| dc.description.abstract | In the recent years, air pollution has exacerbated the greenhouse effect and extreme weather conditions, prompting countries to increasingly prioritize environmental issues. Hydrogen energy has emerged as a highly promising energy source. Among various hydrogen energy technologies, high-temperature proton exchange membrane fuel cell (HT-PEMFCs) combines the advantages of proton exchange membrane fuel cells and high-temperature operation, drawing considerable interest from researchers. This study focuses on the thermal management of HT-PEMFC stacks and investigates the impact of varying the cathode side stoichiometric ratio on the stack performance and thermal characteristic. Additionally, it utilizes temperature distribution measurements and a thermal resistance network model to predict the temperature distribution of components within the fuel cell stack that cannot be directly measured.
This study examines the temperature distribution and performance of high-temperature proton exchange membrane fuel cells under different ambient temperatures and stoichiometric ratios. Temperature distribution measurements are conducted at steady state by measuring the temperature at various positions and depths within the fuel cell with thermocouple. Performance testing involves polarization curve tests and individual cell voltage measurements. A thermal resistance network model, along with the measured temperature data, is used to predict the temperatures of fuel cell components that cannot be directly measured.
Experimental results show that this five-cell battery stack achieved a maximum power density of 991 mA/cm2 at an ambient temperature of 40°C, with an operating temperature of 160°C, a gas flow rate of 20 c.c/min/cell, an anode stoichiometry of 1.2, and a cathode stoichiometry of 2.0. At an ambient temperature of 25°C, the maximum power density was 931 mA/cm2. Without using a heating system and utilizing a constant current to bring the battery stack to a steady-state temperature, the temperature distribution results indicate that the highest temperature of the battery stack occurs at the third cell (center) position. The average temperature of the battery stack at an ambient temperature of 40°C is approximately 10°C higher than that at 25°C. The battery stack temperature decreases with an increase in the cathode stoichiometry, but the performance improves. Voltage measurements of each cell reveal that within an appropriate stoichiometry range, the voltage increase due to higher ambient temperatures is more beneficial than that achieved by increasing the stoichiometry. The temperature error between the measured points predicted by the thermal resistance network model and the actual measurements is less than 5%, indicating that the model′s predictions have a certain reference value. This thermal resistance model can further estimate the temperatures of objects within the battery stack that cannot be measured directly. | en_US |