Entropy generation analysis of topology-optimized porous reactors under pulsating flow conditions

Enhancing electrochemical energy storage and conversion devices through topology optimization enables advanced electrode design and improved performance. Previous research indicates that the performance of topologically optimized porous reactors improves with increasing design dimensionality; however, 2D optimization is often sufficient. This study employs density-based topology optimization to design porous reactors with distinct flow characteristics (FC): one-dimensional (1D) FC, two-dimensional (2D) FC, and three-dimensional (3D) FC. The 1D FC system shows significant performance improvement with 2D optimization, while the 2D FC system also benefits from higher-dimensional optimization, though the difference between 1D and 2D optimization is smaller compared to the improvement observed in the 1D FC system. However, in the 3D FC system, the impact of increasing design dimensionality diminishes, in contrast to the 1D and 2D FC systems, which clearly benefit from higher-dimensional optimization. To overcome this limitation, a fourth-dimensional parameter, namely the temporal variation in species supply (pulsating flow), is introduced to enhance the performance of the 3D FC system. Additionally, entropy generation analysis is derived and applied as a post-processing tool to assess system performance. The results reveal that pulsating flow significantly improves the 3D FC system, achieving the lowest scaled entropy generation compared to constant flow. Higher non-dimensional pressure amplitudes further reduce scaled entropy generation, enhancing system efficiency. Moreover, across all pressure amplitudes, increasing the Womersley number consistently leads to lower scaled entropy generation, demonstrating that systems operating at higher Womersley numbers achieve greater efficiency and adaptability under dynamic flow conditions.