Influence of anisotropic conductive expanded graphite bipolar plates on performance of proton exchange membrane fuel cell

doi:10.3969/j.issn.1674-8484.2024.04.009

Abstract

Abstract:

Established a three-dimensional, two-phase, non-isothermal fuel cell single channel model to investigate the influence of anisotropic structure of Expanded Graphite Bipolar Plates (EGBPs) on thermal management and the performances of proton exchange membrane fuel cell (PEMFC). The distribution of temperature, the current density and the membrane water content under four main material orientations were compared. The coupling effect between EGBPs heat transfer characteristics and the outperformance were revealed. The results show that increasing the conductivity along proton-transport direction k_z from the 5 W·m^-1·K^-1 for a traditional structure to the 280 W·m^-1·K^-1, enhances the voltage by 22 mV under 2.2 A cm^-2. The conductivity along gas-flow direction k_y plays an important role in heat dissipation. Increasing k_y and k_z to 280 W·m^-1·K^-1, or accomplishing isotropic conductivity (k_x = k_y = k_z = 20 W·m^-1·K^-1), reduces the Membrane-Electrode-Assembly (MEA) core-area peak-temperature by 2 ℃. Therefore, enhancing the gas-flow and proton-transport direction conductivities and accomplishing isotropic structure are one of the future main development goal of expanded graphite bipolar plates.

Key words: proton exchange membrane fuel cell (PEMFC), expanded graphite bipolar plates (EGBPs), anisotropic conductivity, thermal and water management, heat dissipation

CLC Number:

TM911.4

DING Yujie, GAN Quanquan, SHAO Yangbin, XU Liangfei, LI Jianqiu, OUYANG Minggao. Influence of anisotropic conductive expanded graphite bipolar plates on performance of proton exchange membrane fuel cell[J]. Journal of Automotive Safety and Energy, 2024, 15(4): 526-535.

Figures/Tables 16

结构编号	石墨片层取向	热导率，k / (W·m^-1·K^-1)			电导率，σ / (S·cm^-1)
结构编号	石墨片层取向	x方向	y方向	z方向	x方向	y方向	z方向
Ⅰ	x - y	280	280	5	1 100	1 100	20
Ⅱ	y - z	5	280	280	20	1 100	1 100
Ⅲ	x - z	280	5	280	1 100	20	1 100
Ⅳ	各向同性	20	20	20	100	100	100

厚度 (j = GDL, MPL, CL, PEM)	δ_j = 151, 10, 15, 18 μm
孔隙率(j = GDL, MPL, CL)	ε_j = 0.77, 0.6, 0.5
绝对渗透率(j = GDL, MPL, CL, PEM)	K_j = 23, 0.25, 0.1, 1.0×10^-6 μm²
CL曲折度	τ_d = 1.5
扩散系数^[28] (i = O₂, H₂)	D_0,_i = 2.652×10^-5, 1.055×10^-4 m² s^-1
活性比表面积	a₀ = 5.0×10⁷ m² m^-3
阳极/阴极参考交换电流密度	j_a,ref = 500 A m^-2, j_c,ref = 10 μm^-2
参考H₂/O₂浓度	C_H₂,ref = 56.4 mol m^-3, C_O2,ref = 3.39 mol m^-3
阳极/阴极传递系数	α_a,a = 0.5, α_a,c = 1.5, α_c,a = 3, α_c,c = 1
阳极/阴极反应级数	γ_H₂ = 0.5, γ_O2 = 1
活化能	ΔG = 8.314 kJ mol^-1
焓差	ΔS = -163.3 J (mol K)^-1
参考温度	T_ref = 343 K
电导率^[29](j = GDL, MPL, CL, PEM)	σ_s,_j = 5.0 kS m^-1
膜干态密度	ρ_m = 1.98 t m^-3
膜离子交换当量	EW = 1.1 kg mol^-1
阳极/阴极CL中离聚物体积分数	l_m,a = 0.6, l_m,c = 0.6

边界	类型	取值
阳极(a)、阴极(b)气体流道入口	质量入口	$m a = ρ a ξ a I a a 2F C H 2$ , $m c = ρ c ξ c I a c 4F C O 2$
阳极(a)、阴极(b)气体流道出口	压力出口	p_b,a, p_b,c
阳极(a)、阴极(b)双极板端面	壁面	$\varphi_{\mathrm{e}}=0 ; \frac{\partial \varphi_{\mathrm{m}}}{\partial y}=0 ; q_{\mathrm{h}, \text { cool }, \mathrm{a}}=\frac{q_{\mathrm{h}, \text { cool }}}{2} \quad \varphi_{\mathrm{e}}=U ; \frac{\partial \varphi_{\mathrm{m}}}{\partial y}=0 ; q_{\mathrm{h}, \text { cool, } \mathrm{a}}=\frac{q_{\mathrm{h}, \mathrm{cool}}}{2}$
侧面边界	对称边界	$\frac{\partial \varphi_{\mathrm{m}}}{\partial x}=0 ; \frac{\partial \varphi_{\mathrm{m}}}{\partial z}=0 ; \frac{\partial \varphi_{\mathrm{e}}}{\partial x}=0 ; \frac{\partial \varphi_{\mathrm{e}}}{\partial z}=0$

边界	类型	取值
阳极(a)、阴极(b)气体流道入口	质量入口	$m a = ρ a ξ a I a a 2F C H 2$ , $m c = ρ c ξ c I a c 4F C O 2$
阳极(a)、阴极(b)气体流道出口	压力出口	p_b,a, p_b,c
阳极(a)、阴极(b)双极板端面	壁面	$\varphi_{\mathrm{e}}=0 ; \frac{\partial \varphi_{\mathrm{m}}}{\partial y}=0 ; q_{\mathrm{h}, \text { cool }, \mathrm{a}}=\frac{q_{\mathrm{h}, \text { cool }}}{2} \quad \varphi_{\mathrm{e}}=U ; \frac{\partial \varphi_{\mathrm{m}}}{\partial y}=0 ; q_{\mathrm{h}, \text { cool, } \mathrm{a}}=\frac{q_{\mathrm{h}, \mathrm{cool}}}{2}$
侧面边界	对称边界	$\frac{\partial \varphi_{\mathrm{m}}}{\partial x}=0 ; \frac{\partial \varphi_{\mathrm{m}}}{\partial z}=0 ; \frac{\partial \varphi_{\mathrm{e}}}{\partial x}=0 ; \frac{\partial \varphi_{\mathrm{e}}}{\partial z}=0$

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