Heat-flux redistribution and performance degradation of printed circuit heat exchangers under channel-wise flow maldistribution

Printed circuit heat exchangers (PCHEs) serving as high-temperature recuperators (HTRs) in supercritical carbon dioxide (sCO₂) Brayton cycles may experience channel-wise flow maldistribution due to local blockage. Existing reduced-order models often neglect transverse conduction through shared walls and therefore cannot represent cross-channel heat-flux redistribution. Multi-channel conjugate heat-transfer simulations were performed with prescribed channel-wise mass-flux reductions, and a reduced-order model incorporating discretized fluid and solid elements was developed to retain transverse wall conduction. Reducing the affected-channel mass flux from 360 to 30 kg/(m²·s) markedly redistributed the wall heat flux, while the maximum wall-temperature deviation from uniform flow and maximum circumferential wall-temperature difference were 8.85 and 2.78 K, respectively. Randomly distributed affected channels caused little variation in total heat-transfer rate, with maximum realization-to-mean deviation below 0.06%. In contrast, clustering the affected channels increased local outlet-temperature maxima by 16.28 K on the cold side and 12.92 K on the hot side relative to a dispersed configuration with the same affected-channel number and mass flux. Heat-transfer degradation varied approximately linearly with affected-channel number and nonlinearly with the individual-channel flow-reduction ratio; at equal overall flow-reduction ratios, fewer, more severely affected channels caused greater losses. These results show that transverse wall conduction buffers local temperature responses, whereas the distribution and severity of channel-wise flow reduction govern overall heat-transfer degradation. The model applies to the validated HTR range, in which the fluid remained at least 47.21 K above the pressure-dependent pseudo-critical temperature.