Numerical Simulation on Effect of Separator Thickness on Coupling Phenomena in Single Cell of PEFC under Higher Temperature Operation Condition at 363 K and 373 K

Abstract

In hydrogen energy systems, the polymer electrolyte fuel cell (PEFC) is an important component. The purpose of this study is to clarify the effect of separator thickness (s.t.) in PEFC on the distributions of mass such as H2, O2, H2O and current density when PEFC is operated at 363 K and 373 K. The relative humidity (RH) of supply gases also impacts the operation. The numerical simulation (using a 3D model) with COMSOL Multiphysics has been conducted to analyze the characteristics of PEFC. It has been observed that the molar concentration of H2 using s.t. of 2.0 mm is smaller compared with the thinner s.t. cases at the initial operation temperature of a cell (Tini) = 363 K and 373 K. The molar concentration of O2 using s.t. of 2.0 mm is smaller compared with the thinner s.t. cases at Tini = 373 K, as well as the case for the RH of supply gases at the anode of 40%RH and cathode of 40%RH (A40%RH/C40%RH) irrespective of Tini. Additionally, it has been clarified that the molar concentration of H2O maintains a low value along with the gas channel at Tini = 373 K using s.t. of 1.5 mm and 1.0 mm. Moreover, it has been clarified that the current density using s.t. of 2.0 mm is the highest among the different s.t. irrespective of Tini, which is the most remarkable in the case of A40%RH&C40%RH.

Impact of separator thickness on relationship between temperature distribution and mass & current density distribution in single HT-PEMFC

“…Regarding PEM and GDL, this study adopts Nafion NRE-211 and TGP-H-030, respectively. This selection follows the results obtained by the previous studies conducted by the authors which optimized the thickness of PEM and GDL [12,13] . This study changes the operation temperature by 353 K, 363 K and 373 K. This study investigates the charcteristics at 353 K, 363 K and 373 K. 353 K is selected as a case of LT-PEMFC for the comparison of the resutls under higher temperature condition.…”

“…As to the validation of the model, the authors have used the similar and the same model in the previous studies [12,43] . The results and discussions using the model have been recognized by the reviewers of these journals.…”

“…Regarding the impact of separator thickness, the temperature change from the inlet to the outlet of cell, i.e., the temperature fluctuation along the gas flow, at Tini = 353 K and 363 K is larger when the separator thickness is 2.0 mm consisting of the saddle thickness = 1.0 mm and the channel height = 1.0 mm. Because the heat capacity of the separator thickness of 2.0 mm was the biggest among the separators investigated in this study, the dehydration of PEM and catalyst layer would be lower compared to the thinner separator thicknesses [12] . Consequently, it is thought that the power generation performance was improved with the increase in the separator thickness [12] .…”

“…(5) (6) where i is the current density (A/m 2 ), i0 is the exchange current density (A/m 2 ), 𝑎 𝑎 is the charge transfer coefficient at anode side (-), 𝜂 is the activation over-potential [29] (V), R is the gas constant (J/(mol•K)), T is the operating temperature (K), 𝑎 𝑐 is the charge transfer constant at the cathode side (-), 𝜑 𝑠 is the electrical potential of solid material [29] (V), Eeq is the equilibrium electric voltage [29] (V). The simulation model developed and used in this study was the same as the authors' previous study [12] . Figure 1 illustrates the model for the separator thickness of 2.0 mm, 1.5 mm and 1.0 mm.…”

“…The analysis points from A to K, as shown in Figure 3, were assigned in this study, which were the same as that in the authors' previous studies [11,12] to examine the impact of separator thickness on the mass such as O2 and H2O distributions, the temperature profile and the current density profile. Figure 3 shows the analysis points from A to K. We have conducted the analysis on the averaged value on the cross-sectional area on the interface between PEM and catalyst layer at the cathode side, covering parts under the gas channel as well as those under the rib.…”