Heat Exchanger Header Baffle for Thermal Separation
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Solution Overview
Problem
Heat exchangers used in aircraft environmental control systems face challenges in efficiently managing high-temperature and high-pressure bleed air, requiring effective cooling and distribution to both On-Board Inert Gas Generation Systems (OBIGGS) and other components, while minimizing thermal mixing and maintaining desired temperature gradients.
Innovation Solution
A heat exchanger design featuring a header with a baffle that divides the header volume into two cavities, allowing controlled airflow through a bypass valve to direct cooled air to OBIGGS or other components, with the baffle positioned to maintain thermal separation and adjust airflow based on system demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a baffle is used to separate the header volume into two cavities, then thermal separation is improved and temperature gradients are maintained, but device complexity increases
Solution Approach 1:
The header volume is segmented into a first cavity and a second cavity using a baffle, allowing separate temperature zones to be maintained. This segmentation enables the hot fluid outlet to supply both OBIGGS (from the first cavity) and other components (from the second cavity) with appropriately differentiated temperatures, resolving the contradiction by physically dividing the thermal zones while maintaining a relatively simple overall header structure.
2Adaptability or versatility
If a bypass valve is added to control airflow through the bypass outlet, then adaptability of the system is improved, but device complexity increases
Solution Approach 1:
The bypass valve provides dynamic control of airflow, allowing the system to adapt between different operating modes. When the bypass valve is closed, all air flows through the heat exchanger outlet; when open, air can flow through the bypass outlet. This dynamic adjustability resolves the contradiction by enabling flexible system operation while using a straightforward valve mechanism rather than a complex control system.
3Object-affected harmful factors
If the baffle extends partially through the header length, then thermal mixing is minimized, but pressure drop increases
Solution Approach 1:
The baffle is positioned to extend from the first end wall toward the second end wall but does not span the entire header length, creating localized thermal separation where needed while maintaining pressure relief pathways. This partial extension resolves the contradiction by providing thermal separation in the critical region near the hot fluid outlet while allowing pressure equalization and reduced pressure drop through the remaining open header space.
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 design effectively cools and distributes air, ensuring the desired temperature is maintained for OBIGGS while minimizing thermal mixing and pressure drops, allowing for efficient operation and reduced system requirements.
Implementation Method 1
heat exchangers may be used to provide thermal air conditioning to the bleed air by crossing the bleed air through an exchanger that uses ram air for cooling the bleed air
Data Source
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AI summary
A heat exchanger (10) for an aircraft includes a hot fluid inlet (46), a hot fluid outlet (48), a cold fluid inlet (40), a cold fluid outlet (44), and a header (26) connected to the hot fluid outlet (48). The header (26) includes a housing (24) defining a header volume, and a baffle (50) separating the header volume into a first volume (76) and a second volume (78), wherein the first volume (76) and the second volume (78) are in fluid communication with each other. The baffle (50) is shaped to split a hot fluid flow (H) exiting hot fluid outlet 48. The portion of hot fluid flow exiting hot fluid outlet 48 closest to a cold-cold corner (56) of the heat exchanger (10) is diverted to the first volume (74). The remainder of hot fluid flow (H) exiting the hot fluid outlet (48) is routed to the second cavity (76)