Effect of channel size on the performance of a PCHE-based supercritical [formula omitted] thermoacoustic engine

Abstract

Thermoacoustic engine is a promising energy conversion device. Recently, supercritical CO2 has been successfully employed as the working fluid in a standing-wave thermoacoustic engine operating under transcritical temperature conditions. The core components of the device are integrated as a printed circuit heat exchanger (PCHE), where the CO2 channel size plays a vital role in the performance of the device. In the present work, guided by approaching two to four times thermal penetration depth, a PCHE module with improved channel size is designed, fabricated, and tested. Results suggest improvements are achieved in pressure amplitude Δp (the highest record increases from 0.419 to 0.455 MPa) and onset temperature difference (the lowest record drops from 14.8 to 11.2 °C), which are attributed to the enhanced thermally-driven expansion and contraction during one oscillation period. This paper shows that the average thermal penetration depth is a notable variable generally positively correlated to the applied temperature difference. By studying the transition and saturation in operation mode observed in the experiments, it is revealed that three to four times the average thermal penetration depth is the best interval for the CO2 channel size. Beyond this interval, the power law relation between dimensionless pressure amplitude and the temperature difference holds. Below this interval, the saturation becomes so strong that the growth of pressure amplitude with temperature difference decelerates significantly.