Fuel Cell Header Baffle for Flow Resistance Reduction
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Solution Overview
Problem
Fuel cell unit cell headers face issues with reduced flow efficiency due to high velocity reactant streams and the formation of 'crescent moon' product water, which can cause blockages through capillary action, and existing solutions like resizing header openings do not effectively address these issues.
Innovation Solution
The introduction of a fluid flow field plate with baffle structures that extend into the flow path, varying in depth and angle, to redirect high velocity flows and prevent water accumulation, thereby enhancing the effective header area and reducing flow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high velocity reactant streams are used in fuel cell headers, then power generation efficiency is improved, but flow resistance increases and effective header area is reduced
Solution Approach 1:
The baffle structure is installed in advance within the header to preemptively manage the high velocity flow before it causes problems. The baffle is positioned to intercept and redirect the reactant stream, creating a velocity/pressure gradient that prevents water accumulation and maintains effective flow area throughout operation.
Solution Approach 2:
The baffle acts as an intermediary element between the high velocity reactant stream and the header flow path. It mediates the interaction by redirecting the flow and creating pressure gradients, preventing direct negative interaction between the high velocity stream and the header geometry that would cause blockages.
2Productivity
If high velocity flows are directed into header outlets, then reactant distribution is improved, but the cross-sectional area for main flow is reduced
Solution Approach 1:
The baffle introduces a spatial dimension to flow management by creating vertical stratification of flow velocities and pressures within the header. The velocity/pressure gradient established by the baffle directs high velocity flow in specific directions while maintaining adequate cross-sectional area for main flow through multi-dimensional flow path optimization.
3Reliability
If product water accumulates in header port areas, then sealing is maintained, but capillary action causes water to be sucked back into ducts causing blockages
Solution Approach 1:
The baffle structure performs preliminary anti-action by creating pressure gradients that counteract capillary forces before water can be sucked back into the ducts. The velocity/pressure gradient established by the baffle prevents the harmful capillary action from occurring in the first place, maintaining both sealing integrity and flow pathways.
4Ease of operation
If header opening size is adjusted to address flow sharing issues, then cell-to-cell flow uniformity is improved, but header area utilization is not increased and wasted space remains
Solution Approach 1:
The baffle creates local variations in flow characteristics at specific locations within the header, providing different flow conditions in different regions. This local quality approach improves cell-to-cell flow uniformity by addressing specific flow distribution issues without requiring overall header resizing, thereby maintaining high header area utilization.
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
The baffle-enhanced fluid flow field plate increases the effective header area, reduces the propensity for blockages, and improves flow efficiency by creating a velocity/pressure gradient that helps manage condensate, resulting in increased flow area and reduced resistance.
Implementation Method 1
creating a velocity/pressure gradient that helps manage condensate
Implementation Method 2
a 'crescent moon' of product water has a tendency to form between the plate pinch cuts in the port area. There is a propensity for this water formation to be sucked back into the small ducts between the port and transition region by capillary action
Data Source
AI summary
A fluid flow field plate for an electrochemical fuel cell that includes a planar body having a first surface, a second surface. More than one header opening extends between the first surface and the second surface to define a flowpath. At least one open flow field channel with an inlet port and an outlet port is provided in the first surface. Each outlet port is in fluid communication with one of the one header openings. At least one of the outlet port or the inlet port has a baffle extending into the flow path.