Development and Validation of a Mathematical Model of Microfilm Formation in Atomization Cooling of Micromachining

2011 ◽  
Author(s):  
Kyle J. Boughner ◽  
John E. Wentz ◽  
Benton J. Garske
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
Rotational Velocity ◽  
Droplet Diameter ◽  
Thickness Effect ◽  
Delivery Tube ◽  
Air Velocity ◽  
Cooling Rates ◽  
System Parameters ◽  
Cutting Zone

Traditional flood cooling processes can cause problems in micromachining due to the collision force between the fluid stream and the tool being greater in magnitude than the cutting forces. The traditional processes produce insufficient cooling rates and are unable to effectively evacuate chips from the cutting zone. Atomization-based cooling addresses these issues through high evaporative cooling rates, low impact forces, and the use of a high velocity air stream to clear the cutting zone of chips. This paper presents a probabilistic model to determine the thickness of a microfilm forming on a rotating cylindrical surface, such as a microturning workpiece or a microendmill, and the relative importance of system parameters on film formation. The rate of microfilm formation is dependent upon droplet losses in the tube, at the nozzle, and the scatter of the atomized spray. Droplet diameters and Weber numbers in the tube and at the cylinder were experimentally determined and modeled as lognormally distributed. Parameters investigated in this model are fluid and mist properties (surface tension and droplet size) and system parameters (delivery tube air velocity, spray air velocity, spray geometry, cylinder diameter, and cylinder rotational velocity). A maximum film thickness effect was found for the variables of delivery tube velocity, droplet diameter, and surface tension with a value for each variable that provided a thickest film. As the variables increased or decreased from that value the film thickness decreased.

scholarly journals Properties of PTFE tape as a semipermeable membrane in fluorous reactions

2015 ◽  
Vol 11 ◽  
pp. 980-993 ◽  
Author(s):  
Brendon A Parsons ◽  
Olivia Lin Smith ◽  
Myeong Chae ◽  
Veljko Dragojlovic
Keyword(s):  
Surface Tension ◽  
Organic Compounds ◽  
Polymer Films ◽  
Semipermeable Membrane ◽  
Reaction Vessel ◽  
Dimethyl Phthalate ◽  
Delivery Tube ◽  
Selective Permeability ◽  
Solvent Uptake ◽  
Solvent Adsorption

In a PTFE tape phase-vanishing reaction (PV-PTFE), a delivery tube sealed with PTFE tape is inserted into a vessel which contains the substrate. The reagent diffuses across the PTFE tape barrier into the reaction vessel. PTFE co-polymer films have been found to exhibit selective permeability towards organic compounds, which was affected by the presence of solvents. In this study, we attempted to establish general trends of permeability of PTFE tape to different compounds and to better describe the process of solvent transport in PV-PTFE bromination reactions. Though PTFE tape has been reported as impermeable to some compounds, such as dimethyl phthalate, solvent adsorption to the tape altered its permeability and allowed diffusion through channels of solvent within the PTFE tape. In this case, the solvent-filled pores of the PTFE tape are chemically more akin to the adsorbed solvent rather than to the PTFE fluorous structure. The solvent uptake effect, which was frequently observed in the course of PV-PTFE reactions, can be related to the surface tension of the solvent and the polarity of the solvent relative to the reagent. The lack of pores in bulk PTFE prevents solvents from altering its permeability and, therefore, bulk PTFE is impermeable to most solvents and reagents. However, bromine, which is soluble in liquid fluorous media, diffused through the bulk PTFE. A better understanding of the PTFE phase barrier will make it possible to further optimize the PV-PTFE reaction design.

Dependence of Film Thickness on Properties of Al Doped ZnO Thin Films

2011 ◽  
Vol 194-196 ◽  
pp. 2305-2311
Author(s):  
Ying Ge Yang ◽  
Dong Mei Zeng ◽  
Hai Zhou ◽  
Wen Ran Feng ◽  
Shan Lu ◽  
...  
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Electrical Parameter ◽  
Substrate Surface ◽  
Rf Magnetron Sputtering ◽  
Thickness Effect ◽  
Visible Range ◽  
Glass Substrates ◽  
Doped Zno

In this study high quality of Al doped ZnO (ZAO) thin films were prepared by RF magnetron sputtering on glass substrates at room temperature in order to study the thickness effect upon their structure, electrical and optical properties. XRD results show that the films are polycrystalline and with strongly preferred (002) orientation perpendicular to substrate surface whatever the thickness is. The crystallite size was calculated by Williamson-Hall method, while it increases as the film thickness increased. The lattice stress is mainly caused by the growth process. Hall measurements revealed electrical parameter very dependent upon thickness when the thickness of ZAO film is lower than 700 nm. The resistivity decreased and the carrier concentration and Hall mobility increases as the film thickness increased. When film thickness becomes larger, only a little change in the above properties was observed. All the films have high transmittance above 90% in visible range. Red shift of the absorption edge was observed as thickness increased. The optical energy bandgap decreased from 3.41eV to 3.30 eV with the increase of film thickness.

scholarly journals Spray adjuvant characteristics affecting agricultural spraying drift

2015 ◽  
Vol 35 (1) ◽  
pp. 109-116 ◽  
Author(s):  
RONE B. DE OLIVEIRA ◽  
ULISSES R. ANTUNIASSI ◽  
MARCO A. GANDOLFO
Keyword(s):  
Surface Tension ◽  
Wind Tunnel ◽  
Aqueous Solutions ◽  
Formation Process ◽  
Droplet Diameter ◽  
Brilliant Blue ◽  
Medium Size ◽  
Blue Dye ◽  
Methods Of Evaluation ◽  
Spray Adjuvants

This study defined the main adjuvant characteristics that may influence or help to understand drift formation process in the agricultural spraying. It was evaluated 33 aqueous solutions from combinations of various adjuvants and concentrations. Then, drifting was quantified by means of wind tunnel; and variables such as percentage of droplets smaller than 50 μm (V50), 100 μm (V100), diameter of mean volume (DMV), droplet diameter composing 10% of the sprayed volume (DV0.1), viscosity, density and surface tension. Assays were performed in triplicate, using Teejet XR8003 flat fan nozzles at 200 kPa (medium size droplets). Spray solutions were stained with Brilliant Blue Dye at 0.6% (m/ v). DMV, V100, viscosity cause most influence on drift hazardous. Adjuvant characteristics and respective methods of evaluation have applicability in drift risk by agricultural spray adjuvants.

Film thickness effect on texture and residual stress sign transition in sputtered TiN thin films

2017 ◽  
Vol 43 (15) ◽  
pp. 11992-11997 ◽  
Author(s):  
Yeting Xi ◽  
Kewei Gao ◽  
Xiaolu Pang ◽  
Huisheng Yang ◽  
Xiaotao Xiong ◽  
...  
Keyword(s):  
Thin Films ◽  
Residual Stress ◽  
Film Thickness ◽  
Thickness Effect ◽  
Tin Thin Films

scholarly journals Aerosol hygroscopicity at high (99 to 100%) relative humidities

2009 ◽  
Vol 9 (4) ◽  
pp. 15595-15640 ◽  
Author(s):  
C. R. Ruehl ◽  
P. Y. Chuang ◽  
A. Nenes
Keyword(s):  
Surface Tension ◽  
Inorganic Compounds ◽  
Droplet Diameter ◽  
Pure Water ◽  
Sodium Dodecyl ◽  
Bulk Solution ◽  
Active Compounds ◽  
Surface Active ◽  
Surface Active Compounds ◽  
Aerosol Hygroscopicity

Abstract. The hygroscopicity of an aerosol largely determines its influence on climate and, for smaller particles, atmospheric lifetime. While much aerosol hygroscopicity data is available at lower relative humidities (RH) and under cloud formation conditions (RH>100%), relatively little data is available at high RH (99.2 to 99.9%). We measured the size of droplets at high RH that had formed on particles composed of one of seven compounds with dry diameters between 0.1 and 0.5 μm, and calculated the hygroscopicity of these compounds. We use a parameterization of the Kelvin term, in addition to a standard parameterization (κ) of the Raoult term, to express the hygroscopicity of surface-active compounds. For inorganic compounds, hygroscopicity could reliably be predicted using water activity data and assuming a surface tension of pure water. In contrast, most organics exhibited a slight to mild increase in hygroscopicity with droplet diameter. This trend was strongest for sodium dodecyl sulfate (SDS), the most surface-active compound studied. The results suggest that partitioning of surface-active compounds away from the bulk solution, which reduces hygroscopicity, dominates any increases in hygroscopicity due to reduced surface tension. This is opposite to what is typically assumed for soluble surfactants. Furthermore, we saw no evidence that micellization limits SDS activity in micron-sized solution droplets, as observed in macroscopic solutions. These results suggest that while the high-RH hygroscopicity of inorganic compounds can be reliably predicted using readily available data, surface-activity parameters obtained from macroscopic solutions with organic solutes may be inappropriate for calculations of the hygroscopicity of micron-sized droplets.

Effect of Nanoparticles on the Fuel Properties and Spray Performance of Aviation Turbine Fuel

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Kumaran Kannaiyan ◽  
Kanjirakat Anoop ◽  
Reza Sadr
Keyword(s):  
Surface Tension ◽  
Physical Properties ◽  
Droplet Diameter ◽  
Cone Angle ◽  
Aviation Fuel ◽  
Alumina Nanoparticles ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Breakup Length ◽  
Sheet Breakup

The influence of nanoparticles' dispersion on the physical properties of aviation fuel and its spray performance has been investigated in this work. To this end, the conventional Jet A-1 aviation fuel and its mixtures with alumina nanoparticles (nanofuel) at different weight concentrations are investigated. The key fuel physical properties such as density, viscosity, and surface tension that are of importance to the fuel atomization process are measured for the base fuel and nanofuels. The macroscopic spray features like spray cone angle and sheet breakup length are determined using the shadowgraph technique. The microscopic spray characteristics such as droplet diameter, droplet velocity, and their distributions are also measured by employing phase Doppler anemometry (PDA) technique. The spray performance is measured at two nozzle injection pressures of 0.3 and 0.9 MPa. The results show that with the increase in nanoparticle concentrations in the base fuel, the fuel viscosity and density increase, whereas the surface tension decreases. On the spray performance, the liquid sheet breakup length decreases with increasing nanoparticle concentrations. Furthermore, the mean droplet diameters of nanofuel are found to be lower than those of the base fuel.

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