Caroline Willich

Spatially Resolved Electrochemical Performance in a Segmented Planar SOFC

Spatially inhomogeneous distributions of current density and temperature in solid oxide fuel cells (SOFC) can contribute significantly to accelerated electrode degradation, thermomechanical stresses, and reduced efficiency. A combined experimental and modeling study of the spatial distribution of the electrochemical performance was performed in order to determine local effects. A planar anode-supported SOFC single cell was locally characterized in a 4x4-segmented cell arrangement in dependence of gas composition and fuel utilization. A two-dimensional elementary kinetic electrochemical model was used to quantitatively interpret experimental observations. The model was validated by comparison to experiments under a wide range of operating conditions. When the cell was operated at high fuel utilization, both measurements and simulations show a strong variation of the electrochemical performance along the flow path. The simulations predict a considerable gradient of gas-phase concentrations along the fuel channel and through the thickness of the porous anode, while the gradients are lower at the cathode side.

Research data supporting “An investigation of heat transfer losses in reciprocating devices”

The paper presents a detailed computational-fluid-dynamic study of the thermodynamic losses associated with heat transfer in gas springs. This forms part of an on-going investigation into high-efficiency compression and expansion devices for energy conversion applications. Axisymmetric calculations for simple gas springs with different compression ratios and using different gases are first presented, covering Peclet numbers that range from near-isothermal to near-adiabatic conditions. These show good agreement with experimental data from the literature for pressure variations, wall heat fluxes and the so-called hysteresis loss. The integrity of the results is also supported by comparison with simplified models. In order to mimic the effect of the eddying motions generated by valve flows, nonaxisymmetric computations have also been carried out for a gas spring with a grid (or perforated plate) of 30% open area located within the dead space. These show significantly increased hysteresis loss at high Peclet number which may be attributed to the enhanced heat transfer associated with grid-generated motions. Finally, the implications for compressor and expander performance are discussed. 2016 The Authors. Published by Elsevier Ltd. This is an openaccess article under the CCBY license (http:// creativecommons.org/licenses/by/4.0/).