Thermoacoustic Refrigeration

Thermoacoustic refrigeration is a type of refrigeration in which sound energy is used for creating the cooling effect. Thus no harmful chemicals are required. Firstly, let us understand what does the thermoaccoustic means-‘Thermoacoustic’ or thermoacoustics explains the relation between heat and sound. It is a science that explains how sound energy can be converted to heat or vice versa, and explains how to realize the conversion practically by means of special kind of engines and refrigerators.

Now, talking about refrigeration-it means the removal of heat from cold place and dumping it to relatively hot place (thereby further cooling the cold place) by means of some kind of ‘mechanical work.

•         The Principle of REFRIGERATION: The main principle of refrigeration is to pump heat from lower temperature to higher using work input. In case of thermoacoustic refrigeration, a   high pressure waves are employed for the required heat transfer. This pressure wave is generated from high frequency sound wave.

Main parts of thermoacoustic Refrigerator-

•      Two main parts

–     Driver

•      Houses the Loudspeaker

–     Resonator

•      Houses the gas (in this case Helium)

•      The hot and cold heat exchangers

•       houses the Stack

Working of the Thermoacoustic Refrigeration(part by part):

•      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!

•      Resonator—where 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

 

Advantages

•      Uses sound for refrigeration –no harmful chemicals (CFC’s, HFC’s, HCFC’s)

•      Few moving parts—more reliable

•      Not harmful to the environment

Disadvantages

•      Most efficient is approaching 40% of Carnot limit

•      20-30% overall efficiency