Thermal Hydraulic Performance Analysis of PCHE Precooler for Supercritical CO2 Brayton Cycle

Printed circuit heat exchanger (PCHE) is a new type of millimeter–level channel heat exchanger. The working fluid in the PCHE precooler of the supercritical carbon dioxide (SCO2) Brayton cycle usually works near or cross the pseudo-critical point, where the thermophysical properties exhibit drastic nonlinear characteristics. This brings challenges to analysis the thermal hydraulic performance of the PCHE. In present paper, a straight channel PCHE precooler model is established by the segment method to accurately account for the change of thermophysical properties. The precooler is designed by adopting the Gnielinski empirical correlations. Local heat transfer and pressure drop characteristics of SCO2 along the length are analyzed. The results show that the designed length obtained by segment method is significantly larger than by logarithmic mean temperature difference (LMTD) method. Overall the local temperature difference decreases from the hot end to the cold end. The heat transfer coefficient on SCO2 side is more relevant to the Prandtl number than the Reynolds number. The research results are of great significance for the development of PCHE design methods.