CFD-DEM and PR-DNS studies of low-temperature densely packed beds

•CFD-DEM and PR-DNS studies are conducted to study the heat transfer mechanisms in a packed bed of particles (~60% Packing Fraction).•Particle-Fluid-Particle Heat Transfer path is identified to play an important role in the overall heat transfer physics.•A new closure model is proposed to resolve the Particle-Fluid-Particle heat transfer path by modeling the effect of intra-particulate temperature gradients.•Proposed closure model provides improved accuracy of CFD-DEM heat transfer simulations at low values of Solid-Fluid Conductivity Ratios (ks/kf).