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2. REFRIGERATION
Refrigeration is a process in which work is done to move
heat from one location to another.
Uses of Refrigeration :
 Industrial uses
 Air conditioning
 Food storage and distribution
 Medical applications

3. CURRENT REFRIGERATION
METHODS
VAPOUR COMPRESSION

4. VAPOUR ABSORPTION

5. DISADVANTAGES
VAPOUR COMPRESSION
 Require CFC, HCFC, or other ozone harming refrigerants
 Increase global warming effect
 Loud/noisy
 Typical efficiency is 40-55% of Carnot limit
 Moving parts and intricate design
 Prone to breakdown
VAPOUR ABSORPTION
 Requires large heat source
 Can't use electricity directly
 Require CFC, HCFC, or other ozone harming refrigerants
 Increase global warming effect
 Inefficient

6. THERMOACOUSTIC REFRIGERATOR
 A thermo-acoustic refrigerator (TAR) is a refrigerator that
uses sound waves in order to provide the cooling.
 In a TAR, the working fluid is a helium-argon mixture, and
the compressor is replaced by a loudspeaker.
WORKING PRINCIPLE
 Pressure variations in sound wave are accomplished by
temperature change due to particle oscillations in the gas.
For a single medium average temperature at that particular
location does not change. When a second medium is present
heat is exchanged with it and an expanded particle will take
heat from it and compressed particles will reject heat to the
second medium.

7. SCHEMATIC FOR TAR

8. ADVANTAGES
 The working fluid is typically helium or other inert, benign
gases such as air which are environment-friendly unlike
common refrigerants.
 The simplicity of the design makes it robust, small, and
lightweight.
 It has almost no moving parts, which translates into a
longer working life with fewer repairs. In turn, this makes
the system less expensive.
 The loudspeaker is TAR’s only moving part which is more
durable than a compressor.
 It has the ability to attain a higher level of the limiting
Carnot efficiency than current refrigeration methods.

9. DISADVANTAGES
 The downside of the TAR is that these failed to achieve
efficiencies as high as those of standard refrigerator units.
 The coefficient of performance of most advanced TAR is only
1 when compared to 3-4 of modern refrigerators.
 Another major problem of TAR is that it is either fully on or
off.
 It leaked an incredible amount of sound that causes ear pain
but produces only a small temperature gradient.
 These refrigerators were able to cool the air for a short
amount of time before the cooled air started raising its
temperature.
 very much essengerators have failed to achieve efficiencies
as high as those as standard refrigeration units.

10. IMPROVEMENTS
 Insulate the sound leaks by isolating the system.
 Replace the closed cap with a speaker to increase the
efficiency by co-generation.
 If both ends of a stack are connected to a heat exchangers
thus coupling the stack to a heat source and sink, the
transfer of heat would be more efficient.
 Use conductive material for hot section of resonator
 Widen the resonator and use a cone to reduce the losses
due to rapid area change.
 More practical and efficient reliable temperature sensors
such as thermistors should be used.
 The composition of stack material may also be changed to
any conducting materials like gold,silveror copper.