Small tube-to-particle-diameter ratio induces a radial heterogeneity in tubular fixed beds on the particle scale. In this complex topology, theoretical models fail to predict wall-to-fluid heat transfer. In order to be more realistic, a deterministic Bennett method is first used to synthesize two packings with a tube-to-sphere-diameter ratio of 5.96 and 7.8, containing 236 and 620 spheres, respectively. In a second step, unsteady velocity and temperature fields are computed by CFD. In the range of Reynolds number lying between 80 and 160, hydrodynamic results are validated with experimental data. The thermal disequilibrium in the near-wall region is described in detail. Several pseudo-homogeneous models are compared to the numerical simulations. The radial and axial profiles of temperature show a clear agreement with the model of Schlunder's research group and the model of Martin and Nilles. (C) 2009 American Institute Of Chemical Engineers AIChE J, 55: 949-867, 2009