Thermo-Hydraulic performance of printed circuit heat exchanger as precooler in supercritical CO2 Brayton cycle

The Printed Circuit Heat Exchanger (PCHE) is one of the potential precooler candidates to be employed in the supercritical carbon dioxide (S-CO2) Brayton cycle with its high compactness, high efficiency and high endurance to extreme condition. Since the S-CO2 precooler operates in the condition close to the pseudo-critical region, it is of importance understanding the performance differences among different types of PCHE with the dramatical change of thermal-physical properties. Thus, in this study the effect of three channel configurations with zigzag, wavy and airfoil fin channel on heat transfer and flow resistance under precooler condition are investigated with numerical method. Based on the local analysis, it is found that the zigzag channel PCHE presents the better heat transfer performance compared to wavy and airfoil fin channel, and differences are increased as the temperature approaches the pseudo-critical region. Meanwhile, the airfoil fin channel shows the lower friction factor with only 6.12% and 41.31% of the zigzag and wavy channel, respectively. Furthermore, comprehensive performances are compared through the methods of entropy number, JF factor (ratio of Colburn j to friction factor) and Q/(m.delta P) (ratio of heat exchange to pressure drop and mass flow). Based on the results, it is recommended for the airfoil channel to be adopted near the pseudo-critical region due to its larger surface area and smoother structural design.