Nanoporous Composite Wick for High-Acceleration Heat Pipes
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Solution Overview
Problem
Conventional heat pipes face challenges in generating sufficient capillary wicking force to overcome external forces like gravity and inertial forces, particularly in aerospace applications where dynamic loads exceed 1 atmosphere, leading to potential dry-out of the evaporator due to insufficient pumping capability.
Innovation Solution
A wicking apparatus with a composite membrane structure featuring a nanoporous filler material and a substrate layer, optimized for pore sizes between 0.2 to 200 nanometers, allowing operation at large negative pressures to overcome external influences and maintain liquid flow against gravity and acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional wicking structures are used, then the heat pipe can operate with simple structure, but the capillary wicking force is insufficient to overcome external forces like gravity and inertial forces in dynamic environments
Solution Approach 1:
The patent employs a composite wick structure consisting of a porous substrate layer (providing mechanical strength) combined with a nanoporous coating layer (providing enhanced capillary action). This composite approach allows the wick to generate sufficient capillary wicking force to overcome external forces like gravity and inertial forces in dynamic environments, while maintaining structural integrity.
Solution Approach 2:
The patent utilizes nanoporous materials with controlled pore sizes (1-100 nanometers) in the coating layer to dramatically enhance capillary action. The nanoporous structure creates extremely fine capillaries that generate high capillary pressures, enabling the wick to pump liquid against strong external forces such as those encountered in aerospace applications with accelerations exceeding 1 g.
2Reliability
If the liquid conduit length is increased to accommodate dynamic environments, then the heat pipe can operate under higher accelerations, but the pressure drop and flow resistance increase
Solution Approach 1:
The patent changes the pore size parameter of the wicking material to the nanometer scale (1-100 nm), which dramatically increases the capillary pressure generation capability. This parameter change allows the system to maintain adequate liquid return flow even when operating at large negative pressures (up to -100 atmospheres) required for long liquid conduits in high-acceleration environments.
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 solution enables heat pipes to operate effectively at negative pressures up to -100 atmospheres, allowing longer liquid conduit lengths and preventing dry-out even under high accelerations, thus enhancing the reliability and efficiency of heat transfer in dynamic environments.
Implementation Method 1
The pumping capability of the wick is adversely affected by height (operation against gravity) and length (mass flow resistance). Careful design consideration must be given to the amount of heat that must be removed via evaporative cooling and assuring an adequate supply of working fluid to accomplish the heat removal.
Implementation Method 2
As one end of the heat pipe is exposed to the heat source, the working fluid in that end draws thermal energy from the heat source and vaporizes, increasing the local vapor pressure in the tube. The latent heat of evaporation absorbed by the vaporization of the working fluid reduces the temperature at the hot end of the pipe.
Implementation Method 3
The vapor pressure over the working fluid at the heat source side of the pipe is higher than the equilibrium vapor pressure over the condensing working fluid at the cooler end of the pipe, and this pressure difference drives a rapid mass transfer to the condensing end where the excess vapor condenses, releases its latent heat, and warms the cool end of the pipe.
Data Source
AI summary
A wicking apparatus includes a composite condenser membrane comprising a substrate layer, a vapor inlet end, a liquid discharge end, a plurality of cavities disposed in the substrate layer fluidly coupling the vapor inlet end to the liquid discharge end, and a nanoporous filler material disposed within the plurality of cavities. The nanoporous filler material has a first plurality of open pores with a maximum diameter in the range of 0.2 to 200 nanometers. The first end of the liquid conduit is fluidly coupled to the liquid discharge end of the composite condenser membrane. The wicking apparatus further includes a wick composite evaporator membrane comprising a substrate layer, a liquid inlet end, a vapor discharge end, a plurality of cavities disposed in the substrate layer fluidly coupling the liquid inlet end to the second end of the liquid conduit, and a nanoporous filler material disposed within the plurality of cavities.