THERMOACOUSTIC REFRIGERATION PPT
THERMOACOUSTIC REFRIGERATION POWERPOINT PRESENTATION BY PAWAN KUMAR SINGH(ME) BY 09ME31 FROM MJP ROHILKHAND UNIVERSITY B...
Presented By Pawan Kumar Singh 09ME31
CONTENTS INTRODUCITON VAPOR COMPRESSION REFRIGERATION DISADVANTAGES OF VAPOUR COMPRESSION REFRIGERATION HISTORY OF THERMO ACOUSTIC REFRIGERATION(TAR) WHAT IS THERMO ACOUSTIC? THERMOACOUSTIC EFFECT
COMPONENTS AND SETUP THERMOACOUSTIC CYCLE MERITS AND DEMERITS OF TAR APPLICATION CONCLUSION REFERENCES
INTRODUCTION Physicists and engineers have been working on a class of heat
engines and compression-driven refrigerators that use no oscillating pistons, oil seals or lubricants. Thermo acoustic devices take advantage of sound waves to
convert a temperature differential into mechanical energy or mechanical energy into a temperature differential. Thermo acoustic devices perform best with inert gases as the
working fluid and don’t produce harmful environment .
VAPOR COMPRESSION REFRIGERATION
The compressor compresses the ammonia gas and heats up.
In condenser the hot ammonia gas dissipate its heat and
condenses into ammonia liquid at high pressure. The high-pressure ammonia liquid flows through the expansion
valve and its pressure dropped. The liquid ammonia boils and vaporizes
dropping to -23 C. This makes the inside of the refrigerator cold. The cold ammonia gas is sucked up by the compressor, and the
VAPOR-COMPRESSION REFRIGERATION CYCLE
DISADVANTAGES OF VAPOUR COMPRESSION REFRIGERATION Uses harmful refrigerants like ammonia, CFC’s and HFC’s. Refrigerants if leaked causes the depletion in the ozone layers. Refrigerants are costly. The moving parts like the compressors require lubrication. Leakage of refrigerant may result in adverse human health
effects including cancers, immune system deficits.
HISTORY OF THERMO ACOUSTIC REFRIGERATION
Lord Rayleigh discussed the possibility of pumping heat with
sound in 1887. S. L. Garrett , Leading Researcher United Technologies
Corporation Professor of Acoustics, The Pennsylvania State University. He invented the thermo acoustic refrigerator in the year 1992. University of Utah began a research project in 2005 called
Thermo Acoustic Piezo Energy Conversion.
WHAT IS THERMO ACOUSTIC? Thermo acoustics is a science that is concerned with the interactions between heat(thermo) and pressure oscillation in gases(acoustics). This field can be broken into two subcategories. The first is the forward effect which is concerned with the
generation of pressure oscillation from heat, is primarily used to create engines known as thermo acoustic engines. The second subcategory is reversed of using acoustic waves to
pump heat, creates thermo acoustic refrigerators.
THERMO ACOUSTIC EFFECT Consider a loudspeaker generate sound waves in a resonator tube close
at both ends. Interference can occur between two waves travelling in opposite direction at certain frequencies. The interference causes resonance creates a standing or acoustic wave. Resonance occurs at resonance frequencies. In the acoustic wave, parcels of gas adiabatically compress & expand.
Variation of temperature and pressure due to compression and
expansion of the gas.
Expanded and compressed gas parcels can take or reject heat on wall.
COMPONENTS Acoustic Loudspeaker, is an electro acoustic transducer that
produces sound in response to an electrical audio signal input. Resonance tube, long hollow tube filled with gas( 97% helium
and 3 % xenon) at high pressure. Stack, consist of honeycombed plastic spacers that do not conduct
heat but temporarily absorb heat & transferred by the sound waves. Heat Exchangers, are the devices used to transfer heat energy
from one fluid to another.
SETUP First take a resonator tube. Customized loudspeaker are attached to the resonator tube. Filled it with inert, pressurized gases such as xenon and helium. Placing the stack at certain position.
Placing heat exchanger
at each side of the stack.
THERMOACOUSTIC CYCLE (cont.) When the loud speaker blast sound at 180 decibels, an acoustic
wave resonate in the resonance tube. Adiabatic compression of the gas: In stack, a gas parcel is
adiabatic compressed from the right to left position and thus the
temperature increases. Now parcel has a higher temperature than stack plate. Isobaric heat transfer: Due to higher
temperature of gas parcel, causing it to transfer
Fig.06 heat to the stack plate at constant pressure losing temperature.
THERMOACOUSTIC CYCLE (cont.) Adiabatic expansion of the gas: Gas parcel is displaced back from
the left to right position and due to adiabatic expansion, the gas is cooled to a temperature lower than stack plate.
Isobaric heat transfer: The parcel's temperature
is now lower than the plate and heat transferred
from the plate to the gas at a constant pressure, increasing the parcel's temperature back to its original value. Heat is moved by placing heat exchangers at each side of the stack.
THERMOACOUSTIC CYCLE (cont.)
MERITS No moving parts, so very reliable and a long life span. The harmful refrigerant gases are removed. Thermo acoustic refrigeration works best with inert gases such as
helium and argon, which are harmless, nonflammable, nontoxic,
non-ozone depleting and is judged inexpensive to manufacture. Use of simple materials, which are commercially available in large
quantities and therefore relatively cheap. Saved energy up to 40% .
DEMERITS Efficiency of thermo acoustic refrigeration is currently less than the
traditional refrigerators. Lack of suppliers producing customized components.
Lack of interest because industry concentration on developing
alternative gases to CFCs. There are not enough people who have expertise in this discipline.
APPLICATIONS Space-Exploration-Mission: It was launched with the Space
Shuttle Discovery (STS-42) on January 22, 1992. Liquefaction of natural gas. Electronic chip cooling. Electricity from sunlight. Upgrading industrial waste heat. Food merchandising where toxicity is an important issue.
CONCLUSION Thermo acoustic engines and refrigerators were already being
considered a few years ago for specialized applications, where their simplicity, lack of lubrication and sliding seals, and their use of environmentally harmless working fluids were adequate compensation for their lower efficiencies. In future let us hope these thermo acoustic devices help to protect
the planet might soon take over other costly, less durable and polluting engines and pumps.
REFERENCE G. W. Swift, “Thermoacoustic engines and refrigerators,”
Phys. Today 48, 22-28 (1995). http://en.wikipedia.org/wiki/thermoacousticengine http://www.thermoacousticscorp.com/news/index.cfm/ID/4. htm. 17 July 2006. S. L. Garrett and S. Backhaus, „„The power of sound,‟‟ Am. Sci. 88, 516–525 (2000). www.arl.psu.edu/capabilities/uss_acou_tre.html
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