Annular Heat Pipe Wick Structure for Capillary Pressure and Condensate Flow
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Solution Overview
Problem
Current heat pipe wick formation technologies face limitations in achieving high power density operation due to high resistance to condensate flow, non-metallic impurities leading to corrosion, and suboptimal capillary pressure rise, which affect the efficiency and longevity of heat pipes, especially in high-temperature applications.
Innovation Solution
A method involving the wrapping of fine mesh screens around a mandrel, followed by diffusion bonding and etching to form a porous wick structure with controlled pore sizes, minimizing non-metallic impurities and maximizing capillary pressure, allowing for efficient condensate return and vapor flow in heat pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If homogeneous wick structure is used, then capillary pressure rise is achieved, but resistance to condensate flow is high
Solution Approach 1:
The wick is segmented into two distinct functional zones: a porous region for capillary action and meniscus formation, and an annular gap region for low-resistance condensate flow. This segmentation allows each zone to optimize its specific function without compromising the other, resolving the contradiction between capillary pressure generation and flow resistance.
Solution Approach 2:
Different regions of the wick are given different structural qualities: the porous region has fine pores for capillary pressure, while the annular gap has larger open space for free flow. This local differentiation of properties allows simultaneous optimization of both capillary pressure rise and condensate flow characteristics.
2Productivity
If fine pores are used to maximize capillary pressure, then heat transfer capability improves, but resistance to condensate flow increases
Solution Approach 1:
The wick structure separates the heat transfer function (porous region with fine pores) from the flow return function (annular gap region). This allows fine pores to maximize capillary pressure for heat transfer while the annular gap provides a parallel low-resistance path for condensate return.
Solution Approach 2:
The condensate flow path is moved from the axial direction through pores to a radial annular gap region. This dimensional change creates an alternative flow path that bypasses the restrictive pore structure, reducing flow resistance while maintaining heat transfer capability.
3Object-generated harmful factors
If compound wick geometry is used, then condensate flow resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The porous wick material is nested within the annular gap structure, with the porous region occupying the central area and the annular gap surrounding it. This nested configuration achieves compound wick functionality while maintaining a relatively simple overall geometry that can be manufactured using conventional techniques.
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 method enhances heat pipe performance by reducing resistance to condensate flow, promoting corrosion-free operation, and achieving stable capillary pressure, thereby improving heat transfer rates and extending the lifespan of high-temperature heat pipes.
Implementation Method 1
diffusion bonding the assembly at a temperature sufficiently high achieving self-diffusion of the plurality of layers of the fine mesh screen, used to form the wick, to themselves
Implementation Method 2
These menisci collectively produce a capillary pressure rise that is a driving potential enabling heat pipe operation
Implementation Method 3
In the heated zone of a heat pipe, evaporation of the liquid produces vapor. Vaporization increases pressure on the concave (vapor) side of the liquid meniscus that wets the wick
Implementation Method 4
etching the mandrel and sheath from the diffusion bonded assembly, leaving the wick as a porous tube
Data Source
AI summary
A method for forming an annular heat pipe wick in a controlled atmosphere includes wrapping a plurality of layers of a fine mesh screen around a mandrel to form a wick. The method also includes inserting the mandrel and the wick into a sheath, and compressing the wick between the sheath and the mandrel to form an assembly. The compressing of the wick comprises applying pressure to an exterior of the mandrel and the sheath. The method further includes diffusion bonding the assembly at a temperature sufficiently high achieving self-diffusion of the plurality of layers of the fine mesh screen used to form the wick to themselves. The method also includes cooling the diffusion bonded assembly to room temperature, and etching the mandrel and sheath from the diffusion bonded assembly, leaving the wick as a porous tube.