Papers by Keyword: Evaporation

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Authors: Hong Cheng Zhao, Hong Tao Peng, Ge Fei Li, Xin Ping Zhang, Bo Xuan Gu
Abstract: In the arid areas of northwest China, sand-mulched field is an indigenous dry farming technique to reduce evaporation and conserve the limited rainfall for reliable crop production. The numerical simulation was carried out for analysis of the rainfall infiltration and evaporation process of sand-mulched field. Simulation results indicated that there were signifecant differences between the sand-mulched soil and that without mulch (control). Sand mulch on surface of soil may be effective in increasing infiltration and reducing runoff and evaporation. When the rainfall intensity is less than soil saturated hydraulic conductivity, sand mulch has little effect on the movement of soil infiltration wetting front. When the rainfall intensity is greater than the saturated permeability, the wetting front speed in sand-mulched soil is faster than that in bare soil during infiltration. During the simulation time, the runoff of sand-mulched soil is less than that of soil without mulch, variation in water potential of the sand-mulched soil is only 11% of that of the bare soil under the condition with evaporation intensity 0.6mm/h. Sand mulch can reduce water movement out of the soil by reducing the evaporation rate.
1182
Authors: S. Torfi, S.M. Hosseini Nejad
Abstract: In this paper, a numerical model is developed to simulate single droplet heat and mass transfer in a two-pieces solution with a saturated solvent vapor environment. Finite volume method and transient SIMPLEC algorithm in spherical coordinates system used for simulation. For simulation of the mass transfer, dimensionless equations of motion, heat transfer and mass transfer (based on mass ratio) are solved simultaneously. All the thermodynamic and transitional solution properties have been considered as a function of temperature and concentration. Verification of method is done by compare these numerical results with analytical and numerical analysis of other studies. Evaporation, absorption and condensation contours in a water droplet at uniform temperature at superheated water vapor and Distribution of Droplet's Surface Temperature, Constant Temperature and concentration lines as the modeling results are presented. The results are shown that 0.5% increase of concentration of droplet cause increase 8 degree C of mean temperature of droplet.
4315
Authors: Bin Xiong, Zhen Lin Yu, Gang Xu, Lei Miao, Ji Fu Shi, Xiu Di Xiao
Abstract: The Ag behaviors of Ag-Al alloy that annealed in air atmosphere have been investigated. Over 600°C, the Ag-Al2O3 composite was prepared. But over 650°C, the size of Ag particles reduced notably. With the annealing time increasing, the amount of Ag particles reduced too. This phenomenon indicated temperature and annealing time play critical roles in annealing process. We attribute the loss of Ag to evaporation. According to discussion, the process of Ag evaporation is described in detail.
1247
Authors: Fernando Gomes, Joaquim Barbosa, Carlos Silva Ribeiro
Abstract: Melting TiAl based alloys in ceramic crucibles often leads to chemical contamination, alloy heterogeneity and non-metallic inclusions. The severity of such phenomena usually depends on the nature of crucible materials, the melting stock composition and the melting parameters, namely superheating time and temperature and melting pressure. Among the referred drawbacks, Al loss during melting is a critical aspect, as its concentration in TiAl based alloys has a very strong effect in their mechanical properties. Although a few studies of critical factors affecting the evaporation behaviour of Al during electron beam and induction skull melting of Ti-Al alloys had been carried out, until now no information was released on this subject for the ceramic crucible induction melting process. In this work a Ti-48Al alloy was induction melted in a zircon crucible with Y2O3 inner layer, using 50 and 100 °C superheating temperatures and 0, 60 and 90 second holding times, and poured into a graphite mould. The effect of different temperature/time combinations in the alloy composition, Al loss by evaporation and extent of the metal/crucible interaction was studied for different melting pressures. Al loss was found to increase significantly for melting pressures below around 10-1 mbar, at a rate that increases as melting pressure decreases, until a maximum rate is reached, remaining constant for lower pressure levels. Metal/crucible interaction increased directly with the melting pressure and superheating time, leading to alloy contamination with yttrium and oxygen. For the experimental set-up and conditions used on this work, optimal superheating time/pressure combinations that lead to acceptable alloy composition and sanity have been identified.
697
Authors: Beata Oleksiak, Leszek Blacha, Lubomir Pikna, Rafał Burdzik
Abstract: In the paper, results of the study on aluminium evaporation from the Ti-Al alloy (6.5%mass) during smelting in a vacuum induction furnace (VIM) are presented as well as the kinetics of the process is discussed. The experiments were performed at 51000 Pa for 1972 K and 2023 K. Based on the determined values of aluminium overall mass transfer coefficient, the mass transfer coefficient in the liquid phase and the evaporation rate constant, the stages that determined the investigated process were defined. It was demonstrated that Al evaporation from the aluminium-titanium alloy is kinetically controlled.
117
Authors: Rachid Bennacer, Mohammed El Ganaoui
Abstract: The control of a process dealing with heat pipe exploitation needs the thermal analysis of the evaporation-condensation cycle and noticeably the imposed external conditions (in instance modeling the heating). In this work a numerical model has been developed to describe the local coupling near the liquid/vapour interface. Simulations exhibits and quantify the response of the capillary motion to the thermal conditions.
209
Authors: Yong Sen Wang, Zheng He Xu
Abstract: The stable isotope compositions of soil water from the profiles at Jinan southern mountain reveal information about the mechanism of soil movement. The stable isotopes in soil water have a wide range from-8.92 to-5.95 forδ18O and-50.01 to-79.44 forδD . The mean isotope values is-7.75 forδ18O and 65.84 forδD. The low-δD of shallow (<5cm) soil water is due to the precipitation infiltration. And deep soil water (>5cm) is enrichment, which indicates the soil water is evaporated before recharging. The stable oxygen and hydrogen isotope are plotted near the meteoric water line. The trend line for the relationship between δ18O and δD of soil water is given.
958
Authors: Cun Yan Cui
Abstract: It was found that evaporation and thermal elastic stress wave and cavity were dominant phenomenon in laser-induced ablation propulsion with liquid propellant according to our perceptual knowledge established in relative experiment and by analysis of physical mechanism of laser-induced ablation of liquid. The research result of the above phenomenon was introduced in this paper in order to give some elicitations to the researchers who were interested in the mechanism of laser propulsion with liquid ablation.
4918
Authors: Hai Jian Qiu, Jin Shui Qiu, Bo Yun Liu, Xiang Lie Yi, Kang Bo Wang
Abstract: This study was intended to solve the problem that fuel evaporation and ignition process on the high-temperature hot surface are difficult to be predicted accurately. The rule of fuel evaporation and ignition delay that various with hot wall temperature have been obtained by utilizing the simulated experiment to study the evaporation and ignition process of aviation kerosene on horizontal hot wall. This study not only complements the related content of the fuel ignition mechanism on hot wall but also provides reference method for the fuel fire engineering practice.
616
Authors: Wei Dong, Xu Peng, Da Chuan Jiang, Yi Tan, Qiang Wang, Guo Bin Li
Abstract: In order to investigate Ca evaporation behavior in the electron beam melting process, metallurgical-grade silicon was melted in an electron beam furnace with different experimental conditions. The results showed that the content of impurity Ca was significantly decreased in the early time, while these changed slowly with the extension of the melting. The removal rate of Ca was controlled by the transfer of Ca atoms from the bulk liquid silicon to liquid/gas phase interface within the range of experiment temperature.
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