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Project A Thermoacoustics


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Basic Idea about Thermocaoustics

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Project A Thermoacoustics

  1. 1. Aravind N. Badiger7 MEUSN:2BA09ME012
  2. 2.  Introduction What is THERMOACOUSTICS? History Sound Waves and Pressure Principle Main Components How it works? What is a Stack? Standing wave Thermo acoustic System Travelling wave TAR Present work Merits of the technology Demerits Applications Conclusions References2
  3. 3.  Thermoacoustics is science of generating or amplifying sound waves withthe help of thermal energy Sound waves are simply pressure oscillations; these pressure oscillationscan be amplified with heat High pressure sound waves have the capacity to drive a piston It can be used as alternative method of refrigeration but this is aneco-friendly3
  4. 4.  Thermoacoustics is a branch of physics whichdeals with thermodynamics, acoustics and theirinteraction with each other The term “Thermoacoustics” was first termed byRott in 1980, who described it as rather selfexplanatory4
  5. 5.  Thermoacoustics is being studied for over the past two centuries. In 1777,Bryon Higgins was able to excite pipe oscillations in alarge tube, open at two ends, by suitable placing in hydrogenflame. Later in 1850,Sondhauss experimented with a open-close tube ,heating it by applying a flame to the bulb at the close end toproduce sound. In 1859, Rijke investigated with similar apparatus but withhydrogen flame replaced by heated mesh wire and also foundthat sound was maximum when mesh heater was quarter to tubelength from the bottom.5
  6. 6. 66(c) Illustration of the Sondhauss tube
  7. 7.  sound waves propagate through the air viamolecular collisions causing a disturbance in theair in a closed tube, gets reflected and which inturn creates constructive and destructiveinterference7
  8. 8.  constructive interference makes the moleculescompress, and the destructive interference makesthe molecules expand. optimal resonant frequency in found to get themaximum heat transfer rate, usingWhere,n- no of moles, f – frequency, v – velocity of thewave, L – length of the tube.f= nv/4L8
  9. 9.  Thermoacoustics is based on the principle that sound waves arepressure waves and they propagate causing compressions andrarefactions in the medium. It is also based on Ideal gas equation, PV=nRT, where P=pressure in Pascal, V= volume in cubic meter, n= no of moles,R=Real gas constant (8.314 J/kgK), T= temperature in Kelvin. And Clausius statement on second law of thermodynamics i.e.,Heat flows from body at higher temperature to a body at lowertemperature but reverse is not possible spontaneously.9
  10. 10. Driver• Houses the LoudspeakerResonator Houses the gas ( Helium) The hot and cold heat exchangers Houses the Stack10
  11. 11. Loudspeaker Creates sound waves up to 200 dB!Resonator—where gas coolingand compression take placeUses inert gas, commonly Helium forrefrigeration11
  12. 12. StackSeries of small parallelchannels through whichpressure and velocity ofwaves changeIn between the heatexchangersHeat ExchangersHot heat exchangerCold heat exchanger12
  13. 13.  Closely spaced surfaces aligned parallel tothe resonator tube. Purpose: provide a medium for heat transfer. Honeycombed plastic spacers used whichabsorb heat locally. Spacing crucially depends on few times thethermal penetration depth.13
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  17. 17.  The Below figure shows a schematic diagram of atravelling wave thermoacoustic engine. It consistsof resonator tube and a loop containing aregenerator, three heat exchanger and a bypassloop. A regenerator is a porous medium with high heatcapacity. It is similar to stack but the plate spacingwill be less than thermal penetration depth.17
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  19. 19. QC =Wa =Co-efficient ofperformance19
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  23. 23.  Studies show that for relatively small heat loads, TARScompares well with VCRS, thus ideal for cooling ofelectronic equipments. TARS run by a thermo acoustic engine may be proveuseful especially in areas where electricity is notavailable. Despite its demerits, TARS will continue to be an area ofinterest due to: no need of lubrication and sliding seals,simplicity,use of environmentally harmless working fluids23
  24. 24. • Jonathan et al., 2006, Thermo acoustic Refrigeration, GSETResearch Journal .• R. Starr et al., 1996, The Reality of a Small HouseholdThermo acoustic Refrigerator, International refrigeration andAir Conditioning Conference.Paper 344.• “Standing Waves.” Rod Nave, Georgia State University.Available: http://hyperphysics.phyastr•
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