Project Title

:

Team Members : P.Vidyasree (CE12B1016) T.Vishnupriya (EE12B1037)

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

CURRENT REFRIGERATION METHODS VAPOUR COMPRESSION

VAPOUR ABSORPTION

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

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.

SCHEMATIC FOR TAR

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.

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.

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.