Numerical Modeling of Conjugate Thermogravitational Convection in a Closed System with a Radiant Energy Source in Conditions of Convective-Radiative Heat Exchange at the External Boundary

Mathematical modeling of conjugate natural convection in a closed rectangular cavity with a radiant energy source in conditions of convective-radiative heat exchange at the external boundary was conducted. The radiant energy distribution was set by the Lambert’s law. Conduction and convection processes analysis showed that the air masses flow pattern is modified slightly over the time. The temperature increases in the gas cavity, despite the heat removal from the one of the external boundary. According to the results of the integral heat transfer analysis were established that the average Nusselt number (Nu[av]) increasing occurs up to [tau]=200 (dimensionless time). Further Nu[av] has changed insignificantly due to the temperature field equalization near the interfaces "gas – wall"

The influence of surface defects on the pinhole formation in silicide thin film

The growth of the CoSi layer was considered within the framework of the grain boundary diffusion model. The time dependences of the temperature due to the exothermic reaction of silicide formation as well as the dependences of the CoSi layer thickness were calculated for various values of the reaction activation energy. It was shown that the heat release at high reaction velocities can lead to the considerable increase of the temperature up to melting of the silicide and covering Co layers. The model of pinhole formation in cobalt silicide films was proposed on the basis of local melting in the reaction area at crystal defects of the silicon surface

Initiation of Ignition of Highly Fuel Particles in The Flow of High Temperature Medium

An approximate analytical solution of ignition of the fuel porous particles has been brought. The impact of thermal radiation on the characteristics and conditions of the ignition has been considered. The verification of the solution has been obtained by comparing the calculated characteristics (delay time of ignition and the ignition temperature) with similar values obtained using the previously derived formulas

Electrophysical properties of meso-porous silicon free standing films modified with palladium

Resistivity and complex impedance voltage dependences for thick mesoporous silicon free layers were studied in this work. The asymmetrical by the sign of applied voltage experimental curves at low frequencies have been obtained. Modification of electrophysical properties due to introduction of palladium particles into the porous matrix is observed. Impedance change regularities during oxidation of the samples have been measured. The explanation of experimental results by asymmetrical distribution of charge carrier traps in the bulk of porous silicon has been suggested. Energy band diagrams and charge transfer mechanisms of these heterostructures are discussed

Numerical Research of Steam and Gas Plant Efficiency of Triple Cycle for Extreme North Regions

The present work shows that temperature decrease of heat rejection in a cycle is necessary for energy efficiency of steam turbine plants. Minimum temperature of heat rejection at steam turbine plant work on water steam is 15°C. Steam turbine plant of triple cycle where lower cycle of steam turbine plant is organic Rankine cycle on low-boiling substance with heat rejection in air condenser, which safely allows rejecting heat at condensation temperatures below 0°C, has been offered. Mathematical model of steam and gas plant of triple cycle, which allows conducting complex researches with change of working body appearance and parameters defining thermodynamic efficiency of cycles, has been developed. On the basis of the model a program of parameters and index cycles design of steam and gas plants has been developed in a package of electron tables Excel. Numerical studies of models showed that energy efficiency of steam turbine plants of triple cycle strongly depend on low-boiling substance type in a lower cycle. Energy efficiency of steam and gas plants net 60% higher can be received for steam and gas plants on the basis of gas turbine plant NK-36ST on pentane and its condensation temperature below 0°C. It was stated that energy efficiency of steam and gas plants net linearly depends on condensation temperature of low-boiling substance type and temperature of gases leaving reco very boiler. Energy efficiency increases by 1% at 10% decrease of condensation temperature of pentane, and it increases by 0.88% at 15°C temperature decrease of gases leaving recovery boiler

Influence of air Gap Between the Transformer of Resistance and Object of Monitoring on Temperature Measurement Error

In operation the description of the developed heattransfer model in thermotransformers of resistance (RTD) in the conditions of air gap between surfaces of the sensor and object of measurement is provided. Research of influence of thickness of air gap on the relative error of temperature measurement by platinum, copper and nickel thermotransformers of resistance in the ranges of temperatures corresponding to each type is executed. Dependences of minimum necessary duration of heating up of sensors on the taken temperatures are received

Terms and Characteristics of Homogeneous Ignition of Coal-Water Particles Coated with a Water Film

The problem of coal-water fuel ignition of particles in a high-temperature heating has been solved numericallyin the framework of a two-layer model of "coal-water". The basic characteristics of the integrated ignition has been shown. The influence of the vaporization process of the water film on the ignition conditions has been shown

ПАРАМЕТРЫ, СВЯЗАННЫЕ С ОТСУТСТВИЕМ ЗНАЧИМОГО КОРОНАРНОГО АТЕРОСКЛЕРОЗА ПО ДАННЫМ «РЕГИСТРА ПРОВЕДЕННЫХ ОПЕРАЦИЙ КОРОНАРНОЙ АНГИОГРАФИИ»

Aim of the study: the study aimed to reveal the sign of coronary atherosclerosis absence using the factor analysis in patients referred for the coronary angiography. Patients and methods: 9409 patients suspected stable coronary artery disease (CAD) or with confirmed diagnosis of CAD from the «Registry of provided coronary angiography» were included in the study. Results of the study: principal factor described about 59% of the variation and included the burdens of 4 parameters (gender, smoking, significant coronary atherosclerosis and hypothyroidism) and was interpreted as factor of coronary atherosclerosis. Conclusions: it was found that the absence of coronary stenosis was associated with female gender, non-smoking status and hypothyroidism. Цель исследования: используя факторный анализ, установить, какие признаки связаны с отсутствием коронарного атеросклероза у пациентов, направленных на коронарную ангиографию. Пациенты и методы: в исследование вошли 9409 стабильных пациентов из «Регистра проведенных операций коронарной ангиографии» как с подозрением на ишемическую болезнь сердца (ИБС), так и с установленным диагнозом ИБС. Результаты: было изучено 5 факторов, объясняющих до 59% вариабельности изучаемого явления. Первый, наиболее значимый фактор объяснял 14% общей дисперсии, содержал нагрузки 4 переменных (пол пациента, курение, значимый коронарный атеросклероз и гипофункция щитовидной железы) и интерпретировался как фактор коронарного атеросклероза. Выводы: продемонстрирована связь отсутствия коронарного атеросклероза с женским полом, отсутствием курения и наличием гипофункции щитовидной железы.

A Plasma Reactor for the Synthesis of High-Temperature Materials: Electro Thermal, Processing and Service Life Characteristics

The three-jet direct-flow plasma reactor with a channel diameter of 0.054 m was studied in terms of service life, thermal, technical, and functional capabilities. It was established that the near-optimal combination of thermal efficiency, required specific enthalpy of the plasma-forming gas and its mass flow rate is achieved at a reactor power of 150 kW. The bulk temperature of plasma flow over the rector of 12 gauges long varies within 5500±3200 K and the wall temperature within 1900±850 K, when a cylinder from zirconium dioxide of 0.005 m thick is used to thermally insulate the reactor. The specific electric power reaches a high of 1214 MW/m{3}. The rated service life of electrodes is 4700 hours for a copper anode and 111 hours for a tungsten cathode. The projected contamination of carbides and borides with elec-trode-erosion products doesn't exceed 0.0001% of copper and 0.00002% of tungsten