Fuel Heat Exchanger Recirculation for ΔT and Flow Trade-Off
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Solution Overview
Problem
Modern jet engine fuel systems face a trade-off between maximizing temperature difference (ΔT) and fluid flow rates in heat exchangers, where high ΔT typically results in low flow rates and vice versa, leading to inefficient heat transfer and larger heat exchanger sizes.
Innovation Solution
Incorporating a circulating pump into the fuel delivery system to recirculate fuel flow through a heat exchanger, ensuring both high ΔT and increased fluid flow rates, thereby enhancing heat transfer efficiency and minimizing heat exchanger size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If maximum differential temperature (ΔT) is provided between fuel and oil in the heat exchanger, then heat exchange performance is improved, but fluid flow rate decreases
Solution Approach 1:
The fuel flow is segmented into two separate paths: a first portion passes through the heat exchanger to maximize temperature difference with the oil, while a second portion bypasses the heat exchanger. This segmentation allows each stream to be optimized independently - the first stream achieves maximum heat transfer efficiency with high ΔT, while the second stream maintains higher flow rate, resolving the contradiction between temperature difference and flow rate.
2Quantity of substance
If maximum fluid flow rate is provided through the heat exchanger, then heat transfer coefficient is improved, but temperature difference (ΔT) decreases
Solution Approach 1:
By dividing the total fuel flow into two portions with different flow rates, the system can optimize heat transfer coefficient through the first portion (which has higher flow rate) while maintaining temperature difference through the second portion (which has lower flow rate but higher ΔT). The combined effect resolves the contradiction between flow rate and temperature difference.
Solution Approach 2:
The system changes the flow rate parameter for different portions of fuel flow. The first portion operates at a higher flow rate to maximize heat transfer coefficient, while the second portion operates at a lower flow rate to maintain temperature difference. This parameter variation across different streams resolves the contradiction.
3Weight of stationary object
If heat exchanger size is minimized, then system weight is reduced, but heat transfer efficiency decreases
Solution Approach 1:
The segmented fuel flow allows the heat exchanger to be optimized for maximum heat transfer efficiency with the first portion of fuel, while the second portion provides additional cooling capacity without requiring additional heat exchanger surface area. This enables smaller heat exchanger size while maintaining or improving overall heat transfer efficiency.
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 achieves a 20% improvement in heat transfer capabilities by matching heat transfer factors, optimizing both temperature difference and flow rates to maximize efficiency and reduce physical size and weight of the heat exchanger.
Implementation Method 1
The circulating pump receives fuel flow downstream of the heat exchanger and recirculates a portion of the fuel flow to a location upstream of the heat exchanger
Implementation Method 2
heat exchanger, which is located downstream of the first pump, receives the pressurized fuel flow
Data Source
AI summary
The present invention provides a heat exchange system for a closed loop fuel delivery system. The heat exchange system generally includes a first pump, a heat exchanger, a high pressure pump pressurizes fuel. The heat exchanger, which is located downstream of the first pump, receives the pressurized fuel flow. The high pressure pump, which is located downstream of the heat exchanger, delivers a predetermined amount of fuel flow to a jet engine. The circulating pump receives fuel flow downstream of the heat exchanger and recirculates the fuel flow upstream of the heat exchanger.