Loop Heat Pipe Wick Compression for Stable Thermal Contact

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Solution Overview

Problem

Conventional loop heat pipes suffer from suboptimal cooling performance due to issues with the wick's ability to maintain stable thermal contact under varying conditions, leading to potential backflow and pressure losses during fluid circulation.

Innovation Solution

Incorporating an elastic wick inside the evaporator that is compressed and deformed to ensure stable contact with the heat receiver, combined with a design that manages capillary pressure and pressure losses through elastic deformation and capillary action to prevent backflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional wick is used in the evaporator, then the structure is simple, but the thermal contact stability is poor and backflow occurs during fluid circulation

Engineering Contradiction:

Improvethermal contact stabilityVSAvoidwick structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The wick is compressed to a specific density range (80-95% of original density) to optimize its mechanical properties. This parameter change enables the wick to generate sufficient elastic restoring force to maintain stable thermal contact with the evaporator wall while preventing backflow of the working fluid during circulation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The wick is designed with elastic properties allowing it to dynamically adjust its position and contact pressure. The elastic restoring force generated by compression enables the wick to adapt to thermal expansion and contraction of the evaporator, maintaining reliable thermal contact under varying operating conditions

Inventive Principle:

Principle #15Dynamics

2Reliability

If the wick is compressed to improve thermal contact, then thermal contact stability improves, but pressure loss during fluid circulation increases

Engineering Contradiction:

Improvethermal contact stabilityVSAvoidpressure loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The wick compression density is optimized to a specific range (80-95% of original density) that balances two competing requirements: sufficient compression to maintain stable thermal contact and prevent backflow, while limiting compression to preserve adequate porosity for fluid circulation. This optimal parameter range minimizes pressure loss while ensuring reliable thermal contact

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the wick is highly compressed to prevent backflow, then backflow prevention improves, but the elastic restoring force becomes insufficient to maintain contact

Engineering Contradiction:

Improvebackflow preventionVSAvoidelastic restoring force

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The wick compression is controlled within an optimal density range (80-95% of original density) that ensures the elastic restoring force remains sufficient. This parameter optimization prevents over-compression that would eliminate elastic recovery capability while still generating enough force to prevent backflow and maintain stable thermal contact during operation

Inventive Principle:

Principle #35Parameter changes

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 enhances the stability and efficiency of the loop heat pipe by maintaining consistent thermal contact and reducing system pressure losses, ensuring reliable operation even under varying temperatures and loads.

Implementation Method 1

the liquid-phase working fluid permeating into the wick and forming a boundary between the liquid phase working fluid and the vapor phase working fluid in the wick

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

a wick having an elasticity and provided inside the evaporator in a compressed and deformed state

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 3

The stress generated in the wick due to compressive deformation is greater than a pressure loss that occurs during circulation of the working fluid from the vapor-phase side of the boundary via the condenser back to the liquid-phase side of the boundary

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS12453049B2Loop heat pipe, cooling system, electronic equipment, and wick

Publication Date: 2025.10.21 RICOH CO LTD

AI summary

Disclosed is a loop heat pipe having an evaporator, a condenser, a vapor line connected between the evaporator and the condenser through which a vapor-phase working fluid flows, a liquid line connected between the condenser and the evaporator through which a liquid-phase working fluid flows, and a wick having an elasticity and provided inside the evaporator in a compressed and deformed state. The liquid-phase working fluid permeates into the wick, and a boundary between the liquid phase working fluid and the vapor phase working fluid is formed in the wick. A stress generated in the wick due to compressive deformation is greater than a pressure loss that occurs during circulation of the working fluid from the vapor-phase side of the boundary via the condenser back to the liquid-phase side of the boundary.