Variable Pore Size Cathode Flow Field for Fuel Cell Water Management
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Solution Overview
Problem
Existing electrochemical cell stacks face challenges in managing water accumulation, particularly in end cells, which can lead to flooding, reduced performance, and instability of the cell stack.
Innovation Solution
The electrochemical cell stack incorporates a porous structure with varying average pore sizes and flow resistances in specific cells, including interdigitated feed and discharge channels, to optimize water management and prevent flooding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If end electrochemical cells are cooled more effectively, then heat removal is improved, but water accumulation increases leading to flooding
Solution Approach 1:
The patent applies different pore sizes to different cells within the stack. Specifically, middle cells have a first pore size while end cells have a second pore size that is larger than the first pore size. This local differentiation allows end cells to have enhanced water drainage capability without requiring different cooling strategies for each cell position.
Solution Approach 2:
The patent changes the physical parameter of pore size in the porous electrode structure to control water management. By increasing the pore size in end cells compared to middle cells, the system optimizes water removal in locations where flooding is more likely to occur due to their thermal and flow characteristics.
2Ease of manufacture
If uniform pore size is used in all cells, then manufacturing is simplified, but water management performance deteriorates due to flooding in end cells
Solution Approach 1:
The patent implements local quality by specifying that end cells have a different pore size (second pore size) compared to middle cells (first pore size). This allows each cell type to be optimized for its specific position in the stack, with end cells having larger pores to prevent flooding while middle cells maintain their original design characteristics.
Solution Approach 2:
The patent segments the stack into different cell types based on position. End cells are distinguished from middle cells and assigned different porous structure parameters. This segmentation enables tailored water management strategies for different locations without requiring complete redesign of all cells.
3Temperature
If end cells have lower operating temperature, then cooling efficiency is improved, but reactant gas flow decreases due to water flooding
Solution Approach 1:
The patent changes the pore size parameter in end cells to compensate for their lower operating temperature. The larger second pore size in end cells facilitates better water drainage and maintains reactant gas flow pathways even in the cooler environment where condensation is more likely to occur.
Solution Approach 2:
The patent applies preliminary anti-action by pre-configuring end cells with larger pore sizes before operation begins. This structural adaptation anticipates and prevents the flooding problem that would otherwise occur in end cells due to their inherent cooling efficiency and lower temperature operation.
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
This design effectively reduces water accumulation in end cells, enhancing the stability and performance of the electrochemical cell stack by maintaining optimal operating conditions and preventing flooding.
Implementation Method 1
a first electrochemical cell... may have a porous structure with an average pore size greater than an average pore size of the porous structures of the plurality of electrochemical cells
Data Source
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AI summary
An electrochemical cell stack is provided, The electrochemical ceil stack has a plurality of electrochemical cells. Each electrochemical cell has a membrane electrode assembly which includes a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the catalyst layer and the anode layer. Each electrochemicai cell also has an anode plate and a cathode plate with the membrane electrode assembly interposed therebetween, and a cathode flow field positioned between the cathode plate and the cathode catalyst layer. The cathode flow field includes a porous structure having a plurality of pores having an average pore size. The plurality of electrochemicai cells has a first electrochemical ceil positioned at a first end of the electrochemicai cell stack. The porous structure of the first eSectrochemical ceil has an average pore size greater than the average pore size of the porous structures of the plurality of electrochemicai cells. And, the porous structure of the first electrochemical cell has a flow resistance less than an average flow resistance of the porous structures of the plurality of electrochemical cells.