The traditional fixed-bed reactor design is usually not suitable for the low tube-to-particle diameter ratios (N=D/d b 8) where the local phenomena of channeling near the wall and backflow in the bed are dominant. The recentsolid particlemeshing method is too complicated for mesh generation, especially for non-spherical particles in large random packed beds, which seriously hinders its development. In this work, a novel high-fidelity mesh model is proposed for simulation of fixed bed reactors by combining the immersed boundary and adaptive meshing methods. This method is suitable for different shapes of particles, which ingeniously avoids handling the complexcontact pointproblem. Several packed beds with two different shapes of particles are investigated with this model, and the local flow in the bed is simulated without geometrical simplification. The predicted pres-sure drop across the fixed bed and heat transfer of the single particle are in good agreement with the correspond-ing empirical relations. Compared with spherical particles, the packed bed packing with pentaphyllous particles has lower pressure drop and better heat/mass transfer performance, and it shows that this method can be used for the screening of particle shapes in a fixed bed.