Optimal design of thermochemical reactors based on constructal approach

This work aims to optimize the design of thermochemical reactors such as solid/gas fixed bed reactors working in dynamic mode. The optimization is based on the constructal approach. A thermodynamic criterion, the ratio of reactor output power to its entropy generation, has to be used to take into account the coupled phenomena and the end purpose of such reactors. Two reactors are considered with same overall volume, but different internal configuration of collectors (constructal scales): a “basic” single-scale configuration (basic reactor), and a “constructal” two-scale configuration (constructal 1 reactor). Reaction rates notably vary with reactor shape, and an optimal shape factor is found for each reactor, depending on the reactant material density. For both reactors, an important remark is pointed out: the correspondence between the maximum of power/entropy ratio (PER) and the highest reaction rate. Comparison between the optimal basic and constructal 1 reactors shows that the latter presents higher energy efficiency (based on second law analysis), but lower output power than the first. © 2007 American Institute of Chemical Engineers AIChE J, 2007