Heat Exchanger Riblet Geometry for Additive Surface Finish Control
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Solution Overview
Problem
Additive manufacturing of plate-fin heat exchangers results in unpredictable surface finishes due to the difficulty in building horizontal features with high surface integrity and uniformity, leading to degraded thermodynamic and hydrodynamic performance.
Innovation Solution
Incorporating non-horizontal surface geometries such as riblets and turbulators with controlled angles in the heat exchanger design to improve surface finish and reduce surface roughness, thereby enhancing the manufacturability and performance of the heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If additive manufacturing is used to manufacture heat exchanger components, then manufacturing complexity is reduced and design flexibility is improved, but surface finish quality deteriorates due to unpredictable surface roughness on horizontal features
Solution Approach 1:
The patent applies asymmetry by designing riblet features with specific non-horizontal orientations (e.g., 45-degree angles) relative to the additive manufacturing build direction. This asymmetric positioning ensures that critical heat transfer surfaces are not built horizontally, thereby avoiding the characteristic surface roughness problems of horizontal additive manufacturing while still utilizing the manufacturing method's overall benefits
Solution Approach 2:
The patent transitions from two-dimensional horizontal heat transfer surfaces to three-dimensional oriented surfaces by incorporating riblets that extend at specific angles to the build direction. This dimensional change allows the heat transfer surfaces to be constructed in multiple orientations, avoiding the problematic horizontal plane while maintaining effective heat transfer area
2Manufacturing precision
If non-horizontal surface geometries such as riblets are incorporated into the heat exchanger design, then surface finish quality and heat transfer performance are improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by adding riblet features only to specific regions where heat transfer enhancement is most beneficial, rather than making the entire heat exchanger complex. The riblets are positioned on particular heat transfer surfaces with specific orientations, while other portions of the component maintain simpler geometries suitable for additive manufacturing
Solution Approach 2:
The patent changes geometric parameters by specifying particular angles (e.g., 45 degrees) and dimensions for the riblet features relative to the build direction. These controlled parameter changes create predictable surface finishes and improve heat transfer performance while maintaining manufacturability through defined geometric relationships
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 achieves a smoother, more uniform surface finish with reduced surface roughness, resulting in improved laminar flow and increased heat transfer efficiency with minimal pressure drop, thus enhancing the overall thermodynamic and hydrodynamic performance of the heat exchanger.
Implementation Method 1
resulting in improved laminar flow
Implementation Method 2
exchanging heat from a hot fluid to a cold fluid
Implementation Method 3
enhancing the manufacturability and performance of the heat exchanger
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
An additively-manufactured heat exchanger includes fluidly-separated alternating first and second layers (62, 64)having respective flow channels (74, 78) which can include one or more features that is either a riblet (32) or a turbulator (42). A riblet includes a riblet peak (34) and/or a riblet valley (3 8), which has a riblet slope (36), and the riblet peak and/or riblet valley has a riblet axis (33) that is generally parallel to either the first fluid flow direction or the second fluid flow direction. A turbulator (42) includes a turbulator peak (44) and/or a turbulator valley (48), which has a turbulator slope (46), and the turbulator peak and/or turbulator valley has a turbulator axis (43) that is generally perpendicular to either the first fluid flow direction or the second fluid flow direction. The respective slope angles are generally 25 - 65 deg. relative to build-axis, thereby resulting in improved surface roughness and uniformity control during the build process.