Fuel Cell EPU Cooling Using Phase-Change Coolant
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Solution Overview
Problem
Traditional thermal management systems for emergency power units in aircraft are physically large, heavy, and induce drag due to their reliance on ram air cooling, which is inefficient and cumbersome.
Innovation Solution
A compact thermal management system utilizing a phase change fluid, such as water, ethanol, or carbon dioxide, that changes from a liquid to vapor phase to cool the fuel cell system near-isothermally, eliminating the need for bulky heat exchangers and ram air cooling, and integrating the coolant directly with the fuel cell system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional thermal management systems use ram air cooling, then cooling effectiveness is achieved, but system size and weight increase significantly
Solution Approach 1:
The patent utilizes the phase change of a coolant from liquid to vapor within the fuel cell stack to achieve cooling. The coolant absorbs heat during evaporation and releases it during condensation, maintaining fuel cell temperature without requiring heavy external cooling systems. This phase transition mechanism enables effective thermal management with significantly reduced system weight compared to traditional ram air cooling systems.
2Temperature
If traditional thermal management systems are designed for adequate cooling, then temperature control is maintained, but system volume and physical size increase
Solution Approach 1:
The patent merges the cooling function with the fuel cell structure itself by integrating coolant flow channels directly into the stack. The coolant circulates through these internal channels, absorbing heat directly at the source of heat generation. This integration eliminates the need for separate external heat exchangers and large cooling components, thereby maintaining effective temperature control while minimizing system volume.
3Temperature
If ram air cooling is used for thermal management, then cooling is provided, but drag on the aircraft increases
Solution Approach 1:
The patent extracts the dependency on ram air cooling by implementing a closed-loop coolant system that operates independently of external air flow. The coolant circulates through the fuel cell stack, absorbs heat, and is condensed and reused in a closed cycle. This extraction of the ram air requirement eliminates the harmful drag effect on the aircraft while maintaining effective fuel cell temperature control.
4Temperature
If traditional thermal management systems are implemented, then heat dissipation is achieved, but system complexity increases
Solution Approach 1:
The patent implements a self-service cooling system where the coolant performs multiple functions within the same system. The same coolant that absorbs heat during evaporation also serves as the working fluid for heat rejection during condensation. This self-service approach, where the coolant circulates through integrated channels and performs both cooling and heat dissipation functions, significantly reduces system complexity compared to traditional multi-component thermal 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 reduces the size and weight of the thermal management system by more than 50%, eliminates ram drag, and maintains fuel cell temperature below 200 F, preventing coking and ensuring reliable power generation during emergencies.
Implementation Method 1
the phase change fluid can be configured to change from a liquid phase to vapor phase upon thermal communication with the heat from the fuel cell system to cool the fuel cell system near isothermally
Implementation Method 2
a heat exchanger disposed in a coolant flow path configured to receive a coolant from a coolant supply to exchange heat between the fuel cell system and the coolant in the coolant flow path
Data Source
AI summary
In accordance with at least one aspect of this disclosure, an emergency power unit for an aircraft includes, a fuel cell system configured to generate power using a fuel and an oxidant. A thermal management system is in thermal communication with the fuel cell system to divert heat from the fuel cell system to the thermal management system.