Thermal performance of finned-tube thermoacoustic heat exchangers in oscillatory flow conditions

• Thermal performance of finned-tube heat exchangers in oscillatory flow conditions is investigated.
• Effects of fin length and fin spacing on the heat transfer coefficient are examined.
• Comparisons of experimental results with theoretical models and empirical correlations are undertaken.
• An empirical correlation of heat transfer effectiveness is proposed.

Heat exchangers play a key role in the overall performance of thermoacoustic devices. Due to the complex nature of oscillatory flows, the underlying mechanism of heat transfer in oscillatory flows is still not fully understood. This work investigates the effect of fin length and fin spacing on the thermal performance of finned-tube heat exchangers. The heat transfer rate between two finned-tube heat exchangers arranged side-by-side in an oscillatory flow was measured over a range of testing conditions. The results are presented in terms of heat transfer coefficient and heat transfer effectiveness. Comparisons are made between experimental results of this work and a number of models, 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, as well as several empirical correlations in literature. A new empirical correlation is proposed to be used for the prediction of thermal performance for finned-tube heat exchangers in oscillatory flows. The uncertainties associated with the measurement of heat flux are estimated.