Vapor-Chamber Performance Evaluation: The Challenge of Impartial Cross-Platform Comparison

The power density of power electronics in electric vehicles (EVs) is expected to be significantly enhanced, which would result in higher heat flux generation. Therefore, it is critical to find an efficient heat spreading and removal technology to reduce the junction temperature for high power density power electronics application. Vapor chamber using evaporation and condensation of the inside working fluid (i.e., water) as a heat spreader can remarkably improve the uniform heat spreading and heat removal for the power electronics compared to the traditional copper heat spreader. Furthermore, high thermal conductivity graphite foam (GF) would be embedded in the vapor core of the vapor chamber to further enhance the heat transfer performance. Numerical heat transfer simulations were performed for copper heat spreader, vapor chambers (with and without the presence of graphite foam) by using ANSYS. Various parametric effects on vapor chamber thermal performance were investigated, including the effects of heat flux from power electronics, heat transfer coefficient at heat sink, vapor chamber thickness, and graphite foam. Through the simulation studies, it was found that thinner vapor chamber (1.35 mm thickness) had better heat transfer performance than thicker vapor chamber (5 mm thickness) because of the extreme high effective thermal conductivities of ultra-thin vapor chamber. Furthermore, the effect of graphite foam on thermal performance improvement was very minor for ultra-thin vapor chamber, but significant for thick vapor chamber. The GF could help reduce the junction temperature by 15–30% in the 5-mm thick vapor chamber. Use of GF embedded vapor chamber could achieve 250–400 W/cm2 local heat removal for power electronics.

Enhancing heat transfer performance of aluminum-based vapor chamber with a novel bionic wick structure fabricated using additive manufacturing

Experimental analysis of thin vapor chamber with composite wick structure under different cooling conditions

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.

Numerical simulation of a heat sink embedded with a vapor chamber and calculation of effective thermal conductivity of a vapor chamber

Performance and two-phase flow pattern for micro flat heat pipes

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.

Competition in China’s electric vehicle industry has intensified significantly in recent years. The production mode of power batteries, serving as the pivotal component in these vehicles, has emerged as a critical challenge for electric vehicle manufacturers. We considered a system comprising an electric vehicle (EV) manufacturer with power battery production technology and another EV manufacturer lacking power battery production technology. In the context of carbon trading policy, we constructed and solved Cournot competitive game models and asymmetric Nash negotiation game models in the CC, PC, and WC modes. We examined the decision-making process of electric vehicle manufacturers regarding power battery production modes and carbon emission reduction strategies. Our research indicates the following: (1) The reasonable patent fee for power batteries and the wholesale price of power batteries can not only compensate power battery production technology manufacturers for the losses caused by market competition but can also strengthen the cooperative relationship between manufacturers. (2) EV manufacturers equipped with power battery production technology exhibit higher profitability within the framework of a perfectly competitive power battery production mode. Conversely, manufacturers lacking power cell production technology demonstrate greater profitability when operating under a more collaborative power cell production mode. (3) Refraining from blindly persisting with and advocating for carbon emission reduction measures is advisable for manufacturers amidst rising carbon trading prices.

Introduction. Since the beginning of 2020, the development of the global economy has come across a long-forgotten factor in the most unexpected way, the new incarnation of which has become COVID-19. The widespread and rapid spread of the virus throughout the planet showed how advanced globalization is. The global economy has found itself vulnerable to the effects of such crises precisely because of its worldwide nature. The study of the problem of electromobility, various factors affecting it, especially such a negative one as COVID-19, deserve its analysis. The purpose of the paper is to investigate in an integrated manner the issues of management of electric mobility, the impact on various modes of transport COVID-19, the advantages of electric vehicles in today's difficult conditions. Results. The development and production of electric vehicles on the planet is carried out by leading automotive corporations. Certain efforts in the direction of electromobility are being made in our country as well. The complexity of this problem is of particular importance here. The real effectiveness of the widespread introduction of electric vehicles and their replacement of traditional vehicles with internal combustion engines are possible only if primary electricity is obtained by ecological methods, otherwise the effect obtained will be only limited. An analysis of the vulnerability of various modes of transport to coronavirus showed that private road and electric vehicle transport has undoubted advantages over many other modes of transport in terms of security from the COVID-19 virus. In addition, electromobility has major environmental and economic benefits. Conclusion. The paper also shows the relevance of the transition to the gradual development of electric vehicles instead of traditionally used cars with internal combustion engines. The importance of the production of Ukrainian electric vehicles, batteries, chargers in combination with the production of equipment for such environmentally friendly sources of electricity as wind farms and solar panels is emphasized. The impact of COVID-19 on the global economy and on various types of transport is considered. The advantages of using individual electric vehicles to prevent the spread of coronavirus are shown.

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

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

A review of microfabrication approaches for the development of thin, flattened heat pipes and vapor chambers for passive electronic cooling applications

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

Cooling efficiency optimization on air-cooling PEMFC stack with thin vapor chambers