The supercritical pressure CO₂ (SCO₂) Brayton cycle is an efficient and compact power cycle that has promising potential in solar and nuclear power generation systems. The printed circuit heat exchanger (PCHE) is an ideal candidate as a regenerator and pre-cooler in the SCO₂ Brayton cycle due to its advantages of high compactness and efficiency. The PCHE with modified airfoil fins has better comprehensive performance than PCHEs with zigzag channels and NACA 0020 airfoil fins and the optimisation of the modified airfoil fins heat exchanger is crucial to the performance improvement of the SCO₂ Brayton cycle system. In this work, the local thermal-hydraulic characteristics of SCO₂ in the modified airfoil fins channel were numerically investigated under conditions of m = 1.06 – 2.26 g/s, T_in = 328.7 – 388.7 K, and q_w = -50 kW/m² and -100 kW/m². The dramatic changes in the thermophysical properties of SCO₂ lead to uneven distributions of local heat transfer coefficient and local temperature difference along the channel, especially in the region near the pseudocritical point (0.99 < T_b/T_pc < 1.02). Based on the uniformity principle of the temperature difference field (TDF), two non-uniform distributions of fins, including the front-dense and rear-sparse (FDRS) and front-sparse and rear-dense (FSRD) distributions of fins, are proposed. The thermal-hydraulic performance of channels with different distributions of fins was compared under constant heat flux conditions and coupled heat exchange conditions. The results showed that the FDRS and FSRD distributions of fins can enhance heat transfer by improving the distribution uniformity of the temperature difference in the channel. The match of the local dense distribution of fins with the region near the pseudocritical point could obtain better overall thermal performance in the modified airfoil fins heat exchanger. The differences of thermal-hydraulic performance among channels with uniform, FDRS, and FSRD distributions of fins can be explained with the field synergy principle. The FSRD distribution of fins is the optimum scheme among the three distributions of the modified airfoil fins channel because its comprehensive performance is 23 – 29% higher than that of the uniform distribution of fins and 2 – 7.6% higher than that of the FDRS distribution of fins. The present work provides insights into the mechanisms of supercritical CO₂ heat transfer characteristics as well as practical guidance on the design and optimisation of relevant components.

 This work has received funding from the National Energy Group Major Pilot Project-China (GJNY2030XDXM-19-10) and the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. [882628].

 This paper (Zengxiao Han, Jiangfeng Guo*, Haiyan Liao, Zhongmei Zhang, Xiulan Huai, Numerical investigation on the thermal-hydraulic performance of supercritical CO₂ in a modified airfoil fins heat exchanger, The Journal of Supercritical Fluids 187 (2022) 105643) can be found in: https://doi.org/10.1016/j.supflu.2022.105643 (Elsevier), and https://www.researchgate.net/publication/360869350_Numerical_investigation_on_the_thermal-hydraulic_performance_of_supercritical_CO2_in_a_modified_airfoil_fins_heat_exchanger (ResearchGate)