This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

A Benchmark Study on the Thermal Conductivity of Nanofluids

The need for energy-efficient and environmentally friendly refrigeration, heat pumping, air conditioning, and thermal energy harvesting systems is currently more urgent than ever. Magnetocaloric energy conversion is among the best available alternatives for achieving these technological goals and has been the subject of substantial basic and applied research over the last two decades. The subject is strongly interdisciplinary, requiring proper understanding and efficient integration of knowledge in different specialized fields. This review article presents a historical and up-to-date account of the energy-related applications of magnetocaloric materials and information about their processing and magnetic fields, thermodynamics, heat transfer, and other relevant characteristics. The article also discusses the conceptual design of magnetocaloric refrigeration and power generation systems and some guidelines for future research in the field.

https://onlinelibrary.wiley.com/doi/epdf/10.1002/aenm.201903741

Energy Applications of Magnetocaloric Materials

The higher voltage blocking capability and faster switching speed of silicon-carbide (SiC) mosfet s have the potential to replace Si insulated gate bipolar transistors (IGBTs) in medium-/low-voltage and high-power applications. In this paper, a state-of-the-art commercially available 325 A, 1700 V SiC mosfet module has been fully characterized under various load currents, bus voltages, and gate resistors to reveal their switching capability. Meanwhile, Si IGBT modules with similar power ratings are also tested under the same conditions. From the test results, several interesting points have been obtained: different to the Si IGBT module, the over-shoot current of the SiC mosfet module increases linearly with the increase of the load current and it has been explained by a model of the over-shoot current proposed in this paper; the induced negative gate voltage due to the complementary device turn- off (crosstalk effect) is more harmful to the SiC mosfet module than the induced positive gate voltage during turn- on when the gate off-voltage is –6 V; the maximum dv / dt and di / dt (electromagnetic interference) during switching transients of the SiC mosfet module are close to those of the Si IGBT module when the gate resistance is larger than 8 Ω but the switching loss of the SiC mosfet module is much smaller; the switching losses of the Si IGBT module are greater than those of the SiC mosfet module even when the gate resistance of the former is reduced to zero. An accurate power loss model, which is suitable for a three-phase two-level converter based on SiC mosfet modules considering the power loss of the parasitic capacitance, has been presented and verified in this paper. From the model, a 96.2% efficiency can be achieved at the switching frequency of 80 kHz and the power of 100 kW.

Performance Evaluation of High-Power SiC MOSFET Modules in Comparison to Si IGBT Modules

The behavior of silicon carbide (SiC) power MOSFETs under stressful short-circuit (SC) conditions is investigated in this paper. Two different SC failure phenomena for SiC power MOSFETs are thoroughly reported. Experimental evidence and TCAD electrothermal simulations are exploited to describe and discriminate the failure sources. Physical causes are finally investigated and explained by means of properly calibrated numerical investigations and are reported along with their effects on devices’ SC capability.

/pdf/a-comprehensive-study-of-short-circuit-ruggedness-of-silicon-1isyxadvdu.pdf

A Comprehensive Study of Short-Circuit Ruggedness of Silicon Carbide Power MOSFETs

Various eutectic systems have been proposed and studied over the past few decades. Most of the studies have focused on three typical types of eutectics: eutectic metals, eutectic salts, and deep eutectic solvents. On the one hand, they are all eutectic systems, and their eutectic principle is the same. On the other hand, they are representative of metals, inorganic salts, and organic substances, respectively. They have applications in almost all fields related to chemistry. Their different but overlapping applications stem from their very different properties. In addition, the proposal of new eutectic systems has greatly boosted the development of cross-field research involving chemistry, materials, engineering, and energy. The goal of this review is to provide a comprehensive overview of these typical eutectics and describe task-specific strategies to address growing demands.

Eutectics: formation, properties, and applications

https://hal.archives-ouvertes.fr/hal-01198584/document

Study of short-circuit robustness of SiC MOSFETs, analysis of the failure modes and comparison with BJTs

Thermal management became a limiting factor in the development of high-power electronic devices, and new methods of cooling are required. Therefore, the use of liquid gallium alloys, whose thermal conductivity (approximately 28 W/m/K) is 40 times greater than thermal conductivity of water, is introduced. In the first part of this paper, we present a numerical modeling and an experimental study of a mini-channel liquid metal cooler. In these experiments, the working fluid is moved via an electromagnetic pump. Numerical and experimental results are compared. Then, a numerical study dealing with the influence of the thermal conductivity of the cooler material is conducted, and a discussion on the use of classical convective heat transfer correlations is presented. In the last part, a numerical study of the cooling of a silicon chip is carried out. The cooling capacity of the liquid metal is compared with that of the water cooling, and very attractive results are obtained. The concept discussed in this paper is expected to provide a powerful cooling strategy for high-power-density electronic devices.

Numerical and Experimental Investigations of the Thermal Management of Power Electronics With Liquid Metal Mini-Channel Coolers

Robustness in short-circuit Mode of SiC MOSFETs

The proposed innovative manufacturing process—described in detail—uses metal foam to create a pressed contact between the top side of a printed circuit board-embedded power die and the rest of the circuit. Initial prototypes were constructed using diodes with die dimensions of 4 mm $\times $ 6.35 mm. The prototypes were electrically characterized: the chip and contact dc and ac impedance values were measured and compared with those obtained for conventional packaging that uses bond wires. The electrical impedance of the prototypes was found to be similar to that of a state-of-the-art industrial package. Moreover, the proposed process is simple and cost-effective. Although the results presented in this letter are promising, further research is necessary to fully assess the benefits and limitations of the process.

/pdf/using-laminated-metal-foam-as-the-top-side-contact-of-a-pcb-3xjuz94jho.pdf

Mickael Petit

Papers

Study of short-circuit robustness of SiC MOSFETs, analysis of the failure modes and comparison with BJTs

Numerical and Experimental Investigations of the Thermal Management of Power Electronics With Liquid Metal Mini-Channel Coolers

Robustness in short-circuit Mode of SiC MOSFETs

Using Laminated Metal Foam as the Top-Side Contact of a PCB-Embedded Power Die

Parameters affecting forced convection enhancement in ferrofluid cooling systems