A fuel cell is an energy device that converts chemical energy to electrical energy. Low temperature fuel cells, namely the hydrogen fuel cell and the direct methanol fuel cell are preferred amongst other fuel cell types for stationary and vehicular applications, due to their small size and their low operating temperature. The direct methanol fuel cell has several advantages over the hydrogen fuel cell including ease of transport and storage since methanol is a liquid. Since methanol is used directly in the cell there is no need for a reforming process, which results in a less complicated system. However, direct methanol fuel cell are in their infancy and many problems need to be overcome before reaching commercialization. The direct methanol fuel cell has several disadvantages, namely, the sluggish methanol oxidation reaction, the high cost of state-of-the-art proton exchange membranes, the high methanol permeability from anode to cathode and the dependence on the conductivity on membrane water content, which limits their use to temperatures below the boiling point of water, while the need is to work at high temperatures. Attempts to overcome the disadvantages of the state-of-the-art membrane were made in this study, including the development on novel proton exchange membranes and also the modification of existing state-of-the-art membranes.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The storage of hydrogen is one of the main problems that needs to be solved before hydrogen can become a real alternative to oil in mobile applications. Physisorption of hydrogen in an adsorbate is one of the possible solutions to this problem. This thesis studies the adsorption of hydrogen in Single-Walled Carbon Nanotubes (SWNTs). Neutron scattering techniques are used to probe the possible adsorption sites and the interaction between the hydrogen and the nanotubes at those sites.

No description available.

Transport phenomena in high porosity open-cell fibrous structures have been the focus of many recent industrial and academic investigations. Unique features of these structures such as relatively low cost, ultra-low density, high surface area to volume ratio, and the ability to mix the passing fluid make them excellent candidates for a variety of thermofluid applications including fuel cells, compact heat exchangers and cooling of microelectronics. This thesis contributes to improved understanding of thermal transport phenomena in fuel cell gas diffusion layers (GDLs) and metal foams and describes new experimental techniques and analytic models to characterize and predict effective transport properties. Heat transfer through the GDL is a key process in the design and operation of a proton exchange membrane (PEM) fuel cell. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the GDL and adjacent surfaces/ layers. The effective thermal conductivity significantly differs in through-plane and in-plane directions due to anisotropy of the GDL micro-structure. Also, the high porosity of GDLs makes the contribution of TCR against the heat flow through the medium more pronounced. A test bed was designed and built to measure the thermal contact resistance and effective thermal conductivity in both through-plane and in-plane directions under vacuum and ambient conditions. The developed experimental program allows the separation of effective thermal conductivity and thermal contact resistance. For GDLs, measurements are performed under a wide range of compressive loads using Toray carbon paper samples. To study the effect of cyclic compression, which may happen during the operation of a fuel cell stack, measurements are performed on the thermal and structural properties of GDL at different loading-unloading cycles. The static compression measurements are complemented by a compact analytical model that achieves good agreement with experimental data. The outcomes of the cyclic compression measurements show a significant hysteresis in the loading and unloading cycle data for total thermal resistance, TCR, effective thermal conductivity, thickness, and porosity. It is found that after 5 loading/unloading cycles, the geometrical, mechanical, and thermal parameters reach a“steady-state”condition and remain unchanged. A key finding of this study is that the TCR is the dominant component of the GDL total thermal resistance with a significant hysteresis resulting in up to a 34 % difference between the loading and unloading cycle data. Neglecting this phenomenon may result in significant errors in evaluating heat transfer rates and temperature distributions. In-plane thermal experiments were performed using Toray carbon paper samples with different polytetrafluoroethylene (PTFE) content at the mean temperature of 65−70◦C. The measurements are complemented by a compact analytical model that achieves good agreement with experimental data. Results show that the in-plane effective thermal conductivity remains approximately constant, k ≈ 17.5W/mK, over a wide range of PTFE content, and it is approximately 12 times higher than the through-plane conductivity. Using the test bed designed for the through-plane thermal conductivity measurement, the effective thermal conductivity and thermal contact resistance of ERG Duocel aluminum foam samples were measured under varying compressive loads for a variety of porosities and pore densities. Also, an experimental program associated with an image analysis technique is developed to find the size and distribution of contact spots at different compressive loads. Results show that the porosity and the effective thermal conductivity remain unchanged with the variation of pressure in the range of 0 to 2 MPa; but TCR decreases significantly with pressure due to an increase in contact area. Moreover, the ratio of contact area to cross-sectional area is 0-0.013, depending upon the compressive force, porosity, and pore density. This study clarifies the impact of compression on the thermal and structural properties of GDLs and metal foams and provides new insights on the importance of TCR which is a critical interfacial transport phenomenon. / Graduate