Start-up characteristics of high-temperature proton exchange membrane fuel cell stacks based on flat heat pipes
High-temperature proton exchange membrane fuel cells(HT-PEMFC)operate at about 160℃ and have the advantages of better electrochemical reaction kinetics,simpler hydrothermal management and higher CO tolerance than conventional low-temperature cells.However,upon the increase of operating temperature,the fast start-up of HT-PEMFC becomes one of the important challenges that restrict its application promotion.In current work,a preheat start-up method using a flat plate heat pipe(FHP)for a HT-PEMFC reactor with a rated power of 500W was attempted.An experimental system was designed and built to evaluate this method in terms of preheating time,temperature distribution,and heat transfer distribution.The experimental results showed that increasing the heating power significantly reduced the preheating time from 3000s at 500W to 980s at 1500W,However,it also caused a deterioration of the temperature uniformity,with a maximum temperature difference of about 28 ℃ in the vertical direction at 500W increased to 80℃ at 1500W.In addition,the temperature difference in the horizontal direction increased with the heating power,especially in the area close to the heat source,up to 15.7℃,which would undoubtedly accelerate the mechanical failure of the proton exchange membrane.In practice,a higher heating power should be selected to reduce the start-up time but not affecting the cell operating life too much.
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