Thermoacoustic Thermoacoustic RefrigerationRefrigeration

ByByP Naga VishnuP Naga Vishnu

&&P Shanmukha ReddyP Shanmukha Reddy

IntroductionIntroduction

Thermoacoustics combines the branches Thermoacoustics combines the branches of acoustics and thermodynamics together of acoustics and thermodynamics together to move heat using sound. to move heat using sound.

Acoustics is primarily concerned with the Acoustics is primarily concerned with the macroscopic effects of sound transfer like macroscopic effects of sound transfer like coupled pressure and motion oscillations.coupled pressure and motion oscillations.

Thermoacoustics focuses on the Thermoacoustics focuses on the microscopic temperature oscillations that microscopic temperature oscillations that accompany these pressure changes.accompany these pressure changes.

Basic PrincipleBasic Principle

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

In the region of In the region of

compression the compression the pressure is high, and in pressure is high, and in the region of rarefaction the region of rarefaction the pressure is low.the pressure is low.

As sound waves are As sound waves are adiabatic in nature adiabatic in nature applying First law of applying First law of thermodynamics here thermodynamics here we get high we get high temperature at temperature at compression and low compression and low temp at rarefaction. temp at rarefaction.

Working Working

Sound waves of required frequency are Sound waves of required frequency are

generated by using the loud speaker.generated by using the loud speaker. These sound waves are allowed to pass These sound waves are allowed to pass

through the Stack & the Resonator in through the Stack & the Resonator in which standing waves are produced.which standing waves are produced.

This resonator is filled with the inert This resonator is filled with the inert gas (Helium) and those gas particles gas (Helium) and those gas particles oscillates back and forth parallel to the oscillates back and forth parallel to the stack due to this standing waves. stack due to this standing waves.

By this a temperature By this a temperature gradient in formed gradient in formed along the stack.along the stack.

At the colder end of the At the colder end of the stack heat is absorbed stack heat is absorbed from the colder from the colder surroundings and at the surroundings and at the hotter end of the stack hotter end of the stack heat is rejected to the heat is rejected to the hotter surroundings.hotter surroundings.

In this way the heat is In this way the heat is removed from the removed from the colder body and it is colder body and it is maintained at required maintained at required temperature. temperature.

Parts of acoustic refrigeratorParts of acoustic refrigerator

There are two main There are two main partsparts

1) Driver1) Driver

- Houses the loud - Houses the loud speakerspeaker

2) Resonator2) Resonator

- Houses the gas - Houses the gas

-The hot and cold -The hot and cold heat exchangersheat exchangers

-Houses the stack-Houses the stack

Description of partsDescription of parts

Moving coil LoudspeakerMoving coil Loudspeaker Inside 2 magnets with metal coil between them, current is induced Inside 2 magnets with metal coil between them, current is induced

causing coil to movecausing coil to move Creates sound waves up to 200 dB!Creates sound waves up to 200 dB!

Resonator—where gas cooling and compression take placeResonator—where gas cooling and compression take place Uses inert gas, commonly Helium Uses inert gas, commonly Helium

StackStack Series of small parallel channels through which pressure and Series of small parallel channels through which pressure and

velocity of waves changevelocity of waves change In between the heat exchangersIn between the heat exchangers

Heat ExchangersHeat Exchangers Hot heat exchanger to remove excess heatHot heat exchanger to remove excess heat Cold heat exchanger for refrigerationCold heat exchanger for refrigeration

Advantages Advantages

Harmful chemicals like CFC’s, HFC’s, Harmful chemicals like CFC’s, HFC’s, HCFC’s are not released into HCFC’s are not released into atmosphere.atmosphere.

As the working fluid is an inert gas As the working fluid is an inert gas there is no toxicity, flammability, or there is no toxicity, flammability, or negative environmental effects.negative environmental effects.

It is more reliable as there are few It is more reliable as there are few moving parts.moving parts.

LimitationLimitation

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

ConclusionConclusion

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

Thank youThank you

Any Queries ???Any Queries ???