Research on nuclear power plant heat exchangers is advancing toward more efficient and sustainable cooling technologies, especially in the design of ad-vanced nuclear plants. Optimizing cooling airflow and improving channel structures enable efficient heat transfer and prevent overheating damage. This study numerically analyzes the pressure drop, drag coefficient, and thermal-fluid performance of BCC, Gyroid, Diamond, and Fin structures at different Reynolds numbers. The results show that with increasing Reynolds number, the pressure drops of all structures increase, with the order of Dia-mond > Gyroid > BCC > Fin, where Diamond and Gyroid show larger in-creases, while Fin's increase is relatively flat. Regarding drag coefficients, Fin's drag coefficient decreases with Reynolds number, BCC shows small changes, Gyroid decreases and then increases, while Diamond decreases with a larger reduction. To further assess thermal-fluid performance, the thermal efficiency index (PEC) was introduced. Current results indicate that all structures have a PEC lower than 1, meaning the increase in pump power outweighs the heat transfer improvement. At different Reynolds numbers, Gyroid's thermal efficiency is 6.64 to 14.73% higher than BCC, and BCC's is 3.79 to 24.56% higher than Diamond. Overall, Gyroid and Diamond structures show greater sensitivity to Reynolds number changes than to heat transfer improvements.