Loop Heat Pipe Evaporator Layout for Tilt-Stable Heat Transport
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Solution Overview
Problem
Miniaturized electronic devices in transportation machines face reduced heat transport efficiency due to position changes, which disrupt the circulation of the working fluid in loop heat pipes using gravity for fluid circulation, leading to decreased heat transport rates.
Innovation Solution
An evaporator design with working fluid outlets located at diagonally opposite corners of the top surface, ensuring that at least one outlet remains above an imaginary liquid surface despite changes in position, maintaining smooth fluid flow and circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the working fluid outlet is located on the side surface of the evaporator, then the structure is simple, but tilting of the evaporator causes the outlet to be below the liquid surface, reducing flow rate and heat transport rate
Solution Approach 1:
The working fluid outlet is relocated from the side surface to the top surface of the evaporator. This dimensional change ensures that the outlet remains above the liquid surface even when the evaporator is tilted, preventing liquid submersion and maintaining proper two-phase flow conditions for heat transport
2Adaptability or versatility
If the evaporator is positioned in a transportation machine that changes position, then the system is adaptable to different applications, but the drive force for working fluid circulation decreases due to position changes
Solution Approach 1:
By positioning the working fluid outlet on the top surface at a corner, the design ensures that gravity and buoyancy forces continuously act to drive two-phase flow toward the outlet regardless of the evaporator's tilt angle, maintaining circulation reliability across different positions
Solution Approach 2:
The outlet is positioned at a corner rather than at the center, creating an asymmetric configuration that ensures one corner remains highest relative to the liquid-vapor interface during tilting, optimizing the drive force for fluid circulation
3Ease of operation
If the working fluid outlet is below the liquid surface, then liquid can easily exit, but the flow rate of working fluid is reduced and heat transport rate decreases
Solution Approach 1:
The outlet is positioned on the top surface rather than the side surface, ensuring it remains above the liquid surface during operation. This allows proper two-phase flow conditions where vapor carries liquid droplets to the outlet without the outlet being submerged, maintaining optimal heat transport rate
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 prevents disruption of the working fluid flow and maintains a stable heat transport rate even when the evaporator is tilted, ensuring continuous and efficient heat transfer in transportation machines.
Implementation Method 1
In the evaporator, the working fluid in a liquid phase is heated by heat transferred from a heat-generating element, and a part of the working fluid changes into a gas phase
Implementation Method 2
a heat-absorbing element disposed on at least one of the front and back surfaces and thermally connected to the heat source
Implementation Method 3
The gas-liquid two-phase working fluid moves in the vapor conduit under the action of pressure difference and buoyancy and reaches the condenser
Implementation Method 4
The gas-liquid two-phase working fluid moves in the vapor conduit under the action of pressure difference and buoyancy
Implementation Method 5
The liquid-phase working fluid returns to the evaporator under the action of capillary force and/or gravity
Implementation Method 6
The liquid-phase working fluid returns to the evaporator under the action of capillary force and/or gravity
Data Source
Figure 1~2
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AI summary
An evaporator includes: a housing having a plurality of surfaces including a front surface and a back surface, at least one of the front and back surfaces having the largest area among the plurality of surfaces; and a heat-absorbing element disposed on at least one of the front and back surfaces and thermally connected to a heat source. The housing includes: at least one working fluid inlet located in a surface of the housing, the surface being other than a top surface of the housing; and at least one pair of working fluid outlets located respectively in opposite longitudinal end portions of the top surface.