Apparatus and Method for Managing Fluids in a Fuel Cell Stack

The flow field plate assembly of claim 5, wherein:

• the cross-sectional geometry of the portion of the periphery of the at least one of the fuel and oxidant manifold openings comprises a slot formed by the first and second flow field plates proximate the reactant manifold openings thereof;
• the slot has a wider end open to the at least one of the fuel and oxidant manifold openings, and a narrower end spaced from the wider end in a direction away from the periphery;
• the wider end has a dimension that prevents a liquid from wicking along the periphery of the at least one of the fuel and oxidant manifold openings, and exhibits reduced capillary forces to promote liquid migration toward at least a portion of the at least one of the fuel and oxidant manifold openings from which the liquid is entrained by a flow of at least one fluid exiting the fuel cell stack, when the flow field plate assembly is installed in the fuel cell stack and the fuel cell stack is in operation or during a purge of the fuel cell stack after operation;
• the slot further comprises a transition region between the wider and narrower ends;
• and
• the transition region comprises portions of the first and second flow field plates forming a substantially rectangular cross-sectional shape;
• a longitudinal cross section of the flow field plate assembly is oriented such that when the flow field plate assembly is installed in the fuel cell stack and the fuel cell stack is in operation or during a purge of the fuel cell stack after operation, the reduced capillary forces and a force of gravity promote liquid migration to a bottom portion of the at least one of the fuel and oxidant manifold openings, from which portion the liquid is entrained by the flow of the at least one fluid exiting the fuel cell stack.

A flow field plate assembly for a fuel cell stack having a plurality of fuel cells, each comprising a membrane electrode assembly (MEA), the flow field plate assembly comprising:

• a first flow field plate having first and second reactant manifold openings and being positionable on an anode side of the MEA of a first fuel cell, a first side of the first flow field plate having at least one reactant flow field channel adapted to direct a fuel to an anode electrode layer of the MEA;
• and
• a second flow field plate having third and fourth reactant manifold openings and being positionable on a cathode side of the MEA of a second fuel cell, adjacent the first fuel cell, a first side of the second flow field plate having at least one reactant flow field channel adapted to direct an oxygen-containing gas to a cathode electrode layer of the MEA;
• wherein,
• the third reactant manifold opening is positioned adjacent the first reactant manifold opening, forming a fuel manifold opening;
• the fourth reactant manifold opening is positioned adjacent the second reactant manifold opening, forming an oxidant manifold opening;
• at least a portion of a periphery of at least one of the fuel and oxidant manifold openings has a cross-sectional geometry that is configured such that when the flow field plate assembly is installed in the fuel cell stack and the fuel cell stack is in operation, capillary forces direct liquid migration toward regions substantially isolated from a flow of reactants;
• the flow field plate assembly further comprises at least one back-feed channel formed between the first and second flow field plates in fluid communication with at least one of the fuel and oxidant manifold openings and at least one of the reactant flow field channels;
• the back-feed channel has at least one of a cross-sectional geometry and a longitudinal geometry that forms regions configured to create high and low capillary forces that direct liquid migration toward regions substantially isolated from a flow of reactants, when the flow field plate assembly is installed in the fuel cell stack and the fuel cell stack is in operation;
• and
• at least a portion of the back-feed channel is fabricated from a hydrophobic material exhibiting an advancing contact angle of at least 90 degrees and a receding contact angle of at least 70 degrees in response to contact with water.

A fuel cell stack comprising a plurality of fuel cells, each fuel cell having a membrane electrode assembly (MEA) that includes an ion-exchange membrane interposed between anode and cathode electrode layers, wherein:

• each MEA is interposed between first and second flow field plates;
• a first flow field plate of each fuel cell, which is situated between those fuel cells that are located at opposite ends of the fuel cell stack, is positioned adjacent a second flow field plate of an adjacent fuel cell;
• the first flow field plate has first and second reactant manifold openings;
• a first side of the first flow field plate has at least one reactant flow field channel adapted to direct a fuel to the anode electrode layer of the corresponding MEA;
• the second flow field plate has third and fourth reactant manifold openings;
• a first side of the second flow field plate has at least one reactant flow field channel adapted to direct an oxygen-containing gas to the cathode electrode layer of the corresponding MEA;
• the first reactant manifold opening of the first flow field plate of the fuel cells positioned between the end fuel cells is positioned adjacent the third reactant manifold opening of the adjacent second flow field plate of the adjacent fuel cell, forming a fuel manifold opening;
• the second reactant manifold opening of each fuel cell positioned between the end fuel cells is positioned adjacent the fourth reactant manifold opening of the adjacent second flow field plate of the adjacent fuel cell, forming an oxidant manifold opening;
• and
• a periphery of at least one of the fuel and oxidant manifold openings has a cross-sectional geometry adapted to form regions of high and low capillary forces configured to direct liquid migration toward regions substantially isolated from a flow of reactants, when the fuel cell stack is in operation.

A method of repelling liquids from at least a first region of a fuel cell stack, through which at least one of a reactant and a coolant flows when the fuel cell stack is in operation, the fuel cell stack having a plurality of fuel cells, each fuel cell including a membrane electrode assembly (MEA), a first flow field plate positioned on an anode side of the MEA and having first and second reactant manifold openings, at least a portion of a first side of the first flow field plate having at least one reactant flow field channel adapted to direct a fuel to at least a portion of an anode electrode layer of the MEA, a second flow field plate positioned on a cathode side of the MEA and having third and fourth reactant manifold openings, at least a portion of a first side of the second flow field plate having at least one reactant flow field channel adapted to direct an oxygen-containing gas to at least a portion of a cathode electrode layer of the MEA, the first flow field plate of each fuel cell between end fuel cells being positioned adjacent the second flow field plate of an adjacent fuel cell, the first reactant manifold opening of the first flow field plate being positioned adjacent the third reactant manifold opening of the adjacent second flow field plate, forming a fuel manifold opening, and the second reactant manifold opening of the first flow field plate being positioned adjacent the fourth reactant manifold opening of the adjacent second flow field plate, forming an oxidant manifold opening, and at least one back-feed channel between the adjacent first and second flow field plates in fluid communication with at least one of the fuel and oxidant manifold openings and at least one of the reactant flow field channels, the method comprising:

• forming regions shaped to create high and low capillary forces in a liquid to promote migration of the liquid toward regions substantially isolated from the first region in the fuel cell stack, when the fuel cell stack is in operation.