Segmented Wick Heat Pipe for Long-Distance Condensate Return

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Solution Overview

Problem

Conventional heat pipes experience a significant performance drop as length increases, particularly in remote heat sink applications, due to reduced condensate return flow, limiting their effectiveness in cooling high-power components like ASICs.

Innovation Solution

A heat pipe design with multiple wick sections, including evaporator and condenser sections with varying porosities and a fluid transport section featuring grooved capillaries, enhanced by a mesh layer to improve condensate return, allowing for longer heat pipe lengths without performance degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If heat pipe length is increased to achieve remote heat sink configurations, then cooling flexibility is improved, but condensate return flow decreases and thermal performance deteriorates

Engineering Contradiction:

Improvecooling flexibilityVSAvoidthermal performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The heat pipe is divided into multiple sections with different wick structures: a first section with a first wick material, a second section with a second wick material, and a third section with a third wick material. Each section has optimized porosity and capillary properties tailored to its specific function, allowing the overall system to maintain performance over longer lengths while providing remote heat sink flexibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the heat pipe are given different local properties through varying wick materials and porosities. The evaporator section has lower porosity for efficient evaporation, the adiabatic section has intermediate porosity for vapor transport, and the condenser section has higher porosity for condensate return, optimizing each local region for its specific thermal task

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If heat pipe length is increased for remote heat sink applications, then adaptability is improved, but condensate return flow decreases

Engineering Contradiction:

Improveremote heat sink configuration capabilityVSAvoidcondensate return flow

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The condenser section is specifically designed with a third wick material having higher porosity than the evaporator section, creating optimized capillary channels that enhance condensate return flow. This segmented approach ensures sufficient condensate transport even in extended heat pipe configurations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The porosity parameter is varied across different sections of the heat pipe. The evaporator section has lower porosity (0.3-0.6), the adiabatic section has intermediate porosity (0.5-0.7), and the condenser section has higher porosity (0.6-0.8), optimizing each section's capillary pressure and condensate return characteristics for the specific thermal task at hand

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 design enhances cooling capacity and flexibility in remote heat sink configurations by increasing condensate return flow and maintaining thermal performance even with extended distances between evaporator and condenser sections.

Implementation Method 1

The evaporator section includes a first wick having a first porosity, the condenser section includes a second wick having a second porosity, and the fluid transport section is configured to transport vapor from the evaporator section to the condenser section, and to return condensate from condenser to evaporator

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

Heat pipes are constructed from a copper tube with sintered porous copper wick lining the inside surface of the tube. The tube is evacuated, water is added to saturate the wick structures and the tube is sealed

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

the evaporator section includes a first wick having a first porosity. The condenser section includes a second wick having a second porosity. The fluid transport section is configured to transport vapor from the evaporator section to the condenser section

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 4

The fluid transport section is configured to transport vapor from the evaporator section to the condenser section, and to return condensate from condenser to evaporator

Methodology Applied

Scientific EffectCondensation: Condensation

Data Source

PatentUS20250321059A1Multiple wick section heat pipe

Publication Date: 2025.10.16 CISCO TECHNOLOGY INC

AI summary

A heat pipe provides effective heat transfer. In one example, a heat pipe includes an evaporator section, a condenser section, and a fluid transport section. The evaporator section includes a first wick having a first porosity. The condenser section includes a second wick having a second porosity. The fluid transport section is configured to transport a fluid between the evaporator section and the condenser section.