质子交换膜燃料电池气体扩散层中的等温冰结晶动力学。

Isothermal ice crystallization kinetics in the gas-diffusion layer of a proton-exchange-membrane fuel cell.

机构信息

Chemical and Biomolecular Engineering Department, University of California, Berkeley, California 94720, USA.

出版信息

Langmuir. 2012 Jan 17;28(2):1222-34. doi: 10.1021/la2033737. Epub 2012 Jan 3.

DOI:10.1021/la2033737

Abstract

Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear ice-crystallization rate expression is developed using Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction times follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. A validated rate expression is now available for predicting ice-crystallization kinetics in GDLs.

摘要

采用等温差示扫描量热法（DSC）研究了质子交换膜燃料电池（PEMFC）纤维状气体扩散层（GDL）中冰的成核和生长。通过热流和诱导时间测量，得到了过冷度的函数的等温结晶速率和准稳态成核速率。在 240 至 273 K 的温度范围内，研究了两种聚四氟乙烯（PTFE）负载量（0 和 10wt%）的商用 GDL 中的冰成核和生长动力学。使用 Johnson-Mehl-Avrami-Kolmogorov（JMAK）理论开发了非线性冰晶生长速率表达式，其中通过移动边界 Stefan 问题确定了传热限制的生长速率。诱导时间遵循泊松分布，并且在添加 PTFE 后会增加，这表明成核在疏水性纤维上比在亲水性纤维上发生得更慢。确定的成核速率和诱导时间遵循经典成核理论的预期趋势。现在有一个经过验证的速率表达式可用于预测 GDL 中的冰晶生长动力学。