Evaporation Time Research Articles

Характеристики прогрева и испарения капель реактивного топлива и его суррогатов

The paper presents the results of experimental study of heating and evaporation of TS-1 aviation kerosene and its surrogates (n-decane and SU4) in a high-temperature gas flow (gas temperature range is 450–750 K, gas flow velocity range is 0–6 m/s). The conditions for temperature and gas flow rate are established, under which it is possible to provide good agreement on the time of complete evaporation, the dynamics of changes in the sizes (radii) and average temperatures of droplets of traditional aviation fuels using the example of kerosene TS-1 and its surrogates (SU4 and n-decane). When processing videograms, we used our own image processing algorithms developed in the MATLAB software package.

Avaliação de sistema de captação de água de chuva através de simulação contínua com dados subdiários

ABSTRACT A rainwater harvesting system, designed for non-potable water uses, can be helpful for runoff generation control. To evaluate this, sub-daily time steps for monitoring and continuous simulations are important tools. Therefore, this paper shows a performance assessment of a rainwater harvesting system for both roof runoff control (maximum flow rate and drained volume) and to meet water demand, from data obtained in a monitoring apparatus and also from continuous simulation using 1-minute time steps data. The model SWMM was calibrated and validated for both a roof and a monitoring apparatus during the monitored period 2018-2019. Thereafter, continuous simulations were accomplished using rainfall, evaporation, and demand time series. For this stage, data satisfied nearly seven years (2014-2020) containing one-minute time step values. Results have shown the control is influenced by the combined action of the first-flush diverter and rainfall regime and was shown to be greater at maximum flow rate than volume.

Changes in bark properties and hydrology following prescribed fire in Pinus taeda and Quercus montana

AbstractIn the eastern United States, the use of prescribed fire as a silvicultural technique to manage for desirable upland tree species is increasing in popularity. Bark physical properties such as thickness, density, and porosity have known associations with fire tolerance among species. These physical properties simultaneously influence rainfall interception and canopy storage and thus are of interest across a range of disciplines. Furthermore, while these characteristics are innate to a species, it is unknown whether repeated exposure to fire facilitates physical change in bark structure and whether these changes are consistent among species. To answer these questions, bark samples were collected from mature pine (Pinus taeda L.) and oak (Quercus montana Willd.) trees from sites across the Bankhead National Forest in Alabama, USA under three different burn regimes: 3‐year cycle, 9‐year cycle, and no fire. Samples were analysed in the laboratory for bulk density, porosity, water storage capacity, and hygroscopicity (the amount of atmospheric water vapour absorbed by bark during non‐rainfall conditions). Drying rates of saturated samples under simulated wetting conditions were also assessed. Oak bark had higher bulk density, lower porosity, and dried slower than pine bark. Interestingly, bark from both species had lower bulk density, higher porosity, greater water storage capacity, and dried faster in stands that were burned every 3 years compared to other fire regimes (p < 0.001). In summary, this study demonstrates that prescribed fire regimes in an eastern US forest alter bark structure and thus influence individual tree control on hydrological processes. The increase in bark water storage capacity, coupled with faster bark evaporation times may lead to less water inputs to the forest floor and drier overall conditions. Further investigation of this fire‐bark‐water feedback loop is necessary to understand the extent of these mechanisms controlling landscape‐scale conditions.

THE EFFECT OF LIQUID PROPERTIES ON HEAT TRANSFER AND EVAPORATION CHARACTERISTICS OF THE LIQUID FILMS FORMED BY UNSTEADY SPRAY-WALL IMPACTS

For intermittent spray-cooling purpose, it is essential to study the unsteady aspects of film evaporation and heat-transfer characteristics. In the present study, total evaporation time and surface temperature variations are investigated for four different liquid films (water, ethanol, n-octane, and n-hexane). The evaporation process is analyzed using a three-dimensional spray-wall impact with Lagrangian wall-film model. The evaporation process occurs in three stages; at the initial moments, most of the heat is used to raise the film temperature, and slight evaporation also exists. The film temperature rises until it reaches the liquid saturation point to evaporate at a constant rate. In the last stage, the evaporation rate decreases with time due to the accumulation of vapor in the bulk flow. The effect of heat flux and initial film thickness on the total evaporation time and the slope of its changes are investigated. The results show that the total evaporation time increases linearly with the initial thickness. Also, the molecular weight and saturation point of liquids are influential parameters after the enthalpy of evaporation. The surface temperature rises to a maximum value before reducing by the film evaporation. The maximum amount of the wall temperature depends on the liquid thermal conductivity and the evaporation rate. Finally, the effect of the initial value of the film temperature is investigated, and a correlation for estimating the total evaporation time is extracted.

THE EXPERIMENTAL STUDY OF EVAPORATION OF WATER AND NANOFLUID DROPLETS ON THE SURFACES OF MATERIALS WITH DIFFERENT THERMAL CONDUCTIVITIES

The article presents the results of experimental studying evaporation of water and nanofluid droplets on the surfaces of various materials. Plates made of materials with significantly different thermal conductivity coefficients have been used as substrates: copper (λ = 401 W/m °С), Teflon (λ = 0.25 W/m °С), and extruded foamed polystyrene (λ = 0.03 W/m °С). In the experiments, the evaporation of water and nanofluid droplets with a volume of 5 μL has been considered at a constant temperature and humidity of the ambient air. A nanofluid (a mixture of water with gold nanoparticles) has been prepared by laser ablation. The concentration of nanoparticles in the nanofluid is about 0.1 wt %. Infrared thermography has been employed to determine the average temperatures of evaporating droplet surfaces. The results obtained have shown that, for all studied materials, the surface temperature of evaporating water droplets is higher than the temperature of adiabatic evaporation. Therewith, the lower the thermal conductivity coefficient of a substrate material, the lower the surface temperature of the droplet and the longer the time of its evaporation. The performed experiments have shown that the minimum temperature of nanofluid droplets is lower than that of water droplets, and the evaporation time of nanofluid droplets is longer than that of water droplets on the corresponding surfaces.

The influence of anion-exchange membrane nanostructure onto ion transport: Adjusting membrane performance through fabrication conditions

We fabricated dense anion-exchange membranes from the same polymer with variations in the self-assembled hydrophilic and hydrophobic domains. We show how the nanostructure forms during membrane formation and how it can be tuned by rationally designing fabrication conditions. We found that the hydrophilic and hydrophobic domain structure evolves during the membrane solidification. This can be controlled by using casting solvents with different evaporation times or by the addition of an ionic liquid which alters the interactions in the polymer film. We could further tailor the structure of solidified membranes by heat or solvent annealing and developed conditions that selectively adjust the nanostructure in different parts of the membrane. With these methods we could significantly optimize the macroscopic properties and ion transport rates of membranes made from the same polymer. The ionic liquid additive led to an almost doubling of the water uptake without influencing the swelling degree and also to a 3-fold higher diffusion rate for HBr. By using a post-treatment with dioxane we also managed to fabricate a membrane with a 5-fold higher ionic conductivity. We further found that different transport mechanisms are involved in ionic conductance and acid diffusion and could relate them to different membrane nanostructures.

Black hole solutions in the quadratic Weyl conformal geometric theory of gravity

We consider numerical black hole solutions in the Weyl conformal geometry and its associated conformally invariant Weyl quadratic gravity. In this model, Einstein gravity (with a positive cosmological constant) is recovered in the spontaneously broken phase of Weyl gravity after the Weyl gauge field (omega _{mu }) becomes massive through a Stueckelberg mechanism and it decouples. As a first step in our investigations, we write down the conformally invariant gravitational action, containing a scalar degree of freedom and the Weyl vector. The field equations are derived from the variational principle in the absence of matter. By adopting a static spherically symmetric geometry, the vacuum field equations for the gravitational, scalar, and Weyl fields are obtained. After reformulating the field equations in a dimensionless form, and by introducing a suitable independent radial coordinate, we obtain their solutions numerically. We detect the formation of a black hole from the presence of a Killing horizon for the timelike Killing vector in the metric tensor components, indicating the existence of the singularity in the metric. Several models corresponding to different functional forms of the Weyl vector are considered. An exact black hole model corresponding to a Weyl vector having only a radial spacelike component is also obtained. The thermodynamic properties of the Weyl geometric type black holes (horizon temperature, specific heat, entropy, and evaporation time due to Hawking luminosity) are also analyzed in detail.

Controlled growth of Ag-ZnO thin films by thermal evaporation technique for optimized thermoelectric power generation

This manuscript is described the facile and cost-effective growth of silver Zinc Oxide (Ag-ZnO) thin films by simple thermal evaporation method for thermoelectric power generation applications. Growth of samples is started by making pellets of pure silver (Ag) and zinc (Zn) powders which are composed of 1:1 ration and evaporated in vacuum tube furnace. The other growth parameters are fixed as; evaporation time (45 min), evaporation temperature (1010 0C) and oxygen flow rate (60 sccm). Five samples are prepared at different source to substrate distances (6.5–8.5 in.) and post deposition annealing of all samples is carried out at 800 °C using semi-programable muffle furnace. Prepared thin films are analyzed using X-Ray Diffraction (XRD), Raman spectroscopy, Scanning Electron Microscope (SEM) and Seebeck measurements to study the impact of various source to substrate distances on the structural morphological and thermoelectric behavior of Ag-ZnO nanocomposite thin films. The obtained results are revealed that different source to substrate distances strongly influence the structural, morphological, and thermoelectric behavior of prepared thin films. Optimal values for electrical conductivity, Seebeck coefficient and powerful factor of synthesized thin films are calculated as 3.05 × 103 S/m, 645 µV/°C and 1.27 × 10−3 Wm−1 oC−2 respectively at source to substrate distance of 7.0 in.

Experimental studies of evaporation of paraffin drops

Paraffin is a low-melting material that can be used as an environmentally friendly and high-energy fuel. It can also be considered as a promising material with phase transitions capable of accumulating heat. It is known that the period of induction of ignition of paraffin droplets consists of successive stages, the main ones of which are melting and evaporation. The paper examines the processes of evaporation of octadecane and docosane droplets in air at different temperatures. A method of studying the kinetics of evaporation of paraffin fuel droplets using digital photography of the research object and computer image processing has been developed.
 It is proved that the evaporation kinetics of the studied alkanes is described by the linear law of the change of the square of the diameter of the drop over time. Evaporation rate constants were found. There are no such data in the literature for these paraffins. The use of evaporation constants made it possible to find the time of complete evaporation of drops and to estimate the diffusion coefficient of paraffin vapor in air at different temperatures. As a result of the experiments, it was established that the rate of evaporation of octadecane is more than 4 times higher than the rate of evaporation of docosane. It was found that when the air temperature reaches the specified values, the rate of evaporation of the specified alkanes increases significantly.

Barrow-type structure and thermodynamics of black holes

The thermodynamics of black holes is investigated in the case of fractal-like event horizon, initially introduced by Barrow. The nature of the horizon surface is controlled by a parameter 0≤Δ≤1 with 0 corresponding to continuous space and 1 to completely fractal one. It is found that the entropy, the Helmholtz free energy, the mass and the heat capacity of the black hole are altered in the presence of non-zero Δ. As the black hole produces Hawking radiation, the dependence of its mass on time becomes softer as Δ increases, resulting in longer evaporation times. This effect makes relatively small primordial black holes to survive long enough so as to be potential ingredients of cold dark matter. The concept of Barrow-type structure can be generalized to the entire space resulting in a modified space-time metric.

A comprehensive simulation analysis to optimize the performance of spray evaporator on treating concentrated brine

The freshwater resources deficient has been dominated the world's science and policy agenda, owing to the population growth, rapid industrialization, and environmental pollution. Spray evaporator, as a promising and high-efficient desalination technology, has been widely applied to desalination or high salinity wastewater treatment industries. However, current studies on the evaporation characteristics of spray evaporator lack comprehensive analysis and further parameter screening that causes the difficulty to effectively choose optimal parameters for optimization. Therefore, the influences of 11 parameters on evaporation performance were systemically studied via computational fluid dynamics, evaluated via evaporation efficiency, a single droplet evaporation time, and atomization effect, and eventually, the most influential parameters were screened out via stepwise multiple linear regression. The results indicated that all parameters influence the evaporation performance, but the hot air temperature and velocity are the most influential parameters affecting the evaporation efficiency that can jointly explain 55.8 %–58.7 % variations and characteristics of evaporation and should be preferentially considered to improve the efficiency. Furthermore, the compressed air pressure is also worth considering since it could enhance evaporation performance and atomization effect simultaneously. This study provides a new insight and understanding for the design and optimization of spray evaporator.

State of the Art of Fuel Droplet Evaporation

The process of fuel droplet evaporating is one of the most important factors that directly affect the efficiency of the combustion process. Therefore, the current study reviews previous studies that focused on the process of evaporation of a drop of fuel. The review is divided into points. The first part is concerned with modeling of the evaporation process under different initial condition and temperature of the droplet. The second part present the experimental studies concerned with measuring the evaporation time of the droplet, as well as the shape of the droplet during the evaporation process. Most of the studies related to this subject can be divided into three categories: The first category is the studies that are concerned with the process of heating the droplet and studying the evaporation time for different types of fuels or by adding nanomaterials to the fuel and studying their effect on the evaporation process. The second category is the studies concerned with the mechanics of droplet evaporation and the study of droplet shape. The third category is the studies that focus on studying the effect of initial conditions, such as temperature and pressure, as well as the concentration of gasses surrounding the drop and their types. There are other studies concerned with projecting the electric field onto the drop during the evaporation process and studying its effect.

Tellurium Treatment for the Modification of Sulfide Inclusions and Corresponding Industrial Applications in Special Steels: A Review

Tellurium treatment is used to control the morphology of manganese sulfide (MnS) inclusions, reduce the mechanical anisotropy, and improve the machinability of sulfur‐bearing steels, such as free‐cutting steels, super free‐cutting steels, medium‐carbon microalloyed steels, and die steels. The boiling point of tellurium is low, and it is mainly added to steel in the form of fine particles wrapped in a cored wire. In steels, tellurium mainly exists in the form of Mn(S, Te) inclusions or MnTe–MnS composite inclusions. The strength of MnS inclusions is increased through tellurium doping; thus, the aspect ratio of sulfide after hot working is significantly decreased through tellurium treatment. However, the tellurium content in steel should not be too high; otherwise, brittle compounds will form and cause embrittlement, particularly in high‐alloyed steels. The Te/S mass ratio is considered an important factor in tellurium treatment. When the Te/S mass ratio in steel is 0.2, the aspect ratio of the as‐cast sulfide could be controlled within the optimal range. During steelmaking, the yield of Te can be improved by reducing the basicity of the slag and decreasing the time of Te evaporation. Through data‐driven material design, Te treatment technology undergoes broader development.

Quantitative evaluation of skin barrier function using water evaporation time related to transepidermal water loss.

Transepidermal water loss (TEWL) is often used as an index for skin barrier function. The skin barrier tester, SBT-100 (Rousette Strategy Inc), measures the TEWL, water evaporation time, and time constant by contacting the skin and diffusing water into the closing measurement chamber. However, the relationship between the TEWL and time constant has not been sufficiently investigated. This study involved analyzing the underlying measurement principle and obtaining data through two experiments. The TEWL and time constant were measured using SBT-100. Experiment 1 produced a simple simulation model for continuous water evaporation from the skin using a moisture-permeable film. In experiment 2, four skin sites of 43 healthy volunteers were examined from May to September 2018. In experiment 1, the TEWL increased and time constant decreased, following an increase in humidity in the external environment. Both parameters demonstrated significant negative correlation (drying: ρ=-0.832, p<0.001). For the 43 healthy volunteers who participated in experiment 2, their TEWL increased and time constant decreased in summer. For all skin measurement sites, both data demonstrated significant negative correlation (forehead: ρ=-0.909, p<0.001; back of the left hand: ρ=-0.829, p<0.001; left lateral elbow: ρ=-0.896, p<0.001; left lateral malleolus: ρ=-0.865, p<0.001). Results indicated that the time constant is significantly correlated with TEWL. Furthermore, the time constant can be used as a parameter for evaluating skin barrier function.

Numerical Investigation of Evaporation Modelling for Different Diesel Fuels at High Temperature and Pressure in Diesel Engine

Diesel engines are used widely in the world due to their capability of handling high torque and heavy loads efficiently. Fuel injection systems in the diesel engine have different processes that affect the complete burning of fuel in the combustion chamber. These include the primary and secondary breakup of liquid fuel droplets and evaporation. Diesel engines use the air as a working substance only. One of the processes is the evaporation of fuel droplets. Complete evaporation of diesel fuel liquid in the combustion chamber is a prerequisite for complete combustion. Hence evaporation of droplets has an impact on the efficiency of the engine and consequently on the output power and torque. In the present paper evaporation of two different diesel fuels is modeled numerically taking into account the turbulence effects present in the cylinder due to high temperature and pressure using the RANS turbulence model. Evaporation of n-heptane diesel fuel and n-decane is controlled by the numerical model that includes the conservation equations of mass, energy, momentum and species transport. During the evaporation phase heat is transferred to the droplet and due to evaporation from the surface of the droplet, the mass of evaporating droplets is decreased. These two processes are controlled by the equations of the Discrete Phase Model present in the Fluent. Then the results are plotted by varying the droplet diameter and temperature. Results include the decay in droplet diameter, increase in the droplet temperature effect on the velocity of droplet and temperature changes in the cylinder due to evaporation of fuel. There are different parameters which affect the rate of evaporation of fuel droplets inside the engine cylinder of an internal combustion engine. These parameters include the diameter of fuel droplets, initial temperature of fuel droplets, and the temperature inside the cylinder after the compression stroke and surface area of droplets. Small droplets need a short time to evaporate while if the size of droplets is large then evaporation times is also increased.

Hawking Radiation: Image of the Invisible

Is it possible to quantify in General Relativity, GR, the entropy generated by Super-Massive Black Holes, SMBH, during its evaporation time, since the intrinsic Hawking radiation in the infinity that, although insignificant, is important in the effects on the thermal quantum atmosphere? The purpose was to develop a formula that allows us to measure the entropy generated during the evaporation time of different types of SMBH of: i. remnant BH of the binary black holes’ merger, BBH: GW150914, GW151226 and LTV151012 detected by the Laser Interferometer Gravitational-Wave Observatory, LIGO, and ii. Schwarzschild, Reissner-Nordström, Kerr and Kerr-Newman, and thus quantify in GR the “insignificant” quantum effects involved, in order to contribute to the validity of the generalized second law, GSL, that directly links the laws of black hole mechanics to the ordinary laws of thermodynamics, as a starting point for unifying quantum effects with GR. This formula could have some relationship with the detection of the shadow’s image of the event horizon of a BH. This formula was developed in dimensional analysis, using the constants of nature and the possible evaporation time of a black hole, to quantify the entropy generated during that time. The energy-stress tensor was calculated with the 4 metrics to obtain the material content and apply the proposed formula. The entropy of the evaporation time of SMBH proved to be insignificant, its temperature is barely above absolute zero, however, the calculation of this type of entropy allows us to argue about the importance of the quantum effects of Hawking radiation mentioned by authors who have studied the quantum effects with arguments that are fundamentally based on the presence of the surrounding thermal atmosphere of the BH.

New Cryoprotectant Loading Method for Cell Droplet Vitrification with Continuous Evaporation.

Droplet-based vitrification is considered to be a promising cryopreservation method, which achieves high cell viability through high cooling rates and low concentrations of cryoprotective agents (CPAs). However, the droplet vitrification cryopreservation process needs in-depth research, such as the balance of the CPA concentration and the cooling rate, the CPA loading process, and the droplet encapsulation method. Here, we developed a chip with a high cooling rate for vitrification droplet encapsulation and provided a new method for continuous loading of low-concentration CPA droplets by evaporation. The results showed that the CPA droplet volume decreased exponentially with the evaporation time, and the larger the initial droplet size, the longer the evaporation time to achieve the critical vitrification concentration. There was no significant difference in the viability of MSCs, NHEK, and A549 cells between the evaporation loading vitrification method and the traditional slow freezing method, but the former was easier to operate and can balance the cooling rate and concentration by controlling the evaporation time. Moreover, a theoretical model was proposed to predict the CPA concentration inside the microdroplets dependent on the evaporation time. The current work provides a potential method to load low-concentration CPAs for cell vitrification preservation, which is more beneficial for cell therapy and other regenerative medicine applications.

Finding a way through the “misty” evaluation of the flammability and explosivity of kerosene aerosols

• JetA1 mist flammability and explosivity are assessed in a confined explosion vessel. • Influence of initial conditions on explosion sensitivity and severity is studied. • JetA1 mists with a small droplet size have a higher rate of pressure rise. • The MIE of JetA1 mist may be lower than that of vapors at low temperatures. • The vapor/liquid ratio of a mist is a key parameter of its explosion severity. In the context of assessing hydrocarbon mist ignition sensitivity and explosion severity, an original test method is proposed, focusing on kerosene JetA1 mists but is applicable to other hydrocarbons. Experiments were carried out in a modified apparatus based on the 20L explosion sphere. Fine control of the gas/liquid ratio and flow rates, the mist concentration, and the ignition energy and duration, was ensured by a specifically customized control system guaranteeing the flexibility and compliance of the test apparatus. The droplet size distribution (DSD) and the level of turbulence of the JetA1 mist cloud were first determined by an in-situ laser diffraction sensor and by Particle Image Velocimetry, respectively. The lower explosive limit (LEL), the minimum ignition energy (MIE), the limiting oxygen concentration (LOC), the maximum explosion overpressure (P max ), and the maximum rate of pressure rise (dP/dt max ) were then determined for different mist concentrations, ambient temperatures, initial turbulence levels, energies, and DSD. Tests showed that the LEL mist of JetA1 mists of an average diameter of 8 µm is around 94 g/m 3 , a value which increases to 220 g/m 3 with increasing DSD. This value also tends to decrease considerably with increasing temperatures. Moreover, at a JetA1 concentration of 125 g/m 3 , P max and dP/dt max as high as 6 bar and 192 bar/s respectively were reached, the latter increasing to about 480 bar/s at T = 60 °C. These mists were shown to be ignitable using energies as low as 200 mJ, which is lower than that of vapors at low temperatures, and a limiting concentration of oxygen of 15.8 % v/v . The potential presence of hydrocarbon mist should therefore be an element that requires reconsidering the classification of hazardous areas. Finally, to stress the influence of the vapor-liquid ratio present in the cloud before ignition on the combustion kinetics, an evaporation model based on the d 2 -law was developed estimating the evaporation time and the vapor quantity at different initial temperatures or droplet diameters. Findings were shown to be well coherent allowing the proposition of a new technique for determining hydrocarbon mist safety criteria. Finally, results have shown that JetA1 mists can ignite at temperatures below the liquid’s flashpoint under varying turbulence levels and droplet size distributions.

INTRODUCING HYDROCOLLOID WOUND DRESSING ENERGY DISRUPTING HUMAN TISSUE METABOLISM

The development in 2016 of a novel Potassium Ferricyanide of formula (K₃[Fe(CN)₆]) based tabletop microscopy method enabled for the recording of electromagnetic energy emissions from plants and animal tissue. The microscopy method was subsequently validated and used to document inter-tissue energy exchanges of both, human blood, and catalase proper with a hair follicle. As of recent in vitro research using hair follicles as sentinels support expanding an endogenous irradiation theory as disease causing mechanism introduced in 1956 and revisited in 2016 to now also include non-biological exogenous irradiation emitted by hydrocolloid based wound dressings (WD). Videos and still images are presented validating the findings of energy emitted by a small fragment of a hydrocolloid based WD penetrating a 1mm glass slide and unexpectedly delaying the evaporation time of a Potassium Ferricyanide solution surrounding a freshly plucked human hair follicle. Absorption of Incoming electromagnetic radiation is a property of (K₃[Fe(CN)₆]). The introduction of energy from an exogenous non-biological material, namely a hydrocolloid wound dressing fragment justifies inclusion in future research protocols.

The use of environmental decision support systems for modeling of atmospheric pollution following the chemical accidents

We studied the possibility of the combined application of screening models to assess the characteristics of sources in accidents at storage facilities for hazardous substances with complex models of atmospheric transport as part of modern decision support systems to calculate air pollution in a wide range of spatial and temporal scales. The evaporation time following an emergency spill, estimated by screening models, is used to set the emission intensity and calculate the atmospheric transport by the RODOS nuclear emergency response system. For the accident in Chernihiv on March 23, 2022, it was estimated that the maximum permissible concentration of ammonia 0.2 mg/m3 was exceeded at distances up to 75 km from the source. The dependence of the calculated maximum concentrations on time is close to asymptote cmax ~ t-4.5 up to 15 h after emission, which is consistent with the asymptote σ ~ t3/2 for the time dependence of the sizes of puffs following turbulent dispersion of instantaneous releases.