Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Mechanical and Materials Engineering


Dr. Kamran Siddiqui

Second Advisor

Dr. Anthony G. Straatman

Third Advisor

Dr. Horia Hangan


This thesis presents a study of thermoacoustic processes. Thermoacoustic science, which can serve as a renewable and sustainable source of energy, involves thermodynamics, acoustics and their interactions. This research investigated the thermoacoustic phenomenon through theoretical and experimental investigations. The theoretical study is comprised of two parts. The first part focused on the development of a comprehensive algorithm for the design, development and performance evaluation of thermoacoustic devices. The developed algorithm is capable of designing and optimizing individual thermoacoustic heat engines and refrigerators and coupled engine-refrigerator systems. In the second part of the theoretical study, the theoretical model of thermoacoustic couples predicting stack temperature difference was modified by incorporating more realistic physical processes that were consistent with practical applications. Significant improvement in the accuracy of the stack temperature difference predictions was observed with the modified model as compared to the previous models through experimental validation. Detailed experimental investigations were conducted to enhance the fundamental understanding of the thermo-fluid behavior in thermoacoustic couples. The first part of the experimental study was focused on the investigation of the influence of drive ratio and stack position on the stack temperature field. The results provided the first evidence of the two-dimensional temperature distribution on both end faces of the stack. A physical explanation for the change in the stack temperature difference profile from sinusoidal to sawtooth form with an increase in the drive ratio was provided. It is concluded that the acoustic dissipation in the stack which influenced the stack cold-end temperature was responsible for this behavior. In the second part, experiments were conducted to investigate streaming velocity fields in a thermoacoustic device using a synchronized PIV technique. The results showed that not only the presence of a stack but also the type and geometrical characteristics of a stack can significantly change the structure and magnitude of acoustic streaming. For both stacks, the streaming velocity field in the region adjacent to the hot-end of the stack was stronger with higher spatio-temporal variations as compared to that adjacent to the cold-end of stack, at almost all the drive ratios.



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