A new channel structure for strengthening heat transfer of SCO2 printed circuit heat exchanger (PCHE): variable sectional semicircular channel

Abstract

In this paper, a mathematical and physical model is established to study the convective heat transfer performance of supercritical carbon dioxide (SCO2) in three kinds of horizontal semicircular channels (uniform cross-sectional channel, diverging and converging channels). The accuracy of the numerical model is verified by comparing with the experimental data. The computational results demonstrate that the converging channel can strengthen heat transfer effectively compared with the uniform cross-sectional channel under the same heat transfer area. In the range of calculated working conditions, the use of a converging channel resulted in a maximum improvement of 42.26% in the heat transfer performance of SCO2. However, the diverging channel deteriorates the heat transfer. It is discovered that the improvement of the field coordination of SCO2 in the converging channel is one of the main reasons for its enhanced heat transfer. In addition, the different distribution of turbulent kinetic energy and thermal conductivity are also an important factor affecting the heat transfer performance of SCO2 in different channels. Finally, we propose a new heat transfer correlation of the SCO2 cooling process in the horizontal semicircular converging channel. Compared with the five selected correlations, the new correlation has the best prediction accuracy, and its mean absolute relative error (MARE) and root mean square error (RMSE) are 9.49% and 10.6%, respectively. Our work will provide new insights and theoretical guidance for the design and optimization of coolers in SCO2 Brayton cycle system.