Compensational Wick Geometry for Heat Pipe Fluid Flow
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Solution Overview
Problem
Conventional two-phase thermodynamic systems, such as heat pipes and vapor chambers, face issues with evaporator regions drying out and condenser regions flooding, which impede the phase-change processes and reduce thermal conductivity, especially at high heat power rates due to increased resistance to liquid flow and reduced cavity sizes.
Innovation Solution
The implementation of a compensational wick geometry with varying geometric features between condenser and evaporator regions to enhance capillary forces while minimizing fluid flow resistance, including narrower and deeper channels, and varying rib undercut angles and shoulder radii, ensures continuous liquid flow to the evaporator regions and prevents flooding at the condenser regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If cavity size is reduced to improve capillary forces, then capillary action is enhanced, but resistance to liquid flow increases
Solution Approach 1:
The wicking structure implements spatially varying geometric features where different regions have different cavity dimensions. Specifically, the structure includes regions with smaller cavity sizes to generate strong capillary forces for liquid absorption, and regions with larger cavity sizes to provide low-resistance flow paths for liquid return, with each region optimized for its specific function in the liquid transport cycle
Solution Approach 2:
The invention transitions from uniform one-dimensional cavity sizing to multi-dimensional geometric variation, incorporating changes in cavity width, depth, and shape across different spatial locations. This dimensional complexity allows simultaneous optimization of capillary force generation and flow resistance reduction in different regions of the same wicking structure
2Productivity
If liquid flow resistance is reduced to prevent evaporator drying, then liquid return is improved, but capillary forces may become insufficient
Solution Approach 1:
The wicking structure implements spatially varying geometric features where different regions have different cavity dimensions. Specifically, the structure includes regions with smaller cavity sizes to generate strong capillary forces for liquid absorption, and regions with larger cavity sizes to provide low-resistance flow paths for liquid return, with each region optimized for its specific function in the liquid transport cycle
Solution Approach 2:
The wicking structure is divided into functionally distinct segments: an absorption region with small cavities for capillary uptake, a transport region with optimized geometry for low-resistance flow, and a release region for liquid delivery to the evaporator. This segmentation allows each zone to be optimized for its specific role without compromising overall system performance
3Reliability
If evaporator regions are kept wet to maintain phase-change processes, then thermal conductivity is improved, but condenser regions may flood
Solution Approach 1:
The wicking structure implements spatially varying geometric features where different regions have different cavity dimensions. Specifically, the structure includes regions with smaller cavity sizes to generate strong capillary forces for liquid absorption, and regions with larger cavity sizes to provide low-resistance flow paths for liquid return, with each region optimized for its specific function in the liquid transport cycle
Solution Approach 2:
The wicking structure creates a self-regulating liquid transport system where capillary forces automatically adjust liquid absorption based on local conditions. When evaporator regions approach dry-out, the capillary pressure gradient increases to draw more liquid; when condenser regions approach flooding, the geometry facilitates liquid redistribution, maintaining stable operation across varying thermal loads
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 design maintains sufficient capillary forces at the evaporator regions and low fluid flow resistance, preventing dry-out and flooding, allowing for higher throughput heat power rates and extended exploitation of phase-change processes for enhanced thermal conductivity.
Implementation Method 1
Various wicking structures have been designed that exploit capillary action to continuously absorb liquid into various solid structures as it condenses at the condenser regions, and to then draw the absorbed liquid back to the evaporator regions.
Implementation Method 2
The absorbed heat causes a working fluid to evaporate from a liquid into a vapor phase, which stored the heat in latent form at a slightly lower temperature.
Implementation Method 3
The vapor then flows to condenser regions, where it condenses back into liquid phase, causing the stored latent heat to be released and dissipated into an ambient environment.
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A thermodynamic system includes a compensational wick geometry to enhance fluid flow between a condenser region and an evaporator region. Geometric features are modulated between a condenser region and an evaporator region to increase capillary forces within wicking structures without excessively increasing hydraulic resistance to the liquid flowing through these return-path wicking structures. The thermodynamic system may include a liquid flow path having channels extending from the condenser region to the evaporator region. At various segments of the channels, individual cavity sizes are reduced to induce capillary action toward the evaporator region. Various geometric features compensate for these cavity size reductions, to mitigate the effects of increased resistances to liquid flow. In this way, capillary forces toward evaporator regions remain sufficiently high, while hydraulic resistance to fluid flow remains sufficiently low so as to prevent evaporator regions from drying out even at high thermal absorption rates.