Effect of particle breakage on heat and mass transfer characteristics of packed bed at low Reynolds numbers: Pore-scale simulation

Packed beds have been extensively utilized in multiple fields, but the influence of particle breakage on their heat and mass transfer characteristics remains insufficiently explored. In this study, the heat and mass transfer characteristics in crushed particle packed beds were investigated at low Reynolds numbers (Re∼1) by combining with particle breakage experiments and DEM-CFD pore-scale simulation based on MATLAB and COMSOL Multiphysics, taking fusion blanket pebble bed as an example. It was found that crushed particles enhance the inhomogeneity of airflow velocity distribution within the packed beds and raises the overall pressure drop gradient and resistance coefficient significantly. The overall temperature distribution remains similar after particle breakage, with a slight increase in peak temperature. The convective heat transfer coefficient and average Nusselt number may first increase and then decrease with the increase of crushed fraction, reaching the peak value with a possible 75 % enhancement at 10 % crushed fraction. This reflects the competitive mechanism between convective heat transfer enhancement and inhibition: crushed particles can enhance convection by increasing the surface area and improving fluid flow state, but it may also result in flow channel blockage, which could hinder transfer behavior. Similarly, the maximum tritium concentration first increases and then decreases with the increase of the crushed fraction, and the convective mass transfer coefficients and average Sherwood number show a similar trend with even 78 % improvement at 10 % crushed fraction. These findings provide a reference for guiding the design optimization and safety analysis of packed bed systems.