Heat Exchanger Thermal Shock Reduction via Air Mixing
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Solution Overview
Problem
Heat exchangers in gas turbine engines face premature fatigue and reduced useful life due to thermal shock caused by high-temperature air, which leads to mismatched thermal expansion rates among parts, resulting in high stresses and potential leaks.
Innovation Solution
A heat exchanger design that mixes conditioned air with hot air before it enters the exchanger, using a Venturi feature to facilitate mixing without additional fans or pumps, and a temperature sensor to control the mixing valve, ensuring a more gradual temperature increase and reduced thermal shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature air is introduced directly into the heat exchanger, then cooling efficiency is improved, but thermal shock causes premature fatigue and reduced useful life
Solution Approach 1:
The system performs preliminary cooling by mixing hot air with conditioned air before the air enters the heat exchanger. The mixing section pre-cools the hot air, reducing the thermal shock to the heat exchanger parts and allowing them to heat up more uniformly, thereby extending useful life while maintaining cooling efficiency
Solution Approach 2:
The mixing section acts as an intermediary between the hot air source and the heat exchanger. It combines hot air with conditioned air from the heat exchanger outlet, creating a blended air stream with reduced temperature that enters the heat exchanger, thus protecting it from direct thermal shock
2Productivity
If high-temperature air is introduced directly into the heat exchanger, then cooling performance is improved, but thermal expansion mismatch causes high stresses and potential leaks
Solution Approach 1:
The system performs preliminary temperature equalization by mixing hot air with conditioned air before heat exchanger entry. This gradual temperature increase allows different parts of the heat exchanger to expand at more similar rates, reducing thermal expansion mismatch and associated stresses
Solution Approach 2:
The system changes the temperature parameter of the air entering the heat exchanger by mixing it with conditioned air. This parameter modification reduces the temperature differential across heat exchanger parts, minimizing differential thermal expansion and stress
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 design reduces thermal shock and extends the useful life of the heat exchanger by allowing parts to heat up and expand at similar rates, delaying the onset of peak thermal stress and reducing part fatigue and leakage rates.
Implementation Method 1
using a Venturi feature to facilitate mixing without additional fans or pumps
Implementation Method 2
a second flow circuit for a second fluid, which is in thermal communication with the first flow circuit
Implementation Method 3
thermal shock caused by high-temperature air, which leads to mismatched thermal expansion rates among parts, resulting in high stresses
Data Source
AI summary
A heat exchanging arrangement includes a first flow circuit for a first fluid to be cooled, which has a first inlet, a first outlet, and a second outlet. The heat exchanging arrangement includes a second flow circuit for a second fluid, which is in thermal communication with the first flow circuit. The heat exchanging arrangement includes a third flow circuit configured to port a portion of the first fluid from a first location of the first flow circuit to a second location of the first flow circuit, the first location being downstream of the second location.