Fuel Cell Wick Passageways for Cold Shutdown Water Purging
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Solution Overview
Problem
Fuel cells face challenges in efficiently removing water from the fuel cell stack during shutdown in cold climates to prevent ice blockage and mechanical stress, especially when using air purging through water permeable wicks, which is inadequate.
Innovation Solution
The implementation of interdigitated coolant water flow fields that allow air to flow through the water permeable wick and porous hydrophilic reactant gas flow field plates, increasing water removal by enhancing the surface area for water transfer and ensuring gas escape to avoid blockage, using water permeable wick layers adjacent to water passageways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air purging is used through water permeable wicks to remove water during shutdown, then water removal is achieved, but the water removal is inadequate and leaves excessive water in the wicks
Solution Approach 1:
The flow field plate is divided into reactant gas flow channels and water passageways that are spatially separated and interdigitated. This segmentation allows independent optimization of gas flow paths and water removal paths, enabling air to be forced through the wick via pressure differential while maintaining proper fuel cell operation during normal conditions
Solution Approach 2:
The system uses pressure differentials created by the interdigitated flow field configuration to force air through the water permeable wick during shutdown. The blocked outlet of reactant gas channels creates positive pressure that drives air through the wick and water passageways, enhancing water removal without requiring additional pumps or complex mechanisms
2Quantity of substance
If water permeable wick layers are added to enhance water supply, then water transfer surface area increases, but device complexity increases
Solution Approach 1:
The water permeable wick layer serves multiple functions simultaneously: it supplies water to the membrane during operation, removes water during shutdown through capillary action and pressure-driven flow, and provides structural support. The reactant gas flow field plate also serves dual purposes as both a gas distribution plate and a water removal channel
Solution Approach 2:
The patent combines the water supply function and water removal function into a single integrated structure. The water permeable wick layer is positioned to contact both the membrane (for water supply) and the water passageways (for water removal), eliminating the need for separate water management systems
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 solution effectively reduces water content in the fuel cell stack, preventing ice blockage and mechanical stress, while maintaining efficient water supply and humidification, ensuring reliable startup and operation.
Implementation Method 1
a water permeable wick layer between the flow field plates, and in intimate contact with all of the water passageways
Implementation Method 2
evaporatively cooled by means of water present in passageways which are adjacent to or within a first surface of at least one of the hydrophilic, porous reactant gas flow field plates
Implementation Method 3
flow through porous, hydrophilic reactant gas flow field plates
Data Source
AI summary
Fuel cells (38) have passageways (83, 84) that provide water through one or both reactant gas flow field plates (75, 81) of each fuel cell, whereby the fuel cell is cooled evaporatively. The water passageways may be vented by a porous plug (not shown), or by a microvacuum pump (89). A condenser (59) may have a reservoir (64); the condenser (59) may be a vehicle radiator. A highly water permeable wicking layer (90) is disposed adjacent to one or both water passageways (83, 84) which exist between individual fuel cells (38). The passageways may be flow-through passageways (83) (FIG. 5) or they may be interdigitated passageways (83a, 83b) (FIG. 6) in order to increase the flow of water-purging air through the wicking layer (90) utilized to clear the stack of water during shutdown in cold environments. The inlet interdigitated channels (83c, 83d) may be only partially blocked at their outlet ends such as by a protrusion (104) or a hole (106) in order to ensure that any gas entering the inlet coolant passageways (83c, 83d) will not accumulate at the outlet end (101) of the inlet coolant passageways.