The content of this PhD thesis deals with the development of Micro Tubular Solid Oxide Fuel Cells (MT-SOFCs) and provides a body of information for any future MT-SOFC stack or testing apparatus design. This information has been achieved through a combination of experimental work, CFD modelling and numerical analysis. CFD models with an additional fuel cell module have been compared to experimental results for single cells with relation to oxygen concentration, fuel utilisation, I/V curves and external cell temperature profiles. All of the above multi physical phenomena match very well to the experimental results. A key finding of the thesis is the importance of including radiation equations in the CFD models. Neglecting radiation can result in temperature errors of up to 200°C for a single cell in cross flow inside a high temperature wind tunnel. . This is interesting information as most modelling work in the field to date has neglected radiation effects. 3D models that include the experimental apparatus and radiation equations have been completed. These models show how the experimental apparatus or stack design may cause large temperature losses if not properly designed. Furthermore the radial temperature gradient across the cell has been experimentally measured using an impedance spectroscopy technique. A thermographic photography technique has been developed to measure the temperature profile on the cathode wall of a MT-SOFC in cross flow within a high temperature wind tunnel. Other simplified 3D CFD models have been compared to numerical calculations to predict the conditions when buoyant flows may occur in bundles of MT-SOFCs in cross flow. The results show that a stack oxidant flow rate, even greater than a few mm per second, can dramatically inhibit the effect of buoyant flows to the point where they will not occur. This is important information that should be useful when designing MT-SOFC stack flow channels. The measurement of the concentration around the perimeter of a MT-SOFC in cross-flow has also been attempted. While it has not been shown conclusively that a method developed in this thesis surely works, it has been shown that there is massive potential for it to work.
|Publication status||Published - 2010|