US 6,686,084 B2 · Gas block mechanism for water removal in fuel cells

Abstract

The present invention is directed to apparatus and method for cathode-side disposal of water in an electrochemical fuel cell. There is a cathode plate. Within a surface of the plate is a flow field comprised of interdigitated channels. During operation of the fuel cell, cathode gas flows by convection through a gas diffusion layer above the flow field. Positioned at points adjacent to the flow field are one or more porous gas block mediums that have pores sized such that water is sipped off to the outside of the flow field by capillary flow and cathode gas is blocked from flowing through the medium. On the other surface of the plate is a channel in fluid communication with each porous gas block mediums. The method for water disposal in a fuel cell comprises installing the cathode plate assemblies at the cathode sides of the stack of fuel cells and manifolding the single water channel of each of the cathode plate assemblies to the coolant flow that feeds coolant plates in the stack.

Drawings

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Drawings

Claims12

Dependent claims

A plate assembly for use in a fuel cell comprised of:

one of a cathode plate with cathode gas and an anode plate with anode gas having a first major surface and a second oppositely opposed major surface;
a flow field for a gas within the first major surface comprised of feed side interdigitated channels and exhaust side interdigitated channels such that in the operation of the fuel cell there is flow of said gas by convection from feed side interdigitated channels to exhaust side interdigitated channels;
at least one porous gas block medium positioned in the one of a cathode and anode plate adjacent to the flow field having pores sized such that liquid water in the flow field is sipped off by capillary flow and said gas is blocked;
a gas diffusion layer positioned over the first surface of the one of a cathode and anode plate and flow field therein;
and
a liquid water channel at the second major surface of the one of a cathode and anode plate and in fluid communication with the at least one porous gas block medium such that liquid water flows from the porous gas block medium to the water channel.

3 more elements

A plate assembly for use in a fuel cell with a pressurized gas and a pressurized water comprised of:

one of a cathode plate with cathode gas and an anode plate with anode gas having a first major surface and a second oppositely opposed major surface;
a flow field for said pressurized gas within the first major surface having:
a feed side having a feed side internal plenum in fluid communication with one or more feed side interdigitated channels having width and with dead-ends;
and
an exhaust side having an exhaust side internal plenum in fluid communication with a plurality of exhaust side interdigitated channels having width and with dead-ends,
wherein the feed side and exhaust side interdigitated channels are in an intedigitated configuration defining land between the interdigitated channels such that in the operation of the fuel cell there is flow of said gas by convection from feed side interdigitated channels to exhaust side interdigitated channels;
a multiplicity of porous gas block mediums positioned in the one of a cathode and anode plate adjacent to each feed side interdigitated channel at points where liquid water forms or collects during the operation of the fuel cell and having pores sized such that liquid water in the feed side interdigitated channels is sipped off by capillary flow and said gas is blocked;
a gas diffusion layer positioned over the first surface of the one of a cathode and anode plate and flow field therein;
and
a water channel at the second major surface of the one of a cathode and anode plate in fluid communication with each porous gas block medium through which pressurized coolant flows and where the pressure of said gas in feed side interdigitated channels is greater than the pressure of coolant in the cooling channel and the pressure difference is less than the bubble point pressure of the gas block such that liquid water flows from each porous gas block medium into the cooling channel.

7 more elements

A cathode plate assembly for use in a fuel cell with a pressurized cathode gas and a pressurized water comprised of:

a cathode plate that is a four sided polygon having a first major surface, a second oppositely opposed major surface, and a first and third and second and fourth oppositely opposed pairs of edges where the first edge is at a higher gravitational potential energy than the third edge;
a flow field for pressurized cathode gas within the first major surface and having:
a feed side internal plenum running parallel to the first edge of the cathode plate;
a plurality of feed side interdigitated channels having widths that are in fluid communication with and substantially perpendicular to the feed side internal plenum that extend toward the third edge and terminate at dead-ends;
an exhaust side internal plenum running parallel to the third edge of the cathode plate;
a plurality of exhaust side interdigitated channels having widths that are in fluid communication with and substantially perpendicular to the exhaust side internal plenum that extend toward the first edge and terminate at dead-ends and which are interdigitated between the feed side interdigitated channels so as to define land between the interdigitated channels;
wherein the ratio of pressure drop of the cathode gas flow over the land between a feed side interdigitated channel and a neighboring exhaust side interdigitated channel and the feed side interdiditated channel cathode gas flow is in the range of about 8:1 to 15:1 such that cathode gas flows by convection from the feed side interdigitated channel to a neighboring exhaust side interdigitated channel;
a multiplicity of porous gas block mediums positioned adjacent to the dead-ends of each of the feed side interdigitated channels having a bubble point in the range of between about 10 psig to about 70 psig such that liquid water is sipped out of the feed side interdigitated channels by capillary flow and cathode gas is blocked;
a gas diffusion layer positioned over the first surface of the cathode plate and flow field therein, and
a water channel at the second major surface of the cathode plate in fluid communication with each porous gas block medium through which pressurized water flows and where the pressure of the cathode gas in feed side interdigitated channels is greater than the pressure of water in water channels and the pressure difference is less than the bubble point pressure such that liquid water flows from the porous gas block medium to the water channel.

7 more elements

Dependencies are inferred from the claim text.

Description7,425 words

Summary2,283 words

#This invention pertains generally to polymer electrolyte membrane fuel cells and more particularly to an apparatus and method for disposal of water.

#In the normal operation of a polymer electrolyte membrane “PEM” fuel cell, liquid water forms at the cathode side of the fuel cell. There are two sources for this liquid water. One source is the oxidizing gas being fed to the cathode side of the fuel cell. This gas is generally moisturized before being supplied to the cathode and some of this moisture condenses. The other source is an electrochemical reaction occurring on the cathode side which produces water. Discharging oxidizing gas has a limited capacity to carry away to outside the cell the liquid water formed at the cathode side.

#When the quantity of liquid water formed on the cathode side exceeds the liquid water carried away by the oxidizing gas, there is a condition called a “flooded state” or “flooding.” In a flooded state, the liquid water remains on the surface of the cathode electrode and obstructs the dispersion of the oxidizing gas onto the surface of the cathode. This in turn results in a drop in the cell's voltage and amperage output. Ultimately, flooding will stop the cell's operation.

Brief description of the drawings7 figures

#FIG. 1A is a top view of the cathode plate according to the present invention showing an interdigitated flow field and porous gas block mediums;

#FIG. 1B is a cross-sectional view of the cathode plate depicted in FIG. 1A taken along line A—A showing the cooling channel, and the gas block mechanism;

#FIG. 1C is a cross-sectional view of the cathode plate depicted in FIG. 1A taken along line B—B showing the cooling channel, and the cathode plate cross-section;

Detailed description4,948 words

#The present invention provides a novel cathode assembly for an electrochemical fuel cell which is operable to distribute cathode gas to a membrane of the fuel cell and remove water produced at the cathode side without a loss of cathode gas. The cathode assembly is useful to avoid a flooded state. A fuel cell comprised of PEM cells employing this cathode assembly is lightweight and small in volume.

#Referring to FIGS. 1A-C, the cathode plate assembly 10 of the present invention may be comprised of the following major components. A cathode plate 12 has an inside surface 14 and an outside surface 16. On the outside surface 16 of the cathode plate 12 there may be a pressurized cooling channel 18 connected to a water reservoir (not shown). On the inside surface 14 of the cathode plate 12 there may be an interdigitated flow field 22 through which cathode gas flows. Inserted into the surface of the cathode plate 12 and adjacent to the flow field 22 are porous gas block mediums 24. Referring to FIG. 3, positioned over the inside surface 14 of the cathode plate with its flow field 22, there may be a gas diffusion layer 26 also known as the cathode side gas diffusion layer.

#Continuing to refer to FIG. 1A, the cathode plate 12 may be made of an electrically conducting material selected from the group of graphite, carbon composites, conducting plastics, or a metal with a corrosion-resistant coating. It serves as a base for the cathode plate assembly 10 and may be a connection surface to an external circuit through which electrons flow.

Facts

Application

10/039,503Filed 4 Jan 2002

Published

US 2003/0129468 A110 Jul 2003

Granted

3 Feb 2004

Term ended

8 Jul 2022

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 185 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification9 codes

H01M 8/023
Collectors; Separators, e.g. bipolar separators; Interconnectors: porous and characterised by the material
H01M 8/0258
Collectors; Separators, e.g. bipolar separators; Interconnectors: characterised by the configuration of channels, e.g. by the flow field of the…
H01M 8/0263
Characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant: having meandering or serpentine paths
H01M 8/0267
Collectors; Separators, e.g. bipolar separators; Interconnectors: having heating or cooling means, e.g. heaters or coolant flow channels

Timeline

4 Jan 2002Application filedUS 10/039,503
4 Jan 2002Assigned to Honeywell International, Inc.assignment of assignor's interest
10 Jul 2003PublishedUS 2003/0129468 A1
10 Dec 2003Assigned to Hybrid Power Generation Systems, LLCassignment of assignor's interest
3 Feb 2004GrantedUS 6,686,084 B2
7 Jul 2004Assigned to Hybrid Power Generation Systems, LLCassignment of assignor's interest
8 Jul 2022Term endedEstimated, includes 185 days of adjustment

Gas block mechanism for water removal in fuel cells

Life of this patent

Gas block mechanism for water removal in fuel cells

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims12

Description7,425 words

Drawings

Classification9 codes

Life of this patent

Description7,425 words