Heat Pipe Wick Expansion Control for Startup Deformation
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Solution Overview
Problem
Heat pipes used in nuclear reactors face issues with wick deformation due to differential thermal expansion between the wick and the heat pipe wall, leading to compromised capillary capability during non-uniform heating conditions, particularly during reactor startup.
Innovation Solution
A thermal expansion modification device is introduced, comprising a wick plug and a tube plug that are coupled together to prevent excessive axial movement of the wick, ensuring sufficient space for thermal expansion, using materials with different thermal expansion coefficients to maintain compatibility and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wick and heat pipe wall are made from different materials with different thermal expansion coefficients, then differential thermal expansion is allowed during operation, but the wick may deform during non-uniform heating conditions (startup) due to lack of locating features
Solution Approach 1:
A locating feature (protrusion and recess) is introduced as an intermediary element between the wick and heat pipe wall. This locating feature prevents excessive axial movement of the wick during non-uniform heating while allowing differential thermal expansion during normal operation. The locating feature acts as a mediator that reconciles the conflicting requirements of material diversity and structural stability.
2Stability of the object's composition
If the wick is constrained at both ends during startup, then the wick is held in place, but large compressive forces develop causing mechanical deformation
Solution Approach 1:
The constraint system is segmented into two parts: the locating feature that provides axial positioning and the floating annular wick design that allows radial and axial differential expansion. This segmentation enables the wick to be positioned stably during startup while preventing the development of large compressive forces that would cause deformation.
3Reliability
If the wick is allowed to float freely, then differential thermal expansion occurs without damage, but excessive axial movement occurs during non-uniform heating
Solution Approach 1:
The wick is designed with dynamic positioning capabilities through the locating feature that allows controlled axial movement. The floating annular wick can adjust its axial position dynamically in response to thermal expansion while the locating feature prevents excessive movement. This dynamic design maintains wick integrity while controlling axial position.
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 effectively prevents wick deformation, ensuring consistent heat transfer performance by allowing for differential thermal expansion without compromising the capillary function of the wick, thus maintaining efficient heat transfer in nuclear reactor applications.
Implementation Method 1
The condensed liquid is then returned to the evaporator section through the wick by capillary action
Implementation Method 2
The working fluid is configured to absorb heat in the evaporator section and vaporize. The saturated vapor, carrying latent heat of vaporization, flows towards the condenser section
Implementation Method 3
The saturated vapor, carrying latent heat of vaporization, flows towards the condenser section
Implementation Method 4
In the condenser section, the vapor condenses into a liquid and gives off its latent heat
Implementation Method 5
providing space between the two to allow for radial and marginal axial differential thermal expansion
Data Source
AI summary
A heat pipe includes: an elongate tube defining a longitudinal axis; an annular wick positioned in the elongate tube; a wick plug positioned in the elongate tube and attached to an end of the annular wick, where the wick plug includes an annular body defining an opening; a thermal expansion modification device including: an annular plug attached to an end of the elongate tube; and an elongate stem extending from the annular plug and through the opening in the wick plug, where the elongate stem defines a protrusion extending radially relative to the longitudinal axis toward the elongate tube, and where the wick plug is positioned intermediate the protrusion and the annular plug; and an end cap attached to the annular plug.