This study focuses on the parametric analysis of a packed bed and investigates the flow and thermal-hydraulic characteristics of the Very High-Temperature Reactor (VHTR) design. By presenting the coding aspect of the LTNE model and incorporating radiation effects using OpenFOAM, we contribute to the study of the nuclear packed bed reactor designs in terms of safety, sustainability, and power generation. Our OpenFOAMbased CFD study shows the influence of coolant flow rate on pressure drop and the effect of particle Reynolds number on outlet temperature. The study highlights the role of convective heat transfer and thermal gradients in determining the temperature distribution within the packed bed and provides valuable insights for optimising the system's performance. It is found that the pressure drop is affected by the coolant mass flow rate and increases with increasing particle Reynolds numbers. Higher Reynolds numbers also resulted in higher outlet temperatures and affected the temperature distribution through convective heat transfer and thermal gradients. These findings contribute to optimising the design and operation of packed bed systems.