Numerical Investigation of Header Design Parameters for Enhanced Flow Distribution in Minichannel Printed Circuit Heat Exchangers for Supercritical Carbon Dioxide Applications

Minichannel printed circuit heat exchangers (PCHEs) are commonly utilized in supercritical CO2 (sCO2) power cycles. In this study, an experimental single plate PCHE with various header configurations is investigated in terms of flow maldistribution using computational fluid dynamics (CFD) techniques. A series of header optimization simulations with different mass flow rates, inlet/outlet configurations, and header sizes are performed and analyzed. The numerical model of this PCHE is set up and solved with ANSYS-CFX. The variation in thermophysical properties of sCO2 was incorporated into the numerical model via real gas property data. Additionally, the computed results for temperature distribution i.e., maximum hotspot temperatures and pressure drop were validated with experimental data, showing a good agreement with a maximum discrepancy of 8.6%. The results from this study indicated that optimizing inlet and outlet positions reduced the maldistribution factor (MDF) by 34% at 40 g/sec and 29% at 90 g/sec, as compared to the baseline configuration of the PCHE. Increasing the header area ratio further reduced the MDF by 51% at 40 g/sec and 48% at 90 g/sec, resulting in uniform temperature distribution and effective mitigation of local hotspots. Furthermore, the suggested header configuration also minimized hot and cold stream mixing inside the collector header which can significantly reduce thermal stresses, extending the life span of PCHEs.