Evaporation Stage Research Articles

Enhanced micro-explosion to improve the yield of light oil in catalytic cracking of water-in-heavy oil emulsion prepared by continuous membrane emulsification

Membrane emulsification provides new ideas for improving the atomization performance of high viscosity heavy oil in catalytic cracking process, thereby improving the distribution of catalytic cracking products. A comprehensive understanding of the micro-explosion characteristics and catalytic cracking of low water content heavy oil emulsion is the key to the application of membrane emulsification technology in heavy oil catalytic cracking process. Therefore, different water droplet sizes and water content of heavy oil emulsion were controllably prepared by continuous membrane emulsification, and their micro-explosion characteristics and catalytic cracking performance were investigated. The evaporation of heavy oil emulsion droplets (water content over 3 vol%) only underwent the heat transfer stage and the fluctuating evaporation stage due to the strong micro-explosion. The micro-explosion delay time of emulsion droplets decreased from 2.631 to 0.434 s/mm2 with increased temperature (300–600 ℃), increased from 0.645 to 1.042 s/mm2 with increased water content (1–5 vol%), and increased from 0.642 to 1.237 s/mm2 with increased average droplet size (1.80–14.6 μm). The child droplets generated after micro-explosion were characterized, and the different heating behaviors were quantitatively distinguished by the average size of the child droplets. Additionally, the micro-explosion performance (i.e. child droplets size and strong micro-explosion probability) of emulsion droplets improved with increasing water content and average water droplet size, while it initially decreased and then increased when the temperature increased. Furthermore, the improvement of micro-explosion performance by membrane emulsification can increase the yield of light oil (up to a maximum increase of 10.82 %) and reduce the yield of coke (up to a maximum decrease of 5.99 %) in the heavy oil emulsion catalytic cracking.

Can a laboratory experiment express the size effect on the drying of refractory castables?

Refractories play an important role in societies’ progress as they enable extensively consumed materials to be processed such as steel and cement. Because of the high demand of these supplies, refractory-lined equipment comprises massive structures that have large dimensions and weighs several tons. Conversely, laboratory samples, used to study the behavior of these materials, are orders of magnitude smaller and often found weighing less than 1 kg. Within the context of refractory castable drying, this work aims to investigate the impact of size effects on water removal dynamics during thermogravimetry tests. The analysis of mass loss and its derivative with respect to temperature indicates that increasing the heating rate applied in the small samples can lead to a better reproduction of the evaporation and ebullition stages of the drying of large ones, due to the compensation effect of the faster temperature increase on the smaller sample sizes leading to similar thermal gradients. Furthermore, the presence of polymeric fibers and their influence on the size effect are also examined, showing that the increased permeability induced by such additives reduces the intensity of the scale effect. Additionally, it was found that for cubic samples with sizes equal to or larger than 10 cm, a kink in the temperature evolution measured at the center of the samples took place. A hypothesis based on the results and on observations of recent studies is proposed to explain this phenomenon, attributing it to the rapid evaporation of accumulated liquid water at those positions. This study also highlights the importance of considering the size-dependent nature of drying dynamics in refractory castables, as conventional thermogravimetry on laboratory scale samples may overlook important phenomena. Understanding the mechanisms occurring at real structural scales during water removal is crucial for predicting their behavior upon heating and enabling faster and safer drying processes for refractories.

Flame propagation characteristics and surface functional groups changes of corn starch dust during the combustion process

Corn starch (CS) is one of the most common powders in industrial production and daily life, but its inherent risks of ignition and explosion cannot be disregarded. In this study, the flame propagation behaviors of CS at various concentrations were studied by a dust ignition experiment system. Meanwhile, the combustion process was analyzed in detail by differential scanning calorimetry tests, and the changes of key groups in molecules during the combustion process were monitored in real time by in-situ diffuse reflectance infrared Fourier transform spectroscopy tests. Based on this, the reaction process of CS combustion was analyzed. It was found that the dust concentration had a marked influence on the flame propagation characteristics. The oxidation process of CS underwent four stages in sequence: water evaporation stage, transition stage, rapid combustion stage, and coke carbonization stage. There were four key functional groups in the CS molecule: C-O-C, CH, CO, and -OH.

A modified approach to model the hydrological effects of living moss and fallen leaves on carbonate-derived laterite in karst forests

Due to recent vegetation restoration projects in karst mountainous areas of China, the living moss and litter layer play important roles in controlling soil water dynamics in karst forests. However, the underlying mechanisms of the effects of moss and the litter layer on soil water dynamics are still controversial. To explore the underlying mechanisms, we employ the CoreKarHydro model, capturing soil water content dynamics driven by evapotranspiration and influenced by living moss and fallen leaves. This model integrates surface changes' impact on evapotranspiration, categorizing the domain into: no cover (S), moss (SM), pine needles (SP), and both (SMP). Model validation employs the MOCOM-UA method, using diverse metrics (RMSE, R2, ACC, ED, KGE and SA) against lysimeter data with 4 moss biomass levels and 3 pine needle biomass levels. The results indicated: 1) The CoreKarHydro model exhibited reliable performance in simulating the soil water content curves, with an RMSE ranging from 1.49% to 4.21% and an R2 value ranging from 0.60 to 0.77. 2) Among the factors that influenced evaporation processes, soil hydraulic properties emerged as the most sensitive parameters, whereas the properties of the moss and pine needles played a relatively lesser role. 3) The impact of moss cover on evaporation processes varied depending on the soil texture and the stage of evaporation. Moss cover reduced evaporation loss in 8 out of 12 soil textures (loamy sand, loam, silt, silt loam, sandy clay loam, silty clay loam, sandy clay, and silty clay). On the other hand, moss cover increased evaporation loss in 4 out of 12 soil textures (sand, sandy loam, clay loam, and clay). This study contributes to the understanding of the mechanisms of coupled soil-moss(litter)-hydrological processes in karst areas.

Template-Directed Replication and Chiral Resolution during Wet-Dry Cycling in Hydrothermal Pools.

The commonly supposed template-based format for RNA self-replication requires both duplex assembly and disassembly. This requisite binary provision presents a challenge to the development of a serviceable self-replication model since chemical reactions are thermochemically unidirectional. We submit that a solution to this problem lies in volcanic landmasses that engage in continuous cycles of wetting and drying and thus uniquely provide the twofold state required for self-replication. Moreover, they offer conditions that initiate chain branching, and thus furnish a path to autocatalytic self-replication. The foundations of this dual thermochemical landscape arise from the broad differences in the properties of the bulk water phase on the one hand, and the air/water interfacial regions that emerge in the evaporative stages on the other. With this reaction system as a basis and employing recognized thermochemical and kinetic parameters, we present simulations displaying the spontaneous and autocatalyzed conversion of racemic and unactivated RNA monomers to necessarily homochiral duplex structures over characteristic periods of years.

Droplet Evaporation Process of a Fluorobenzene + n-Octane + Polystyrene Mixture.

The vapor-liquid equilibrium of the fluorobenzene-polystyrene binary polymer solution at 303.15 K was measured using a static pressure device. The vapor-liquid equilibrium of the fluorobenzene-n-octane-polystyrene ternary solution in a partial concentration range under normal pressure was determined using an improved Othmer equilibrium still, in which the octane concentration was low. Three activity coefficient models, poly-NRTL, UNIQUAC, and M-UNIQUAC-LBY, were utilized to correlate the experimental data of binary and ternary solutions, and the component activities of the fluorobenzene-n-octane-polystyrene solution at 303.15 K were predicted. A mathematical model based on the Stefan flow was developed to simulate the evaporation process of composite spherical droplets. The activity predicted by the activity coefficient model was used for numerical simulations, and compared with simulations using the activity following Raoult's law. The comparative analysis revealed that simulations based on Raoult's law and activity coefficient models yielded similar results when the mass fraction of fluorobenzene exceeded 0.6. However, in the later stages of evaporation, the calculations based on Raoult's law predicted a 10% shorter drying time for fluorobenzene. The activity coefficient models provided a better approximation and exhibited similar droplet diameter shrinking behaviors to the actual evaporation process.

Asymmetric droplet evaporation on inclined surfaces

A computational model based on disjoining pressure is developed to study the asymmetric evaporation of droplets on an inclined substrate. In the proposed formulation, the disjoining pressure is combined with the arbitrary Lagrange-Euler method (ALE) to describe the solid-liquid interaction and investigate the contact angle hysteresis during evaporation. This model can be used to simulate the droplet evaporation modes of constant contact radius (CCR), constant contact angle (CCA) and “Stick-Slip” (mix evaporation mode), while the results are in good agreement with the experimental data. The obtained droplet shape for different inclined angles shows an asymmetric variation in contact angle at the front and rear ends, with the mean contact angle decreasing as the tilt angle increases. The evaporation flux is symmetric in the case of a horizontal substrate, however, when the substrate is tilted, the front and rear contact angles are modified, which leads to a larger evaporation flux on the rear contact line. Moreover, the asymmetric droplet morphology leads to asymmetric temperature field and vortex in the initial stage of evaporation; as evaporation proceeds, however, the flow and temperature fields within the droplet exhibit a gradual convergence towards symmetry. Moreover, when droplets evaporate on a pair of substrates with complementary tilt angles, their lifetimes exhibit a remarkable similarity. From the evaporation rate evolution, it yields that the larger the percentage of pinning time on the contact line, the faster the evaporation rate of the droplet. The evaporation rate of droplets was 14.76% higher at a tilt angle of α=0° than the case of α=45°.

Investigation on sub-to-supercritical transition of diesel: Gas–liquid interface properties

ABSTRACT By establishing a high-temperature droplet evaporation test device, the influence of ambient temperature on droplet morphology and droplet diameter is studied using diesel oil (D100). The variation of droplet evaporation characteristics is studied. The phase transition model of n-heptane in a supercritical environment is established and verified by the molecular dynamics simulation method. The diffusion coefficient, radial distribution function (RDF), surface tension, interfacial thickness, and liquid film temperature of n-heptane liquid film are analyzed. The results show that when the environmental conditions change from subcritical to supercritical, the diffusion coefficient decreases first and then increases from 8.55 × 10−4 cm/s−1 to 71.75 × 10−4 cm/s−1. The peak value of RDF decreases from 1627 to 438, and the smaller peaks after the main peaks tend to be smooth, indicating that n-heptane appears as a gas under supercritical conditions, and the phase transition changes from evaporation to diffusion. Cases 5(T = 973 K P = 5 MPa), 6(T = 573 K P = 7 MPa), 8(T = 773 K P = 7 MPa), and 9(T = 973 K P = 7 MPa) are high-supercritical calculation cases, with MSD of 1.71 × 105 Å2, 4.03 × 105 Å2, 2.49 × 105 Å2, 4.07 × 105 Å2, compare with case 1(T = 573 K P = 3 MPa), MSD increased by 11 times. When T/Tc ≥1.5 and P/Pc ≥1.5, n-heptane undergo three stages of transition from subcritical state to supercritical state. The first stage is the subcritical evaporation stage. With the evaporation of n-heptane, the fuel surface tension gradually disappears, the subcritical evaporation stage ends, and the transition stage begins. When the liquid film temperature exceeds the critical value, the transition phase ends, and the supercritical diffusion phase begins. In addition, when the ambient pressure is 5 MPa and 7MPa, the ambient temperature rises from 773 K to 973 K. The proportion of the transition process in the evaporation process increases by 19% and decreases by 3%, respectively.

Thermal analysis of suspended single droplet evaporation measurements with a coupled lumped parameter model

The measurement data of single droplet evaporation experiments are often biased due to the extra heat input through the fiber suspension and the presence of thermal radiation in hot environments. This encumbers model validation for heat and mass transfer simulations of liquid droplets. In this paper, a thermal analysis of this measurement layout is presented with a coupled lumped parameter model, considering heat conduction through the suspension. The model was validated by experimental data from the literature and good agreements were found. The thermal analysis focused on fiber material and geometry, and thermal radiation properties. Calculations were performed on a broad range of ambient conditions for liquids with different volatility characteristics. Temporal squared droplet diameter- and temperature-profiles, furthermore, droplet stationary evaporation rate were used to characterize vaporization phenomena. The thermal balance of the droplet is dominated by the convective heat rate from the environment in the early stage of evaporation. The effect of heat conduction through the fiber becomes important at the end of the droplet lifetime when the droplet size is decreased. Temperature sensor suspension may seriously bias droplet temperature due to the larger thermal conductivity compared to quartz fiber. Large droplets in high-temperature environments show significant sensitivity to thermal radiation properties, which should be considered in measurements and model validation.

Decoding the performance of module-scale interfacial desalination from a thermodynamic perspective

Passive solar-driven interfacial evaporation (PSDIE) is a highly efficient desalination technology that localizes heating at the evaporation surface, resulting in low heat loss and high evaporation rates. While many studies have focused on improving solar absorber performance, few have systematically analyzed the PSDIE thermodynamics. In this study, we propose a novel PSDIE distiller that effectively avoids salt accumulation. A module-scale model is developed that captures the mass and heat transfer characteristics of the distiller, and comprehensive thermodynamic analysis is performed. Our results show that the relative thickness between the evaporation and condensation layers, namely α, is a critical design parameter that optimizes process performance. An evaporation restricted region (α>5) and a condensation restricted region (α<5) can be identified. We also investigate the influence of hydrophobic membrane properties, finding that their effects depend on α. Our analysis demonstrates that inlet salinity of seawater feed has a detrimental effect on the water productivity of the distiller, while distiller with larger α tends to be more salt tolerable. Finally, we propose a design for a multistage distiller system and evaluate its water production performance, the results show that additional evaporation stages are beneficial to the distiller with smaller α.

Characteristics of coal oxidation and spontaneous combustion in Baishihu Mine, Xinjiang, China

The characteristics of oxidized spontaneous combustion of coal can reflect the performance of coal, and an appropriate structural model can reflect it more intuitively. In this study, samples from Baishihu Coal Mine were used to study the macromolecular structure, microcrystal structure, and oxidation process of coal by X-ray photoelectron spectroscopy (XPS), carbon nuclear magnetic resonance (13C-NMR), and Fourier infrared spectroscopy (FTIR). The molecular formula C198H164O40N2 and the molecular structure model were obtained. ChemDraw and Materials Studio were used for the experimental data, and high-resolution transmission electron microscopy (HRTEM) was used to verify the aromatic ring structure built to make the constructed structural model more accurate. In the water evaporation stage, the high ring aromatic layer is converted into the low ring number. Furthermore, in the high-temperature stage, the low ring aromatic layer is transformed due to the coking and condensation reaction of the coal sample. The C element in the coal sample mainly participates in the reaction in C–C and C–H forms. The spacing and effective number of aromatic layers are relatively stable. The aggregation state of coal is a macromolecular group formed between molecules with different aromatic structures and fat structures, which is formed by the interaction of internal defects and pores of molecular groups. With the increase in the treatment temperature, water loss is heavier, oxygen absorption and weight gain are perplexing, and the value of the burnout temperature is higher. The apparent activation energy of the coal–oxygen reaction increases, and the reaction is more intricate to achieve. This study furthers the understanding of coal spontaneous combustion in this mining area, provides a reference for the prevention and control of coal spontaneous combustion.

Influence of fiber orientation on the moisture adsorption of continuous bamboo fiber composites

Recently, a considerable interest is being shown in the use of plant fibers as reinforcement for polymer composites. Indeed, researchers and scientists are trying to overcome the environmental bias by using bio-composites in several engineering applications. Their attractive specific mechanical properties, low cost, lightness and biodegradability may promote them to substitute expensive and non-renewable fibers such as carbon, kevlar and glass fibers. However, the hydrophilic behavior of natural fibers is of a great concern for their possible outdoor applications. Indeed, the entrapment of water molecules at the fiber lumen, voids and porosities may reduce the tensile strength and modulus of plant fiber composites. Hence, this work aims to evaluate the moisture adsorption behavior of bamboo fiber epoxy composites at different fiber orientations (tangential and radial directions). Firstly, bamboo fibers are extracted using a combination of compression and manual techniques. Morphological and thermogravimetric analyses are carried out to deeply understand the physical properties of the extracted fibers. The findings show that the fibers consist of parallel microfibrils enclosed by some impurities and amorphous constituents. The moisture content of bamboo fibers at 50RH% is deduced from the moisture evaporation stage in the thermogravimetric curve and is about 8.07%. Thereafter, hand layup and compression techniques are used to manufacture the composite samples for the moisture adsorption test. The obtained results show that the equilibrium moisture capacity and diffusion rate values are higher along the fiber direction, which is mainly due to the exposure of the fiber lumen and interfacial voids. The mechanism of moisture transport into composites is found to follow Fick’s law.

Azeotropic Binary Solvent System Containing Nonfluorinated Polymer-Grafted Silica Nanoparticles for the Fabrication of a Superhydrophobic Surface.

This study describes a method for fabricating a superhydrophobic surface on glass via a colloidal deposition technique based on solvent evaporation-induced aggregation. Silica nanoparticles with a low grafting density of long-chain poly(cyclohexyl methacrylate) (PCH) were dispersed in a binary solvent system consisting of tetrahydrofuran (THF) and methanol (MeOH) with an azeotropic point and the nonfluorinated and hydrophobic PCHMA having a solubility parameter similar to that of THF. In the early stages of evaporation, the binary mixtures tend to induce the aggregation of PCH-NP due to the azeotropic point of the solvent components, leading to the formation of surface structures ranging from smooth to rough on the substrate. By adjusting the initial ratio of the binary solvents, a superhydrophobic coating with a water contact angle of 154 ± 2° and a sliding angle of less than 10° was achieved at a THF content of 60 wt %. This facile approach using azeotropes successfully shows that changes in the solvent composition of the binary solvent system during evaporation can be used to prepare superhydrophobic coatings with well-controlled surface structures.

Thermodynamic properties of Schwarzschild black hole in non-commutative gauge theory of gravity

In this paper, we use the non-commutative (NC) gauge theory of gravity to investigate the thermodynamic properties of a deformed Schwarzschild Black Hole (SBH). Our results present a new scenario of black hole evaporation. As a first step, we describe the Arnowitt–Deser–Misner (ADM) mass, the Hawking temperature, and the entropy of NC SBH. The non-commutativity removes the divergent behavior of temperature, and the result shows a difference in the pole-equator temperature. These corrections also reveal a new fundamental length at the Planck scale order, Θ∼10−35m. In the last stage of evaporation, the NC correction exposes a remnant entropy S0Θ of the NC SBH with a minimal mass mˆ0, where the non-commutativity prevents the black hole from evaporating more than this minimal mass. Then, the description of the heat capacity and the Helmholtz free energy of the deformed black hole shows the effect of the NC gauge theory on the thermodynamic stability and the phase transitions. Finally, we investigate the influence of the black hole pressure on the stability and the phase transition of SBH in NC space–time. In the final stage of this scenario, the remnant black hole is thermodynamically stable. In this study, we find that the NC parameter plays a role similar to the thermodynamic variable. The results show a second-order phase transition of NC SBH.

Inter-Domain Repulsion of Dumbbell-Shaped Calmodulin during Electrospray Ionization Revealed by Molecular Dynamics Simulations.

The mechanisms whereby protein ions are released from nanodroplets at the liquid-gas interface have continued to be controversial since electrospray ionization (ESI) mass spectrometry was widely applied in biomolecular structure analysis in solution. Several viable pathways have been proposed and verified for single-domain proteins. However, the ESI mechanism of multi-domain proteins with more complicated and flexible structures remains unclear. Herein, dumbbell-shaped calmodulin was chosen as a multi-domain protein model to perform molecular dynamics simulations to investigate the structural evolution during the ESI process. For [Ca4CAM], the protein followed the classical charge residue model. As the inter-domain electrostatic repulsion increased, the droplet was found to split into two sub-droplets, while stronger-repulsive apo-calmodulin unfolded during the early evaporation stage. We designated this novel ESI mechanism as the domain repulsion model, which provides new mechanistic insights into further exploration of proteins containing more domains. Our results suggest that greater attention should be paid to the effect of domain-domain interactions on structure retention during liquid-gas interface transfer when mass spectrometry is used as the developing technique in gas phase structural biology.

Study on the Drying Process and the Influencing Factors of Desiccation Cracking of Cohesive Soda Saline-Alkali Soil in the Songnen Plain, China

The surface of cohesive soda saline-alkali soil in the Songnen Plain of China exhibits obvious desiccation cracking phenomenon during water evaporation. Quantitative research on the process and influencing factors of desiccation cracking are significant for determining the mechanical properties of salt-affected soil, improving the salinization status and the local ecological environment. This study aims to conduct laboratory-controlled cracking experiments on soda saline-alkali soils, and to regularly measure the soil moisture and the cracking status of 40 soil samples. After processing the crack images uniformly, crack characteristics including crack length, crack area, contrast texture feature, and box-counting fractal dimension are extracted. The results indicate that the decrease in soil moisture can be divided into three stages such as fast evaporation stage, slow evaporation stage and stable evaporation stage, and that the evaporation rate shows a linear negative correlation with soil salinity. The measurements also indicate that crack length rapidly increases and reaches stability with a decrease in water content compared with the crack area. The high correlation between different crack characteristics and the soil total salinity (correlation coefficient from 0.44 to 0.95) shows that salt content is the dominant factor affecting the desiccation cracking of soda saline-alkali soil. A multiple linear regression prediction model was finally established based on crack characteristics for different salinity parameters with high prediction accuracy for Na+, EC and total salinity (R2 &gt; 0.91 and RPD &gt; 2.5) and also certain prediction accuracy for Cl− and CO32− (R2 &gt; 0.66 and RPD &gt; 1.5).

O- and H- Isotope constraints on Neogene high-K calc-alkaline and shoshonitic volcanic rocks and borates in the Kırka (Eskişehir) basin, W Anatolia

ABSTRACT The O and H isotopic ratios of borates, clay minerals, and volcanic rocks from the Kırka basin (south of Eskişehir, W Anatolia) have been analysed in order to better constrain the conditions that led to precipitation of the borates. The δ18Owr values of the volcanic rocks range from + 7.6 to + 15.9‰, but many samples are enriched in 18O by post-eruption hydration, as evidenced by the positive correlation between 18O and H2O (LOI up to 3.1 wt.%) contents. The δ18O values of the borate and clay minerals (smectite) range from 10.0 to 18.8‰, and 19.5 to 31.3‰, respectively. The large variation among the δ18O values of the borate minerals either is likely related to oxygen isotope fractionation during their formation and/or indicates that they formed at different stages of evaporation of the original brines over a range of temperatures. Considering that borax was a primary phase in the basin, decreasing δ18O values from borax to colemanite and ulexite is compatible with decreasing formation temperatures. The δD values of borate and clay minerals do not show significant differences (−64 – −88‰, and −106 – −125‰, respectively). The calculated δ18OH2O and δDH2O values of the fluid in equilibrium with the borate minerals (−11.6–5.93‰ and −85 – −65‰, respectively) and in equilibrium with the smectite (14.4–17.0‰ and −126 – −67‰, respectively) indicates that the basin brines were dominated by geothermal fluids. Overall, the oxygen isotope systematics of the borates and smectite in the Kırka basin are consistent with the smectite and borate minerals forming from brines that resulted from the ponding and evaporation of geothermal fluids that had undergone water-rock interaction with the local felsic volcanic rocks.

Methanol, ethanol and propanol droplets evaporation characteristics with a dilute concentrations of hematite and magnetite nanoparticles

Evaporation characteristics of a single suspended fuel droplet with nanoparticles were experimentally investigated. Three ambient temperatures of 100, 200 and 300 °C were considered. The droplet initial volume of 1.5 µL was used and the whole evaporation process was recorded using a high-speed camera at 500 frame per second. Methanol, ethanol and propanol were selected as the base fuels. Hematite and magnetite nanoparticles were added to the alcohols at concentrations of 100, 200, 300 mg/L to examine their effects on the droplet evaporation. The alcohol/nano additive droplet experienced different evaporation characteristics compared to this of pure alcohol. The variation of normalized square diameter was linear during the evaporation process for the considered blends. Methanol droplet experienced the same evaporation stages with hematite and magnetite along with 10% and 8.3% increase in the evaporation rate respectively at 300 °C and a nanoparticles concentration of 300 mg/L. Ethanol droplet containing hematite and magnetite nanoparticles evaporation rate was retarded by 15.9% and 12.6%, respectively at 300 mg/L and 300 °C. Propanol droplet evaporation was increased by 14.9% with hematite additives. On the other hand, a decrease in the constant by 26% was observed at 300 °C and a concentration of 300 mg/L.

Characterizing Internal Flow Field in Binary Solution Droplet Combustion with Micro-Particle Image Velocimetry

Droplet internal flow participates in liquid-phase mass transfer during multicomponent solution droplet combustion. In this work, internal flow fields in the binary droplet combustion of two polyoxymethylene dimethyl ethers (CH3O(CH2O)nCH3, n ≥ 1, abbreviated as PODEn), i.e., PODE2 and PODE4, are characterized using micro-particle image velocimetry (Micro-PIV). The buoyancy-driven upward vapor flow around the droplet is found to initiate two opposite radial flows in the droplet, which form two vortex cores near the surface, while the gravitational effect and Marangoni effect resulting from the content and temperature gradients in the binary droplets can induce disturbance to the two flows. The binary droplets have comparable spatially averaged flow velocities at the stable evaporation stage to those of pure droplets, which are around 3 mm/s. The velocity curves are more fluctuant and tend to slightly increase and reach the peak values at around 250 ms, and then decrease until droplet atomization. The flow velocities in the droplet interior are generally higher than those near the droplet surface, forming a parabolic velocity profile along the horizontal radial direction. The peak velocity first increases to 5–9 mm/s as the radial flow and vortex structure start to form and then decreases to around 3 mm/s until droplet atomization. The radial flow with a spatially averaged velocity of 3 mm/s can run around one lap during the stable evaporation stage, which implies that the convection-induced mass transfer is relatively weak, and consequently, the content gradient of the binary droplet is still mainly controlled by mass diffusion.

Development of a simple algorithm for pre-fragment formation in proton-nucleus spallation reactions

A Monte-Carlo algorithm is developed and coded in FORTRAN to calculate the energy, mass and charge distribution of the pre-fragments produced in proton induced spallation. The algorithm is based on Glauber’s theory together with a reasonable assumption on the type of the promptly emitted nucleons. For the evaporation stage, correlated values of pre-fragment mass, charge and excitation energy were fed into a properly modified version of the code MCEF (Monte-Carlo Evaporation-Fission) written in Java. A good agreement is obtained with the experimental mass and charge distributions of residues observed in 56Fe+p spallation reactions at 300, 500 and 750 MeV/A