Variable-Length Annular Fin Heat Exchanger for Lower Pressure Drop
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Solution Overview
Problem
Existing heat exchangers in turbomachines face high pressure drops due to shape drag, limited fin density, and non-uniform heat exchange coefficients, leading to inefficiencies and imbalances in thermal resistance.
Innovation Solution
A heat exchanger design with staggered, annular fins that vary in length and pitch radially, optimizing the exchange surfaces and compensating for flow variations to enhance thermal performance and reduce pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of fins is increased to improve heat exchange performance, then the heat exchange efficiency is improved, but the pressure drop increases due to high shape drag
Solution Approach 1:
The patent applies local quality by varying the fin length along the flow direction, with fins being shorter at the inlet and progressively longer toward the outlet. This non-uniform fin configuration optimizes heat exchange at different locations while managing pressure drop, as each section of the heat exchanger is tailored to the local flow and thermal conditions.
Solution Approach 2:
The patent implements dynamics through the progressive variation of fin length along the flow direction. Rather than using uniform fins, the dynamic configuration adapts the heat exchange surface area to the changing flow characteristics, allowing the system to maintain optimal performance across different operating conditions while controlling pressure losses.
2Quantity of substance
If the cross-sectional area of the fluid passage is increased to accommodate flow, then the flow capacity is improved, but the flow speed decreases leading to reduced exchange coefficient
Solution Approach 1:
The patent addresses this contradiction by making the fin length variable along the flow direction. This creates different local heat exchange characteristics: shorter fins at the inlet maintain higher exchange coefficients where flow speed is higher, while longer fins at the outlet compensate for the reduced flow speed, thereby maintaining overall heat exchange effectiveness despite the cross-sectional area increase.
3Area of stationary object
If the hydraulic diameter of the exchange surface increases linearly with distance from inlet, then the heat exchange surface area is improved, but the exchange coefficient decreases resulting in heterogeneity of heat exchange
Solution Approach 1:
The patent resolves the heterogeneity issue by implementing non-uniform fin length distribution. The fins are designed to be shorter at the inlet where the hydraulic diameter is smaller and exchange coefficient is higher, and progressively longer toward the outlet where the hydraulic diameter increases and exchange coefficient decreases. This compensates for the natural variation and achieves more uniform heat exchange distribution across the entire exchanger.
Solution Approach 2:
The patent applies parameter changes by systematically varying the fin length parameter along the flow direction. This geometric parameter modification allows control over the heat exchange characteristics at different locations, transforming the uniform fin design into a variable fin design that adapts to the changing hydraulic conditions and maintains exchange coefficient homogeneity.
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 improves overall exchange coefficients and maintains consistent thermal performance across the exchanger, reducing pressure drops and mass impact while enhancing integration into turbomachines.
Implementation Method 1
The heat exchanger comprises a plurality of fins configured to be swept by a first fluid in a first direction, the fins extending in a second direction between a first panel and a second panel
Implementation Method 2
a first fluid, for example hot exhaust gases, and a second fluid, for example an air flow circulating in the turbomachine, pass through the heat exchanger in two different directions
Implementation Method 3
the fins being arranged in a plurality of rows in a third direction and being staggered, each row of fins being parallel to one another and connected to one another
Data Source
AI summary
A heat exchanger for a turbomachine of an aircraft, the heat exchanger having a plurality of fins intended to be swept by a first fluid in a first direction, the fins extending in a second direction between a first panel and a second panel, being arranged in several rows in a third direction, and being arranged in a staggered manner, each row of fins being parallel and connected to one another. The heat exchanger can be annular, centered on the third direction and can have an inner cylindrical surface defining an inlet and an outer cylindrical surface defining an outlet, and the fins can have a length which decreases radially in the heat exchanger, in the first direction, between the inner cylindrical surface and the outer cylindrical surface.