Abstract
In this study a two-phases, single-domain and non-isothermal model of a Proton Exchange Membrane (PEM) fuel cell has been studied to investigate thermal management effects on fuel cell performance. A set of governing equations, conservation of mass, momentum, species, energy and charge for gas diffusion layers, catalyst layers and the membrane regions are considered. These equations are solved numerically in a single domain, using finite-volume-based computational fluid dynamics technique. Also the effects of four critical parameters that are thermal conductivity of gas diffusion layer, relative humidity, operating temperature and current density on the PEM fuel cell performance is investigated. In low operating temperatures the resistance within the membrane increases and this could cause rapid decrease in potential. High operating temperature would also reduce transport losses and it would lead to increase in electrochemical reaction rate. This could virtually result in decreasing the cell potential due to an increasing water vapor partial pressure and the membrane water dehydration. Another significant result is that the temperature distribution in GDL is almost linear but within membrane is highly non-linear. However at low current density the temperature across all regions of the cell dose not change significantly. The cell potential increases with relative humidity and improved hydration which reduces ohmic losses. Also the temperature within the cell is much higher with reduced GDL thermal conductivities. The numerical model which is developed is validated with published experimental data and the results are in good agreement.
Highlights
The proton exchange membrane (PEM) fuel cell is a promising alternative to traditional power sources for a wide range of portable, automotive and stationary applications
Many parameters consist of operating cell voltage, cell operating temperature, feed gas relative humidity and thermal conductivity of the GDL that are expected to dominate the thermal behavior of the PEM fuel cell are investigated
At higher current density of 0.7-1.1 A cm−2, it becomes almost linear in the Temperature Difference T-Tc (K) Cell Potential (V)
Summary
The proton exchange membrane (PEM) fuel cell is a promising alternative to traditional power sources for a wide range of portable, automotive and stationary applications. Modeling of transport and electrochemical phenomena has been considered extensively in the literature and provides good insight on fuel cell operation, but still a complete model of non-isothermal, two-phase and single-domain to determine temperature and the effect of thermal management on the performance of PEM fuel cell dose not exist. In this work a non-isothermal, two phases and single-domain, one-dimensional with the coupled electrochemical and thermal phenomena and unsaturated reactant gas streams is modeled in a fivelayer membrane-electrode assembly of a PEM fuel cell to analyze the impact of cell voltage, operating temperature, relative humidity and GDL thermal conductivity on thermal behaviors of PEM fuel cell. A source term is needed to account for mass transfer between the dissolved and vapor phases within the catalyst layer. The average composition between inlet and outlet in the channels is determined using an integral mass balance on the gas chambers[10]
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