Thermoacoustic Refrigeration
ABSTRACT
The answer to current global warming effect due to conventional refrigeration is Thermoacoustic Refrigeration.
All refrigerator and air conditioning, contains refrigerants that are harmful to environment, CFC’s the original refrigerant, are depleting the ozone layer and replaced by HCFC’s or HFC’s the new product do not appear to harm ozone layer, but they do have the potential to lead to between 100 to 5000 times more global warming than CO2.
It is possible to build refrigerators using acoustic waves to pump heat. This technique is called thermoacoustic refrigeration and is based on the interaction between pressure oscillation and temperature oscillation of a gas. Briefly, when a sound wave is sent down a half wave length tube in a inert gas medium with a vibrating diaphragm or a loud speaker, the pressure pulsation make the gas inside slosh back and forth. This forms region where compression and heating takes place, plus other areas characterized by gas compression and cooling.
The principle of thermoacoustics is applied primarily in refrigeration and air conditioning system. The model can also be used to create heat engines to produce electricity.
The main advantage of using thermoacoustic refrigeration is that refrigerants do not change state within system. This makes possible to use inert gases like Argon which are readily available and not harmful to the environment unlike CFC’s HCFC’s and HFC’s, more over the temperature can be adjusted very easily. Also they are good proportional controllers. It has efficiencies as high as 89% at up to 5 kw of power all without the use of ‘lubricants’ or ‘sliding seals’ which means it has the potential for a very long life with ‘low maintenance’. However thermoacoustic refrigerators are 20% to 30% less efficient than conventional refrigeration, which increases operational costs. But the technology is still new and many scientists believe it will be possible to improve the performance of thermoacoustics systems considerably after a few more years of research viz. modifying geometry of stacks.
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