THERMOACOUSTIC REFRIGERATION PPT

July 13, 2017 | Author: Pawan Kumar Singh | Category: Gas Compressor, Refrigeration, Acoustics, Engineering Thermodynamics, Heat
Share Embed Donate


Short Description

THERMOACOUSTIC REFRIGERATION POWERPOINT PRESENTATION BY PAWAN KUMAR SINGH(ME) BY 09ME31 FROM MJP ROHILKHAND UNIVERSITY B...

Description

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

its temperature

dropping to -23 C. This makes the inside of the refrigerator cold.  The cold ammonia gas is sucked up by the compressor, and the

cycle repeats.

VAPOR-COMPRESSION REFRIGERATION CYCLE

Fig.01

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.

Fig.03

 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.

COMPONENTS(cont.)

Loudspeaker

Stack

Resonator tube

Fig.04

Heat Exchanger

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.

Fig.05

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

Fig.07

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.)

Fig.08

Fig.09

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

THANK YOU

ANY QUERIES ?

View more...

Comments

Copyright ©2017 KUPDF Inc.