The presented conjugated heat and mass transfer model is applied for flow and chemical reaction in a wall cooled tube (D t = 21 mm) filled with ring shaped VPO catalyst particles (d p,outer /h p /d p,inner = 1/1/0.4, Dt /dp,outer = 3.75). As characteristic size d p of the ring, the diameter of a sphere with identical specific surface is used. The fixed bed (see Figure , bottom) is synthetically generated with the rigid body approach implemented in the open source game engine Blender 2.79 ). The employed filling algorithm based on the work of Partopour and Dixon (2017) generates individual particles above the tube with randomized position and orientation. The particles fall down due to gravity and fill up the tube. The algorithm stops generating new rings after 100 particles have been dropped, which results in a packed bed length of L t = 69 mm. The mesh with polyhedral cells is generated according to the routine described detailed in . To ensure a high quality mesh, particle-particle and particle-wall contacts are locally replaced by a defined gap of size 0.8 %d p,outer containing fluid cells, i.e., a modified local caps methods. The base size, which is a characteristic dimension for the cell size in Simcenter STAR-CCM+, is set to 7 mm. The size of the mesh on the particle surface is defined as 5 % of the base size. At the outer particle surface and the tube wall, three prism layers are generated with a total thickness equal to the size of the momentum boundary layer calculated according to Equation 26. In addition, three layers of prismatic cells with a total thickness of 0.2 mm are introduced on the solid side of the particle surface. For close proximity surfaces, the surface mesh is refined and the number of prismatic cells are reduced or completely rejected to reach a higher mesh quality. The cell count of the resulting mesh is 3.1 million for the fluid and 2.5 million for the solid phase. demonstrated by a mesh dependency study that the used mesh size and settings provide a physical accurate solution in a reasonable computational time for the applied particle and tube dimensions. The uniformly distributed inlet velocity is specified to achieve a particle Reynolds number of 200. The outlet pressure is set to 1013.25 kPa. The tube wall is impermeable to the species mass transport. Furthermore, at the tube wall, a no-slip boundary for the flow and a constant temperature T wall are imposed as boundary conditions. The composition of the entering fluid and the temperatures at the inlet and wall are comparable to the conditions in the inlet region of an industrial scale MA reactor (T in = T wall = 673 K,