A model of an irreversible proton exchange membrane （PEM） fuel cell working at steady-state was established, in which overpotenfials, internal currents, and crossover losses were taken into account. The expressions of some key parameters of the fuel cell were derived from the point of electrochemistry and thermodynamics. Based on the irreversible model of the PEM fuel ceil, the influence of multi-irreversibilities on fuel cell performance were characterized and compared systematically. The general performance characteristic curves were generated. Moreover, when the electrical circuit was dosed with a load in it, the relations between the load resistance and power output density and efficiency were analyzed. The results provide a theoretical basis for both the operation and optimal design of real PEM fuel cells.
建立柱坐标系下层流降膜吸收水蒸气的传热传质模型,通过Laplace变换,由Stehfest方法导出定温边界条件下温度场与水的质量分数场。计算不同刘易斯数(Lewis number, Le )下层流降膜吸收水的质量分数梯度,分析了压力对降膜吸收水蒸气流量的影响。结果表明:与绝热边界条件相比,定温边界条件下降膜温度较低、水的质量分数较高;对于整个流动长度, Le 的增大使降膜吸收水的无量纲流量增大;随着压力的上升,吸收的水蒸气流量几乎呈线性上升。
