THERMOACOUSTIC REFRIGERATION

Introduction Thermo acoustic 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 motioned oscillation. Thermo acoustic focuses on microscopic temperature oscillation that is accompanied by pressure changes.

Principle It is based on the principle that sound waves are pressure waves and they propagate causing compression and rarefactions in the medium.

In the region of compression pressure is low and in the region of rarefaction pressure is high. As sound is adiabatic in nature thereby applying first law of thermodynamics ,there is high temperature in compression region and low temperature in rarefaction region.

Components used: Driver- It houses the loud speaker to produce necessary sound . Resonator-Houses the gas Houses the stack Houses hot and cold exchangers

Description of the components used

Moving coil loudspeaker When the electrical current flows through the electromagnetic wire coil it reverses the coil’s polar orientation. So positive end of electromagnetic attracted towards the negative end of the permanent magnet so when electric current signals are passed through, the direction of attraction and repulsion reverses making the cone to vibrate back and forth and producing the sound waves.

STACK It is the small parallel channels through which pressure and velocity of waves changes.

Resonator The resonator contains stack , gas and the heat exchanger. So it typically takes heat from the cold heat exchanger and deposits it to the hot heat exchanger and other stack locations

Working

Working Sound of required frequency is produced from loudspeaker. Sound waves thus produced is allowed to pass through the stack and resonator tube which gets reflected back from reflecting surface which is at the end of the resonator tube creating standing wave Thus due to the standing wave the helium particles vibrate back and forth

Thus temperature gradient is created Thus heat is removed from colder body and it is maintained at the required temperature

Advantages Harmful chemicals are not released into the atmosphere . More reliable as there are no moving parts As the working fluid used is inert gas there is no toxicity , flammability and other negative environmental effects

Conclusion Thermo acoustic 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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