交错通道型三维流场的强化传质效果与对面内水分布均一性的改善

Flow channel design in a proton exchange membrane fuel cell： From 2D to 3D

Jun Shen

Zhengkai Tu

Abstract

Flow channel design has attracted more and more attention with the evolution of fuel cell technology． Compared with conventional 2D flow channel， 3D flow channel has been proved to improve the performance of proton exchange membrane fuel cell with great enhancement of reactant transport in many researches． In this paper， flow fields of parallel 2D， simplified 3D and 3D with inclination are presented to study the transport and distribution characteristics of reactant and water inside a fuel cell， and efficiency evaluation criterion is proposed to evaluate the superiority of the flow channel design． It is found that 3D flow fields are superior compared with parallel 2D flow channel， with improved capacity of mass transfer， uniform water distribution and advanced water removal ability． The performance improvements of both 3D flow channel designs become significant at elevated current density， with the output voltage increasing to 4．4％ at 1．6 A cm−2 and up to 10％ at 2 A cm−2． Compared with 3D flow channel with inclination， simplified 3D flow channel shows smaller pressure drop， and it has better performance than that of 2D flow channel． Considering both the performance and flow resistance， simplified 3D flow channel performs the best with high efficiency and easy－processing， thus it is the future direction of flow design．

Fig． 1 e Schematic of different flow fields （a） Parallel 2D flow channel； （b） Simplified 3D flow channel； （c） 3D flow channel with inclination．

冲断片段型流场？波纹板的拼接？

这个结构过于理想化，不仅石墨板做不了，金属板也比较困难。但可以作为研究性课题。

Fig． 2 e Schematic of PEMFC with simplified 3D flow channel （a） from isometric view （b） from front view．

图中和计算下来图形，并不是左右对称的。不仅仅是交错排布。

Table 1 e Physical dimension of PEMFC．

三维在长度方向的间隔为1mm

Table 2 e Operating condition of PEMFC．

Table 3 e Physical parameters of PEMFC．

Fig． 3 e Model validation

Fig． 4 e Performance comparison of different flow fields

3D flow channel with inclination of 45度

Simulation results

At 1．6 A cm2， the output voltage of 3D flow channel with and without inclination were 0．616 V and 0．614 V， while it was 0．590 V with parallel 2D flow channel

按照文中的说法作的四个面的位置

Fig． 5 e Velocity distribution along flow direction at 1．6 A cm¡2 （a） Parallel 2D flow channel （b） Simplified 3D flow channel （c） 3D flow channel with inclination．

在同一个图中色标如果能调成同一个坐标的就好辨识一些。

如果在流速图上把流动的流通截面画出来就更直观一些。

从图5c的流速上看尾端倾斜角面似乎进行了封闭，而三维图1上似乎是开放的。似乎并不是接近下面的图。在靠尾端倾斜角文章未做完全封闭。

虽然间隔了1mm，流体已经进行了发展，不局限于尾端倾斜面受限。

Because the height of outlet section was only half of the
original height in 3D flow channel with inclination， the height
of Y＝0．5225 mm and Y＝0．7225 mm were chose to analysis
the velocity distribution． Y＝0．5225 mm and Y＝0．7225 mm were the locations of 1／4 and 1／2 height of the cathode gas channel．

文中只是说描述位置，但是没有把绝对坐标系画清楚，具体Y＝0在什么位置，造成这个流道高度的绝对值比较费解。不清楚Y＝0．5225具体在这个图中的哪个位置。

Fig． 6 e Quantification analysis of velocity distribution along flow direction （a） Parallel 2D flow channel （b）Simplified 3D flow channel （c） 3D flow channel with inclination．

通过图5z的值，我的理解z＝0在直流道的中心，为什么直流道不同的Y，流速会有偏低到大的状态，这个地方最初没有理解。看到z的坐标是m，我才理解。但这个入口流体竟然还不是充分发展的，因此图5a中z为负值时的流速不具有太多意义。

但可以看出扰动让充分发展段的长度显著减短。

不理解为什么z＝－55．5mm的位置三种构型的输入为什么有差异。

Fig． 7 e The distribution of velocity vector in gas channel （a） Parallel 2D flow channel （b） Simplified 3D flow channel （c） 3D flow channel with inclination．

Fig． 8 e Molar concentration of oxygen and water in gas channel （a） Parallel 2D flow channel （b） Simplified 3D flow channel （c） 3D flow channel with inclination．

同样的，不理解为什么z＝－55．5mm的位置三种构型的输入为什么有差异。

Fig． 9 e Contours of water content in proton exchange membrane （a） Parallel 2D flow channel （b） Simplified 3D flow channel （c） 3D flow channel with inclination．

第二种水含量分布看上去整体更加均匀。

Fig． 10 e Water content of membrane along flow direction （a） Parallel 2D flow channel （b） Simplified 3D flow channel （c） 3D flow channel with inclination．

Fig． 11 e Cathode pressure drop with different current densities．

这个构型的计算结果比较有趣，如果能够对结构参数对结果的敏感性进行进一步分析应该可以看出有些参数会以较大权重促进效果。

Conclusions

Parallel 2D flow channel， simplified 3D flow channel and 3D
flow channel with inclination have been investigated to
optimize the design of flow field． The following conclusions
could be obtained．
（1） PEMFC with 3D flow channels performed better than
parallel 2D flow channel， especially at high current
densities， and the performance improvement was
mainly due to the stagger arrangement of flow
units．
（2） The water content of 3D flow channels was lower than
parallel 2D flow channel， indicating that 3D flow fields
could accelerate the water removal． Besides， the uniformity
of water distribution with 3D flow fields was
better than that with parallel 2D flow fields．
（3） According to concentration gradient， convective mass
transfer coefficient and Sherwood number， 3D flow
channels showed superior mass transfer
characteristics．

（4） Considering both the performance and flow resistance，
simplified 3D flow channel performed the best with the
high EEC value and easy－processing．