Aqueous Ionic Liquid Solution based Two-phase Thermal Management for Adverse Gravity Applications

Construction of phase change n-Octadecane microencapsulated in carbon nanotubes-modified polymer for thermal management applications of finned heat sinks

Objectives: To review the suitability of Phase Change Material (PCM) for the thermal management of electronic components. Methods/analysis: Day by day, physical world has been changing to digital world by involving electronic components such as computers, digital meters, smart phones, high sensitive sensors, high precision devices etc. One of the important issues pertaining to smooth running of electronic components is their thermal management. Electronic components generate heat during operation and this heat has to be driven out to safeguard the equipment. Researchers have proposed various methods such as heat sinks, nano-fluids, micro-channels etc to reduce and dissipate heat from the components. The requirement for the usage of miniaturization of electronic components has further increased the complexity to effectively dissipate the heat from the confined space of these electronic components. Various techniques provide their own set of benefits and trade-offs for thermal management of electronics to reduce operating temperatures, dissipate excess heat and long-term reliability. The present study aims to address the usage of PCMs with their advantages and disadvantages for the thermal management of electronic components. Findings: PCM based heat sinks can be an alternative technique for effective dissipation of heat and maintain safer temperature range for the electronic devices. Novelty/improvement: The study provides an insight about the applicability of PCM especially for the thermal management of electronic components such as computer processors, IC boards etc. to maintain with in maximum allowable temperature range. Based on the study it can be suggested that the usage of PCM can satisfy the present demand of cooling system.

This paper reviews recent progress in the development of silicon-based vapor chambers for heat spreading in electronic packages. Effective hotspot mitigation is an increasingly challenging issue in electronics thermal management, and the use of silicon vapor chambers creates opportunities for thermal-expansion matched, high performance heat spreaders that can be directly integrated with the semiconductor die. While silicon microheat pipes have been extensively studied as one-dimensional heat transport mechanisms for heat routing in semiconductor substrates, silicon vapor chambers require special consideration and different manufacturing approaches due to the different heat transport configurations involved. The following review therefore provides an overview on the evolution of silicon vapor chambers in terms of fabrication strategies and performance characterization. Particular focus is given to opportunities and challenges associated with using silicon as the vapor chamber envelope material rather than more traditional metal-based vapor chambers, such as the ability to optimize the wick geometry with greater fidelity and issues with manufacturing scalability.

The extensive use of lithium-ion batteries and other energy storage systems (ESS) in recent years has resulted in a critical need for effective thermal management solutions that ensure safe and reliable operations. Carbon-based materials (C-bMs) are a promising candidate for addressing the thermal challenges in ESS due to their unique thermal, electrical, and structural properties. This article provides a concise overview of C-bM thermal management solutions for improved battery safety. The key thermal management requirements and failure modes associated with battery systems are highlighted, underscoring the importance of effective battery thermal management (BTM). Various forms of C-bMs, including graphite, graphene, carbon nanotubes, carbon foams, nanodiamonds, and graphdiyne, are examined for their potential applications in battery thermal management systems. The recent innovations and advancements in C-bM thermal management solutions, such as phase change composites, heat pipes, and thermal interface materials, are highlighted. Furthermore, the latest research trends focus mainly on the development of hybrid battery thermal management solutions, carbon-based aerogels, and complex C-bM structures with tailored thermal pathways for optimized thermal management. Most of the current innovations are still at the laboratory scale; hence, future research efforts will be focused on developing integrated multi-functional C-bMs, sustainable and scalable manufacturing techniques, self-healing C-bMs composites, intelligent C-bMs, and further explorations of uncommon C-bMs. These advancements are bound to enhance performance, sustainability, and application-specific adaptations for BTM. This article provides valuable insights for researchers, and stakeholders interested in leveraging C-bMs for BTM.

A cascaded multicore vapor chamber (CMVC) is designed for dissipating heat from high-flux hotspots simultaneously with a high-total-power background. Current thermal management strategies rely on spreading high local heat fluxes by conduction in the lid of electronics packages. Embedding vapor chambers (VCs) within the lid is an attractive option to directly address intrapackage hotspots. We investigate the design of intralid VCs, for a generic device having a total heat load of 476 W having a background heat flux of 0.75 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , with hotspots of 8 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> over a 1-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area. A conventional VC design, having a single vapor core, will require a thick evaporator wick to avoid the capillary limit for large total power. The necessity for a thick wick then imposes a large thermal conduction resistance when the VC is exposed to high heat flux hotspots. The proposed CMVC architecture aims to address this limitation. The cascaded architecture comprises a bottom-tier VC having an array of multiple small vapor cores for spreading heat from the small hotspots. These small vapor cores have short paths of liquid return to the evaporator, such that they can handle their footprint heat load while using thin wicks, resulting in a low hotspot thermal resistance. Furthermore, local dampening of the hotspots by the bottom tier then reduces the thermal conduction resistance across the necessarily thick wick in the top tier. Hence, the cascaded architecture has the potential to significantly reduce the overall thermal resistance, relative to a single tier. To substantiate this design rationale, experiments are performed to illustrate that the resistance of a commercial VC can be significantly reduced by interfacing the heat source with an intermediate heat spreader. Reduced-order models are then used to understand the effect of the wick properties (porosity and particle size) and geometric parameters on the thermal performance of the CMVC for the representative power map. The optimal CMVC design offers a thermal resistance (0.66 K/W) that is significantly lower compared to a conventional single-core VC (1.76 K/W) owing to a reduction in the conduction resistances across the internal wicks. That parametric optimization results demonstrate that the thermal resistance of the CMVC is more sensitive to the wick porosity compared to the particle diameter. Furthermore, there exists a wide range of wick properties and vapor core sizes for which near-optimum thermal performance can be attained, which is particularly attractive from the standpoint of flexibility in design and manufacturing.

Experimental study on ultra-thin silicon-based VC for chip-level heat dissipation

We introduce the concept of an intra-lid cascaded multi-core vapor chamber (CMVC) for heat spreading in heterogeneous packages that simultaneously generate large total heat loads and high-power-density hotspots. Current thermal management strategies rely on spreading high local heat fluxes by conduction in the package lid, ultimately dissipating the total heat load using a mounted heat sink. Embedding vapor chambers within the lid is an attractive option to directly address intra-package hotspots, but their design must be reconsidered to simultaneously manage the large total heat load at low thermal resistance. We investigate the design of intra-lid vapor chambers, with water as the working fluid, for a representative device generating a total heat load of 476 W having a background heat flux of 0.75 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , with hotspots of 8 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> over a 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area. Conventional vapor chamber designs have a single vapor core, which requires thick evaporator wicks to avoid the capillary limit at high total heat loads; directly subjecting this thick wick to high heat flux hotspots imposes a large conduction resistance. To address this drawback, the CMVC concept comprises of a bottom-tier core having many small vapor cores that can each attenuate high heat flux hotspots before they pass through to the top tier, which has a single vapor core functioning as a conventional vapor chamber. Experimentally validated, reduced-order models predict that the CMVC offers an order of magnitude reduction in thermal resistance (0.66 K/W) compared to a solid copper benchmark (7.4 K/W) and conventional single-core vapor chamber (1.8 K/W) owing to a reduction in the conduction resistances across the internal wicks.

Epoxy resin-hydrated halt shaped composite thermal control packaging material for thermal management of electronic components

Shape stabilized three-dimensional porous SiC-based phase change materials for thermal management of electronic components

The worldwide power electronics market is expected to expand at an annual growth rate of 4.7% from USD 35.1 billion in 2020 to USD 44.2 billion by 2025 [1]. This rise is fueled by the use of renewable energy sources throughout the world, and the increasing utilization of power electronics in the production of electric vehicles. The expanding implementation of power electronics in consumer products is another key driver of the market's growth. The most significant impediment in the electronic systems is their thermal management. Two-phase cooling is currently the standard thermal-management solution in all its forms, including heat pipes, vapor chambers, thermosyphons, and so on. But comparing the performance of different systems poses many challenges, thus making decision making difficult in the absence of complete information for each device.In this study, a list of ten critical elements or parameters required to unambiguously characterize the design and performance of a promising two-phase heat-transfer system for future deployment and development, namely the vapor chamber, is presented. This "Decalogue" is inspired by three main factors. First, the rising demand for better and more effective vapor chamber assemblies, which has prompted both industry and academia to invest substantially in related R&D. Second, this investment has resulted in a plethora of new systems (i.e. [2] –[6] etc.) where each design has been accompanied with insufficient description, making it difficult, if not impossible, to perform detailed comparisons across different designs/approaches. Third, the need to develop a common set of standards for describing such systems so that similar designs/philosophies may be compared successfully by researchers and developers seeking to duplicate results and improve on previous performance, especially in commercialized systems.We seek to gather all criteria needed to characterize each vapor chamber system, while exhibiting all benefits and limitations of its design, and illustrating what type of technical application the design may be helpful for, using a simple tabular method. The suggested approach might serve as a reference point or a standard way of accurately representing this type of heat transfer component. This description should benefit researchers in the area by clearly stating what the actual measurements/attributes of each system are, while also emphasizing the relevance/importance of each design by simply comparing it to others. The ten (deca) points presented here merely illustrate the most essential aspects of the design and performance of any vapor chamber.

Passive phase-change thermal spreaders, such as vapor chambers have been widely employed to spread the heat from small-scale high-flux heat sources to larger areas. In this paper, a numerical model for ultrathin vapor chambers has been developed, which is suitable for reliable prediction of the operation at high heat fluxes and small scales. The effects of boiling in the wick structure on the thermal performance are modeled, and the model predictions are compared with experiments on custom-fabricated vapor chamber devices. The working fluid for the vapor chamber is water and a condenser side temperature range of 293 K-333 K is considered. The model predictions agree reasonably well with experimental measurements and reveal the input parameters to which thermal resistance and vapor chamber capillary limit are most sensitive. The vapor space in the ultrathin devices offers significant thermal and flow resistances when the vapor core thickness is in the range of 0.2 mm-0.4 mm. The performance of a 1-mm-thick vapor chamber is optimized by studying the variation of thermal resistance and total flow pressure drop as functions of the wick and vapor core thicknesses. The wick thickness is varied from 0.05 to 0.25 mm. Based on the minimization of a performance cost function comprising the device thermal resistance and flow pressure drop, it is concluded that the thinnest wick structures (0.05 mm) are optimal for applications with heat fluxes below 50 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , while a moderate wick thickness of 0.1 mm performs best at higher heat flux inputs 50 (>;W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ).

Miniaturization of electronic products and a consequent rapid increase in power density of advanced microprocessors and electronic components have created a need for improved cooling techniques to efficiently remove heat from such devices. Traditional air-cooled heat sinks have been utilized for several decades as the most cost-effective cooling technique for electronic cooling applications. However, the existing thermal management solutions are unable to maintain the temperature of the next generation of complex electronic systems within acceptable limits without adding considerable weight and complexity. This paper reports a microstructured wick for application in passive thermal management systems such as heat pipes and vapor chambers. The wick structure consists of mushroom-like composite copper-carbon nanotubes (Cu-CNT) micropillars. The small spacing between micropillar heads provides a higher capillary pressure whereas the large spacing between the base of micropillars provides a higher permeability for liquid flow. The micropillar array was fabricated on a copper substrate using an electroplating technique. The micropillar array was then tested in a controlled environment to experimentally measure its thermal performance under several operating conditions. A heat removal capability of 80 W/cm2 was demonstrated at a wall superheat of 15° C. In addition, a computational study was performed using ANSYS Fluent to predict the thermal performance of the micropillar array. Model predictions were compared with the experimental results and good agreement was obtained.

Immersion liquid cooling for electronics: Materials, systems, applications and prospects

Experimental investigation on thermal performance of aluminum vapor chamber using micro-grooved wick with reentrant cavity array

Rapid thermal response and sensitivity analysis of proton exchange membrane fuel cell stack with ultra-thin vapor chambers