相对湿度、电流密度、装配力对燃料电池水传递(净曳力系数)的影响
Effects of clamping force on the watertransport and performance of a PEM (proton electrolyte membrane) fuel cell withrelative humidity and current density
Dowon Cha
Jae Hwan Ahn
Hyung Soon Kim
Yongchan Kim
Abstract
The clamping force should be applied to aproton electrolyte membrane (PEM) fuel cell due to its structuralcharacteristics. The clamping force affects the ohmic and mass transportresistances in the PEM fuel cell. In this study, the effects of the clampingforce on the water transport and performance characteristics of a PEM fuel cellare experimentally investigated with variations in the relative humidity andcurrent density. The water transport characteristics were analyzed bycalculating the net drag coefficient. The ohmic resistance decreased with theincrease in the clamping force due to the reduced contact resistance and moreeven membrane hydration. However, the mass transport resistance increased withthe increase in the clamping force due to the gas diffusion layer compression. The net drag coefficient decreased with theincrease in the clamping force due to high water back-diffusion.Additionally, the relationship between the total resistance and the net dragcoefficient was investigated.
以前没有考虑过装配力对燃料电池水传递(净曳力系数)还会产生一定影响。
Fig. 1. Schematic diagram of the experimental setup.
Fig. 2. Flow channel design
Table 1 Experimental conditions.
Fig. 3. Schematic diagram of water transport in a PEM fuel cell.
Fig. 4. Ohmic resistance according to the clamping force at a relative humidity of 40%.
Fig. 5. Mass transport resistance according to the clamping force at a relative humidity of 40%.
Fig. 6. Ohmic resistance according to the clamping force at a relative humidity of 80%.
Fig. 7. Mass transport resistance according to the clamping force at a relative humidity of 80%.
Fig. 8. Variation in the voltage according to the clamping force at a relative humidity of 40%.
Fig. 9. Polarization curves according to the clamping force at a relative humidity of 80%.
到这里才开始重点:
Fig. 10. Net drag coefficient according to the clamping force at a relative humidity of 40%.
Generally, the net drag coefficient increases with increasing the membrane thickness due to lower backdiffusion rate
Fig. 11. Net drag coefficient according to the clamping force at a relative humidity of 80%.
as the relative humidity increased, the reduction in the net drag coefficient became larger as the clamping force increased.
Fig. 12. Total resistance according to the net drag coefficient.
The total resistance represents the sum of the ohmic and mass transport resistances
Conclusions
This study experimentally investigated the effects of the clamping force on the water transport and performance of a PEM fuel cell. The internal resistance was investigated using the EIS tests. The water transport in the PEM fuel cell was analyzed by calculating the net drag coefficient. The ohmic resistance was observed to decrease as the clamping force increased due to the decrease in the contact resistance and more even membrane hydration. However, the mass transport resistance increased as the clamping force increased due to the higher water flow resistance through the membrane. At a relative humidity of 40%, the performance of the PEM fuel cell increased as the clamping force increased above 5.9 N-m due to the decrease in the ohmic resistance. At a relative humidity of 80%, the increase in the clamping force significantly degraded the performance of the PEM fuel cell due to the higher mass transport resistance. The net drag coefficient decreased as the clamping force increased due to the high level of water back-diffusion. However, for a net drag coefficient below 0.2, the total resistance significantly increased as the clamping force increased.不知道这一条的通用性如何。
Therefore, the clamping force has to be controlled to an optimal level according to the water content in the PEM fuel cell. In addition, the net drag coefficient can be used as a parameter to determine the occurrence of water flooding.
参与评论
登录后参与讨论 0/1000