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Development of small-scale thermoacoustic engine and thermoacoustic cooling demonstrator
Thermoacoustics is a science and technology field that studies heat and sound interactions. Sound waves in any fluid consist of coupled pressure, motion, and temperature oscillations. When the sound travels through a narrow channel, an oscillating heat flow between the fluid and the channel's wall becomes significant. The present study deals with the effects of thermoacoustic cooling with closed and open ended tubes and also investigates the performance of a small-scale thermoacoustic heat engine. The first part of this document presents the design, construction, and testing of a miniature standing-wave thermoacoustic heat engine. The main objective was to build and test a miniature heat engine without moving parts. Recorded parameters included the temperature difference across the stack and the corresponding acoustic pressure amplitude of the sound produced by the engine. The system was also tested for different stack materials and tube lengths. The most efficient system is described in detail in this document. The critical temperature difference across the stack was measured to be approximately 350°C for the 5.8 cm engine and 250°C for the 9.3 cm engine. The average acoustic RMS pressure of the sound produced was about 2.7 Pa at 30 cm from the engine for both lengths and the frequency of the sound was about 1.4 kHz for the 5.8 cm engine and about 1 kHz for the 9.3 cm engine. The second part of this document presents the effects of thermoacoustic cooling with closed and open ended tubes. The position of the stack and sound frequencies were varied to establish the most effective configuration. For each configuration, the pressure amplitude inside the tube and the sound frequency were the controlled parameters, and the temperature difference across the stack was measured. The experimental results of the thermoacoustic cooling system are compared to the theoretical results. For the closed-end system the temperature of the top of the stack was higher than the bottom and for the open-end system the temperature of the top of the stack was lower than the bottom. The maximum temperature difference was about 32°C for the closed-end and 16°C for the open-end