THERMOACOUSTIC REFRIGERATION

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It is a refrigerator suing sound waves to produce refrigeration.

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THERMOACOUSTIC REFRIGERATION:

THERMOACOUSTIC REFRIGERATION

WHAT IS REFRIGERATION?:

WHAT IS REFRIGERATION? THE PROCESS IN WHICH WORK IS DONE TO MOVE HEAT FROM ONE LOCATION TO ANOTHER. HEAT IS REMOVED FROM LOW TEMPEATURE REGION AND MOVED TO HIGH TEMPERATURE REGION.

DOMESTIC REFRIGERATOR:

DOMESTIC REFRIGERATOR WORKS ON VAPOUR COMPRESSION CYCLE. USES CFC -11 AS THE BLOWING AGENT FOR THE POLYURETHANE FOAM WHICH INSULATES AND PROVIDES STRUCTURAL SUPPORT USES CFC-12 AS A REFRIGERANT AS CFCs ARE RESPONSIBLE FOR “OZONE DEPLETION” IT IS NOT ENVIRONMENT FRIENDLY.

Slide 4:

WHAT IS THERMOACOUSTIC REFRIGERATION? 1. THERMOACOUSTIC REFRIGERATION IS A BRANCH OF THERMOACOUSTICS WHICH USES PRINCIPLES OF BOTH THERMODYANAMICS AND ACOUSTICS TO PRODUCE REFRIGERATION 2.IT WORKS ON THE PRINCIPLE OF REVERSED CARNOT CYCLE.

WHY TO USE THERMOACOUSTIC REFRIGERATOR?:

WHY TO USE THERMOACOUSTIC REFRIGERATOR? DOMESTIC REFRIGERATOR THERMOACOUSTIC REFRIGERATOR NOT ENVIRONMENT FRIENDLY AS IT USES CFCs CONSTRUCTION IS COMPLICATED OCCUPIES LARGE SPACE POSSIBILITY OF LEAKAGE OF LIQUID REFRIGERANT ENVIRONMENT FRIENDLY AS IT USES INERT GASES SUCH AS ARGON,HELIUM CONSTRUCTION IS SIMPLE OCCUPIES LESS SPACE DOES NOT USE ANY LIQUID REFRIGERANT

PRINCIPLES OF THERMODYNAMICS USED IN THERMOACOUSTIC REFRIGERATION:

PRINCIPLES OF THERMODYNAMICS USED IN THERMOACOUSTIC REFRIGERATION TEMPERATURE OF FLUID RISES WHEN COMPRESSED AND DECREASES WHEN EXPANDED -: When a gas is compressed, work is done on the gas molecules. That means that additional energy is transferred to the gas molecules from the source of compression so as to increase temperature of gas and vice-a-versa. HEAT FLOWS FROM HIGHER TEMPERATURE REGION TO LOWER TEMPERATURE REGION - : When two substances are placed in direct contact, heat will flow from the hotter substance to the cooler one unless both the bodies attain equal temperatures.

PRINCIPLES OF ACOUSTICS USED IN THERMOACOUSTIC REFRIGERATION:

PRINCIPLES OF ACOUSTICS USED IN THERMOACOUSTIC REFRIGERATION IT RELIES ON THE FOLLOWING PRINCIPLES SOUND WAVES ARE PRESSURE WAVES. THESE WAVES TRAVEL THROUGH THE MEDIUM VIA MOLECULAR COLLISIONS. THE CONSTRUCTIVE INTERFERENCE OF 2 WAVES INTERACTING IS KNOWN AS ANTINODE WHICH COMPRESSES THE GAS. THE DISTRUCTIVE INTERFERENCE IS KNOWN AS NODE WHICH EXPANDS THE GAS TO OBTAIN MAXIMUM HEAT TRANSFER RATE WE HAVE TO USE RESONANT FREQUENCY f= nv /4l

THERMOACOUSTIC REFRIGERATOR:

THERMOACOUSTIC REFRIGERATOR MAIN COMPONENTS OF THERMOACOUSTIC REFRIGERATOR-: ACOUSTIC DRIVER-:TO PRODUCE SOUND WAVES STACK-:TO ABSORB HEAT HEAT EXCHANGERS-:TO CREATE TEMPERATURE DIFFERENCE RESONATOR TUBE-:TO PROVIDE HOUSING FOR THE WHOLE SETUP

WORKING OF THERMOACOUSTIC REFRIGERATOR :

WORKING OF THERMOACOUSTIC REFRIGERATOR Starting from left, the packet of gas is compressed and moves towards hot heat exchanger and thus gets heated. When the gas packet is at maximum compression, the gas ejects the heat back into the hot heat exchanger In the second phase of the cycle, gas packet moves back towards the right, at the same time the sound wave expands the gas and ejects remaining heat to the stack. This process results in a net transfer of heat to the the stack Finally, as the temperature of gas is less than the temperature of the cold heat source the packets of gas reabsorb heat from the cold reservoir to repeat the heat transfer process which is a refrigeration part of a cycle .

Slide 10:

CARNOT HEAT ENGINE CYCLE THERMOACOUSTIC REFRIGERATION CYCLE PISTON HEAT SOURCE HEAT SINK CYLINDER SOUND WAVES COLD HEAT EXCHANGER HOT HEAT EXCHANGER RESONATOR TUBE

FACTORS AFFECTING PERFORMANCE OF THERMOACOUSTIC REFRIGERATOR:

FACTORS AFFECTING PERFORMANCE OF THERMOACOUSTIC REFRIGERATOR PENETRATION DEPTH CRITICAL TEMPERATURE THE THERMAL PENETRATION DEPTH IS THE DISTANCE HEAT CAN DIFFUSE IN A STACK PLATE OVER A CERTAIN AMOUNT OF TIME SPACING BETWEEN THE WALLS OF THE STACK IS THE IMPORTANT FACTOR WHILE DESIGNING THE REFRIGERATOR IF THE WALLS ARE TOO CLOSE, THE SOUND CAN’T PASS THROUGH THE STACK EFFICIENTLY. IF THE WALLS ARE TOO FAR HEAT TRANSFER WILL NOT BE EFFECTIVE. ACCORDING TO G.W.SWIFT THE IDEAL SPACING IS 4 TIMES THE PENETRATION DEPTHS. δ=[ k/( f₰ Cp)]^[0.5] IT IS THE TEMPERATURE AT WHICH NO HEAT WILL BE TRANSFERRED THROUGH THE STACK. IF TEMPERATURE DIFFERENCE INDUCED BY SOUND WAVES IS GREATER THAN THIS IT WILL ACT AS REFRIGERATOR OTHEWISE IT WILL FUNCTION AS HEAT ENGINE. Tcrit= [(p)/ ( ε₰ Cp)]

ADVANTAGES OF THERMOACOUSTIC REFRIGERATION:

ADVANTAGES OF THERMOACOUSTIC REFRIGERATION SIMPLE CONSTRUCTION NO NEED FOR LUBRICANTS USES CHEAP AND REDILY AVAILABLE INERT GASES ENVIRONMENT FRIENDLINESS LOW LIFE CYCLE COST POWER SAVING BY PROPORTIONAL CONTROL MORE ECONOMIC THAN DOMESTIC REFRIGERATOR

APPLICATIONS OF THERMOACOUSTIC REFRIGERATION:

APPLICATIONS OF THERMOACOUSTIC REFRIGERATION SEPARATION OF CARBON DIOXIDE FROM NATURAL GAS LIQUEFACTION OF INDUSTRIAL GASES NATURAL GAS LIQUIDS RECOVERY FROM NATURAL GAS COAL MINE VENT GAS PROCESSING IN CRYOGENICS SPACE SHUTTLES.(IT WAS USED IN DISCOVERY STS-42,LAUNCHED BY NASA)

WHY STILL NOT COMMERCIALISED ? :

WHY STILL NOT COMMERCIALISED ? MANY SCIENTISTS WORKING ON IT BELIEVE THAT IF IT IS DEVELOPED IN THE BEST POSSIBLE MANNER IT CAN ACHIEVE THE MAXIMUM EFFICIENCY OF CARNOT CYCLE BUT IT HAS STILL NOT BEEN COMMERCIALISED BECAUSE-: LESS EFFICIENCY THAN DOMESTIC REFRIGERATOR TALENT BOTTLENECK IN THE FIELD OF THERMOACOUSTIC REFRIGERATION LACK OF SUPPLIERS PRODUCING CUSTOMISED COMPONENTS LACK OF INTEREST AND FUNDING FROM INDUSTRY

CONCLUSION:

CONCLUSION THE THERMOACOUSTIC REFRIGERATORS ARE ENVIRONMENT FRIENDLY AND IF DEVELOPED WELL THEY CAN REPLACE DOMESTIC REFRIGERATORS,BUT IN ORDER TO REPLACE THEM ,INDUSTRIES MUST TAKE AN INITIATIVE AND MUST CONTRIBUTE TO STOP OZONE DEPLETION AND GLOBAL WARMING.

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