self heating
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Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 106
Author(s):  
Yingshuo Qin ◽  
Changchun Chai ◽  
Fuxing Li ◽  
Qishuai Liang ◽  
Han Wu ◽  
...  

The self-heating and high-power microwave (HPM) effects that can cause device heating are serious reliability issues for gallium nitride (GaN) high-electron-mobility transistors (HEMT), but the specific mechanisms are disparate. The different impacts of the two effects on enhancement-mode p-gate AlGaN/GaN HEMT are first investigated in this paper by simulation and experimental verification. The simulation models are calibrated with previously reported work in electrical characteristics. By simulation, the distributions of lattice temperature, energy band, current density, electric field strength, and carrier mobility within the device are plotted to facilitate understanding of the two distinguishing mechanisms. The results show that the upward trend in temperature, the distribution of hot spots, and the thermal mechanism are the main distinctions. The effect of HPM leads to breakdown and unrecoverable thermal damage in the source and drain areas below the gate, while self-heating can only cause heat accumulation in the drain area. This is an important reference for future research on HEMT damage location prediction technology and reliability enhancement.


2022 ◽  
Author(s):  
Immani Mckenzie ◽  
Seecharran Diana ◽  
Sirpaul Jaikishun ◽  
Abdullah Ansari

Composting is a self-heating, aerobic, bio-decomposition process of organic waste that has advantages over other disposal strategies since it reduces waste volume by 40-50% and kills pathogens by the heat generated during the thermophilic phase. This process uses organic waste (food scraps, grass chipping, etc.), water, soil (for added microbes) and either incorporation of air by turning the compost (aerobic) or lack of air within the compost (anaerobic). This study is designed to comparatively assess aerobic and anaerobic composting mechanisms on the productivity rate and analyse the different variables influencing the process. Based on the results obtained the time taken to completely compost the organic materials might not always be the same, because composting time is dependent on the percentage of microorganisms, water content, temperature and C:N ratio present in the pile at the said time along with the amount of material to be composted. Finally, this study will not only help farmers but also the general public in choosing a cost-effective and environmentally friendly way of reducing organic waste from landfills and reduction of greenhouse gases in the ozone layer.


Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 380
Author(s):  
Aekjuthon Phounglamcheik ◽  
Nils Johnson ◽  
Norbert Kienzl ◽  
Christoph Strasser ◽  
Kentaro Umeki

Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This study investigates biochar self-heating upon its contact with O2 at low temperatures, i.e., 50–300 °C. First, kinetic parameters of O2 adsorption and CO2 release were measured in a thermogravimetric analyzer using biochar produced from a pilot-scale pyrolysis process. Then, specific heat capacity and heat of reactions were measured in a differential scanning calorimeter. Finally, a one-dimensional transient model was developed to simulate self-heating in containers and gain insight into the influences of major parameters. The model showed a good agreement with experimental measurement in a closed metal container. It was observed that char temperature slowly increased from the initial temperature due to heat released during O2 adsorption. Thermal runaway, i.e., self-ignition, was observed in some cases even at the initial biochar temperature of ca. 200 °C. However, if O2 is not permeable through the container materials, the temperature starts decreasing after the consumption of O2 in the container. The simulation model was also applied to examine important factors related to self-heating. The results suggested that self-heating can be somewhat mitigated by decreasing the void fraction, reducing storage volume, and lowering the initial char temperature. This study demonstrated a robust way to estimate the cooling demands required in the biochar production process.


Author(s):  
Anton A. Artanov ◽  
Edmundo A. Gutierrez-D. ◽  
Alfonso R. Cabrera-Galicia ◽  
Andre Kruth ◽  
Carsten Degenhardt ◽  
...  

2022 ◽  
pp. 990-1002
Author(s):  
Dmitry Strebkov

The investigation has shown that the main cause of the global climate change is “anthropogenic thermal pollution,” which is created by the activity of mankind and creates the prerequisites for breaking the heat balance of the planet and transferring the climate into a state of self-heating. By different estimates, in 20-60 years there could be a point of no return for the warming of the climate of Earth when no material resources of mankind are able to stop the global disaster connected with thawing of glaciers, increasing level of the ocean of 80-100 m and the transition of the Earth climate to a condition incompatible with biological life. Urgent transition to fuel-free power and a change of radiation balance of Earth by increasing the albedo of the cities and deserts is necessary. Calculating the area of specular reflectors and the area of deserts necessary for their location, are necessary to prevent global warming, and showed that the required area is 0.95-1.21% of the area of the African desert.


Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 224
Author(s):  
Kalina Detka ◽  
Krzysztof Górecki

The paper proposes a new electrothermal model of a coupled inductor containing a nanocrystalline core dedicated to the analysis of electrical energy conversion systems. The formulated model has a form of a subcircuit for SPICE. The model takes into account the influence of direct current, frequency, skin effect, temperature, self-heating, and mutual thermal couplings on the parameters and characteristics of the coupled inductors. The form of the developed model and the method of model parameter estimation are presented. The applied measuring system is presented. The results of measurements and calculations made with the use of the proposed model are presented and commented on.


Author(s):  
Б. А. Бондарев ◽  
П. В. Комаров ◽  
А. В. Ерофеев ◽  
В. А. Баязов

Постановка задачи. Для определения выносливости полимерных композиционных материалов используют различные методы ускоренных испытаний. Одним из таких методов является температурный, который имеет свои ограничения применения. Это подразумевает необходимость установления возможности его применения для эпоксидных полимерных материалов. Результаты. Предложена формула для определения величины усталостной долговечности эпоксидного композиционного материала, опытным путем установлена достоверность величин, рассчитываемых по данной формуле. Доказано, что интенсивность роста температуры зависит от скорости загружения. Выводы. Достоверность расчетов по предложенной формуле для расчета показателей усталостной долговечности подтверждена сравнением результатов с опытными данными, значения достаточно близко коррелируют, что позволяет применять эту формулу при расчете выносливости для образцов из эпоксидного композита. Statement of the problem. Various methods of accelerated testing are used to determine the endurance of polymer composite materials. One of these methods is the temperature method which has its own limitations of application. Thus the possibility of its application for epoxy polymer materials should be established. Results. The article proposes a formula for identifying the value of the fatigue life of an epoxy composite material. The reliability of the values calculated using this formula is experimentally established. It is proved that the intensity of the temperature increase depends on the loading speed. Conclusions. The reliability of the calculations according to the proposed formula for calculating the fatigue life indicators is confirmed by comparing the results with experimental data, the values are quite closely correlated, which allows us to use this formula when calculating the endurance for samples made of epoxy composite.


2021 ◽  
Author(s):  
Vaibhav Purwar ◽  
Rajeev Gupta ◽  
Pramod Kumar Tiwari ◽  
Sarvesh Dubey

Abstract Dielectric Pocket Double-Gate-All-Around (DP-DGAA) MOSFETs are one of the preferred choices for ULSI applications because of significantly low off-current, reduced power dissipation, and high immunity to short channel effect. However, DP-DGAA MOSFETs suffer from self-heating owing to the unavailability of proper heat take-out paths. In this paper, the electrothermal (ET) simulations have been performed with hydrodynamic and thermodynamic transport models to analyze the self-heating effects (SHEs) in DP-DGAA MOSFETs. The electrothermal characteristics against various device parameters such as spacer length, device thickness, thermal contact resistance, and drain voltage have been investigated. The effect of SHE on the drive current has also been evaluated. Further, the impact of thermal contact resistance and ambient temperature variations of the device on SHE and thermal noise have been analyzed using Sentaurus TCAD simulator.


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