Numerical investigation on thermal-hydraulic performance of variable cross section printed circuit heat exchanger

CO2 transcritical power cycle (CTPC) systems have attracted considerable research focus in the fields of thermoelectric conversion and waste heat recovery. The regenerator is a key component affecting the CTPC system's efficiency. To improve the comprehensive performance of the regenerator, extensive research has been conducted to optimize the regenerator flow channel design. However, the optimization of the traditional Z-channel printed circuit heat exchanger structure (ZPCHE) is limited to constant cross-sectional configurations along the flow direction, which can lead to low channel space utilization. To solve this problem, an efficient variable cross section Z-channel structure (UAPCHE) is proposed in this study. The structure is designed with different cross-sectional shapes along the flow direction to fit the flow path of the main fluid. UAPCHE achieves a coordinated optimization of the heat transfer (Nu), flow (dP), and compactness performance (Q/V) by increasing the effective utilization of the channel space and weakening the damage to the fluid boundary layer. The design principle of the UAPCHE is introduced, and based on this, the structural parameters of the UAPCHE are optimized to achieve the best comprehensive performance. The results show that, compared with the ZPCHE, Nu of UAPCHE can be increased by 16.79%, dP can be reduced by 19.48%, and Q/V can be increased by 22.65%.