Staggered 3D Coolant Ducts for Fuel Cell Pressure Drop
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Solution Overview
Problem
High power density fuel cell stacks face significant coolant pressure drops in coolant transition regions, leading to non-uniform coolant distribution, overheating, and increased risk of wet spots, which complicates stack preparation and startup, especially in extreme conditions, and requires larger, more powerful pumps.
Innovation Solution
The design increases the height of coolant ducts in the coolant transition regions by staggering them between adjacent cells and using non-planar membrane electrode assemblies, allowing coolant flow rate enhancement without affecting reactant flow, and maintaining overall stack volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If coolant ducts are formed transverse to reactant transition channels in high power density stacks, then coolant flow rate increases, but coolant pressure drop increases significantly
Solution Approach 1:
The patent transitions from planar, two-dimensional coolant ducts to three-dimensional coolant ducts that extend through the flow field plate thickness. This dimensional change allows coolant to flow through a larger cross-sectional area and longer path, reducing pressure drop while maintaining flow rate. The 3D ducts are formed by creating cavities that penetrate through the plate, allowing coolant to bypass the restrictive transverse path through reactant transition channels.
Solution Approach 2:
The coolant ducts are nested within the flow field plate structure itself, utilizing the plate's thickness to create internal coolant passages. The ducts are formed by removing material from the plate to create cavities that are then connected to form continuous coolant flow paths. This nesting allows the coolant system to be integrated into the existing plate structure without adding external components that would increase pressure drop.
2Reliability
If coolant duct height is increased to reduce pressure drop, then coolant distribution uniformity improves, but stack volume increases
Solution Approach 1:
The patent employs a modular flow field plate design where the coolant duct configuration can be adjusted or optimized for different operating conditions. The ducts are designed with specific geometries and arrangements that adapt to the thermal and flow requirements of the fuel cell stack, allowing uniform coolant distribution without requiring excessive duct height that would increase stack volume.
Solution Approach 2:
The coolant ducts are strategically positioned and sized at different locations within the flow field plate based on local heat generation and coolant distribution requirements. Areas with higher heat generation receive enhanced coolant flow through larger or more numerous ducts, while areas with lower heat generation have smaller ducts. This localized optimization achieves uniform coolant distribution throughout the stack without uniformly increasing duct height everywhere, thereby avoiding unnecessary volume increase.
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 reduces coolant pressure drop by up to a factor of 4, improving coolant distribution uniformity and reducing the risk of overheating and wet spots, while allowing for higher power density without increasing stack mass or reactant flow obstruction.
Implementation Method 1
Stacks designed to achieve high power density (e.g. automotive stacks) typically circulate liquid coolant throughout the stack in order to remove heat quickly and efficiently
Data Source
AI summary
The pressure drop associated with the coolant flow in the coolant transition regions of a typical high power density, solid polymer electrolyte fuel cell stack can be significant. This pressure drop can be reduced by enlarging the height of the coolant ducts in this region of the associated flow field plate so that the ducts extend beyond the plane of the plate. The height change can be accommodated by offsetting the ducts in adjacent cells in the stack and by employing non planar MEAs in this region. By reducing the pressure drop, improved coolant flow sharing is obtained.