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THERMOACOUSTIC REFRIGERATION

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Major project on Development of Thermoacoustic Refrigeration

Publié dans : Ingénierie
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THERMOACOUSTIC REFRIGERATION

  1. 1. Department of Mechanical Engineering 1. AAGAM SHAH -14071A0361 2. CH NIKHIL REDDY -14071A0365 3. CH PAVAN -14071A0367 4. U PHANI ABHINAV -14071A03A8 5. VAISHALI DAS -14071A03B0 Under the guidance of : Dr. B. Satyanarayana, Professor, Department Of Mechanical Engineering, VNR VJIET DEVELOPMENT OF THERMOACOUSTIC REFRIGERATOR
  2. 2. Department of Mechanical Engineering Abstract Introduction Literature Review Work Plan Methodology Work Progress Result Conclusion Scope of work Applications References LIST OF CONTENTS
  3. 3. Department of Mechanical Engineering Thermo-acoustics is a phenomenon that deals with the interaction between the sound and thermal energies. Its recent use is to develop heat Engines and Pumps/Refrigerators. Thermo-acoustic refrigeration is one such phenomenon that uses high intensity sound waves in a pressurized gas tube to transfer heat from one place to other to produce refrigeration effect. In this type of refrigeration, refrigerants are eliminated, and Sound waves take their place. A loud speaker and an acoustically insulated tube are used for the purpose. Further, this system eliminates lubricants and results in 40% less energy consumption. Hence, in this project, a prototype of low cost environmental friendly thermoacoustic refrigerator is developed. Thermo-acoustic refrigerator operates with inert gases and without moving parts, making them highly efficient devices for environmentally-safe refrigeration with almost zero maintenance cost. ABSTRACT
  4. 4. Department of Mechanical Engineering INTRODUCTION Over the past two decades, 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. These so called Thermo-acoustic devices take advantage of sound waves reverberating within them to convert a temperature differential into mechanical energy or mechanical energy into a temperature differential. Such materials thus can be used, for example, to generate electricity or to provide refrigeration and air conditioning. Because Thermo-acoustic devices perform best with inert gases as the working fluid, they do not produce the harmful environmental effects such as global warming or stratospheric ozone depletion that have been associated with the engineered refrigerants such as CFCs and HFCs. Recent advances have boosted efficiencies to levels that rival what can be obtained from internal combustion engines, suggesting that commercial Thermo-acoustic devices may soon be a common place.
  5. 5. Department of Mechanical Engineering OBJECTIVE The aim of present work is “To design and develop a model of Standing Wave Thermoacoustic Refrigerator” (TAR) worked by a sound wave of 385Hz frequency. The prime objectives of this project are as follows • To theoretically examine the impact of various working parameters and working medium on TAR execution. • To design and construct a TAR model as per the theoretical parameters and to test the model experimentally. • To compare theoretical and experimental models of TAR and to estimate the practical viability of the current research.
  6. 6. Department of Mechanical Engineering LITERATURE REVIEW 1. Paek I, Braun J.E., Mongeau L., “Evaluation of standing-wave thermoacoustic cycles for cooling applications”, International Journal of Refrigeration 30, pp 1059-1071, (2007). 2. Tijani M.E.H., “Loudspeaker Driven Thermoacoustic Refrigeration”, PhD Dissertation, Technical University of Eindhoven, Netherlands, (2001) 3. Poese M.E., Garrett S.L., “Performance measurements on a thermoacoustic refrigerator driven at high amplitudes”, Journal of the Acoustical Society of America 107, pp 2480- 2486, (2000). 4. Hofler T.J., “Thermoacoustic Refrigerator Design and Performance”, Ph.D. dissertation, Physics Department, University of California, San Diego, (1986).
  7. 7. Department of Mechanical Engineering WORK PLAN Phase-I • Project Selection and Research • Feasibility Study and Market Survey Phase-II • Project Design and Analysis • Cost Approximations and Material Procurement Phase-III • Fabrication of Demonstrative Prototype • Testing and Analysis cum Feedback • Project Report Generation
  8. 8. Department of Mechanical Engineering METHODOLOGY 1. INITIAL RESEARCH DETERMINING THE CHARACTERISTICS OF THE COMPONENTS OF THERMOACOUSTIC REFRIGERATOR. 2. DETERMINING THE OPERATIONAL PAREMETERS, DESIGN PARAMETERS AND MATERIAL PROPERTIES. 3. EXPERIMENTAL FEASIBILITY AND MARKET SURVEY. 4. ARRIVING ON A FINAL THEORITICAL MODEL FOR THE THERMOACOUSTIC REFRIGERATOR. 5. FABRICATION USING THE THEORITICAL PARAMETERS AND VALUES. 6. TESTING THE THERMOACOUSTIC REFRIGERATOR FOR MAXIMUM EFFICIENCY. 7. FINDING THE EXPERIMENTAL COP AND COMPARING IT WITH THEORITICAL COP.
  9. 9. Department of Mechanical Engineering INITIAL RESEARCH DETERMINING THE CHARACTERISTICS OF THE COMPONENTS OF THERMOACOUSTIC REFRIGERATOR 1. Working Medium 2. Acoustic driver 3. Resonator 4. Stack 5. Heat exchanger
  10. 10. Department of Mechanical Engineering DETERMINING THE OPERATIONAL PAREMETERS, DESIGN PARAMETERS AND MATERIAL PROPERTIES.
  11. 11. Department of Mechanical Engineering WORK PROGRESS  FEASIBILITY STUDY We can summarize that the theory of standing wave thermoacoustics is well established, stating back over a century. Recent developments are encouraging in the field with the improving efficiency starting from 12% of Carnot COP by Tom Hofler in 20th century, yet many aspects of the thermoacoustic refrigerator are not known like gas behavior inside the resonating column. Also, the low efficiency of the acoustic driver results in overall low efficiency of the system.
  12. 12. Department of Mechanical Engineering WORK PROGRESS  PROJECT STUDY Various parts of the thermoacoustic refrigerator, namely, acoustic driver, resonator, stack, gas & their characteristics were studied as stated in methodology. 1. ACOUSTIC DRIVER • In order to create an acoustic standing wave in the gas at the fundamental resonant frequency of the resonator. • The acoustic driver converts electric power to the acoustic power. • The range of operating frequency of the acoustic device is between 350-450Hz depending on the working fluid medium employed in the resonator and is driven by a power amplifier. .
  13. 13. Department of Mechanical Engineering WORK PROGRESS 2. RESONATOR • Shape, weight, length are important parameters for designing the resonator • Length of the resonator is decided by the frequency of the resonator and minimal losses at the wall of the resonator • For an acoustic device of 385Hz frequency a resonator of 474mm length and dia 52.3mm is selected for air medium. • Due to easy availability, strength as well as design considerations Nylon rod was used for resonator. • A rod of 90mm Dia was used and a bore of 52.3mm was machined inside.
  14. 14. Department of Mechanical Engineering WORK PROGRESS 3. STACK • The stack forms the heart of the refrigerator where the process of heat pumping takes place and it is thus an important element which determines the performance of the refrigerator • The stack material must have a low thermal conductivity (Ks) and a heat capacity (Cs) must be larger than the heat capacity of working gas in order that the temperature of the stack plate remains steady. • The distance b/w the stack plates is determined using thermal penetration depth. • Stack used for the initial prototype is a spiral stack made by using Teflon sheets with Nylon rod(6mm) at the core. Alternatively, Mylar sheets can be used.
  15. 15. Department of Mechanical Engineering WORK PROGRESS BLOCK DIAGRAM FOLLOWED IN DETERMINING THE DESIGN CALCULATIONS
  16. 16. Department of Mechanical Engineering WORK PROGRESS GRAPHICAL CALCULATIONS FOR AIR AND HELIUM GASES
  17. 17. Department of Mechanical Engineering WORK PROGRESS COP (Vs) Lsn for He-Xe gaseous mixture
  18. 18. Department of Mechanical Engineering WORK PROGRESS 4. HEAT EXCHANGER • Heat exchanger plays an important role in cooling the hot end of the stack. • Heat exchangers can be of convective air flow type or conductive water flow type. • Copper H.E. can be effectively used to dissipate heat from the resonator.
  19. 19. Department of Mechanical Engineering WORK PROGRESS 5. WORKING MEDIUM • The working medium should have high sound speed • The gas must have low thermal conductivity so that loss of cooling due to axial conduction is low • High specific heat capacity • Low viscosity • Gas must be safe, cheap, easily available. • Air is chosen as the working medium for the initial prototype purpose. • An operating pressure of 10Bar is to be maintained inside the resonator column for the drive ratio to be ‘0.02’.
  20. 20. Department of Mechanical Engineering WORK PROGRESS THERMOACOUSTIC CYCLE
  21. 21. Department of Mechanical Engineering WORK PROGRESS THE MODEL • Resonator • Stack • Driver • Heat exchanger
  22. 22. Department of Mechanical Engineering WORK PROGRESS FINAL MODEL
  23. 23. Department of Mechanical Engineering VALUES OF PARAMETRES 1. Medium – Air 2. Velocity of Medium – 351.9m/s 3. Frequency – 385Hz 4. Stack Length – 50mm 5. Distance of centre of stack from speaker - 44mm 6. Cooling Power – 10Watts 7. Acoustic Power – 9.75 Watts 8. Pressure - 10Bar 9. Length of resonator – 457mm 10. Radius of Resonator – 26.48mm 11. Length of Cold HE – 17.132mm 12. Length of Hot HE – 34.265mm
  24. 24. Department of Mechanical Engineering RESULTS 1.TEST-I Involved testing without heat exchangers installed. The result obtained was not satisfactory. 2.TEST-II Theoretically, a temperature drop of 15.69 degrees can be achieved considering all the other parameters constant, but a temperature of 29 degrees from the hot end temperature of 33degrees (drop of 4degrees) could be achieved, the reason is because the theoretical calculations were done at 10 bar and the experiment was conducted at 1 bar pressure. Time(mi n) 5 15 25 35 45 55 Temperat ure cold end(oC) 32 31 30.5 30 29.5 29
  25. 25. Department of Mechanical Engineering RESULTS Temperature of cold end vs Time 26.5 27 27.5 28 28.5 29 29.5 30 30.5 0 10 20 30 40 50 60 Temperature Time(min) Temperature vs Time
  26. 26. Department of Mechanical Engineering CONCLUSION • A standing-wave TAR was designed by using the dimensionless parameter approach as suggested by Tijani. • The detailed theoretical discussion of various design parameters influencing thermoacoustic refrigerator's COP and efficiency are discussed. • Operating air at maximum pressure sustainable by the setup (1.5bar) resulted in efficiency of 3K over a span of 60minutes, which indicated that the efficiency of the system is very low. • Efect of working pressure is immense on the temperature difference of the system as working pressure is directly proportional to the power density. With increase in the working pressures, the thermal penetration depth decreases which makes the stack fabrication more difficult.
  27. 27. Department of Mechanical Engineering SCOPE OF WORK This promising “green technology” leaves immense scope of improvement. We have, in our design analysis chapter, theoretically shown the increase in COP of the system with the improvement in the following areas of the thermoacoustic refrigerator system: • A TEST-3 is desired to be conducted at elevated pressures of up to 10bar inside the resonator. • Improving the driver efficiency by matching it to the natural frequency of the gas parcel. • Using more efficient materials like Delrin for resonator and Mylar sheets for stack. • To achieve the efficient driver construction, magnetic materials with higher strength and pole piece material having high permeability shall be employed. • Using rubber material for the speaker diaphragm instead of a paper-type diaphragm. • Better and efficient heat exchanger design. • Using lighter gases, especially Helium. This gas provides superior sound velocity and results in better COP of the thermoacoustic system. • Using noble gas mixture, preferably, He-Xe mixture with roughly 70% weightage of the lighter gas (He) results in a 60-70% increase in efficiency of the system. • Employing an open-ended buffer volume at the opposite side of the driver on the resonator column. It results in better output as they are void of non-linear effects. Using the buffer volume decreases the power consumption because of lesser surface area and reduces the probability of gas and pressure leakages in the system.
  28. 28. Department of Mechanical Engineering APPLICATIONS Existing: • Ben and Jerry’s Ice-cream parlor in USA. • NASA: Preserve blood and urine samples • US NAVY: Cool radar electronics onboard warships Potential: • Liquefication of natural gas: combustion of natural gas in thermoacoustic engine generates sound energy. This acoustic energy is utilized in a thermoacoustic heat pump to compress and liquidity natural gas. • Chip cooling: In this case a piezoelectric element generates a sound wave. A thermoacoustic heat pump cools the chip. • Space applications as spacecraft cryocooler. • Electronic equipment cooling on naval ships. • Electricity from sunlight. • Food preservation on naval ships. • To cool domestic use products vis-à-vis a general refrigerator. • Upgrading industrial waste heat. • Cooling of highly reactive metals like sodium, potassium.
  29. 29. Department of Mechanical Engineering REFERENCES [1] N. Rott, Thermoacoustics, Advances in Applied Mechanics, 20:135-175, 1980. [2] J. Wheatley, T. Hofler, G. W. Swift, and A. Migliori, Understanding some simple phenomena in thermoacoustics with applications to acoustical heat engines, Am. J. Phys. 53 (2), February 1985 [3] B. Higgins, Nicholson’s Journal I, 130 (1802) [4] P. L. Rijke, Notiz uber einen neue Art, die bieden ende offenen Rohre enthaltene Luft in Schwingungen zu versetzen, Ann. Phys. (Leipzig) [2] 107,339 (1859) [5] C. Sondhauss, Ueber die Schallschwingungen der Luft in erhitzten Glas-Rohren und in gedeckten Pfeifen von ungleicher Weite, Ann. Phys. (Leipzig) [2] 79, 1(1850) [6] G.W. Swift, Thermo acoustics: A unifying perspective for some engines and refrigerators., short course, March 1999, Berlin. [7] Ram Chandrashekhar Dhuley, "Investigations on a thermoacoustic refrigerator.", Master of technology project. ;2010 (IIT-B). [8] Tijani M.E.H., Zeegers J.C.H., and De Waele A.T.A.M. “Construction and performance of a thermoacoustic refrigerator.” Cryogenics, 42(1):59-66, 2001.

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