Thermal Performance of a Thin Wick-free Vapor Chamber with Liquid-assisted Cooling

Core Concepts

Thin wick-free vapor chambers with wettability-patterned surfaces can achieve significantly lower thermal resistances compared to non-patterned designs, while maintaining performance across a wide range of fluid charging ratios.

Abstract

The paper presents the development and experimental evaluation of a thin (3 mm) wick-free vapor chamber (VC) with liquid-assisted cooling. The key highlights are:

A specialized experimental setup was developed to test thin wick-free VCs, with charging and degassing ports on the condenser side to ensure proper sealing during experimentation.

Two VC designs were tested - one with a uniformly hydrophobic condenser and superhydrophilic evaporator, and another with wettability-patterned condenser and evaporator surfaces.

The patterned VC exhibited significantly lower thermal resistance (0.12 K/W) compared to the non-patterned VC (0.40 K/W), at a power input of 10 W and 22.5 W respectively.

The patterned VC's thermal resistance was found to be largely independent of the fluid charging ratio, unlike the non-patterned VC where higher charging ratios were required at higher power inputs to prevent thermal dry-outs.

The wettability patterns on the evaporator confine the liquid within superhydrophilic tracks, ensuring adequate liquid supply to the heated area without dry-out. The patterned condenser efficiently drains the condensate onto the evaporator, enabling unhindered vapor flow.

The results demonstrate the effectiveness of wettability patterning in improving the thermal performance and operational range of thin wick-free VCs.

Stats

The lowest thermal resistance of 0.12 K/W was observed for the patterned VC at a power input of 10 W and a charging ratio of 24%.
The lowest thermal resistance of 0.40 K/W was observed for the non-patterned VC at a power input of 22.5 W and a charging ratio of 24%.

Quotes

"The patterned VCs exhibit low thermal resistance independent of fluid charging ratio, while withstanding higher power inputs without thermal dry-outs."
"The wettability patterns on the evaporator confine the liquid within superhydrophilic tracks, ensuring adequate liquid supply to the heated area without dry-out."

Key Insights Distilled From

Thermal Performance of a Liquid-cooling Assisted Thin Wickless Vapor Chamber

by Arani Mukhop... at arxiv.org 05-01-2024

https://arxiv.org/pdf/2404.19203.pdf

Deeper Inquiries

How can the wettability patterns on the evaporator and condenser be further optimized to achieve even lower thermal resistances in thin wick-free vapor chambers?

To achieve even lower thermal resistances in thin wick-free vapor chambers, the wettability patterns on the evaporator and condenser can be further optimized in several ways:

Enhanced Pattern Design: The design of the wettability patterns can be optimized to ensure efficient drainage of condensate from the condenser to specific locations on the evaporator. By refining the patterns to facilitate rapid and directed transport of the working fluid, the heat transfer efficiency can be improved.

Advanced Surface Functionalization: Utilizing advanced surface functionalization techniques, such as nanostructuring or chemical treatments, can enhance the wettability patterns. By creating surfaces with tailored properties at the micro and nanoscale, the effectiveness of the patterns in promoting fluid transport and heat transfer can be increased.

Optimized Material Selection: Choosing materials with specific surface properties that complement the wettability patterns can further enhance their performance. Selecting materials with high thermal conductivity and compatibility with the patterning process can improve the overall heat transfer characteristics of the vapor chamber.

Integration of Active Elements: Incorporating active elements, such as microfluidic channels or sensors, into the wettability patterns can enable dynamic control of fluid flow and temperature distribution within the vapor chamber. This integration can lead to more precise thermal management and lower thermal resistances.

By implementing these optimization strategies, the wettability patterns on the evaporator and condenser can be fine-tuned to achieve even lower thermal resistances in thin wick-free vapor chambers, enhancing their heat spreading capabilities.

What are the potential challenges in scaling up the manufacturing of these thin wick-free vapor chambers with wettability-patterned surfaces for real-world applications?

Scaling up the manufacturing of thin wick-free vapor chambers with wettability-patterned surfaces for real-world applications may face several challenges:

Precision and Consistency: Maintaining the precision and consistency of the wettability patterns across large-scale production can be challenging. Variations in pattern quality or alignment can impact the heat transfer performance of the vapor chambers.

Cost and Scalability: The cost of manufacturing wettability-patterned surfaces on a large scale may be prohibitive. Scaling up the production process while ensuring cost-effectiveness and scalability can be a significant challenge for commercial deployment.

Material Compatibility: Ensuring the compatibility of the materials used for the vapor chambers with the patterning techniques and surface treatments at a larger scale is crucial. Material selection and processing methods must be optimized for mass production.

Quality Control and Testing: Implementing robust quality control measures and testing protocols for large-scale production is essential to guarantee the performance and reliability of the vapor chambers. Ensuring consistent thermal characteristics and durability across all manufactured units is a key challenge.

Integration and Application: Integrating the manufactured vapor chambers with electronic devices or thermal management systems in real-world applications poses challenges in terms of design compatibility, installation, and performance optimization. Customization for specific applications may be required.

Addressing these challenges through advanced manufacturing techniques, quality assurance processes, and collaboration with industry partners can facilitate the successful scaling up of thin wick-free vapor chambers with wettability-patterned surfaces for diverse real-world applications.

Could the principles of wettability patterning demonstrated in this work be applied to other passive two-phase heat transfer devices beyond vapor chambers, such as heat pipes or thermosyphons?

The principles of wettability patterning demonstrated in this work can indeed be applied to other passive two-phase heat transfer devices beyond vapor chambers, such as heat pipes or thermosyphons. Here's how:

Heat Pipes: By incorporating wettability patterns on the inner surfaces of heat pipes, the efficiency of heat transfer through phase change processes can be enhanced. The patterns can facilitate the movement of the working fluid, improving heat spreading and overall thermal performance.

Thermosyphons: Wettability patterning can be utilized in thermosyphons to optimize the condensation and evaporation processes. Tailored patterns can promote efficient fluid transport and heat exchange, leading to improved thermal management in thermosyphon systems.

Microchannels: Wettability patterning can also be applied to microchannel heat exchangers to enhance heat transfer efficiency. By creating structured surfaces that promote fluid flow and phase change processes, the thermal performance of microchannel devices can be optimized.

Heat Sinks: Integrating wettability patterns on heat sink surfaces can improve the heat dissipation capabilities of these devices. The patterns can enhance liquid spreading, evaporation, and condensation, leading to more effective cooling of electronic components.

Overall, the principles of wettability patterning demonstrated in this work can be extended to various passive two-phase heat transfer devices to enhance their heat transfer efficiency, thermal performance, and applicability in diverse thermal management applications.