Fuel Cell Heat Exchanger With Immersed Combustion Cooling
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Solution Overview
Problem
Hot fuel cells generate high-temperature gases that are difficult to handle with standard boiler systems, as most boilers are made with low-performance materials that are not suitable for high-temperature applications, leading to increased costs when using high-performance materials.
Innovation Solution
A heat exchanger design that immerses a first combustion gas, second fuel gas, and combustion chamber circuits in a shared heat transfer fluid, allowing for post-combustion of gases from the fuel cell and incorporating a pre-mixing chamber to optimize fuel/oxidizer mixture homogeneity, reducing the temperature of gases and combustion chamber, enabling the use of low-cost materials and minimizing NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high-performance materials are used to handle high-temperature gases from fuel cells, then the ability to process high-temperature gases is improved, but the cost of the cogeneration system increases considerably
Solution Approach 1:
The system is divided into two separate heat exchangers: a first heat exchanger that handles high-temperature gases using high-performance materials, and a second heat exchanger that handles lower-temperature gases using low-cost standard materials. This segmentation allows each component to be optimized for its specific temperature range, reducing overall system cost while maintaining the ability to process high-temperature gases.
Solution Approach 2:
A thermal energy storage tank acts as an intermediary between the two heat exchangers. The first heat exchanger transfers thermal energy from high-temperature gases to the storage tank, and the second heat exchanger transfers thermal energy from the storage tank to the water circuit. This intermediary allows the decoupling of high-temperature processing from the water heating process, enabling the use of standard materials in the second heat exchanger.
2Ease of manufacture
If standard boiler systems are used to recover heat from high-temperature gases, then the cost is reduced, but the ability to control and process high-temperature gases deteriorates
Solution Approach 1:
The heat recovery system is segmented into two stages with different material requirements. The first heat exchanger, designed for high-temperature gas handling, uses standard materials optimized for thermal efficiency. The second heat exchanger, operating at lower temperatures, uses standard boiler materials. This segmentation allows standard materials to be used throughout while maintaining proper control capability at each temperature stage.
3Temperature
If high-performance materials are used throughout the heat exchanger system, then the temperature handling capability is improved, but the quantity of high-performance materials required increases cost
Solution Approach 1:
The system is divided into two heat exchangers with different material specifications. Only the first heat exchanger, which is in direct contact with high-temperature gases, uses high-performance materials. The second heat exchanger, which handles lower-temperature thermal energy from the storage tank, uses standard materials. This segmentation minimizes the quantity of expensive high-performance materials required while maintaining the system's ability to handle high temperatures.
Solution Approach 2:
Different material qualities are applied to different parts of the system based on local temperature requirements. The first heat exchanger uses high-performance materials locally where high-temperature gases are present, while the second heat exchanger and storage tank use standard materials where temperatures are lower. This local quality approach optimizes material usage and reduces overall system cost.
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
The heat exchanger effectively recovers thermal energy from high-temperature gases while reducing the number of components in contact with high-temperature gases, allowing the use of low-cost materials and lowering NOx emissions, thus achieving efficient heat recovery without the need for high-performance materials.
Implementation Method 1
immersing the various gas circulation circuits (oxidizer, fuel and combustion fumes) and the combustion chamber in the same heat transfer fluid... ensure the recovery of all the thermal energy
Implementation Method 2
a combustion chamber supplied with the gaseous mixture from the pre-mixing chamber and with combustion gases from the first circuit
Implementation Method 3
a pre-mixing chamber supplied with fuel gases from at least the second circuit and with oxidizing gases
Data Source
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AI summary
The invention relates to a heat exchanger (100) that is intended to operate at the outlet of a hot fuel cell that supplies the exchanger with oxidizing and fuel gases, said heat exchanger comprising: a first oxidizing gas flow circuit (111); a second fuel gas flow circuit (112); a pre-mixing chamber (142) supplied with fuel gases from at least the second circuit and moreover supplied with oxidizing gases; a combustion chamber (140) supplied with the gas mixture from the pre-mixing chamber and moreover supplied with oxidizing gases from the first circuit; and a flue gas flow circuit (114) that receives the flue gases coming from the combustion chamber. The first oxidizing gas flow circuit, the second fuel gas flow circuit, the combustion chamber, and the flue gas flow circuit are submerged in a single heat transfer fluid.