Convection heat transfer coefficients in thermoacoustic heat exchangers: an experimental investigation

his paper investigates the thermal performance of thermoacoustic heat exchangers subjected to acoustically oscillating flows. The analysis is carried out by experimental measurements of the heat fluxes sustained by the ambient heat exchanger of a prime mover of the standing wave type. A home-made parallel-plate heat exchanger is considered for the study. The gas-side convection heat transfer coefficients expressed as Nusselt numbers are determined over a wide range of velocity amplitudes of the oscillating flow. The experimental results are then compared to the predictions of a number of theoretical models currently applied in thermoacoustics such as the time-average steady-flow equivalent (TASFE) model, the root mean square Reynolds number (RMS-Re) model, and the boundary layer conduction model. The comparison suggests that the boundary layer model performs better than the rms-Re and TASFE models in predicting the heat transfer coefficients in oscillating flows. The relative difference between the model predictions and the experimental data amounts to 19%. A new correlation law, based on regression of the experimental data, is also proposed.