Performance characterization of thermoacoustic cooler components and systems

Insu Paek, Purdue University


A standing wave thermoacoustic cooler is composed of three critical components: (1) the electroacoustic driver; (2) the heat exchangers; and (3) the stack. Accurate models of the behavior of these components are necessary to characterize the performance of thermoacoustic coolers, and to improve design. The electroacoustic driver performance was characterized. A method to identify equivalent driver parameters from measured total electrical impedance and velocity-voltage transfer function data was developed. The method allowed for the possible frequency and amplitude dependence of the driver parameters to be estimated. The results demonstrated that driver parameters measured in-vacuo using this method can be used to predict the driver efficiency and performance for operating conditions which may be encountered under load. The heat exchangers performance was characterized. Experimental procedures and calculation methods to evaluate the oscillating flow heat transfer coefficients were developed. Dimensionless heat transfer coefficients, or Colburn-j factors, were estimated based on the oscillating-flow variables and compared with results from steady-flow measurements. Accurate predictions of heat transfer coefficients in oscillating flows were obtained using a steady-flow correlation and a modified Reynolds number that accounts for the oscillating flow field. A model to accurately predict the performance of a thermoacoustic cooling system was developed. Empirical models for the heat gain in the cold-side heat exchanger and for the exchanger performance were included in the analysis. The model utilized with a thermoacoustic simulation program known as DELTAE, which is only available as an executable file. The new model yielded accurate predictions of the performance of a prototype. Finally, a design optimization program for thermoacoustic cooling systems that interacts with DELTAE was developed. It was applied to find the best second law efficiencies for various temperature spans between hot-side and cold-side stack-end temperatures. From the results, it was found that the second law efficiency of thermoacoustic coolers increases with temperature span and reaches a maximum, for temperature lifts around 80 °C. From a second law efficiency perspective, thermoacoustics performs best for operating temperatures consistent with refrigeration applications.




Mongeau, Purdue University.

Subject Area

Mechanical engineering|Acoustics

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