Academic literature on the topic 'Capillary freezing'
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Journal articles on the topic "Capillary freezing"
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MAEDA, NOBUO, and VASSILI V. YAMINSKY. "EXPERIMENTAL OBSERVATIONS OF SURFACE FREEZING." International Journal of Modern Physics B 15, no. 23 (September 20, 2001): 3055–77. http://dx.doi.org/10.1142/s0217979201007051.
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Capillary phase transitions and those induced by interfaces, like pre-melting, have been studied for decades. The related phenomenon of surface freezing has not been explored so extensively. We review experiments on surface freezing, those of long-chain n-alkanes in particular, and place the results within the wider thermodynamic framework of surface phase transitions. Surface freezing plays an important role in nucleation and crystallization of bulk long-chain n-alkanes. Implications for capillary melting and freezing of substances at nanoscales are discussed. Theoretical aspects of condensed capillary phase transitions will be reviewed separately.
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Erlandsen, S., A. Holzer, M. Gavin, C. Frethem, and C. Wells. "High Pressure Freezing/Freeze Substituion: Comparison of Chemical Fixation Versus Cryoimmobilization of Candida Albicans Cultured in Cellulose Tubing." Microscopy and Microanalysis 5, S2 (August 1999): 434–35. http://dx.doi.org/10.1017/s143192760001549x.
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In the interactions of Candida albicans with host cells, the cell wall of the yeast may play important roles in the adhesion of yeast cells to tissues. The outer cell wall of yeast (e.g. Saccharomyces cerevisiae, C. albicans) has been shown to consist of a dense network of radially projecting fibrils composed of mannoproteins that are known as fimbriae and which previously have required cryopreservation either by jet propane freezing or by plunge freezeing for their visualization. High pressure freezing provides an advantage over jet or plunge freezing in terms of the higher consistancey in the quality of freezing, and the minimization of formation of ice I with this method. Hohenberg et al reported a method utilizing cellulose capillary tubes to cryoimmobilize suspensions of microoganisms by high pressure freezing (HPF) and freeze substitution (FS), and herein, we describe an adaptation of this method by culturing microorganisms within the tubing to increase cell density prior to high pressure freezing and freeze substution.
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Christenson, H. K. "Liquid Capillary Condensates below the Freezing Point." Physical Review Letters 74, no. 23 (June 5, 1995): 4675–78. http://dx.doi.org/10.1103/physrevlett.74.4675.
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Tad Pfeffer, W., Tissa H. Illangasekare, and Mark F. Meier. "Analysis and Modeling of Melt-Water Refreezing in Dry Snow." Journal of Glaciology 36, no. 123 (1990): 238–46. http://dx.doi.org/10.1017/s0022143000009497.
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AbstractA dynamic zone of thermal disequilibrium is described which separates wet snow at 0 ° C from dry, sub-freezing snow. The dynamic zone tends to be eliminated by thermal equilibrium through freezing, but is sustained and propagated into the sub-freezing snow by water flow from the wet snow. The width of the dynamic zone is controlled by the rate of water inflow, and by the rate of freezing of water on to sub-freezing ice grains, which is in turn controlled by the ice/water geometry. Two ice/water geometries are investigated: isolated ice spheres and capillary tubes of ice into which water is pulled by capillary suction. The rate of freezing of water is calculated for the two models for various initial dimensions and temperatures. Equilibrium times are short (typically about 0.5 s), but depend on the assumed geometry, which is poorly constrained by existing data. Equilibration times and freeze-on mass fluxes are calculated for a variety of general conditions. These results can be used in numerical models of wetting-front propagation into cold snow.
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Tad Pfeffer, W., Tissa H. Illangasekare, and Mark F. Meier. "Analysis and Modeling of Melt-Water Refreezing in Dry Snow." Journal of Glaciology 36, no. 123 (1990): 238–46. http://dx.doi.org/10.3189/s0022143000009497.
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AbstractA dynamic zone of thermal disequilibrium is described which separates wet snow at 0 ° C from dry, sub-freezing snow. The dynamic zone tends to be eliminated by thermal equilibrium through freezing, but is sustained and propagated into the sub-freezing snow by water flow from the wet snow. The width of the dynamic zone is controlled by the rate of water inflow, and by the rate of freezing of water on to sub-freezing ice grains, which is in turn controlled by the ice/water geometry. Two ice/water geometries are investigated: isolated ice spheres and capillary tubes of ice into which water is pulled by capillary suction. The rate of freezing of water is calculated for the two models for various initial dimensions and temperatures. Equilibrium times are short (typically about 0.5 s), but depend on the assumed geometry, which is poorly constrained by existing data. Equilibration times and freeze-on mass fluxes are calculated for a variety of general conditions. These results can be used in numerical models of wetting-front propagation into cold snow.
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Basavappa, Ravi, Edward T. Petri, and Blanton S. Tolbert. "A quick and gentle method for mounting crystals in capillaries." Journal of Applied Crystallography 36, no. 5 (September 8, 2003): 1297–98. http://dx.doi.org/10.1107/s0021889803014006.
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The capillary mounting of protein crystals is still necessary under some circumstances, despite its being supplanted by loop mounting/flash freezing as the favored method for crystal mounting prior to data collection. Traditional capillary mounting methods require a degree of dexterity and finesse that causes apprehension among many crystallographers. Here a simple method for capillary mounting that uses a loop for depositing the crystal in the capillary is described.
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Henry, Karen S., and Robert D. Holtz. "Geocomposite capillary barriers to reduce frost heave in soils." Canadian Geotechnical Journal 38, no. 4 (August 1, 2001): 678–94. http://dx.doi.org/10.1139/t01-010.
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We investigated the potential for geosynthetic capillary barriers to reduce frost heave in soils by freezing upright, cylindrical soil specimens with horizontal disks of geosynthetics placed in them. During freezing, water was freely available at 25 mm above the base of 150 mm high specimens. The geosynthetics were located 5 mm above the water supply. We measured frost heave and final water content profiles of specimens containing geosynthetic capillary barriers and control specimens. The thermal conditions of the tests were typical of pavements in cold regions. Geotextiles prepared to simulate field conditions (i.e., moistened and containing soil fines) failed to significantly reduce frost heave. However, geocomposites comprising needle-punched polypropylene geotextiles sandwiching a drainage net, prepared in the same way as the moistened geotextiles containing soil fines, reduced frost heave when the soil water suction head in the overlying soil was 1800 mm or more. The geocomposites did not significantly reduce heave when the soil water suction head in the overlying soil was 800 mm or less. This is probably due to water migration between the two layers of soil, through the geotextiles and along the net of the geocomposite.Key words: capillary barrier, frost heave, geosynthetic, geotextile, geocomposite, soil freezing.
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Yakovlev, S., and K. Downing. "Freezing in Sealed Capillary as an Alternative to HPF." Microscopy and Microanalysis 17, S2 (July 2011): 240–41. http://dx.doi.org/10.1017/s1431927611002078.
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Fretwell, H. M., J. A. Duffy, M. A. Alam, and R. Evans. "Anomalous freezing and melting behaviour of capillary confined CO2." Journal of Radioanalytical and Nuclear Chemistry Articles 210, no. 2 (November 1996): 575–82. http://dx.doi.org/10.1007/bf02056398.
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Zhang, Jiwen, Qingyi Mu, Hongjian Liao, and Jie Cao. "An unfrozen water retention curve for capturing soil density and specific surface effects." E3S Web of Conferences 195 (2020): 02018. http://dx.doi.org/10.1051/e3sconf/202019502018.
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Unfrozen water retention curve (UWRC) defines the relationship between temperature and unfrozen water content in frozen soils. Although many models have been proposed for the UWRC, these existing models cannot predict UWRC well over a wide temperatures range. In this study, a new UWRC model is proposed with explicit considerations of both capillarity and adsorption. In this model, capillarity is considered dominating when the freezing of soil pore water at higher temperatures (above -2oC), whereas the effects of adsorption pronounce at temperatures below -2oC. Moreover, effects of void ratio on the freezing of capillary water are incorporated. The proposed model was applied to predict UWRCs of silt and clay at different initial void ratios over a wide temperature range (from -50 to 0oC). Predicted results by this new model are compared with predictions by three well-known existing models. The new model can capture the density effects on UWRC. Moreover, the new model can predict better UWRC over a wide temperature range since it explicitly considers both effects of capillarity and adsorption.
Dissertations / Theses on the topic "Capillary freezing"
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Hung, Francisco Rodolfo. "Capillary Condensation and Freezing of Simple Fluids Confined in Cylindrical Nanopores." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-08092005-232433/.
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We present a molecular simulation study aimed at understanding the phase behavior of pure simple fluids, when they are confined inside nanopores of cylindrical geometry. In this situation, new surface-driven phases can appear, and phase transitions typical of bulk systems (gas-liquid, freezing) can be shifted to different conditions. A fundamental understanding of these phenomena is necessary for applications in separations, catalysis and nanotechnology. Studies of these phenomena can also provide important insights on the effect of surface forces, confinement and reduced dimensionality on the phase behavior of host molecules. We have performed two independent, but directly related studies: (1) freezing of carbon tetrachloride within multi-walled carbon nanotubes (MWCNT) of different diameters, and (2) capillary condensation and freezing of krypton within templated mesoporous silica materials (MCM-41). MWCNT and MCM-41 are representative of materials with strongly and weakly attractive walls, respectively. In the first part of this project, the structure and thermodynamic stability of the confined phases, as well as the temperatures and the order of the phase transitions were determined using dielectric relaxation spectroscopy measurements and Monte Carlo simulations in the grand canonical ensemble. A rich phase behavior with multiple transition temperatures was observed for such systems. In the second part of this project we developed realistic, atomistic models of MCM-41 type materials that include pore surface roughness and morphological defects in agreement with experimental results. Grand Canonical Monte Carlo simulations show that these variables have a profound influence on gas-liquid and freezing transitions in confinement.
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Maeda, Nobuo, and nobuo@engineering ucsb edu. "Phase Transitions of Long-Chain N-Alkanes at Interfaces." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20011203.151921.
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An experimental study of phase transitions of long-chain n-alkanes induced by the effect of interfaces is described.
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The phase behaviour of long-chain n-alkanes (carbon number 14, 16, 17, 18) adsorbed at isolated mica surfaces and confined between two mica surfaces has been studied in the vicinity of and down to several degrees below the bulk melting points, Tm. Using the Surface Force Apparatus we have measured the thickness of alkane films adsorbed from vapour (0.97 [equal to or greater-than] p/p[subscript o] [equal to or greater-than] 0.997), studied capillary condensation transition, subsequent growth of capillary condensates between two surfaces, and phase transitions in both the adsorbed films and the condensates. By measuring the growth rate of the capillary condensates we have identified a transition in the lateral mobility of molecules in the adsorbed films on isolated mica surfaces. This transition to greater mobility occurs slightly above Tm for n-hexadecane, n-heptadecane and n-octadecane but several degrees below Tm for n-tetradecane, and is accompanied by a change in wetting behaviour and a measurable decrease in adsorbed film thickness for n-heptadecane and n-octadecane. Capillary condensates that form below Tm remain liquid, but may freeze if the degree of confinement is reduced by separation of the mica surfaces. An increase in the area of the liquid-vapour interface relative to that of the liquid-mica interface facilitates freezing in the case of the long-chain alkanes, which show surface freezing at the liquid-vapour interface.
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Although thermodynamic properties of the surface freezing transition have been rather well documented, the kinetics involved in formation of such ordered monolayers has so far received very little attention. We studied the surface tension of n-octadecane as a function of temperature in the vicinity of Tm, using the static Wilhelmy plate and the dynamic maximum bubble pressure methods. The two methods give different results on cooling paths, where nucleation of the surface ordered phase is involved, but agree on heating paths, where both methods measure properties of the equilibrium surface phase. On cooling paths, the surface of bubbles may supercool below the equilibrium surface freezing temperature. The onset of surface freezing is marked by a sharp drop in the surface tension. The transition is accompanied by an increased stability of the films resulting in longer bubble lifetimes at the liquid surface, which suggests that the mechanical properties of the surfaces change from liquid-like to solid-like. Our results suggest occurrence of supercooling of the monolayer itself.
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Rogers, Maile Anne. "Water Vapor Movement in Freezing Aggregate Base Materials." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4013.
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The objectives of this research were to 1) measure the extent to which water vapor movement results in water accumulation in freezing base materials; 2) evaluate the effect of soil stabilization on water vapor movement in freezing base materials; 3) determine if the corresponding changes in water content are sufficient to cause frost heave during winter; 4) determine if the corresponding changes in water content are sufficient to cause reductions in stiffness during spring; 5) evaluate relationships between selected material properties, freezing conditions, and the occurrence and impact of water vapor movement; and 6) numerically simulate heat and water movement in selected pavement design scenarios. The research involved extensive laboratory and field testing, statistical analyses, and numerical modeling. The results of the laboratory testing, which included gradations, Atterberg limits, soil classifications, specific gravity and absorption values, electrical conductivity values, moisture-density relationships, soil-water characteristic curves, moisture-stiffness curves, hydraulic conductivity values, and frost susceptibility assessments, were used to characterize each material and enable subsequent statistical analyses. Testing of both treated and untreated materials enabled investigation of a wide variety of material properties. The results of the field testing, which included temperature, moisture content, water potential, elevation, and stiffness data over time, provided the basis for comparing pavement sections with and without capillary barriers and established the framework for numerical modeling. In a pavement section with a capillary barrier underlying the base layer, water vapor movement from the subgrade through the capillary barrier may be expected to increase the water content of the base layer by 1 to 3 percent during a typical winter season in northern Utah for base materials similar to those studied in this research. During winter, cold temperatures create an ideal environment for water vapor to travel upward from the warm subgrade soil below the frost line, through the capillary barrier, and into the base material. Soil stabilization can lead to increased or decreased amounts of water vapor movement in freezing base materials depending on the properties of the stabilized soil, which may be affected by gradation, mineralogy, and stabilizer type and concentration. Accumulation of water from long-term water vapor movement into frost-susceptible base materials underlain by a capillary barrier can lead to frost heave of the base layer as it approaches saturation, as water available in the layer can be redistributed upwards to create ice lenses upon freezing. However, the incremental increase in total water content that may occur exclusively from water vapor movement during a single winter season in northern Utah would not be expected to cause measurable increases in thaw weakening of the base layer during spring. Because water in a base layer overlying a capillary barrier cannot drain until nearly reaching positive pore pressures, the base layer will remain indefinitely saturated or nearly saturated as demonstrated in this research. For materials similar to those studied in this research, potentially important material properties related to the occurrence of water vapor movement during freezing include dry density, percent of material finer than the No. 200 sieve, percent of material finer than 0.02 mm, apparent specific gravity, absorption, initial water content, porosity, degree of saturation, hydraulic conductivity, and electrical conductivity. The rate at which water vapor movement occurs is also dependent on the thermal gradient within the given material, where higher thermal gradients are associated with higher amounts of water vapor movement. The numerical modeling supported the field observations that the capillary barrier effectively trapped moisture in the overlying base material, causing it to remain saturated or nearly saturated throughout the monitoring period. Only non-frost-susceptible aggregate base materials should be specified for use in cold climates in conjunction with capillary barriers, and the base material in this case should be assumed to remain in a saturated or nearly saturated condition during the entire service life of the pavement. Further study is recommended on water vapor movement in freezing aggregate base materials.
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Maeda, Nobuo. "Phase Transitions of Long-Chain N-Alkanes at Interfaces." Phd thesis, 2001. http://hdl.handle.net/1885/47795.
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An experimental study of phase transitions of long-chain n-alkanes induced by the effect of interfaces is described. ¶ The phase behaviour of long-chain n-alkanes (carbon number 14, 16, 17, 18) adsorbed at isolated mica surfaces and confined between two mica surfaces has been studied in the vicinity of and down to several degrees below the bulk melting points, Tm. Using the Surface Force Apparatus we have measured the thickness of alkane films adsorbed from vapour (0.97 [equal to or greater-than] p/p[subscript o] [equal to or greater-than] 0.997), studied capillary condensation transition, subsequent growth of capillary condensates between two surfaces, and phase transitions in both the adsorbed films and the condensates. By measuring the growth rate of the capillary condensates we have identified a transition in the lateral mobility of molecules in the adsorbed films on isolated mica surfaces. This transition to greater mobility occurs slightly above Tm for n-hexadecane, n-heptadecane and n-octadecane but several degrees below Tm for n-tetradecane, and is accompanied by a change in wetting behaviour and a measurable decrease in adsorbed film thickness for n-heptadecane and n-octadecane. Capillary condensates that form below Tm remain liquid, but may freeze if the degree of confinement is reduced by separation of the mica surfaces. An increase in the area of the liquid-vapour interface relative to that of the liquid-mica interface facilitates freezing in the case of the long-chain alkanes, which show surface freezing at the liquid-vapour interface. ¶ Although thermodynamic properties of the surface freezing transition have been rather well documented, the kinetics involved in formation of such ordered monolayers has so far received very little attention. We studied the surface tension of n-octadecane as a function of temperature in the vicinity of Tm, using the static Wilhelmy plate and the dynamic maximum bubble pressure methods. The two methods give different results on cooling paths, where nucleation of the surface ordered phase is involved, but agree on heating paths, where both methods measure properties of the equilibrium surface phase. On cooling paths, the surface of bubbles may supercool below the equilibrium surface freezing temperature. The onset of surface freezing is marked by a sharp drop in the surface tension. The transition is accompanied by an increased stability of the films resulting in longer bubble lifetimes at the liquid surface, which suggests that the mechanical properties of the surfaces change from liquid-like to solid-like. Our results suggest occurrence of supercooling of the monolayer itself.
Book chapters on the topic "Capillary freezing"
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Tsybulskyi, Vitalii. "IMPROVEMENT OF CALCULATION METHOD OF ROAD PAVEMENT EMBANKMENT ON THE APPROACHES TO ROAD BRIDGES." In Integration of traditional and innovation processes of development of modern science. Publishing House “Baltija Publishing”, 2020. http://dx.doi.org/10.30525/978-9934-26-021-6-41.
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The laws of unsaturated and capillary movement of water in soils are analyzed, which are complex and insufficiently studied, but significantly affect the condition of the ground. Experience in the design and construction of the subsoil has shown that during the excavation works can significantly change the conditions of soils and their water-thermal regime. Therefore, the characteristics of soils used in stability calculations should be determined taking into account the subsequent condition of the soil in the conditions of occurrence, as well as the possible change of these conditions during construction and maintenance. One of the urgent tasks is to improve the methods of regulating the water-thermal regime of roads. By changing the conditions of its course or the type of water-thermal regime itself, significant successes can be achieved in improving the maintenance of roads, engineering and transport facilities. Dangerous effect of these factors on the embankment of the ground is manifested in the formation of wetting, wetting of the soil and layers of pavement, resulting in reduced density, strength of soils, subsidence, swelling and loss of continuity due to cracking. As a result, the strength of the road structure, the flatness of the carriageway, the durability of the pavement and the adhesion of the wheels to the roadway are reduced. The most dangerous for roads are moisture accumulation, freezing, thawing of the ground, intensive heating and intensive cooling of the layers of pavement. The analysis of regularities of formation of a water-thermal regime of a ground and its regulation at the expense of the device of optimum capillary-interrupting layers is carried out. The laws of soil moisture when raising capillary water showed that when the layer of the embankment with a high coefficient of impregnation is dehydrated over the layer with a lower coefficient, the speed of moving capillary water into the upper soil layers drops sharply. This fall occurs as a result of changes in the relationship between the driving forces of the menisci and the forces of resistance of capillary water in the soil. The process of unsaturated movement of water in the soil is determined by the combination of many factors that characterize the capillary system of the soil. The calculation uses complex indicators of soil water movement conditions, which are established experimentally for each variety and soil density at optimal humidity, as well as water filtration coefficients in the soil. To establish the relationship between these experimental data and the required values that determine the capillary system of the soil, the filtration of water in the soil was considered. Determining the optimal capillary system of the soil and establishing the unstable distribution of own capillary water in the structures of high embankments will ensure the strength of approaches to road bridges. The method of calculating the determination of the optimal composition of the road layers taking into account the processes of water-thermal regime and capillary movement of water has been improved. The algorithm of calculation in the program Microsoft Excel for selection of optimum structure of a ground cloth of a high embankment on approaches to automobile bridges is offered.
Conference papers on the topic "Capillary freezing"
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Teraoka, Yoshikazu, Ryo Fukuno, and Koji Matsumoto. "Crystal Orientation Rotation of Ice During Growth in a Bended Capillary." In ASME/JSME 2011 8th Thermal Engineering Joint Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajtec2011-44367.
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A control technique of crystal orientation of ice can presumably help to improve freezing processes of various industries. However, the technique without seed ice has not been established yet. The author had found that crystal orientation of ice rotated gradually during high-rate growth along a cooling wall. The purpose of this paper is to examine the crystal orientation rotation of ice during growth in several types of bended capillaries at supercooling temperature. We show that, after growing through the capillaries, c-axis of ice crystal is within a certain angle range. On the basis of the measurement the rotation of crystal orientation before and after the growth through some sections of the capillaries, we constructed an empirical model of c-axis rotating gradually during ice growth in the capillary. The calculation of the model can explain the approach process of c-axis of ice crystal growing in the bended capillary to the specified direction.
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Pillapakkam, Shriram, N. A. Musunuri, and P. Singh. "Self-Assembly of Monolayers of Submicron Sized Particles on Thin Liquid Films." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65324.
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In this paper, we present a technique for freezing monolayers of micron and sub-micron sized particles onto the surface of a flexible thin film after the self-assembly of a particle monolayer on fluid-liquid interfaces has been improved by the process we have developed where an electric field is applied in the direction normal to the interface. Particles smaller than about 10 microns do not self-assemble under the action of lateral capillary forces alone since capillary forces amongst them are small compared to Brownian forces. We have overcome this problem by applying an electric field in the direction normal to the interface which gives rise to dipoledipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another liquid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film.
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Supowit, Jacob, Sean Reilly, Ladan Amouzegar, and Ivan Catton. "A Novel Inorganic Aqueous Solution and its Effect on Liquid Spreading and Freeze/Thaw Processes." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17773.
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Frozen startup of phase change heat transfer devices is a complex problem that can have a large impact on heat transfer systems. A patented novel working fluid developed at UCLA comprised of an inorganic aqueous solution (IAS) was investigated for potential effects on the freeze/thaw capabilities in phase change heat transfer devices by examining the melting process of droplets. Preliminary visual tests were conducted to gain insight into any physical processes that surface augmentation created by this fluid may have on the freezing and melting process. These tests demonstrated significant differences in liquid spreading, the melting process, and the melting rate of droplets on surfaces pre-treated with IAS. Contact angle measurements exhibited enhanced wetting properties. SEM images of frozen droplets showed that liquid freezes in the small capillary wick formed by the initial evaporation of IAS. Video of melting droplets showed a significant increase in melting rate when the surface was first treated with IAS due to superior liquid spreading.
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Scott, David A., and B. Rabi Baliga. "Thermophysical Properties of a Slurry of Distilled Water and Microencapsulated Phase-Change Materials." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61337.
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This paper presents experimental measurements of some effective thermophysical properties of slurries consisting of microencapsulated phase change materials (MCPCMs) suspended in distilled water. The related apparatus and procedures are also presented and discussed. The MCPCMs considered here consist of a core of phase-change material (PCM), in this case a substance akin to octadecane, surrounded by a solid shell. The effective density of the slurries was measured using hydrometers. The effective thermal conductivity of the slurries was measured using an in-house designed apparatus. The effective kinematic viscosity of the slurries was measured using a series of glass capillary viscometers. A differential scanning calorimeter (DSC) was used to obtain the effective specific heat, melting and freezing temperatures of the core PCMs, and the latent heat of the slurries. Slurry concentrations between 0% (pure distilled water) and 20% by mass of the MCPCMs were considered in this investigation, at temperatures ranging from 5°C to 65°C. Where possible, the results have been compared to predictions obtained using available analytical expressions with properties of the constitutive materials as inputs.
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Yang, Zhenning, Carlton L. Ho, Richard Joy, and Nandan C. Dabhade. "Influence of Water Content on the Behavior of Partially Saturated Fouled Ballast." In 2016 Joint Rail Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/jrc2016-5724.
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The water content of fouled ballast is important when considering the shear strength and deformability of the ballast, and therefore critical in evaluating whether the track is at risk of excessive deformations warranting a speed restriction order. Fouled ballast from northeastern United States was tested in the laboratory to assess changes in shear strength and deformability as a function of water content. X-ray fluorescence analysis determined that the fouling material was 95% by weight basalt in origin. No more than 5% of the fouling material could be attributed to the abraded concrete ties. The field capacity of the fouled ballast was measured to be at a water content of 10%. Freezing and thawing tests indicated that approximately 4% of mass loss could be expected as a result of 25 freeze/thaw cycles. 6-inch triaxial tests, TX-CIDC, were conducted on the ballast at water contents between dry and field capacity (10%). As the ballast was partially saturated, volume change was measured using circumferential string potentiometers. The water content had an influence on the shear strength and the modulus of elasticity of the fouled ballast. The Mohr-Coulomb friction angle decreased from 47.3° for the dry ballast to 42.5° for the field capacity ballast. The Mohr-Coulomb cohesion decreased from 3.38 psi to nearly zero with initial addition of water, but increased to 6.18 psi as the water content reached field capacity. This is likely attributable to changes in capillary tension of the partially saturated fouling material. The average shear strength, Mohr-Coulomb friction angle, Mohr-Coulomb cohesion, modulus of elasticity and Poisson’s Ratio all showed weakening and strengthening effect by addition of water.
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Bamido, Alaba, and Debjyoti Banerjee. "A Thermally Actuated Microvalve for Smart Irrigation in Precision Agriculture Applications." In ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-65899.
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Abstract A normally-open thermally-actuated microvalve was designed (using microfabrication/soft-lithography techniques involving 3D Printed molds), assembled and tested. The motivation of the research work is to develop an array of microvalves for precise delivery of water to individual plants in a field (with the goal of developing smart irrigation systems for high value cash-crops in the agricultural sector). It is currently impossible to control application of irrigation-water at the level of a single plant. If such a capability were practically available on farms, the result would be a step change in precision agriculture, such that the output of every plant in a farm field could be optimized (i.e., food-water-energy nexus in sustainability applications). The aim of this study is to develop and test a microfluidic system (consisting of a microvalve array) that could be controlled, capillary by capillary, to deliver the needed amount of water to individual plants in a large field. Two types of test fluids were leveraged for thermo-hydraulic actuation of the microvalves developed in this study: (a) Design-I: using air, and (b) Design-II: using Phase Change Material (PCM). The PCM used in this study is PureTemp29. The proposed approach enabled a simple and cheap design for microvalves that can be manufactured easily and are robust to weather conditions (e.g., when exposed to the elements in orchards and open fields). Other advantages include: safe and reliable operation; low power consumption; can tolerate anomalous pressure loads/fluctuations; simple actuation; affords easy control schemes; is amenable for remote control; provides long-term reliability (life-cycle duration estimated to be 3∼5 years); can be mass produced and is low maintenance (possibly requiring no maintenance over the life time of operation). The microvalve consists of two layers: a flow layer and a control layer. The control layer is heated from below and contains a microfluidic chamber with a flexible polymeric thin-membrane (200 microns in thickness) on top. The device is microfabricated from Poly-Di-Methyl-Siloxane (PDMS) using soft lithography techniques (using a 3D Printed mold). The control chamber contains either air (thermo-pneumatic actuation) or PCM (thermo-hydraulic actuation involving repeated melting/freezing of PCM). The flow layer contains the flow channel (inlet and outlet ports, horizontal section and valve seat). The experimental results from testing the efficacy of the two types of micro-valves show a 60% reduction (for thermo-pneumatic actuation using air) and 40% reduction (for thermo-hydraulic actuation using PCM) in water flow rates for similar actuation conditions (i.e., heater temperature values). PCM design is expected to consume less power (lower OPEX) for long-term actuation but may have slower actuation speed and have higher manufacturing costs (CAPEX). Air actuation design is expected to consume more power (higher OPEX) for longer-term operation but may have faster actuation speeds and lower manufacturing costs (CAPEX). Computational Fluid Dynamics (CFD) simulations were performed to investigate the effect of flowing water (in the microfluidic channel) on the average absolute pressure and temperature of air in the actuation chamber. The CFD simulations were performed using a commercial tool (Ansys™ 2019R1®). The results from the CFD simulations are presented in this study.