Detailed comparison of the performance between a simple and a modified mono-block-layer-built type solid oxide fuel cell

Abstract

A detailed comparison of the performance between a simple Mono-Block-Layer-Build (MOLB) type Solid Oxide Fuel Cell (SOFC) geometry and a MOLB type SOFC with an embedded porous pipe in the air supply channel is carried out. The study considers constant and variable porosities along the porous pipe, fed with an airflow in a counter-flow arrangement. Four cases are analyzed: a) without the porous pipe, b) with a pipe of constant porosity, c) with two different porosities, and d) with four variable porosities. This work is based in a three-dimensional Computational Fluid Dynamics (CFD) model that considers the phenomena of mass transfer, heat transfer, species transport and electrochemical reactions. Detailed comparisons of the voltage, temperature and species concentration are illustrated. The electrode-electrolyte interface contours of species concentration, temperature and electric fields are compared. The results show that there is approximately twice the current density in the geometry that considers the two different porosities compared to the simple geometry. The consumption of hydrogen has the same behavior for the entire tested current density, while the availability of oxygen at the cathode-electrolyte interface is improved in cases with porous pipe compared to the simple MOLB-type geometry. The use of a porous pipe embedded in the air channel showed that it is possible to have a wider operating range of a MOLB-type SOFC, and allowed to obtain a more homogeneous temperature distribution on the electrode-electrolyte interface of the SOFC, consequently, there is the possibility of reducing the thermal stress in the SOFC.