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Show EXPERIMENTS ON THE EFFECTS OF PRESSURIZATION OF A THERMOACOUSTIC REFRIGERATOR David Grow,(Orest Symko) Department of Physics, University of Utah This abstract outlines some tests done with a pressurized ther- moacoustic refrigerator using air as the working fluid. Ther- moacoustic refrigerators are devices that use sound to pump heat from a cold heat exchanger to a hot one. These refrigerators have essentially no moving parts and use environment-friendly gases. The basic unit has an acoustic driver (loudspeaker), reso-nator, stack made of a material with a large surface area, heat exchangers, and a working fluid. If the performance of these de-vices can be optimized, they will surely find application in many areas including the cooling of computers and other high power electronics. An existing thermoacoustic refrigerator was modified to handle pressurization of the working fluid to 15 atmospheres. Equipment to measure sound and temperature was tested and installed. For this refrigerator to operate well, the driver must match the fun-damental frequency of the chamber. This frequency was calcu-lated based on the device's length of 3.1 cm to be 5.5 kHz. This prediction was verified through experimental measurement. The amplitude of this resonance was then measured as a function of working-gas pressure using a frequency response. The sound pressure amplitude was found to increase linearly with pressure from 1.4 to 23.8 mV as the working gas was pressurized to 13 atm. The amount of cooling, in turn, also increased with pressure. These results agree with theory. The impedance match between the driver and air is poor at atmospheric pressure. Pressurizing the device improves the impedance match since the working gas, air, becomes denser. Consequently, the power density of the re-frigerator is raised. These results are important as they verify pressurization's effect on enhancing the performance of this type of refrigerator. Pres- surization of these devices can be done easily and inexpensively, broadening their potential commercial use. David Grow Physics (Pre-Professional) Faculty Sponsor Orest Symko |
