Water removal channel for PEM fuel cell stack headers
View Patent ↗A bipolar plate for a fuel cell is disclosed including a first unipolar plate having an active surface with a plurality of flowfield channels formed therein. The first unipolar plate further includes an inlet header disposed at a first end of the unipolar plate that is in communication with the active surface, and an outlet header disposed at a second end of the unipolar plate having an exhaust opening formed therethrough. A peripheral edge of the exhaust opening is chamfered and is also in communication with the active surface. The chamfered exhaust opening forms a water removal channel in the bipolar plate. A fuel cell stack including the bipolar plate is also disclosed.
1. A bipolar plate for a fuel cell comprising:
a first unipolar plate and a second unipolar plate, the second unipolar plate having an active surface with a flowfield formed therein;
an inlet header disposed at a first end of the first unipolar plate and in communication with the active surface; and
an outlet header disposed at a second end of the first unipolar plate and including an exhaust opening formed therethrough, a peripheral edge of the exhaust opening being chamfered and in communication with the active surface,
wherein the first unipolar plate is bonded to the second unipolar plate, and a non-chamfered surface of the second unipolar plate cooperates with the chamfered peripheral edge of the first unipolar plate to form a water removal channel, the water removal channel in communication with the active surface.
2. The bipolar plate of claim 1 , wherein the water removal channel is a triangular groove.
3. The bipolar plate of claim 1 , wherein the exhaust opening further includes a drainage portion in communication with the water removal channel.
4. The bipolar plate of claim 1 , wherein the water removal channel includes a hydrophilic coating disposed thereon.
5. The bipolar plate of claim 1 , wherein a surface of the water removal channel is textured.
6. The bipolar plate of claim 1 , wherein the water removal channel has an acute corner angle.
7. The bipolar plate of claim 6 , the water removal channel having a static contact angle and a chamfer angle, wherein the sum of the static contact angle and one half of the channel angle is less than 90 degrees.
8. The bipolar plate of claim 3 , wherein a cross-sectional area of the water removal channel decreases along a length of the water removal channel.
9. The bipolar plate of claim 8 , wherein the decrease in the cross-sectional area is continuous.
10. A fuel cell stack comprising:
at least one fuel cell having a membrane electrode assembly disposed between a pair of bipolar plates, each bipolar plate including a first unipolar plate and a second unipolar plate, the second unipolar plate having an active surface with a flowfield formed therein, an inlet header disposed at a first end of the first unipolar plate and in communication with the active surface, and an outlet header disposed at a second end of the first unipolar plate and including an exhaust opening formed therethrough, a peripheral edge of the exhaust opening being chamfered and in communication with the active surface,
wherein the first unipolar plate is bonded to the second unipolar plate, and a non-chamfered surface of the second unipolar plate cooperates with the chamfered peripheral edge of the first unipolar plate to form a water removal channel,
wherein the water removal channel is in communication with the active surface and induces a capillary-driven flow of water from the active surface.
11. The fuel cell stack of claim 10 further comprising a drainage conduit in communication with the water removal channel.
12. The fuel cell stack of claim 11 , wherein the drainage conduit is formed by an exhaust opening in each bipolar plate.
13. The fuel cell stack of claim 12 , wherein the drainage conduit includes a hydrophilic coating disposed thereon.
14. The fuel cell stack of claim 12 , wherein a surface of the drainage conduit is textured.
15. The fuel cell stack of claim 12 , wherein the drainage conduit includes a pillar of hydrophilic material disposed therein.
16. The fuel cell stack of claim 15 , wherein the hydrophilic material is porous.
17. The fuel cell stack of claim 15 , wherein the hydrophilic material is selected from the group consisting of plastics, elastomers, ceramics, and glasses.
18. The fuel cell stack of claim 17 , wherein the plastic includes polyoxymethylene.
19. A fuel cell stack comprising:
at least one fuel cell having a membrane electrode assembly disposed between a pair of bipolar plates, each bipolar plate including a first unipolar plate and a second unipolar plate, the second unipolar plate having an active surface with a flowfield formed therein, an inlet header disposed at a first end of the first unipolar plate and in communication with the active surface, and an outlet header disposed at a second end of the first unipolar plate and including an exhaust opening formed therethrough, a peripheral edge of the exhaust opening being chamfered and in communication with the active surface,
wherein the first unipolar plate is bonded to the second unipolar plate, and a non-chamfered surface of the second unipolar plate cooperates with the chamfered peripheral edge of the first unipolar plate to form a triangular water removal channel,
wherein a drainage conduit is formed by the exhaust opening in each bipolar plate and is in communication with the water removal channel, the drainage conduit having a pillar of hydrophilic material disposed therein, and
wherein the water removal channel is in communication with the active surface and induces a capillary-driven flow of water from the active surface to the drainage conduit, thereby militating against an accumulation of water in a flowfield channel during operation of the fuel cell stack.