Abstract
Water transport and removal in the proton exchange membrane fuel cell (PEMFC) is critically important to fuel cell performance, stability, and durability. Water emerging locations on the membrane-electrode assembly (MEA) surface and the channel surface wettability significantly influence the water transport and removal in PEMFC. In most simulations of water transport and removal in the PEMFC flow channel, liquid water is usually introduced at the center of the MEA surface, which is fortuitous, since water droplet can emerge randomly on the MEA surface in PEMFC. In addition, the commonly used no-slip wall boundary condition greatly confines the water sliding features on hydrophobic MEA/channel surfaces, degrading the simulation accuracy. In this study, water droplet is introduced with various locations along the channel width direction on the MEA surface, and water transport and removal is investigated numerically using an improved model incorporating the sliding flow property by using the shear wall boundary condition. It is found that the water droplet can be driven to the channel sidewall by aerodynamics when the initial water location deviates from the MEA center to a certain amount, forming the water corner flow in the flow channel. The channel surface wettability on the water transport is also studied and is shown to have a significant impact on the water corner flow in the flow channel.
Highlights
Proton exchange membrane fuel cell (PEMFC) is a promising clean power source for future applications, especially for the automobiles, due to its low emission, high efficiency, and high current density
The water droplet introduced on the membrane-electrode assembly (MEA) surface has a diameter of 0.6 mm
When the water droplet is introduced, the air velocity is seen to be asymmetric with regard to the water droplet shown in Figure 6b–d, leading to a larger air shear force acting on the water droplet at the side closer to the central line of the MEA surface, such that the water droplet bears a net driving force that is always pointing to the center of the MEA surface, and the water droplet can be transported along the channel width direction
Summary
Proton exchange membrane fuel cell (PEMFC) is a promising clean power source for future applications, especially for the automobiles, due to its low emission, high efficiency, and high current density. Liquid water is formed and accumulated in the porous electrode when water vapor is condensed, and it is mainly removed by the air flow in the cathode flow channel after emerging from the membrane-electrode assembly (MEA) surface. The sliding angle, which is defined as the critical angle when the liquid droplet begins to slide on an inclined solid surface under the gravity force, as illustrated, is usually employed to measure the resistance of water moving and sliding on the solid surface in the experimental study [29], and it needs to be introduced in the numerical simulation of water flow in PEMFC. Water transport and removal in PEMFC gas flow channel will be investigated numerically using the VOF method incorporating the water sliding property, which is measured by the sliding angle. The channel surface wettability (including both the contact angle and sliding angle) on water removal from the MEA surface will be discussed
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