Thermoacoustic Refrigeration By P Naga Vishnu P Shanmukha

Thermoacoustic Refrigeration By P Naga Vishnu & P Shanmukha Reddy

Introduction n 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.

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

n n 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.

Working

n n n 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.

n n n 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.

Parts of acoustic refrigerator n 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

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

Advantages n n n Harmful chemicals like CFC’s, HCFC’s 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.

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

Conclusion n 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.

Thank you

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