Permeability Gradient Wicks for Uniform Vapor Chamber Fluid Delivery
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Solution Overview
Problem
High heat fluxes from multiple heat sources interfaced with vapor chambers can lead to large variations in fluid mass flux, causing pressure drops and potential dryout in the porous wick structure, resulting in inadequate fluid supply to heat sources, which increases thermal resistance and reduces cooling efficiency.
Innovation Solution
A porous wick structure with a permeability gradient is introduced, featuring regions of higher permeability near heat sources to ensure uniform fluid flow, achieved through sintered particles or chemical treatments, optimizing fluid distribution and minimizing flow resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform porous wick structure is used, then the structure is simple to manufacture, but the fluid flow becomes non-uniform causing dryout near heat sources
Solution Approach 1:
The wick structure is designed with spatially varying permeability properties - higher permeability regions are positioned near heat sources to enhance fluid delivery, while lower permeability regions are positioned away from heat sources. This local differentiation ensures uniform fluid distribution across all heat sources and prevents dryout, while maintaining manufacturability through controlled variation in particle size or pore structure during fabrication.
2Power
If high heat fluxes are applied to multiple heat sources, then the cooling power is sufficient, but the fluid mass flux varies greatly causing pressure drops
Solution Approach 1:
The permeability parameter of the wick structure is deliberately varied across different spatial locations to compensate for the non-uniform fluid mass flux caused by high heat fluxes from multiple heat sources. By positioning higher permeability regions where fluid demand is highest (near heat sources), the structure reduces flow resistance and minimizes pressure drops, enabling reliable operation under high power density conditions.
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 permeability gradient ensures a uniform fluid flow to heat sources, maintaining continuous fluid supply and enhancing cooling efficiency by reducing thermal resistance and preventing dryout, thus effectively managing high power density heat loads.
Implementation Method 1
A porous wick structure lining the inside of the vapor chamber holds and pumps the liquid back to the heat sources via capillary action
Implementation Method 2
The vapor chamber utilizes two-phase boiling/condensing phenomena in order to uniformly spread the heat from the surface of the heat sources
Implementation Method 3
The vapor chamber utilizes two-phase boiling/condensing phenomena in order to uniformly spread the heat from the surface of the heat sources
Implementation Method 4
The vapor flows away from the hotspot and condenses over a heat rejection surface adjacent to a heat sink
Implementation Method 5
The evaporator-feeding wick comprises a first region having a higher permeability than at least a second region to form a permeability gradient thereon, such that the working fluid has a uniform flow to the plurality of heat sources
Data Source
AI summary
Embodiments described herein disclose a vapor chamber including a thermally-conductive evaporator wall, a thermally-conductive condenser wall and a volume therebetween defining a vapor core for transporting a vapor of a working fluid from the evaporator wall to the condenser wall. The outer surfaces of the evaporator wall and the condenser wall are configured to be in thermal contact with a plurality of heat sources and a heat sink respectively. The vapor chamber further includes a porous wick structure for holding and pumping the working fluid towards the plurality of heat sources. The wick structure comprises an evaporator-feeding wick having an inner surface in thermal contact with an inner surface of the evaporator wall. The evaporator-feeding wick comprises a first region having a higher permeability than at least a second region to form a permeability gradient, such that the working fluid has a uniform flow to the plurality of heat sources.