Experimental study of heat transfer characteristics of finned-tube and circular-pore heat exchangers in oscillatory flow

This work is concerned with an experimental investigation of the thermal performance of two thermoacoustic heat exchangers characterized by different pore geometries, namely a circular-pore geometry and a finned-tube geometry. A standing wave engine, where the heat exchangers under test play the role of ambient HXs, is used as test-rig. Heat transfer rates measurements by standard energy balance techniques and dynamic pressure measurements are used to assess the impact of the two heat exchangers on the engine performance. The gas-side heat transfer coefficient, expressed as Nusselt number, is also determined for the finned-tube heat exchanger. The resulting values are compared to the heat transfer coefficients estimated in analogous experimental studies and by predictive models. Results show that the circular-pore heat exchanger reduces the performance of the engine compared to the finned-tube heat exchanger by about 23%, being affected by higher thermal and viscous irreversibility. Moreover, the boundary layer conduction model exhibits a better agreement with the measured heat transfer coefficients compared to other models. A new correlation law, based on regression of the experimental data, is also derived.