low.
• As sound waves are adiabatic in nature applying
  First law of thermodynamics here we get high
  temperature at compression and low temp at
  rarefaction.

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Working
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• Sound waves of required frequency are generated
  by using the loud speaker.
• These sound waves are allowed to pass through the
  Stack the Resonator in which standing waves are
  produced.
• This resonator is filled with the inert gas
  (Helium) and those gas particles oscillates back
  and forth parallel to the stack due to this
  standing waves.

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• By this a temperature gradient in formed along
  the stack.
• At the colder end of the stack heat is absorbed
  from the colder surroundings and at the hotter
  end of the stack heat is rejected to the hotter
  surroundings.
• In this way the heat is removed from the colder
  body and it is maintained at required
  temperature.

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Parts of acoustic refrigerator

• There are two main parts
• 1) Driver
• - Houses the loud speaker
• 2) Resonator
• - Houses the gas
• -The hot and cold heat exchangers
• -Houses the stack

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Description of parts

• Moving coil Loudspeaker
• Inside 2 magnets with metal coil between them,
  current is induced causing coil to move
• Creates sound waves up to 200 dB!
• Resonatorwhere gas cooling and compression take
  place
• Uses inert gas, commonly Helium
• Stack
• Series of small parallel channels through which
  pressure and velocity of waves change
• In between the heat exchangers
• Heat Exchangers
• Hot heat exchanger to remove excess heat
• Cold heat exchanger for refrigeration

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Advantages

• Harmful chemicals like CFCs, HFCs, HCFCs are
  not released into atmosphere.
• As the working fluid is an inert gas there is no
  toxicity, flammability, or negative environmental
  effects.
• It is more reliable as there are few moving parts.

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Limitation

• COP is less when compared with the present
  refrigerating systems.

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Conclusion

• Thermoacoustic refrigeration is an innovative
  alternative for cooling that is both clean and
  inexpensive. The refrigeration effect is achieved
  by using sound waves and an inert gas which will
  not cause any damage to the atmosphere.

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Thank you
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Any Queries ???