Phase Evaporation Research Articles

A fully transient approach on evaporation of multi-component droplets

This paper deals with multi-component droplet evaporation. For this purpose, species, momentum, and energy equations for the gas phase are solved numerically together with species and energy equations of the liquid phase. A fully transient (FT) approach with variable properties in terms of time and space is employed. The results are compared with available experimental data in the literature for binary- and multi-component droplets at various temperatures and satisfactory agreements are seen. In order to study the effect of volatility on the droplet evaporation, heptane, decane, and hexadecane are examined and multi-staged feature of evaporation is captured. Also, the range of droplet internal bubbling is estimated by investigating internal temperature and mass fraction variations. The results indicate that diffusion enthalpy term in the liquid phase plays a significant role in the deviation of multi-component droplet evaporation trend from the single component. Furthermore, the quasi-steady (QS) assumption in the gas phase of droplet evaporation is evaluated. The comparison between FT and QS approaches shows that the amount of heavier component in the droplet composition and increasing volatility difference of components increase the deviation of two approaches.

The effect of different n-butanol-fatty acid methyl esters (FAME) blends on puffing characteristics

The droplet suspension technology was used under the condition of atmospheric pressure and 873K. The n-butanol concentration ranged from 0% to 75% to investigate the effect of n-butanol concentration on the puffing characteristics of a n-butanol-fatty acid methyl esters (FAME) droplet. Experimental results showed that BUT25, BUT50 and BUT75 (BUT’XX’ represented XX% n-butanol by mass fraction in the n-butanol-FAME blend) underwent three phases, namely the transient heating phase, fluctuation evaporation phase and equilibrium evaporation phase. The temperatures of BUT25, BUT50 and BUT75 were similar at the start and end of the transient heating phase. The duration of BUT75’s transient heating phase was much longer than that of BUT25 and BUT50. Therefore, the evaporation cooling of BUT75 was the most prominent because the temperature growth rate of BUT75 was significantly less than that of BUT25 and BUT50. Furthermore, the fluctuation evaporation phase could be divided into the strong and weak fluctuation stages. The violent fluctuation was only observed in the strong fluctuation stage. The weak fluctuation stage was similar as the stable evaporation. The active rupture was found in the strong fluctuation stage and the passive rupture was found in the weak fluctuation stage. The active and passive ruptures were caused by the fast bubble expansion and surface evaporation respectively. In addition, many periodic processes were contained in the strong fluctuation stage. The similarity degree of the periodic process showed a slump and a gradual increase, which were caused by bubble expansion and droplet recovery respectively. The bubble expansion of BUT50 was greater than that of BUT75. Significant bubble expansion led to the violent deformation after bubble rupture. The recovery time of BUT50 was longer than that of BUT75. Therefore, the similarity degree of BUT50 exhibited a wavy structure and BUT75 displayed a comb-like structure in the strong fluctuation stage.

New insights into saline water evaporation from porous media: Complex interaction between evaporation rates, precipitation, and surface temperature

AbstractUnderstanding salt transport and deposition patterns during evaporation from porous media is important in many engineering and hydrological processes such as soil salinization, ecosystem functioning, and land‐atmosphere interaction. As evaporation proceeds, salt concentration increases until it exceeds solubility limits, locally, and crystals precipitate. The interplay between transport processes, crystallization, and evaporation influences where crystallization occurs. During early stages, the precipitated salt creates an evolving porous structure affecting the evaporation kinetics. We conducted a comprehensive series of experiments to investigate how the salt concentration and precipitation influence evaporation dynamics. Our results illustrate the contribution of the evolving salt crust to the evaporative mass losses. High‐resolution thermal imaging enabled us to investigate the complex temperature dynamics at the surface of precipitated salt, providing further confirmation of salt crust contribution to the evaporation. We identify different phases of saline water evaporation from porous media with the corresponding dominant mechanisms in each phase and extend the physical understanding of such processes.

Ultra-Thick Electrodes for Li-Ion Battery

In order to meet the challenge of a transition from fossil fuels to green energies, the rapid development of technology is crucial. A characteristic of energy produced from renewable sources is to be discontinuous in time (e. g. photovoltaic or wind turbines). So, as a result of the development of this kind of systems, it is really important to establish a reliable electric energy storage grid. Nowadays, advanced devices that convert and store energy are the focus of intensive attentions and lithium-ion batteries hold the promise of effective solution for a clean electric future. Nevertheless, the needs to improve performances and reduce costs of Li-ion batteries encourage different research strategies. Among them, an increase in the basis weight of the electrodes active material allows to improve the energy density and to reduce the costs associated with the electrochemical inactive materials (current collectors and separator). The maximum loading achievable by the current industrial reference process, the coating, is limited by the migration of the binder during solvent evaporation phase. Thus, an innovative and effective process, the filtration, is here proposed for the production of ultra-thick electrodes (> 20 mAh / cm² or > 50 mg / cm²). In particular, this research is focused on the adaptation of filtration with the aim to obtain Li-ion battery electrodes and on the development of a pseudo 3D current collector. This innovative current collector is suitable for the filtration process, participates in the transversal electrical conductivity and improves the adhesion of the active layer. The active materials used in this research are commercial LiNiMnCo (NMC) for the cathode and graphite for the anode. The mechanical properties of ultra-thick electrodes are, of course, critical and will be discussed. Moreover, the remarkable mechanical stability along with the improved adhesion of active material layer with the metallic current collector allows electrodes to be pressed and to attain low porosity, resulting in improved energy density and increased electrical conductivity due to a better contact between particles. The electrochemical performances of electrodes based on NMC/graphite and of a full cells composed of these ultra-thick electrodes will be presented. These ultra-thick electrodes feature a volumetric energy density greater than the state of art Li-ion electrodes, making them particularly suitable for stock energy produced from renewable and natural sources, giving the possibility to increase the capacity of future electricity grid. Fig. 1: Ambient temperature galvanostatic cycling behavior of a NMC/graphite ultra-thick cell at different C-rate. Inset shows typical potential vs. specific capacity profile. Figure 1

Key Odorants of Lazur, a Polish Mold-Ripened Cheese.

Application of gas chromatography-olfactometry (GC-O) carried out on the volatile fraction isolated by solvent-assisted flavor evaporation (SAFE) and solid phase microextraction (SPME) from Lazur mold-ripened cheese revealed 17 odor-active compounds. The highest flavor dilution factor (FD) has been obtained for methanethiol (2048) with a burnt odor note and for 2(3)-methylbutanoic acid (2048) with a cheesy, pungent odor. Further quantitation of the 15 most aroma-active compounds allowed for calculation of their odor activity values (OAV). The highest OAVs were obtained for methanethiol (500), 3(2)-methylbutanoic acid (321), 3-(methylthio)propanal (210), 2,3-butanedione (65), dimethyl trisulfide (22), butanoic acid (20), 1-octen-3-ol (18), ( Z)-4-heptenal (14), dimethyl disulfide (14), dimethyl sulfide (13), phenylacetaldehyde (6), 2-ethyl-3,5-dimethylpyrazine (5), and acetic acid (4). An aroma recombination experiment showed slight differences in the perception of cheesy/sweaty and moldy/musty notes. To verify the influence of methyl ketones on the aroma profile of mold-ripened cheese, recombinant has been additionally supplemented with 2-pentanone, 2-heptanone, and 2-nonanone in concentrations determined in Lazur cheese. The aroma profile remained unchanged, which would suggest that methyl ketones, in this particular cheese, do not play a significant role in the formation of aroma.

Experimental study on puffing characteristics of biodiesel-butanol droplet

In order to research puffing characteristics of biodiesel-butanol blends, single droplet experiments of BUT25 and BUT75 were conducted under the condition of atmospheric pressure and 800°C. Experimental results showed that BUT25 only demonstrated core mode, while BUT75 demonstrated both surface and core mode simultaneously. The core mode was a periodic process including bubble nucleation, bubble expansion and bubble rupture inside the droplet. The surface mode was featured by the appearance of many micron sized child droplets. Two new parameters were proposed to analysis puffing characteristics, namely the similarity degree and the deformation degree. The puffing process usually contained the transient heating phase, fluctuation evaporation phase and equilibrium evaporation phase. Both the transient heating phase and equilibrium evaporation phase were stable evaporation processes. Analysis indicates that the three phases of the puffing process are more appropriately distinguished through the profile of similarity degree than that of the normalized squared diameter. Furthermore, the similarity degree of BUT25 displayed a wavy structure and BUT75 displayed a trapezoid structure in the fluctuation evaporation phase. On the other hand, the deformation degree remained unchanged in stable evaporation processes but exhibited a sharp rise at the instant of bubble expansion or rupture.

Heat and Mass Transfer of the Droplet Vacuum Freezing Process Based on the Diffusion-controlled Evaporation and Phase Transition Mechanism.

A frozen phase transition model is developed to investigate the heat and mass transfer of a single water droplet during the vacuum freezing process. The model is based on the diffusion-controlled evaporation mechanism and phase transition characteristics. The droplet vacuum freezing process can be divided into three stages according to the droplet states and the time order. It includes the evaporation freezing stage, the isothermal freezing stage and the sublimation freezing stage. A numerical calculation is performed, and the result is analysed. The effects of the vacuum chamber pressure, initial droplet diameter and initial droplet temperature on the heat and mass transfer characteristics at each stage are studied. The droplet experiences supercooling breakdown at the end of the evaporation freezing stage before the isothermal freezing stage begins. The temperature is transiently raised as a result of the supercooling breakdown phenomenon, whose effects on the freezing process and freezing parameters are considered.

An accelerated water evaporation optimization formulation for discrete optimization of skeletal structures

Water Evaporation Optimization (WEO) is a recently developed physics-based metaheuristic algorithm that mimics the well-known rules governing the evaporation process of water molecules from a solid surface with different wettability. In the WEO algorithm, molecules are updated globally and locally respectively in two independent sequential phases: monolayer and droplet evaporation phases. In this study, the computational cost of the WEO is improved through the simultaneous utilizing of both phases. The new formulation is tested on classical discrete optimization problems achieving a significant enhancement in convergence rate compared to the basic WEO.

Numerical investigation of effect of fill ratio and inclination angle on a thermosiphon heat pipe thermal performance

Computational Fluid Dynamic (CFD) modelling of a heat pipe is a powerful tool that can be used to investigate the complex physical phenomena of the evaporation and condensation phase change processes inside thermosiphon heat pipes. In this work, a new CFD simulation of two phase flow inside thermosiphon heat pipe is carried out to investigate the effect of fill ratio (ratio of liquid volume to the evaporator volume) and inclination angle on its thermal performance in terms of temperature distribution and thermal resistance using FLUENT (ANSYS 15). Results of the CFD simulation were compared to published experimental data showing good agreement with maximum deviation of 4.2% and 8.1% for temperature distribution and thermal resistance, respectively. In addition, numerical results of inclination angle were also compared with experimental data in terms of thermal resistance giving maximum deviation of 1.3%. Using the validated CFD modelling, results showed that at low fill ratio and low inclination angle, there was a significant increase in the evaporator temperature. Regarding the thermal resistance, a fill ratio of 65% and inclination angle of 90° produced the lowest thermal resistance for all the heat input values used. Also, as heat input increases, the effect of the fill ratio and inclination angle becomes more significant.

The effects of irrigation on leaf nutrient content in pomegranate ‘İzmir 1513’

Pomegranate (Punica granatum L.) is a characteristic species of the Mediterranean area whose use and culture have longstanding tradition. It is well adapted to the growth conditions in Turkey and Mediterranean countries and is frequently found growing in wild or semi wild conditions. Pomegranate is known as a drought tolerant crop, but regular irrigation is mandatory in commercial production. Water quantity applied and optimal irrigation regime depends on some factors as soil type, tree size, physiological phase of tree and potential evaporation. Irrigation frequency and quantity affect nutrient uptake of the trees. In this study leaf nutrient content of 'Izmir 1513' pomegranate was determined under different irrigation water quantities during two consecutive years. Three water quantities (0, 50 and 100% of estimated evapotranspiration by considering class A pan evaporation) were applied to trees by drip irrigation. Leaf content of potassium, iron, and copper was not affected, but nitrogen, calcium and magnesium increased with higher quantity of irrigation water in the first year. In the second year, nitrogen, phosphorus, calcium, magnesium and manganese were affected by the irrigation levels.

The Las Salinas palaeo-lagoon in the Sechura Desert (Peru): Evolution during the last two millennia

The Sechura Desert provides a unique example of a vast palaeo-lagoon system on the Peruvian coast that was active during the first millennium AD. Reconstruction of coastal evolution is made possible by the good resolution of the sedimentary records of the Las Salinas Noroeste coastal plain. Evidence from morphostratigraphy and sedimentary facies indicates marked environmental diversity between the 3rd and the 8th centuries AD and a wide variability of sedimentary dynamics: lagoon foreshores received alternately fine distal marine sediments and coarser continental sediments in pro-deltaic sheets. Evaporation phases periodically occurred in these foreshores causing the formation of salt crusts. After a last high water level in the 8th century AD, the lagoon ultimately dried out and remains dry today. The malacofauna and sedimentary facies indicate that marine marshes bordered by vegetation, perhaps mangrove, developed in the higher parts of these lagoons. This palaeogeography is explained by the progressive build-up of a sand bar which started at least in the middle Holocene. From the 3rd to 8th centuries AD, the lagoon had limited connection to the sea in its northern end and hosted a warm-water and productive ecosystem that was exploited by pre-Hispanic populations. Wetter conditions in the Andes and occasional El Niño rainfalls maintained the lagoon during this period. The freshwater input likely stopped in the 8th century AD, which led to the closing of the shore bar under the influence of the longshore drift rapidly followed by the drying up of the lagoon, and the abandonment of the archaeological site.

Development of porous nanocomposite membranes for gas separation by identifying the effective fabrication parameters with Plackett–Burman experimental design

In this research, Plackett–Burman experimental design was used as a screening method to investigate seven processing factors in the preparation of new polyethersulfone based porous nanocomposite membrane. Polymer concentration, nanoparticle type, nanoparticle concentration, solvent type, solution mixing time, evaporation time, and annealing temperature are variables that were evaluated to fabricate mixed matrix membranes using the evaporation phase inversion method for gas separation. According to obtained results, polymer concentration, nanoparticle concentration, solution mixing time, and evaporation time processing factors had significant effects on gas permeation. In addition, the nanoparticle type, nanoparticle concentration, and polymer concentration had substantial effects on membrane selectivity. From analysis of variance, it was found that the model used for membrane gas permeability and membrane selectivity as response values were more reliable within spaced levels. Scanning electron microscope, gas permeation experiments and statistical analysis showed that polymer concentration, nanoparticle type, nanoparticle loading and evaporation time significantly affected the final membrane morphologies and performances. According to this study, trade-off limitation between gas permeability and membrane selectivity could be eliminated by identifying the effective fabrication parameters.

Primordial Black Holes: Observational characteristics of the final evaporation

Many early universe theories predict the creation of Primordial Black Holes (PBHs). PBHs could have masses ranging from the Planck mass to 105 solar masses or higher depending on the size of the universe at formation. A Black Hole (BH) has a Hawking temperature which is inversely proportional to its mass. Hence a sufficiently small BH will quasi-thermally radiate particles at an ever-increasing rate as emission lowers its mass and raises its temperature. The final moments of this evaporation phase should be explosive and its description is dependent on the particle physics model. In this work we investigate the final few seconds of BH evaporation, using the Standard Model and incorporating the most recent Large Hadron Collider (LHC) results, and provide a new parameterization for the instantaneous emission spectrum. We calculate for the first time energy-dependent PBH burst light curves in the GeV/TeV energy range. Moreover, we explore PBH burst search methods and potential observational PBH burst signatures. We have found a unique signature in the PBH burst light curves that may be detectable by GeV/TeV gamma-ray observatories such as the High Altitude Water Cerenkov (HAWC) observatory. The implications of beyond the Standard Model theories on the PBH burst observational characteristics are also discussed, including potential sensitivity of the instantaneous photon detection rate to a squark threshold in the 5–10 TeV range.

Multiparticle versus single sequential emission in nuclear evaporation processes

The role of simultaneous particle emission processes in the evaporation phase is investigated in the high-energy regime of compound nucleus excitation. A Monte Carlo simulation is employed to consider the effect of different emission channels on the particle yield and on the fission process occurrence. A significant change is shown on evaporation-phase results due to the inclusion of multiparticle emission channels in the calculation of the compound nucleus modes of deexcitation. The total yield of neutrons and charged particles suffer an significant change in respect to results obtained in the conventional approach restricted to the sequential one-particle emission mechanism. These particle multiplicities, determined as a function of the excitation energy, present a qualitative change at the high-excitation-energy regime of the compound nucleus. This behavior is confirmed when a different mass formula is used to determine separation and nuclear binding energies. This finding is an important aspect for the study of spallation reaction in acceleration driven system (ADS) reactors, since the majority of neutrons generated in these reactions come from the evaporation stage of the reaction.

The use of poly(vinylidenefluoride-co-hexafluoropropylene) for the preparation of polymer inclusion membranes. Application to the extraction of thiocyanate

Abstract The successful use of the solvent evaporation casting technique for the preparation of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) based polymer inclusion membranes (PIMs) is described for the first time. PIMs consisting of 70 wt% PVDF-HFP as the base polymer and 30 wt% Aliquat 336 as the carrier were prepared by the solvent evaporation casting and phase inversion techniques from solutions of the membrane components in tetrahydrofuran (THF) and N,N-dimethylformamide. These PIMs were compared in terms of their ability to extract the thiocyanate anion as a model target chemical species whose removal from gold mining process and tailings waters is of considerable technological and environmental interest. Best results were achieved with the PIMs produced by solvent evaporation from THF solutions. These membranes were translucent, flexible and homogeneous. Scanning electron microscopy images did not reveal the presence of a pore structure. The 30 wt% Aliquat 336 PVDF-HFP-based PIMs also exhibited significantly higher extraction and back-extraction rates for SCN− and long-term stability compared to PVC-based PIMs containing the same Aliquat 336 concentration. The results obtained in this study indicate that the use of PVDF-HFP as the base polymer in PIMs, prepared by conventional solvent evaporation casting, improves their performance in comparison to PIMs with traditionally used polymers such as poly(vinyl chloride) (PVC) and cellulose triacetate (CTA).

Stick-Jump (SJ) Evaporation of Strongly Pinned Nanoliter Volume Sessile Water Droplets on Quick Drying, Micropatterned Surfaces.

We present an experimental study of stick-jump (SJ) evaporation of strongly pinned nanoliter volume sessile water droplets drying on micropatterned surfaces. The evaporation is studied on surfaces composed of photolithographically micropatterned negative photoresist (SU-8). The micropatterning of the SU-8 enables circular, smooth, trough-like features to be formed which causes a very strong pinning of the three phase (liquid-vapor-solid) contact line of an evaporating droplet. This is ideal for studying SJ evaporation as it contains sequential constant contact radius (CCR) evaporation phases during droplet evaporation. The evaporation was studied in nonconfined conditions, and forced convection was not used. Micropatterned concentric circles were defined having an initial radius of 1000 μm decreasing by a spacing ranging from 500 to 50 μm. The droplet evaporates, successively pinning and depinning from circle to circle. For each pinning radius, the droplet contact angle and volume are observed to decrease quasi-linearly with time. The experimental average evaporation rates were found to decrease with decreasing pining radii. In contrast, the experimental average evaporation flux is found to increase with decreasing droplet radii. The data also demonstrate the influence of the initial contact angle on evaporation rate and flux. The data indicate that the total evaporation time of a droplet depends on the specific micropattern spacing and that the total evaporation time on micropatterned surfaces is always less than on flat, homogeneous surfaces. Although the surface patterning is observed to have little effect on the average droplet flux-indicating that the underlying evaporation physics is not significantly changed by the patterning-the total evaporation time is considerably modified by patterning, up to a factor or almost 2 compared to evaporation on a flat, homogeneous surface. The closely spaced concentric circle pinning maintains a large droplet radius and small contact angle from jump to jump; the result is a large evaporation rate leading to faster evaporation.

Preparation of Polyvinylchloride Nanofiltration Membrane: Investigation of the Effect of Thickness, Prior Evaporation Time and Addition of Polyethylenglchol as Additive on Membrane Performance and Properties

In this work, polyvinylchloride (PVC) membrane prepared via casting solution technique and phase inversion method. N, N dimethylacetamide (DMAC) was used as primary solvent and Tetrahydrofuran (THF) was used as a co-solvent. The effects of parameters such as membrane thickness, evaporation time of casting film before immersion precipitation and addition of polyethylenglchol (PEG) on PVC membrane were studied in terms of deionized water flux (DIW), tensile strength, phase inversion time in non-solvent, water content, final wet thickness, permeability flux, salt rejection and antifouling properties. It consulted; DIW has an overhand relation by increasing of membrane thickness and prior casting film evaporation time. In addition there was a liner relation between membrane thickness and prior casting film evaporation time versus phase inversion time in non-solvent. The results revealed that by increasing prior casting film evaporation time, the tensile versus of strength force increase. In addition, water content percent was decreased by increasing of prior evaporation time. Besides, addition of PEG as a hydrophilic additive improved membrane performance by increasing of flux and less fouling during experiments.

On the nucleon effective mass role to the high energy proton spallation reactions

We explore the effect of the nucleon effective mass to the dynamic evolution of the rapid phase of proton–nucleus spallation reactions. The analysis of the relaxation time for the non-equilibrium phase is studied by variations in the effective mass parameter. We determine the final excitation energy of the hot residual nucleus at the end of cascade phase and the de-excitation of the nuclear system is carried out considering the competition of particle evaporation and fission processes. It was shown that the excitation energy depends of the hot compound residual nucleus at the end of the rapid phase on the changing effective mass. The multiplicity of particles was also analyzed in cascade and evaporation phase of the reaction.The use of nucleon effective mass during cascade phase can be considered as an effect of the many-body nuclear interactions not included explicitly in a treatment to the nucleon–nucleon interaction inside the nucleus. This procedure represents a more realistic scenario to obtain the neutron multiplicity generated in this reaction, which is a benchmark for the calculation of the neutronic in the ADS reactors.

Tunable functionalization of graphene nanosheets for graphene-organic hybrid photodetectors

Graphene-organic hybrid thin films are promising candidates for use as advanced transparent electrodes and high-performance photodetectors. In this work, we fabricated hybrid thin film structures consisting of graphene and either tetraphenyl-porphyrin (H2TPP) or metalloporphyrins such as aluminum (III) tetraphenyl-porphyrin (Al(III)TPP) and zinc tetraphenyl-porphyrin (ZnTPP). The optical and electrical characteristics of ultrathin photodetectors based on the graphene-organic hybrid layers were subsequently evaluated. A hybrid deposition system capable of both thermal evaporation and vapor phase metalation was employed to synthesize the tunable metalloporphyrin-based thin films. As a proof of concept, we successfully fabricated various graphene-based photodetectors via the simple and efficient vapor-phase metalation of porphyrin. This work may facilitate the development of new architectures for flexible graphene-organic devices.

SIMULTANEOUS IRIS AND HINODE/EIS OBSERVATIONS AND MODELING OF THE 2014 OCTOBER 27 X2.0 CLASS FLARE

ABSTRACT We present a study of the X2-class flare which occurred on 2014 October 27 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature emission (≳10 MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blueshifted Fe xxi line profiles, up to 200 km s−1 during the rise phase of the flare, indicating that the site of the plasma upflows is resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric, which we interpret as being due to the lower spatial resolution of EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot emission (log(T[K]) > 7.2) is first concentrated at the footpoints before filling the loops. Density-sensitive lines from IRIS and EIS give estimates of electron number density of ≳1012 cm−3 in the transition region lines and 1010 cm−3 in the coronal lines during the impulsive phase. In order to compare the observational results against theoretical predictions, we have run a simulation of a flare loop undergoing heating using the HYDRAD 1D hydro code. We find that the simulated plasma parameters are close to the observed values that are obtained with IRIS, Hinode, and AIA. These results support an electron beam heating model rather than a purely thermal conduction model as the driving mechanism for this flare.