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Pseudo-isothermal ice-crystallization kinetics in the gas-diffusion layer of a fuel cell from differential scanning calorimetry

机译:差示扫描量热法在燃料电池气体扩散层中的伪等温冰晶动力学

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摘要

Non-isothermal ice-crystallization kinetics in the fibrous gas-diffusion layer (GDL) of a proton-exchange-membrane fuel cell is investigated using differential scanning calorimetry (DSC). Non-isothermal ice-crystallization rates and ice-crystallization temperatures are obtained from heat-flow measurements in a water-saturated commercial GDL at cooling rates of 2.5, 5, 10, and 25 K/min. Our previously developed isothermal ice-crystallization rate expression is extended to non-isothermal crystallization to predict ice-crystallization kinetics in a GDL at various cooling rates. Agreement between DSC experimental results and theory is good. Both show that as the cooling rate increases, ice-crystallization rates increase and crystallization temperatures decrease monotonically. Importantly, we find that the cooling rate during crystallization has a negligible effect on the crystallization rate when crystallization times are much faster than the time to decrease the sample temperature by the subcooling. Based on this finding, we propose a pseudo-isothermal method for obtaining non-isothermal crystallization kinetics using isothermal crystallization kinetics evaluated at the non-isothermal crystallization temperature.
机译:使用差示扫描量热法(DSC)研究了质子交换膜燃料电池纤维气体扩散层(GDL)中的非等温冰晶动力学。非等温冰晶化速率和冰晶化温度是通过在水饱和的商用GDL中以2.5、5、10和25 K / min的冷却速率进行热流测量获得的。我们先前开发的等温冰结晶速率表达式已扩展到非等温结晶,以预测GDL在各种冷却速率下的冰结晶动力学。 DSC实验结果与理论吻合良好。两者都表明,随着冷却速率的增加,冰的结晶速率增加,而结晶温度单调下降。重要的是,我们发现,当结晶时间比通过过冷降低样品温度的时间快得多时,结晶过程中的冷却速率对结晶速率的影响可忽略不计。基于此发现,我们提出了一种拟等温方法,该方法使用在非等温结晶温度下评估的等温结晶动力学来获得非等温结晶动力学。

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  • 作者单位

    Chemical and Biomoiecular Engineering Department, University of California, Berkeley, CA 94720, United States ,Environmental Energy Technology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States;

    Chemical and Biomoiecular Engineering Department, University of California, Berkeley, CA 94720, United States;

    Chemical and Biomoiecular Engineering Department, University of California, Berkeley, CA 94720, United States;

    Chemical and Biomoiecular Engineering Department, University of California, Berkeley, CA 94720, United States ,Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States;

    Environmental Energy Technology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    crystallization; kinetics; solidification; heat transfer; differential scanning calorimetry; gas-diffusion layer;

    机译:结晶;动力学;凝固;传播热量;差示扫描量热法;气体扩散层;

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