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Two-phase flow pressure drop in PEM fuel cell flow channel bends
International Journal of Multiphase Flow ( IF 3.8 ) Pub Date : 2021-07-24 , DOI: 10.1016/j.ijmultiphaseflow.2021.103759
Mehdi Mortazavi 1
Affiliation  

During the operation of a proton exchange membrane (PEM) fuel cell water is produced as a byproduct of electrochemical reactions. As the produced water passes through the porous structure of the electrodes and enters the flow channels, liquid–gas two-phase flow forms within the flow channels. If a reliable model that can accurately predict the pressure drop is available, then the two-phase flow pressure drop can be used as an in-situ diagnostic tool to quantify the water content within the flow channels. While the two-phase flow pressure drop is investigated for straight sections of PEM fuel cell flow channels, few attention has been paid to evaluate the pressure drop across flow channel bends. In this study, liquid–gas two-phase flow across a flow channel bend is investigated with an ex-situ approach. A 90 flow channel bend was fabricated across a channel with a hydraulic diameter of 1 mm. Experiments were conducted by supplying air and hydrogen as the gas phase and injecting liquid water into the flow channel in order to represent the two-phase flow condition in the cathode and anode flow channels, respectively. The two-phase flow across the bend was visualized with a CCD camera and the pressure drop values were measured for the PEM fuel cell flow conditions. A comparison between the experimental data and predictions from some of the existing models prompted the need for a model that can accurately predict the two-phase flow pressure drop across PEM fuel cell flow channel bends. In this study, a new model to predict the frictional two-phase flow pressure drop across flow channel bends was developed based on the separated flow model. Because the two-phase flow in PEM fuel cell flow channels is dominated by the gas phase, the new model incorporated the gas minor loss which was defined as the pressure drop caused by the flow channel bend. In order to predict the gas minor loss, a correlation for the loss coefficient was obtained based on the gas single-phase pressure drop. In addition, a correlation was proposed for the C parameter as the two-phase flow across the flow channel bend featured an enhanced interaction between the two phases of liquid and gas. Results indicated that the proposed two-phase flow pressure drop model along with the proposed C correlation were able to predict the pressure drop with mean absolute error values of 7.74% for air–water runs and 10.77% for hydrogen–water runs.



中文翻译:

PEM 燃料电池流道弯曲处的两相流压降

在质子交换膜 (PEM) 燃料电池运行期间,水是电化学反应的副产品。随着采出水通过电极的多孔结构进入流道,在流道内形成气液两相流。如果有可以准确预测压降的可靠模型,那么两相流压降就可以作为原位诊断工具来量化流道内的含水量。虽然研究了 PEM 燃料电池流道直线段的两相流压降,但很少有人关注评估流道弯曲处的压降。在这项研究中,通过非原位研究了流道弯曲处的液-气两相流方法。一个 90流道弯头是在水力直径为 1 毫米的通道上制造的。通过提供空气和氢气作为气相并将液态水注入流道进行实验,以分别代表阴极和阳极流道中的两相流动状态。使用 CCD 相机观察穿过弯管的两相流,并测量 PEM 燃料电池流动条件下的压降值。实验数据与一些现有模型的预测之间的比较促使需要一种模型,该模型可以准确预测 PEM 燃料电池流道弯曲处的两相流压降。在这项研究中,基于分离流模型开发了一种新模型来预测跨流道弯曲的摩擦两相流压降。由于 PEM 燃料电池流道中的两相流以气相为主,新模型纳入了气体小损失,定义为流道弯曲引起的压降。为了预测气体次要损失,基于气体单相压降获得了损失系数的相关性。此外,还提出了 C 参数的相关性,因为通过流道弯曲的两相流具有增强的液体和气体两相之间的相互作用。结果表明,提出的两相流压降模型以及提出的 C 相关性能够预测压降,空气-水运行的平均绝对误差值为 7.74%,氢-水运行的平均绝对误差值为 10.77%。新模型包含气体轻微损失,其定义为流道弯曲引起的压降。为了预测气体次要损失,基于气体单相压降获得了损失系数的相关性。此外,还提出了 C 参数的相关性,因为通过流道弯曲的两相流具有增强的液体和气体两相之间的相互作用。结果表明,提出的两相流压降模型以及提出的 C 相关性能够预测压降,空气-水运行的平均绝对误差值为 7.74%,氢-水运行的平均绝对误差值为 10.77%。新模型包含气体轻微损失,其定义为流道弯曲引起的压降。为了预测气体次要损失,基于气体单相压降获得了损失系数的相关性。此外,还提出了 C 参数的相关性,因为通过流道弯曲的两相流具有增强的液体和气体两相之间的相互作用。结果表明,提出的两相流压降模型以及提出的 C 相关性能够预测压降,空气-水运行的平均绝对误差值为 7.74%,氢-水运行的平均绝对误差值为 10.77%。基于气体单相压降获得了损失系数的相关性。此外,还提出了 C 参数的相关性,因为通过流道弯曲的两相流具有增强的液体和气体两相之间的相互作用。结果表明,提出的两相流压降模型以及提出的 C 相关性能够预测压降,空气-水运行的平均绝对误差值为 7.74%,氢-水运行的平均绝对误差值为 10.77%。基于气体单相压降获得了损失系数的相关性。此外,还提出了 C 参数的相关性,因为通过流道弯曲的两相流具有增强的液体和气体两相之间的相互作用。结果表明,提出的两相流压降模型以及提出的 C 相关性能够预测压降,空气-水运行的平均绝对误差值为 7.74%,氢-水运行的平均绝对误差值为 10.77%。

更新日期:2021-08-01
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