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Research Papers

Exploring Transient Behavior at Startup of a Polymer Electrolyte Membrane Fuel Cell

[+] Author and Article Information
Bikash Mishra1

Center for Computational Sciences, Mississippi State University, P.O. Box 9627, Mississippi State, MS 39762-9627mishra.ccs@gmail.com

Junxiao Wu

Center for Computational Sciences, Mississippi State University, P.O. Box 9627, Mississippi State, MS 39762-9627

1

Corresponding author.

J. Fuel Cell Sci. Technol 7(2), 021004 (Jan 05, 2010) (14 pages) doi:10.1115/1.3206968 History: Received January 25, 2008; Revised June 09, 2009; Published January 05, 2010; Online January 05, 2010

A two phase nonisothermal 3D unsteady model is used to study the transients at start-up of a polymer electrolyte membrane fuel cell. The model is used to simulate start-up under different starting or initial conditions. The objective is to study the transient behavior of current and the phenomena affecting it. The transient current density obtained from simulation under purged and inflow/equilibrium initial conditions are plotted. The saturation and the temperature profile evolution within the gas diffusion layer under different conditions are also studied. The effect of gas diffusion layer thickness and reaction rate on the current density evolution is analyzed. It is found that the transient current density depends on the initial condition. Mass transport is the major phenomenon influencing the current density profile, and the mass transport transients are found to be subsecond in nature. The consumption and transport time scales are seen to affect the current undershoot at high loads. The liquid water evolution and distribution behaves very differently, under different initial conditions, as well as different inflow conditions. However, the total time taken by liquid water and temperature to reach steady state for different initial conditions is very close. It is also seen that the temperature transient is less than the liquid water transient, overall.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Comparison between experimental and model data for a (a) fully humidified and (b) 80% RH anode inlet and cathode inlet air relative humidity ranging from 100% to 50%

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Figure 4

Transient cathode and ohmic overpotential profile for (a) 0.1 V and (b) 0.4 V

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Figure 7

Current density for inflow initial condition for the original geometry and with GDL thickness increased by five times with different reaction rates at V=0.1

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Figure 8

Saturation profile in the GDL at (a) t=0.3 s, (b) t=0.5 s, (c) t=1 s, (d) t=2 s, (e) t=5 s, and (f) t=10 s for fully humidified inflow purged initial condition at V=0.1

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Figure 9

Saturation profile in the GDL at (a) t=0.2 s, (b) t=1 s, (c) t=5 s, and (d) t=10 s for fully humidified inflow initial condition at V=0.1

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Figure 10

Saturation profile in the GDL at (a) t=0.5 s, (b) t=1 s, (c) t=5 s, and (d) t=10 s for drier cathode inflow purged initial condition at V=0.1

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Figure 11

Temperature profile in the GDL at (a) t=0.2 s, (b) t=0.4 s, (c) t=1 s, and (d) t=3 s for fully humidified inflow purged initial condition at V=0.1

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Figure 12

Temperature profile in the GDL at t=0.1 s for fully humidified inflow initial condition

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Figure 3

Transient current profile for (a) 0.1 V and (b) 0.4 V

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Figure 2

Slice of GDL at y=0.01 m where contour plots are shown and the regions that are referred to in the text

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Figure 5

Oxygen mass fraction in the GDL at (a) t=0.0 s, (b) t=0.1 s, (c) t=0.25 s, (d) t=0.4 s, and (e) t=20 s for fully humidified inflow purged initial condition at V=0.1

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Figure 6

Oxygen mass fraction in the GDL at (a) t=0.0 s, (b) t=0.05 s, (c) t=0.1 s, (d) t=0.2 s, and (e) t=20 s for inflow initial condition at V=0.1

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