Effect of low gravity on water removal inside proton exchange membrane fuel cells (PEMFCs) with different flow channel configurations

Abstract

a b s t r a c tPractically investigate water removal and cell performance for PEMFCs under low gravity circumstance is an urgent task, especially as a promising power supply unit applied to space engineering. PEMFC with an in-situ optical flow field was used to explicate two-phase flow and water removal inside cathode flow field from terrestrial gravity to microgravity. The cell was tested in the vertical and horizontal flow channel orientations. A 3.6 s short-time micro-gravity circumstance was provided by National Microgravity Laboratory. Results show that gravitational level has an essential influence on gas-liquid twophase flow characteristics for PEMFC with different configurations. The cell placed in different channel orientations also shows distinguished operating behavior because of the complicated impact of the changed gravity and configuration. Under the operating condition of a vertical flow channel orientation, accumulated water and droplets in terrestrial are pushed by oxygen flow to continuous removal toward the outlet of the fuel cell to alleviate water flooding, and the cell performance is slightly enhanced in a 3.6 s micro-gravity circumstance. Operating in a horizontal flow channel orientation, the generated water throughout the micro-gravity circumstance duration is not prone to move and flood flow channels in micro-gravity, meanwhile the cell performance is slightly deteriorated.

Seeing is Believing: In Situ/Operando Optical Microscopy for Probing Electrochemical Energy Systems

“…The two‐phase flow in gas channels can be affected by factors such as flow rate, humidity, [ 43,45 ] channel dimensions and profiles (parallel, serpentine, and interdigitated), [ 46,47 ] temperature, current density, [ 48 ] gas diffusion layer (GDL) materials, [ 49 ] and gravitational orientations. [ 50 ] Zhan et al. found that the generation of water on the electrode is not uniform with a higher production rate under the channel backs than that in channel.…”

Impact of the temperature on calendar aging of an open cathode fuel cell stack

“…In addition, it was observed during the experiments that the fuel cell was more difficult to restart when it had remained stored for a long time at room temperature and that it had to be purged much more regularly to be able to restart it. It could be due to flooding as it has been observed that water flooding in PEMFCs is gravity dependent [61].…”

Effects of needle orientation and gas velocity on water transport and removal in a modified PEMFC gas flow channel having a hydrophilic needle

“…In PEMFC, water is produced as hydrogen is consumed in the electrochemical reaction. Liquid water, if not removed effectively, will block the porous catalyst layer (CL) and gas diffusion layer (GDL), as well as the gas flow channel in the cathode of PEMFC . The so‐called water flooding impedes reactant transport to the reaction sites and hence causes severe PEMFC performance degradation.…”

“…Liquid water, if not removed effectively, will block the porous catalyst layer (CL) 2 and gas diffusion layer (GDL), 3,4 as well as the gas flow channel in the cathode of PEMFC. 5 The so-Nomenclature: D droplet , water droplet diameter (m); f , volume fraction of the fluid; F s , external force term (N m −3 ); g, gravitational force (m s −2 ); n, surface normal; b n, surface unit normal; P, pressure (Pa); t, time; b t, surface unit tangent; T B , the breaking off time (ms); T D , the detaching time (ms); T L , the landing time (ms); T T , the touching time (ms); v, velocity component (m s −1 ); V, velocity vector (m s −1 ) Subscripts/Superscripts: 0, initial; 1, 2, liquid water, air; c, capillary force; channel, flow channel surface; GDL, GDL surface; lg, liquid-gas interface; needle, needle; s, source term or suspension; T, transpose; w, wall; x, y, z, axes Greeks: α needle , the needle inclination angle (°); ΔT c , the needle capillary force duration (ms); ΔT s , the water suspension time (ms); θ, contact angle (°); κ, surface curvature; μ, viscosity (kg m −1 s −1 ); ρ, density (kg m −3 ); σ, surface tension coefficient (N m −1 ) called water flooding impedes reactant transport to the reaction sites and hence causes severe PEMFC performance degradation. To improve water removal from PEMFC, effective water management strategies, which include the design of fuel cell operating conditions, geometric parameters, and surface wettability, need to be implemented in PEMFC.…”