Fuel Cell Flow Field Plate Capillary Liquid Management
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Solution Overview
Problem
Conventional fuel cell systems face issues with water accumulation and ice blockage in flow field channels and ports, leading to reduced efficiency and potential cessation of gas flow, which existing methods like purging or operating in extremely dry conditions cannot completely prevent.
Innovation Solution
The design of flow field plates with reactant manifold openings and back-feed channels featuring regions of high and low capillary forces, directing liquid migration away from reactant flow paths, and incorporating hydrophobic materials or coatings to prevent water accumulation and ice formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional fuel cell systems operate in extremely dry conditions to prevent water accumulation, then water accumulation and ice blockage are reduced, but system performance and fatigue life are impaired
Solution Approach 1:
The flow field plate incorporates regions with different capillary characteristics (high capillary force regions and low capillary force regions) in specific locations. The high capillary force regions are positioned to draw liquid away from critical areas, while low capillary force regions allow controlled liquid retention in non-critical areas, creating a spatially differentiated quality distribution that solves the contradiction between preventing water accumulation and maintaining system performance
Solution Approach 2:
Instead of trying to prevent water accumulation through extreme drying conditions, the invention inverts the approach by using capillary forces to actively manage and redirect liquid flow. The system embraces the presence of liquid and uses structured capillary forces to move it to designated regions, thereby preventing ice blockage without impairing system performance through excessive drying
2Object-affected harmful factors
If purging methods are used to remove water from the system, then water accumulation is reduced, but regions of low purge velocity retain water and capillary forces cause water to wick back into blocked regions
Solution Approach 1:
The flow field plate design incorporates high capillary force regions strategically positioned to counteract the low purge velocity problem. These high capillary force regions actively draw liquid away from areas where purge velocity is low, preventing water retention and wick-back effects that plague conventional purging systems
Solution Approach 2:
The invention replaces reliance on mechanical purging velocity with capillary force-driven liquid management. Instead of depending on high-speed gas flow to remove water, the system uses capillary forces in the flow field plate structure to actively manage liquid distribution, making the system effective even in regions where purging velocity is insufficient
3Reliability
If water is allowed to accumulate in the system, then extreme drying conditions are avoided and system performance is maintained, but ice formation blocks reactant flow paths and causes fuel starvation
Solution Approach 1:
The flow field plate creates a spatial differentiation where low capillary force regions allow controlled liquid retention that maintains system performance, while high capillary force regions actively draw liquid away from critical reactant flow paths. This local quality variation enables the system to tolerate water presence without suffering from ice blockage
Solution Approach 2:
The flow field plate acts as an intermediary structure that mediates between the presence of water and the reactant flow paths. Through its capillary force distribution, it creates a buffer zone that allows water to exist in controlled regions while preventing it from blocking critical fuel and oxidant pathways, thus avoiding fuel starvation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively prevents water retention and ice blockage, ensuring uninterrupted reactant flow and maintaining fuel cell efficiency without the need for extreme drying, which can impair system performance.
Implementation Method 1
a periphery of at least one of the fuel and oxidant manifold openings having a cross-sectional geometry that forms regions of high and low capillary forces configured to direct liquid migration toward regions substantially isolated from a flow of reactants
Implementation Method 2
incorporating hydrophobic materials or coatings to prevent water accumulation and ice formation
Data Source
AI summary
A plurality of flow field plate assemblies forms a fuel cell stack. Each flow field plate assembly has a first flow field plate positionable on an anode side of a membrane electrode assembly (MEA) of a first fuel cell, a second flow field plate positionable on a cathode side of an MEA of a second fuel cell, adjacent the first fuel cell. At least one back-feed channel is interposed between the first and second flow field plates. At least a portion of the back-feed channel or a reactant manifold opening formed by the first and second flow field plates has a geometry that forms regions of high and low capillary forces, promoting liquid migration toward regions substantially isolated from a flow of reactants, to prevent water collection and ice formation. The migrated liquid is purged during a purge of the fuel cell stack after operation.