Fuel Cell Inlet Humidification via Shallow Flow Field Channels
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Solution Overview
Problem
Fuel cell stacks employing proton exchange membranes face membrane failure due to dryness, particularly near air inlets, which is not effectively addressed by existing humidification methods that either require external hardware or reduce power density by rendering parts inactive.
Innovation Solution
Shallowing reactant gas channels near inlets in hydrophilic, porous flow field plates increases the thickness of water transport plate webs, reducing resistance to moisture transfer and enhancing humidification without external humidification mechanisms or reduced active area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external humidification mechanisms are used to increase relative humidity at the inlet, then membrane dryness is prevented, but device complexity and hardware requirements increase
Solution Approach 1:
The flow field plate performs self-humidification by utilizing its own water transport capability. The hydrophilic porous structure automatically transfers water from the water transport plate to the reactant gas channels, eliminating the need for external humidification hardware while preventing membrane dryness at the inlet region
Solution Approach 2:
The flow field plate serves multiple functions: it conducts electricity, transports water, and humidifies the reactant gas. By integrating the humidification function into the existing flow field plate structure, the invention eliminates the need for separate humidification devices while maintaining all necessary functions
2Reliability
If a portion of the fuel cell planform is rendered inoperative near the inlets to prevent membrane dryness, then membrane failure is prevented, but power density is reduced
Solution Approach 1:
The flow field plate is designed with spatially varying properties: the web thickness and channel dimensions are modified specifically in the inlet region to enhance water transport and humidification, while the rest of the plate maintains its original design for optimal power generation. This localized modification prevents membrane dryness without sacrificing active area
3Quantity of substance
If the channel depth is reduced to enhance humidification, then mass transfer resistance is decreased, but the web thickness must be increased which may affect structural integrity
Solution Approach 1:
The invention modifies geometric parameters of the flow field plate: reducing channel depth and increasing web thickness in the inlet region. These parameter changes enhance water transport capability and humidification while the overall plate structure maintains sufficient mechanical strength through optimized geometry
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 approach increases relative humidity at the fuel cell inlet, extending membrane life and improving cell performance by enhancing gas phase mass transfer and evaporation rates, thus preventing membrane dryness and maintaining power density.
Implementation Method 1
decreases the resistance to gas phase mass flow, that is, transfer of moisture, from wetted walls of hydrophilic, porous water transport plates to the gas in the channels
Implementation Method 2
The shallower reactant gas channels result in thicker webs, which are defined herein as the regions of the water transport plate which are underneath or otherwise adjacent to the shallow portion of the reactant gas channels, which results in an increase in the rate of evaporation of water into the reactant gas entering the fuel cell
Data Source
AI summary
In a proton exchange membrane fuel cell power plant (9) in which each of the fuel cells (11) employ reactant gas flow field channels (51) extending inwardly from a first surface of a conductive, water permeable reactant gas flow field plate (50), for at least one of the reactants of the fuel cell, a region (63) of the reactant gas flow field channels is substantially shallower than the remaining portion (60) of the flow field channels (51) thereby decreasing resistance to gas phase mass transfer from the wetted walls of the flow field plate to the gas in the region (63), the resulting increase in thickness of the web (58) adjacent the region (63) reduces the resistance to liquid water transport from the first coolant channel (52) to the inlet edge (55) of the plate (50) so that the plate supports a higher evaporation rate into the reactant gas in the shallow region (63).