Numerical study of thermal diffusion in a passive autocatalytic recombiner: Possible effects on catalyst temperature and hydrogen distribution

This paper describes a numerical study of the influence of thermal diffusion (the Soret effect) on the operational behaviour of a passive autocatalytic recombiner (PAR). The study pro-poses a detailed three-dimensional computational fluid dynamics (CFD) model of hydrogen oxidation along a cylindrical-type PAR catalyst section (RVK-500, RET, Russia) inside a small-scale vertical channel. The CFD model was developed in STAR-CCM+ and uses multi-step chemical kinetics with a conjugated approach (surface and gas-phase included). The cata-lyst temperature and hydrogen conversion with and without the Soret effect in the model were determined numerically and compared against experimental measurements. The ex-periments reported here have previously been conducted on the cylindrical-type catalyst section, for 5-7 vol % inlet H2 concentration. Numerical simulations demonstrate that local hydrogen concentration can be increased due to thermal diffusion at the lower side of the stainless-steel frame. Results identified that the catalyst temperature can be underpredicted by 10-20 degrees C without thermal diffusion included in the model.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.