Papers by Keyword: Liquid Film

Abstract: The impacting of liquid droplet on the liquid film appears in many engineering processes. In the fusion reactor, liquid metal is used as the heat transfer media, moderator and breeder in the condition of high heat flux. The paper analyzes the flow behavior of liquid droplet impinging on the liquid film from the aspects of experiment research. In the impinging, splashing means the production of secondary drop coming from the cusp of the crown flow or Worthington jet. Impinging velocity, liquid film thickness, droplet diameter, fluid properties and impinging angle have been analyzed separately.

Abstract: Two-dimensional models of inclined flat and corrugated walls are established based on VOF method to numerically simulate the flow characteristics of liquid film. The impact of wall structures on the wave profile of the film is studied. The results indicate that the wall structure plays an important role on the liquid film, there are vortexes generated on the trough of wavy wall, the vortex has the "rolling" effect in machinery, which reduces the viscous resistance. and continuous film is easier to form on the wall whose corrugated size is smaller.

Abstract: Integral analysis of heat transfer of a laminar falling liquid film along a vertical heated plate with specified heat flux boundary condition was investigated. The temperature distribution of liquid film was obtained by utilizing an integral analysis method, which was compared with numerical solution and other researcher’s results. In this analysis a new concept of thermal changing point was put forward. It’s found that the Nusselt number has a characteristic relationship with thermal changing point, which is obtained by calculation. When the film flow distance is less than thermal changing point, the Nusselt number decreases rapidly. When the film flow distance is greater than or equal to thermal changing point, the Nusselt number reaches to a fixed value. A larger Peclet number or lower initial temperature generally leads to a larger Nusselt number in entrance region, whereas the wall heat flux is found to have no influence on the Nusselt number.

Abstract: In this paper, the mathematical model of a horizontal-tube falling film evaporator that used in air condition and refrigeration system was founded. The evaporative tubes of the evaporator were cold and staggered arrangement. The numerical simulation of the intervascular flow of the oil-bearing refrigerant R134a was carried out, under the conditions of varies flow mode and varies structures of distributed equipment. Under the standard condition of air conditioning, the study of the intervascular two-phase flow characters of the horizontal-tube falling film evaporator were analyzed in the last. The research achievements can provide theoretical laws for relief the effects of the intervascular vapor shear stress on the quality of the liquid film formed outside the evaporative tubes. And the conclusions have practical and guide means for the horizontal-tube falling film evaporator design and evaporative tubes arrangement optimization.

Abstract: Liquid mulching film was prepared with technical gramineae lignin from waste pulping liquid via hydroxymethylation and then cross-linking reaction with urea or aromatic ring of lignin. Results showed the amount of lignin added had an influence on the property, viscosity and water resistance of liquid film material. This influence was little when lignin dosage was less than 30%, but turned apparent when lignin dosage was higher than 30%. The optimum lignin quantity was 30%. The growth of plant was accelerated when the concentration of liquid film material was around 1000 mg/L. Both planstic and liquid mulching film could improve soil temperature, the result of liquid film was a little worse than that of plastic film, but was better than the control. The optimum lignin dosage was 30% which had the best heat incubation effect.

Abstract: Surface mulch is regarded as an effective manner to reducing soil water evaporation, but limited with the adverse influence of plastic film mulch on agro-ecosystems. In this paper, liquid films were prepared with the foundation of kelp as a bio-material. The results showed that the films prepared with the mixture of kelp and polyvinyl alcohol (PA) had superimposed layering structure with tiny pores and gaps, and were stable as well as degradable under field water conditions. The results of the simulative experiments with both of aquic sand-loamy soil and yellow silt-loamy soil that mulching with the film of the mixture of kelp and polyvinyl alcohol (PA) could significantly (P<0.01) reduce water evaporation from soil. It was also found that mulching with the liquid films could increase the water retention capacity of the tested soils. As the initial material – kelp is available, the application of the developed liquid film based on kelp for efficient soil moisture management in agricultural production should be recommended.

Abstract: This paper reports progress in the numerical simulations of a droplet impingement upon the wall film of the same liquid. The full Navier-Stokes equations are solved in axisymmetric formulation. The surface tension force is modeled by a continuum surface force (CSF) model. An adapting local refinement technique is used to provide the fine grid coupled by the volume-of fluid (VOF) method for tracking the interface between the gas and the droplet and liquid film. Results indicate that the motion behavior of droplet impingement upon the liquid film is dominantly influenced by the initial kinetic energy and the thickness of the film as well as the surface tension and the liquid viscosity.

Abstract: Transient-liquid-phase (TLP) joining and liquid-film-assisted joining (LFAJ) exploit thin metallic films that melt at relatively low temperatures as part of a multilayer, multimaterial interlayer to enable joining at reduced temperatures. These methods are attractive for assemblies that include temperature-sensitive components, however, unlike conventional low-temperature joining methods, they also offer the potential for service at temperatures approaching or even exceeding the original joining temperature. In successful TLP joining and LFAJ, the wetting behavior of the liquid plays a critical role. In TLP joining, the liquid ultimately disappears during joining due to interdiffusion and chemical homogenization. In contrast, in LFAJ the liquid persists at the joining temperature, provides a high-diffusivity transport path that accelerates joint formation, and ultimately undergoes a morphological transition that disrupts the initially continuous film. The resulting isolated liquid droplets solidify on cooling. Current studies of these joining methods are described, and promising future directions are indicated.

Abstract: The design of microstructure in materials, ranging from ultrafine, moderately sized, duplex to single crystalline, has long been a challenging subject to material scientists. A basic means to achieve this goal is related to the control of grain growth. Taking BaTiO3 as a model system, this investigation shows that control of grain boundary structure between rough and faceted and control of initial grain size can allow us to achieve the goal. When the grain boundary is rough, normal grain growth occurs with a moderate rate. On the other hand, for faceted boundaries, either abnormal grain growth or grain growth inhibition occurs resulting in a duplex grain structure or fine-grained structure, respectively. Growth of single crystals is also possible when the boundary is faceted. During crystal growth amorphous films can form and thicken at dry grain boundaries above the eutectic temperature. As the film thickness increases, the growth rate of the crystals is reduced. This observed growth behavior of grains with boundary structure is explained in terms of the difference in mobility between the two types of boundaries. The results demonstrate the basic principles of obtaining various microstructures from the same material.