Performance measurements on a thermoacoustic refrigerator driven at high amplitudes

Since the power density in a thermoacoustic device is proportional to the s quare of the acoustic Mach number, there is strong motivation to design the rmoacoustic refrigerators to operate at larger pressure amplitudes. Measure ments are reported of a modified version of the Space Thermo-Acoustic Refri gerator (STAR), driven at peak-to-mean pressure ratios up to 6%. This press ure ratio corresponds to 30 W of cooling power-five times as large as repor ted for STAR in 1993. The results of these measurements are compared to a D ELTAE computer model of the few-amplitude (linear) performance that matches experimental conditions on a point-by-point basis. It is found that there is a small but measurable deviation in heat pumping power from the power pr edicted with a linear acoustic computer model at moderate amplitudes. This deviation in heat pumping power at 6% pressure ratio is about 23%. A large disagreement in the acoustic power needed to attain a specific pressure rat io is found between measured data and DELTAE results. An overview of the in strumentation, including a measurement of exhaust heat with an absolute acc uracy of 65 mW, is also presented. (C) 2000 Acoustical Society of America. [S0001-4966(00)00504-X].