Computational Fluid Dynamics Modeling of Thermally Integrated Microchannel Reforming Reactors for Hydrogen Production

Junjie Chen

doi:10.31586/ojes.2022.228

Abstract

Many attempts have been made to improve heat transfer for thermally integrated microchannel reforming reactors. However, the mechanisms for the effects of design factors on heat transfer characteristics are still not fully understood. This study relates to a thermochemical process for producing hydrogen by the catalytic endothermic reaction of methanol with steam in a thermally integrated microchannel reforming reactor. Computational fluid dynamics simulations are conducted to better understand the consumption, generation, and exchange of thermal energy between endothermic and exothermic processes in the reactor. The effects of wall heat conduction properties and channel dimensions on heat transfer characteristics and reactor performance are investigated. Thermodynamic analysis is performed based on specific enthalpy to better understand the evolution of thermal energy in the reactor. The results indicate that the thermal conductivity of the channel walls is fundamentally important. Materials with high thermal conductivity are preferred for the channel walls. Thermally conductive ceramics and metals are well-suited. Wall materials with poor heat conduction properties degrade the reactor performance. Reaction heat flux profiles are considerably affected by channel dimensions. The peak reaction heat flux increases with the channel dimensions while maintaining the flow rates. The change in specific enthalpy is positive for the exothermic reaction and negative for the endothermic reaction. The change in specific sensible enthalpy is always positive. Design recommendations are made to improve thermal performance for the reactor.

Highlights

The steam reforming of hydrocarbon or alcohol fuels has attracted increasing interest in the context of the production of hydrogen [1, 2]
The results indicate that the thermal conductivity of the channel walls is fundamentally important
Materials with high thermal conductivity are preferred for the channel walls

Summary

Introduction

The steam reforming of hydrocarbon or alcohol fuels has attracted increasing interest in the context of the production of hydrogen [1, 2]. A traditional steam reforming reactor system consist of a reformer, which contains an appropriate reforming catalyst to facilitate the endothermic reforming reaction and a large industrial furnace to provide the necessary thermal energy for the reaction [3, 4]. A hydrocarbon or alcohol fuel and steam are supplied to the reformer, and hydrogen must be separated from the undesired product, carbon monoxide. An industrial steam methane reforming reactor typically contains an array of long and narrow tubes [5, 6], which are usually made of refractory alloys.

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