Fuel Cell Thermal Management Using Hydrogen-Heated Condensation
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Solution Overview
Problem
Fuel cell systems using liquid hydrogen face inefficiencies due to low operating temperatures and the size and mass of condensers in Rankine cycles, which hinder their suitability for vehicle propulsion, especially in aircraft applications.
Innovation Solution
A fuel cell system incorporating a pre-heater that heats coolant fluid within a Rankine cycle cooling circuit, allowing heat from the coolant to be transferred to gaseous hydrogen en route to the fuel cell stack, reducing the size and weight of the condenser and enhancing thermal efficiency by utilizing waste heat for both cooling and heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a Rankine cycle cooling circuit is used for a low-temperature fuel cell stack, then cooling function is provided, but the condenser has significant size and mass making the system unattractive for vehicle propulsion
Solution Approach 1:
The patent combines the cooling circuit and heating system into a single integrated thermal management system. The condenser serves dual functions: cooling the fuel cell stack and heating the gaseous hydrogen fuel. By merging these previously separate functions into one system, the condenser size is reduced while maintaining both cooling and heating capabilities, directly resolving the contradiction between providing adequate cooling and minimizing condenser mass.
Solution Approach 2:
The cooling circuit is designed to perform multiple functions simultaneously: it cools the fuel cell stack through the condenser while also heating the hydrogen fuel through thermal contact in the conveying means. This multi-functionality allows the same thermal management system to address both cooling requirements and fuel temperature requirements, reducing the need for separate heavy components.
2Temperature
If a Rankine cycle cooling circuit is used for a low-temperature fuel cell stack, then cooling function is provided, but the system complexity and mass make it unsuitable for aircraft propulsion
Solution Approach 1:
The patent merges the cooling circuit and fuel heating system into a single integrated thermal management system. The condenser serves dual functions: cooling the fuel cell stack and heating the gaseous hydrogen fuel. By merging these previously separate functions into one system, the overall device complexity is reduced while maintaining both cooling and heating capabilities.
Solution Approach 2:
The cooling circuit is designed to perform multiple functions simultaneously: it cools the fuel cell stack through the condenser while also heating the hydrogen fuel through thermal contact in the conveying means. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall system architecture.
3Loss of energy
If cold gaseous hydrogen from boil-off is used to condense coolant in a Rankine cycle, then some heating is achieved, but the temperature is insufficient for efficient fuel cell operation
Solution Approach 1:
The patent applies preliminary heating action by using the pre-heater to heat the liquid hydrogen before it enters the conveying means. This preliminary heating ensures that when the hydrogen receives additional heat from the coolant in the conveying means, it reaches the required temperature for efficient fuel cell operation. The pre-heater's combustion of a portion of the hydrogen provides the initial thermal energy needed.
Solution Approach 2:
The patent changes the temperature parameters of the hydrogen through a two-stage heating process. First, the pre-heater raises the temperature of liquid hydrogen through combustion heating. Second, the thermal contact in the conveying means further heats the hydrogen using waste heat from the coolant. This parameter change ensures the hydrogen reaches the optimal temperature range for fuel cell efficiency.
4Ease of operation
If the pre-heater heats only the liquid hydrogen without heating the coolant, then vaporization is achieved but thermal efficiency is reduced
Solution Approach 1:
The patent ensures continuous useful action by having the pre-heater perform dual functions: vaporizing the liquid hydrogen and heating the coolant fluid simultaneously. The combustion process in the pre-heater continuously transfers thermal energy to both the liquid hydrogen (for vaporization) and the coolant (for temperature increase), maximizing the utility of the combustion process and improving overall thermal efficiency.
Solution Approach 2:
The pre-heater is designed with multi-functionality to simultaneously vaporize liquid hydrogen and heat the coolant fluid. By making the pre-heater perform both functions, the system improves thermal efficiency as the waste heat that would otherwise be lost is now utilized to heat the coolant, which then transfers heat to the gaseous hydrogen in the conveying means.
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 configuration reduces the size and weight of the condenser, increases the thermodynamic efficiency of the Rankine cycle, and ensures efficient heating of gaseous hydrogen for the fuel cell stack, making the system more suitable for aeronautical applications.
Implementation Method 1
a fuel pre-heater arranged to heat a flow of liquid hydrogen provided to an input of the pre-heater to provide a flow of gaseous hydrogen at an output of the pre-heater
Implementation Method 2
the cooling circuit implements a Rankine cycle and includes a condenser arranged to condense gaseous coolant within the cooling circuit
Implementation Method 3
the conveying means and the cooling circuit are arranged such that coolant fluid within the cooling circuit is in thermal contact with gaseous hydrogen within the conveying means during operation of the fuel cell system
Implementation Method 4
the cooling circuit implements a Rankine cycle
Data Source
AI summary
A fuel cell system includes a fuel pre-heater, a fuel cell stack and a cooling circuit which is arranged to implement a Rankine cycle and includes a condenser. The fuel pre-heater is arranged to heat a flow of liquid hydrogen provided to an input thereof to provide a flow of gaseous hydrogen. The system further includes a conveying apparatus arranged to convey the gaseous hydrogen to a fuel input of the fuel cell stack such that the gaseous hydrogen is in thermal contact with coolant fluid in the condenser. The size and mass of the condenser may thereby be reduced. The pre-heater is arranged to heat coolant fluid within the cooling circuit, thereby increasing the efficiency of the Rankine cycle.