Entropy production minimization in a tubular ammonia synthesis reactor: a mathematical optimization approach with variable geometry and heat flux control

Ammonia is one of the most widely produced chemicals worldwide and is increasingly considered a promising hydrogen carrier for energy storage. We propose a novel thermodynamic optimization strategy for tubular ammonia reactors based on second-law analysis and variable reactor geometry. Assuming thermal performance is already maximized through heat exchange, we explore how variations in reactor radius can further minimize entropy generation. Our steady-state mathematical model shows that geometry optimization alone can reduce total entropy production by 57% and pressure drop by 96%, without affecting ammonia yield or catalyst usage. Sensitivity analysis highlights the role of thermal boundary conditions on reactor performance. This study demonstrates that integrating geometric design with entropy minimization principles can significantly enhance the thermodynamic efficiency and sustainability of industrial chemical reactors.