Dual-Loop Aircraft Thermal Management for Fuel Cell Heat Rejection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Aircraft using hydrogen fueled fuel cells face challenges in efficiently managing thermal loads, particularly during start-up and varying flight phases, due to the high heat rejection rates and limited ambient air availability.

Innovation Solution

The implementation of a dual-loop thermal management system, comprising a high temperature loop for fuel cell stack management using a nacelle heat exchanger and a low temperature loop for cooling various heat loads using the heat capacity of liquid hydrogen, along with a ram air cooler system to enhance airflow and reduce heat exchanger size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional single-loop thermal management system is used, then the system structure is simpler, but it cannot efficiently manage both high temperature fuel cell stacks and low temperature heat loads simultaneously

Engineering Contradiction:

Improvethermal management capabilityVSAvoidsystem structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The thermal management system is divided into two separate loops: a high-temperature loop for fuel cell stack cooling and a low-temperature loop for other heat loads. This segmentation allows each loop to be optimized for its specific temperature range, improving overall thermal management efficiency while maintaining manageable system complexity through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The high-temperature loop serves multiple functions: it cools the fuel cell stacks and simultaneously provides heating for cabin and wing anti-ice systems. The low-temperature loop cools various electronic and mechanical components. This multi-functionality approach allows a single system architecture to handle diverse thermal requirements across different temperature zones.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If larger heat exchangers are used to improve cooling efficiency, then heat rejection is more effective, but the system weight and drag increase

Engineering Contradiction:

Improvecooling efficiencyVSAvoidthermal management system weight

Core Design Contradiction:

ProductivityVSWeight of moving object

Solution Approach 1:

The system utilizes variable parameters including coolant flow rates, heat exchanger surface areas, and thermal conductivity materials to optimize cooling efficiency. By adjusting these parameters rather than simply increasing heat exchanger size, the system achieves effective cooling while minimizing weight penalties.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system leverages phase change materials and two-phase heat transfer processes in the heat exchangers to dramatically increase cooling efficiency per unit mass. Phase transitions provide high heat transfer coefficients that enable compact, lightweight heat exchanger design while maintaining superior cooling performance.

Inventive Principle:

Principle #36Phase transitions

3Productivity

If more ambient air is available for cooling, then heat rejection improves, but during ground operation or low-speed flight, ambient air availability is limited

Engineering Contradiction:

Improveheat rejection rateVSAvoidoperational phase adaptability

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The system pre-cools the incoming ambient air using the low-temperature loop before it enters the high-temperature heat exchanger. This preliminary cooling action increases the temperature differential and heat rejection efficiency of the fuel cell cooling system, allowing effective operation even when ambient air flow is limited during ground operations or low-speed flight.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The low-temperature coolant loop acts as an intermediary between the ambient air and the high-temperature fuel cell cooling system. It mediates the heat transfer process by first absorbing heat from various components and then rejecting it to the ambient air through the heat exchanger, enabling efficient heat rejection across different flight conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively manages the temperature of fuel cell stacks and cools heat loads efficiently, reducing the size and weight of thermal management systems, while minimizing drag and enhancing overall aircraft performance.

Implementation Method 1

The high temperature loop is configured to manage a temperature of a fuel cell stack in a nacelle using a nacelle heat exchanger

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

The low temperature loop is configured to cool a number of heat loads in a nacelle using a heat capacity of liquid hydrogen

Methodology Applied

Scientific EffectHeat capacity: Heat Sink

Implementation Method 3

a set of fans configured to increase airflow through the nacelle heat exchanger

Methodology Applied

Scientific EffectForced convection: Forced Convection

Data Source

PatentUS20250058891A1Fuel Cell Aircraft Thermal Management System

Publication Date: 2025.02.20 THE BOEING CO

AI summary

An aircraft thermal management system comprising a high temperature loop and a low temperature loop. The high temperature loop is configured to manage a temperature of a fuel cell stack in a nacelle using a nacelle heat exchanger. The low temperature loop is configured to cool a number of heat loads in a nacelle using a heat capacity of liquid hydrogen.