Fuel Cell Stack Drying Using Residual Cooling Fluid Heat
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Solution Overview
Problem
After shutdown, fuel cell stacks face moisture condensation issues due to cold environments, which can damage the membrane electrode assemblies (MEAs) when dry air is used for drying, leading to reduced drying efficiency and potential blockage of flow channels.
Innovation Solution
The system employs a combination of using the residual heat from the cooling fluid to maintain thermal equilibrium within the stack and heating the drying air through a cathode input gas heat exchanger or an additional heat exchanger to prevent condensation, ensuring the drying air is warmer than the stack, thus effectively removing moisture without causing condensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cold dry air is used for drying the fuel cell stack after shutdown, then the drying process can remove moisture from the stack, but condensation forms in the flow channels due to temperature difference, blocking the channels and reducing drying efficiency
Solution Approach 1:
The patent changes the temperature parameter of the drying air from cold to warm by heating it before introduction into the stack. This parameter change prevents condensation formation while maintaining effective moisture removal capability
Solution Approach 2:
The patent applies preliminary heating to the drying air before it contacts the stack components. This preliminary anti-action prevents the harmful condensation effect from occurring in the first place, rather than trying to remove it afterward
2Object-affected harmful factors
If warm air is used for drying the fuel cell stack, then condensation is prevented in the flow channels, but additional energy is required to heat the air
Solution Approach 1:
The patent merges the drying air heating function with the existing cathode input gas heat exchanger that is already part of the fuel cell system. This combination allows warm air generation without adding separate heating equipment, reducing overall system complexity and energy consumption
Solution Approach 2:
The system uses its own internal resources (the heat exchanger and existing thermal management infrastructure) to provide the heating function needed for drying, rather than requiring external heating equipment. The cathode input gas heat exchanger serves dual purposes
3Object-affected harmful factors
If the drying air temperature is higher than the stack temperature, then condensation is prevented, but thermal shock may damage the membrane electrode assemblies
Solution Approach 1:
The patent carefully controls the temperature parameter of the drying air to be warmer than the stack (preventing condensation) but not excessively hot (avoiding thermal shock). This optimized parameter change achieves both protection goals
Solution Approach 2:
The system uses temperature sensing and control to monitor stack conditions and adjust the drying air temperature accordingly. This feedback mechanism ensures the air temperature remains in the optimal range that prevents condensation while avoiding thermal shock to sensitive components
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 prevents condensation in the fuel cell stack flow channels, enhances drying efficiency by using warm air to remove water vapor, and reduces the risk of damage to MEAs by maintaining a stable temperature, ensuring effective stack drying post-shutdown.
Implementation Method 1
using the heat still available in the cooling fluid immediately after shutdown to provide a thermal equilibrium in the stack
Implementation Method 2
The cooling fluid is pumped through the flow channels in the bipolar plates after the system is shutdown
Implementation Method 3
the heated cooling fluid still available immediately after system shutdown is sent through a cathode input gas heat exchanger so that drying air from the system compressor is heated by the cooling fluid
Data Source
AI summary
A system and method for drying a fuel cell stack after stack shutdown. In one embodiment, a cooling fluid is pumped through the fuel cell stack after the system is shutdown to use the heat still available in the cooling fluid immediately after shutdown to provide thermal equilibrium in the stack. In another embodiment, the heated cooling fluid still available immediately after system shutdown is sent through a cathode input gas heat exchanger so that drying air from the system compressor is heated by the cooling fluid before it enters the stack. In another embodiment, a separate heat exchanger is provided that receives the drying gas prior to it being sent into the fuel cell stack.