Hybrid Wick Heat Pipe for Freeze-Thaw Protection
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Solution Overview
Problem
Current heat pipes are susceptible to freeze/thaw damage due to excess working fluid and have issues with fluid distribution, especially in extreme conditions like subfreezing temperatures and low gravity, where capillary action is insufficient for fluid replenishment, leading to dry-out and inefficient heat transfer.
Innovation Solution
A hybrid wick design with a thicker portion for the reservoir region to hold fluid when idle and a thinner portion for the evaporator region, combined with a wickless condenser region, allows for efficient fluid management and heat transfer, using a second heat source to promote drying and fluid circulation between the evaporator and condenser regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform layer of wick is used throughout the heat pipe, then the wick structure is simple and easy to manufacture, but the wick thickness is uniformly thicker resulting in higher ΔTwick and reduced heat transfer efficiency
Solution Approach 1:
The patent applies local quality by varying the wick thickness in different regions of the heat pipe. The wick is thinner in the evaporator region to reduce thermal resistance and improve heat transfer efficiency, while being thicker in the reservoir region to provide adequate fluid storage. This localized variation optimizes the thermal performance without significantly complicating the manufacturing process.
2Device complexity
If excess working fluid is supplied in the heat pipe, then the wick can be simpler and shorter, but fluid pools form in certain areas that are not absorbed by the wick and are susceptible to freeze/thaw damage
Solution Approach 1:
The patent uses local quality by creating a thicker wick region specifically in the reservoir area to absorb and retain excess working fluid, preventing pooling in other regions. This localized fluid management eliminates the reliability issue of freeze/thaw damage while keeping the overall wick structure relatively simple.
Solution Approach 2:
The patent applies preliminary action by pre-positioning the excess working fluid in the reservoir region during manufacturing, so that when the heat pipe operates, the fluid is already in the correct location to be absorbed by the thicker wick portion, preventing pooling and freeze/thaw damage before they can occur.
3Weight of moving object
If capillary action is used to draw liquid from reservoir to heat input zone, then the wick can be thinner and lighter, but the heat input zone becomes more susceptible to dry-out condition
Solution Approach 1:
The patent applies local quality by making the wick thinner in the evaporator region to reduce weight, while maintaining adequate thickness in the reservoir region to ensure sufficient fluid supply. The thinner wick in the evaporator reduces overall weight but is compensated by the fluid storage capacity of the reservoir region's thicker wick.
Solution Approach 2:
The patent uses copying by creating a condensed fluid film on the inner wall of the heat pipe that serves as a backup fluid source. This fluid film acts as a copy or alternative supply mechanism that can replenish the wick in the evaporator region if capillary action becomes insufficient, preventing dry-out conditions.
4Power
If a very large ratio of condenser area to heat input area is used (as in space radiator), then the heat dissipation capacity is increased, but it becomes particularly difficult to address simultaneous challenges of freeze/thaw and low ΔTwick
Solution Approach 1:
The patent applies local quality by concentrating the fluid storage function in a localized thicker wick region in the reservoir, while keeping the wick thin in the evaporator region. This allows the system to handle large condenser-to-evaporator area ratios by efficiently managing fluid distribution through localized wick structure variations, addressing both freeze/thaw prevention and low ΔTwick requirements simultaneously.
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 hybrid wick design effectively prevents fluid pooling and freeze/thaw damage, ensuring consistent heat transfer and reducing the risk of dry-out, even in extreme environments by maintaining fluid circulation and utilizing the working fluid efficiently between the evaporator and condenser regions.
Implementation Method 1
replenishment of the wick in the heat input zone depends on capillary action to draw liquid from a reservoir
Implementation Method 2
a first part of a remainder of the working fluid has been heated to a vapor form
Implementation Method 3
a second part of the remainder of the working fluid is in condensed form on the inside wall of the tube in the condenser region
Implementation Method 4
a sealed tube having along its length a reservoir region, an evaporator region, and a condenser region
Data Source
AI summary
A heat pipe system for conducting thermal energy. The heat pipe system includes a sealed tube having along its length a reservoir region, an evaporator region, and a condenser region, the tube having a first end and a second end and an inside wall. The system also includes a wick disposed adjacent the inside wall of the tube, the wick including a first portion at the first end of the tube and a second portion adjacent the first portion, wherein the first portion of the wick is thicker than the second portion of the wick, and wherein the second portion of the wick does not extend to the second end of the tube. The system also includes a working fluid contained within the tube.