الفهرس 
SummaryOnly 14 pages are availabe for public view
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Abstract
A fuel cell is an electrochemical energy conversion device. It is more efficient than an internal combustion engine in converting fuel to electrical power. A fuel cell produces power, water, and heat utilizing fuel and oxygen in the air. Water is the only emission when hydrogen is used as the fuel. Among an extensive variety of fuel cells, proton exchange membrane fuel cells (PEMFC) are conservative and lightweight, work at low temperatures with a high yield power density, and superior system startup and shutdown performance. Essentially the majority of fuel cells are consisted of two cathodes surrounding the electrolytic material. The arrangement of the electrodes and the electrolyte recognize one fuel cell from another. In a PEMFC, the electrolyte material is a polymer and the electrodes are carbon paper water-sealed with teflon, hydrogen molecules enter a fuel cell at the anode where a chemical reaction strips them of their electrons. The hydrogen particles are currently ionized and convey a positive electrical charge. Oxygen enters the fuel cell at the cathode and joins with electrons coming back from the electrical circuit and hydrogen particles that have gone through the electrolyte from the anode creating the water emission. This thesis describes a theoretical model to examine impacts of air condition parameters effects on the performance of proton exchange membrane fuel cell system. The MATLAB/SIMULINK tool is applied to study data from a progression of different states of air delivery system, with a specific end goal to achieve the ideal working states of the fuel cell system. In this study, effects of utilized air mass flow rate, pressure, temperature and relative humidity on the execution of the considered fuel cell system are investigated. Fuel cell considered output parameters are polarization curves, output power and cell efficiency. The study is applied on a fuel cell stack consisted of 110 cells with cell active area of 218 × 10-4 m2 stacked in series to produce more than 20 kW capable to power a sedan vehicle. The model investigates effects of air parameter conditions for two cases, the first with steady relative humidity, and the second with a variable relative humidity. The model describes the performance of the fuel cell through the investigation of the polarization and the power density versus current density curves and the cell electric efficiency. Obtained results demonstrate that, operating conditions of inlet air have a significant effect on the performance of the fuel cell. The influence air relative humidity is more significant compared to other operating parameters. The overall cell performance is improved as the air relative humidity increases as well as its temperature and pressure while with air mass flow rate the fuel cell performance decreased.