Modeling of radial heat transfer in cooled fixed-bed reactors by one- and two-dimensional models: Fischer-Tropsch synthesis as a case study

New correlations for the overall heat transfer coefficient U_th, designed for use in one-dimensional reactor models for wall-cooled tubular fixed-bed reactors, are presented. These correlations are applicable for estimating both critical conditions related to thermal runaway and reactor performance under safe operating conditions. They were derived by comparing a 1D and a 2D model, initially for Fischer-Tropsch synthesis (FTS) as a case study, and subsequently extended beyond this specific reaction system. Additionally, a novel approach is introduced for estimating critical runaway conditions without relying on a reactor model. This method is based solely on reaction kinetics, the effective thermal conductivity λ_rad, and the heat transfer coefficient α_wall, which accounts for heat transfer near the reactor wall.