Fractal Flow Splitters for Heat Exchanger Thermal Stress Reduction
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Solution Overview
Problem
Heat exchangers operating at elevated temperatures face short service lives and increased maintenance due to high cyclic thermal stress caused by mismatched thickness and mass in manifolds, leading to thermal discontinuities.
Innovation Solution
An additively-manufactured heat exchanger with fractal flow splitters and an additively-manufactured heat exchanger core, where fractal splitters are used in the inlet and outlet manifolds to manage fluid flow and reduce thermal stress through optimized geometric design and material selection, such as nickel and Inconel alloys, allowing for improved thermal robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If manifolds are made thick to withstand pressure loads, then pressure containment is improved, but thermal stress increases due to mass discontinuity
Solution Approach 1:
The manifold is segmented into multiple flow channels separated by thin walls, allowing the overall structure to maintain pressure containment while individual thin walls reduce thermal mass and thermal stress. The fractal splitter further segments the flow distribution, creating a hierarchical structure that balances structural integrity with thermal performance.
Solution Approach 2:
The patent employs composite construction where the manifold integrates both thick regions for pressure containment and thin walls for thermal performance. This composite approach allows different parts of the same component to have different thicknesses optimized for their specific functions, resolving the contradiction between pressure strength and thermal stress resistance.
2Reliability
If manifold thickness is reduced to improve thermal robustness, then thermal stress decreases, but pressure containment capability deteriorates
Solution Approach 1:
Instead of using a single thick wall, the manifold uses multiple thin-walled flow channels arranged in parallel. This segmentation allows the structure to contain pressure effectively through the collective strength of multiple channels while each individual thin wall maintains low thermal mass and high thermal robustness.
Solution Approach 2:
The patent transitions from a simple thick-walled pressure vessel to a complex three-dimensional network of thin-walled channels. By utilizing the third dimension and creating a spatially distributed flow channel network, the design achieves pressure containment through geometric arrangement rather than relying on increased wall thickness.
3Ease of manufacture
If conventional flow distribution is used, then manufacturing is simpler, but thermal stress increases due to flow imbalances
Solution Approach 1:
The fractal splitter creates locally optimized flow distribution where each branch is specifically designed to deliver equal flow to its associated heat exchanger channels. This local quality optimization ensures uniform thermal loading across all channels, reducing thermal stress while maintaining manufacturability through additive manufacturing processes.
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 solution enhances the thermal robustness of heat exchangers by reducing thermal stress and extending service life through optimized fluid flow management and material properties, improving heat transfer efficiency while maintaining structural integrity.
Implementation Method 1
Heat exchanger with fractal flow splitters... fractal splitters are used in the inlet and outlet manifolds to manage fluid flow
Implementation Method 2
Heat exchangers are well known in the aviation arts and in other industries for providing a compact, low-weight, and highly-effective means of exchanging heat from a hot fluid to a cold fluid
Implementation Method 3
exchanging heat from a hot fluid to a cold fluid
Implementation Method 4
Heat exchangers that operate at elevated temperatures often have short service lives and/or require increased maintenance as a result of high cyclic thermal stress
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A flow manifold for a heat exchanger core includes a number of fractal flow splitters (50) arranged in a grid pattern of layers each fluidly connected to a corresponding first circuit layer, a flow plenum having a number of flow channels (52) that are fluidly connected to an associated fractal flow splitter, one or more flow dividing vanes (56) located in each flow channel thereby dividing the associated flow channel into two or more sub-channels, and an outer manifold surrounding the fractal flow splitters and configured to direct a first circuit flow into or out of the heat exchanger core. Each fractal flow splitter has an open end and a plenum end, and provides a transition from the open end to the flow plenum.