Structural relaxation in Ag-Ni nanoparticles: Atomistic modeling away from equilibrium

The out-of-equilibrium structural relaxation of Ag-Ni nanoparticles containing about 1000--3000 atoms was investigated computationally by means of molecular dynamics trajectories in which the temperature is decreased gradually over hundreds of nanoseconds. At low silver concentration of 10--30\%, the evolution of chemical ordering in Ni$_{\rm core}$Ag$_{\rm shell}$ nanoparticles with different surface arrangements is found to proceed spontaneously and induce some rounding of the nickel core and its partial recristallization. Fast cooling of an initially hot metal vapor mixture was also considered, and it is shown to disfavor silver aggregation at the surface. Silver impurities are also occasionally produced but remain rare events under the conditions of our simulations.

Decreasing the Weight-Size Parameters of Gas-Steam Turbine Plant by Increasing the Efficiency of Thermodynamic Processes in the Condenser

The aim of this work is decreasing the weight-size parameters of the contact gas-steam turbine plant and contact condenser elements by increasing the efficiency of thermal-gas dynamic processes of condensation through rational irrigation of countercurrent gas-steam flow. To achieve the goal the total efficiency of water-return drops ranging from 0.1 to 1 mm at different initial velocities from 5 to 35 m/s emitted by the multi-nozzle sprinkler was determined by mathematical modeling of the liquid droplet movement processes, heat and mass transfer between the liquid droplet and gas-vapor mixture, and gas-vapor mixture pressure loss. The effect of increasing the gas-steam mixture velocity from 3.3 to 6 m/s on the overall efficiency of water return was determined. The novelty of the obtained results was defined by an increase in the water return into cycle from 12 to 13% with a droplet diameter of 0.3 -- 0.4 mm and the initial velocity from the sprinkler of 5--10 m/s. The velocity of the mixture was to 6 m/s at rational correlations of the initial velocity of the droplets’ escape, which increased the total amount of heat withdrawn to 11%. The positive effect conditions of irrigation processes on thermogasdynamic and weight-size parameters of the condenser elements for the contact gas and steam turbine plant at full pressure recovery coefficients of over 0.967 were substantiated. The most significant result was the reduction of the weight-size parameters of the marine infrastructure object power plant from 8 to 19%.

Assessment of the contribution of the air-vapor mixture volume exceeding over the volumes injected to oil and petroleum product losses from evaporation

В настоящее время при экспериментальном определении потерь нефтепродуктов от «больших дыханий» резервуаров используют формулу Черникина - Валявского. При этом «однако» не учитывается, что объем вытесняемой в атмосферу паровоздушной смеси, как правило, превышает объем закачиваемой нефти (нефтепродукта). Соответствующий параметр - коэффициент превышения, - по экспериментальным данным, может принимать значения более 8. До недавнего времени не до конца были ясны даже причины этого явления, соответственно, эмпирические зависимости для расчета коэффициента превышения не учитывали всех влияющих факторов. Авторами статьи на основе уравнения Менделеева - Клапейрона в дифференциальной форме получено аналитическое выражение для вычисления среднего коэффициента превышения. Установлено, что данная величина зависит от молярной массы и температуры паровоздушной смеси в начале и конце закачки, а также от соотношения объемов газового пространства резервуара и закачиваемого продукта. Для анализа полученной зависимости был спланирован и проведен вычислительный эксперимент, предусматривающий изменение определяющих параметров в широком диапазоне. Расчеты выполнялись для нефти и бензина. По результатам 25 вычислительных «опытов» определено, что при операциях с бензином средний коэффициент превышения (за одну операцию заполнения резервуара) в исследованном диапазоне температур принимает значения от 1,029 до 1,678, а при операциях с нефтью - от 1,016 до 1,338, то есть, как правило, превышает погрешность инструментальных замеров потерь нефти (нефтепродуктов) от испарения. Математическое ожидание рассматриваемой величины при операциях с бензином составляет 1,26, с нефтью - 1,16. Таким образом, учет среднего коэффициента превышения при обработке результатов инструментальных измерений потерь углеводородов от испарений вследствие «больших дыханий» резервуаров является обязательным. Currently, the Chernikin - Valyavsky formula is used in the experimental determination of petroleum product losses from “large breaths” of reservoirs. However, it does not take into account that the volume of air-vapor mixture displaced into the atmosphere usually exceeds the volume of pumped oil/petroleum product. The corresponding parameter, the excess ratio, according to the experimental data can have values of more than 8. Until recently, even the causes of this phenomenon were not completely clear, and thus, the empirical dependencies for calculating the excess ratio did not take into account all the influencing factors. Based on the Mendeleev-Clapeyron equation in differential form, the analytic expression to calculate the average excess ratio was obtained. It was found that this value depends on the molar mass and temperature of the air-vapor mixture at the beginning and the end of the injection, as well as on the ratio of the tank gas space volume and the injected product volume. To analyze the resulting dependency, a computational experiment involving changes in the defining parameters over a wide range was planned and conducted. The calculations were performed for oil and gasoline. According to the results of 25 computational experiments, it was determined that during operations with gasoline the average excess ratio (per one tank filling operation) in the investigated temperature range has values from 1.029 to 1.678, and during operations with oil - from 1.016 to 1.338; that generally exceeds the instrument error of oil/petroleum product losses from vaporization measurement. The mathematical expectation of the value in question during operations with gasoline is 1.26, it is 1.16 with oil. It is therefore mandatory to take into account the average excess ratio when processing the results of instrumental measurements of hydrocarbon losses from evaporation due to “large breaths” of reservoirs.

Analysis of Passive Tube Condensation With Non-Condensable Gas Using Heat and Mass Analogy Model

In this study, we used the heat and mass analogy model to be able to predict the heat transfer properties of a condenser tube operating in passive mode. The most important advantage of analogy model comparing boundary layer model is simplicity and fast computation, that’s why it can be applied to various engineering problems for many cases. The heat and mass analogy model is based on the heat transfer balance between liquid film and gas mixture area. The main problem for the liquid film region is the heat transfer coefficient (HTC) which is affected negatively in the presence of non-condensable gas. Therefore, our main goal is to increase the HTC and condensation heat transfer rate by updating the analogy code. In the gas-vapor mixture region, heat transfer mainly occurred as latent condensation and sensible heat transfer. In order to maintain this balance between the mixture and liquid film, the interface temperature is iterated. After defining a specified tolerance value of the heat and mass analogy model codes, this iteration process was started to be used at the entrance of a condenser tube. The gas and vapor mixture is considered to be saturated at the liquid/gas interface in the heat and mass transfer analogy model. Via boundary layer study of species concentration and energy balance, the non-condensable gas effect on condensation is added into the equation. For the condensation heat transfer coefficient of turbulent vapor flow associated with laminar condensate, numerical predictions were made and they were satisfactory. The predictions were compared with the experimental data from the literature to be able to test the model. Non-condensable gas mass fraction and vapor-non-condensable mixture temperature were presented in the form of radial and axial profiles.

GROWTH RATE OF DIAMOND-LIKE COATINGS SYNTHESIZED IN RF DISCHARGE AT VARIOUS RATIOS OF THE CONCENTRATIONS OF Ar AND C6H6

Diamond-like coatings (DLC) synthesized by plasma-chemical deposition from a vapor mixture of C6H6 and Ar have been investigated. The growth rate of the coating was measured, which showed a nonlinear dependence on the partial pressure of Ar. The mathematical model of the deposition has been developed, which qualitatively and quantitatively describes the dependence of the ion flux density and deposition rate on the partial pressure of argon.

Selective separation of branched alkane vapor by thiacalixarene supramolecular crystals having shape-recognition properties

Activated crystals of a supramolecular assembly of bromothiacalix[4]arene propyl ether with preorganized channel-like voids can selectively and effectively adsorb isooctane vapor from a vapor mixture of isooctane and n-heptane.

Numerical simulation of single and double slope solar still for temperature distribution

Water and the use of conventional energy sources are two significant problems of the world. Water is essential for sustenance. Human beings need of potable water at less consumption of non- renewable energy resources. There are many techniques to convert saline water into potable water. In this paper, three-phase, three dimensional a single slope and double slope single basin still both were prepared and simulated by using ANSYS FLUENT v19.2. Simulation results of solar stills were made by using evaporation as well as condensation process at the climate conditions of Delhi (27.0238° N, 74.2179° E). Within the scope of this study, simulation results of both systems were calculated and compared with each other. It is examined that temperature inside the single slope solar still is maximum from 13:00 to 14:00 hrs while double slope still has low temperature compared to single still. The maximum and minimum temperature of water-vapor mixture inside the single slope still were calculated 435.39K and 22.283K and maximum and minimum temperature on glass were 379 K and 16.22 K whereas in double slope, maximum and minimum temperature of water-vapor mixture inside the still were 92.12K and 25.60K and glass temperature were 76.154K and 19.22K Hence, due to temperature difference between glass surface and outer environment, more condensation will be in single slope. Inner water temperature is responsible for more evaporation and higher temperature more than 50? can be found in single slope still as compared to double slope. Hence, single slope still could be better there.

Four Firefighters Injured in Lithium-Ion Battery Energy Storage System Explosion -- Arizona

On April 19, 2019, one male career Fire Captain, one male career Fire Engineer, and two male career Firefighters received serious injuries as a result of cascading thermal runaway within a 2.16 MWh lithium-ion battery energy storage system (ESS) that led to a deflagration event. The smoke detector in the ESS signaled an alarm condition at approximately 16:55 hours and discharged a total flooding clean agent suppressant (Novec 1230). The injured firefighters were members of a hazardous materials (HAZMAT) team that arrived on the scene at approximately 18:28 hours. The HAZMAT team noted low-lying white clouds of a gas/vapor mixture issuing from the structure and nearby components and drifting through the desert. The team defined a hot zone and made several entries into the hot zone to conduct 360-degree size-ups around the ESS using multi-gas meters, colorimetric tubes, and thermal imaging cameras (TICs). The team detected dangerously elevated levels of hydrogen cyanide (HCN) and carbon monoxide (CO) during each entry. The team continued to monitor the ESS and noted the white gas/vapor mixture stopped flowing out of the container at approximately 19:50 hours. The HAZMAT leadership developed an incident action plan with input from a group of senior fire officers and information about the ESS provided by representatives from the companies that owned, designed, and maintained the ESS. The HAZMAT team made a final entry into the hot zone and found that HCN and CO concentrations in the vicinity of the ESS were below an acceptable threshold. In following with the incident action plan, the team opened the door to the ESS at approximately 20:01 hours. A deflagration event was observed by the firefighters outside the hot zone at approximately 20:04 hours. All HAZMAT team members received serious injuries in the deflagration and were quickly transported to nearby hospitals. Note: The lithium-ion battery ESS involved in this incident was commissioned prior to release of a first draft of the current consensus standard on ESS installations, NFPA 855 [1]; the design of the ESS complied with the pertinent codes and standards active at the time of its commissioning.