Thin Heat Pipe Variable Wick Structure for Capillary Pressure
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Solution Overview
Problem
Determining the optimal wick structure shape, pore radius, and size for thin heat pipes to facilitate efficient heat transfer and prevent drying out of the working fluid remains a challenge, as existing designs struggle to balance capillary pressure differential and heat flux transfer.
Innovation Solution
A thin heat pipe design with a wick structure disposed only on the lower inner wall, featuring varying thickness and shapes of wick structure portions to maximize vapor flow passage area, ensuring capillary forces effectively pull the working fluid from condenser to evaporator sections without drying out, using sintered metal powder for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wick structure thickness is increased to improve capillary pressure differential, then the heat flux transfer capability is improved, but the thickness of the thin heat pipe increases
Solution Approach 1:
The wick structure is designed with varying thickness along the heat pipe: thicker at the evaporator end to provide high capillary pressure for liquid return, and thinner at the condenser end to minimize overall thickness while maintaining vapor flow passage area. This local variation in wick thickness allows each section to be optimized for its specific function.
Solution Approach 2:
The patent transitions from a uniform wick structure to a variable thickness wick structure, adding dimensional variation to the wick design. This allows the system to achieve high capillary pressure where needed while maintaining thin overall profile, resolving the contradiction between thickness and capillary performance.
2Productivity
If the vapor flow passage area is increased to improve vapor flow, then the heat flux transfer is improved, but the wick structure coverage area is reduced
Solution Approach 1:
The wick structure coverage is optimized locally: full coverage at the evaporator section to maximize liquid supply and capillary action, and reduced coverage at the condenser section to maximize vapor flow passage area. This local optimization allows the system to achieve high heat flux transfer without requiring full wick coverage throughout.
3Reliability
If the pore radius is decreased to increase capillary pressure, then the liquid return capability is improved, but the heat flux transfer capability is reduced
Solution Approach 1:
The wick structure employs different pore sizes in different sections: smaller pores at the evaporator end to generate high capillary pressure for liquid return, and larger pores at the condenser end to facilitate high heat flux transfer and vapor flow. This spatial variation in pore radius allows the system to achieve both high liquid return capability and high heat flux transfer.
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 enhances thermal performance by increasing the vapor flow passage area and maintaining fluid circulation, preventing drying out and improving heat dissipation efficiency, with a 10-16% increase in heat dissipation capacity compared to standard designs.
Implementation Method 1
Heat pipes can include wick structures disposed within the heat pipes to facilitate movement (e.g., capillary force) of working fluid within the heat pipes, particularly movement of the working fluid from condenser sections of the heat pipes to evaporator sections of the heat pipes.
Implementation Method 2
Sintered metal powder capillary structures adhere to inner walls of the heat pipes with high contact, reducing heat resistance between the wick structure and the inner walls of the heat pipes.
Implementation Method 3
Heat pipes are passive two-phase heat transfer devices using evaporation and condensation cycles of working fluid to move heat from a heat source on the electronics device to a location spaced away from the heat source
Implementation Method 4
Heat pipes are passive two-phase heat transfer devices using evaporation and condensation cycles of working fluid to move heat from a heat source on the electronics device to a location spaced away from the heat source
Data Source
AI summary
A thin heat pipe including a thin heat pipe container, wick structure, working fluid, and vapor flow passage section is provided. The thin heat pipe container includes a lower inner wall and upper inner wall. The wick structure is disposed on the lower inner wall and includes a first wick structure portion connected to a second wick structure portion. The vapor flow passage section is configured for vapor to flow therethrough. A thickness of the second wick structure portion is lesser than a thickness of the first wick structure portion and the second wick structure portion does not contact, contact points between the upper inner wall and lower inner wall. The wick structure defines the vapor flow passage section. The first wick structure contacts the upper inner wall and second wick structure. Working fluid is pulled from vapor condenser sections to high temperature sections via the wick structure.