Thematische Bibliographien / Freezing droplets

Inhaltsverzeichnis

Zeitschriftenartikel
Dissertationen
Bücher
Buchteile
Konferenzberichte

Auswahl der wissenschaftlichen Literatur zum Thema „Freezing droplets“

Autor: Grafiati

Veröffentlicht am 28. Juni 2021

Zuletzt aktualisiert am 3. Februar 2022

Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an

Wählen Sie eine Art der Quelle aus:

Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Freezing droplets" bekannt.

Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.

Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.

Zeitschriftenartikel zum Thema "Freezing droplets"

Hoffmann, N., A. Kiselev, D. Rzesanke, D. Duft und T. Leisner. „Experimental quantification of contact freezing in an electrodynamic balance“. Atmospheric Measurement Techniques 6, Nr. 9 (12.09.2013): 2373–82. http://dx.doi.org/10.5194/amt-6-2373-2013.

Der volle Inhalt der Quelle

Annotation:

Abstract. Heterogeneous nucleation of ice in a supercooled water droplet induced by external contact with a dry aerosol particle has long been known to be more effective than freezing induced by the same nucleus immersed in the droplet. However, the experimental quantification of contact freezing is challenging. Here we report an experimental method to determine the temperature-dependent ice nucleation probability of size-selected aerosol particles. The method is based on the suspension of supercooled charged water droplets in a laminar flow of air containing aerosol particles as contact freezing nuclei. The rate of droplet–particle collisions is calculated numerically with account for Coulomb attraction, drag force and induced dipole interaction between charged droplet and aerosol particles. The calculation is verified by direct counting of aerosol particles collected by a levitated droplet. By repeating the experiment on individual droplets for a sufficient number of times, we are able to reproduce the statistical freezing behavior of a large ensemble of supercooled droplets and measure the average rate of freezing events. The freezing rate is equal to the product of the droplet–particle collision rate and the probability of freezing on a single contact, the latter being a function of temperature, size and composition of the contact ice nuclei. Based on these observations, we show that for the types of particles investigated so far, contact freezing is the dominating freezing mechanism on the timescale of our experiment.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Hoffmann, N., A. Kiselev, D. Rzesanke, D. Duft und T. Leisner. „Experimental quantification of contact freezing in an electrodynamic balance“. Atmospheric Measurement Techniques Discussions 6, Nr. 2 (10.04.2013): 3407–37. http://dx.doi.org/10.5194/amtd-6-3407-2013.

Der volle Inhalt der Quelle

Annotation:

Abstract. Heterogeneous nucleation of ice in a supercooled water droplet induced by an external contact with a dry aerosol particle has long been known to be more effective than freezing induced by the same nucleus immersed in the droplet. However, the experimental quantification of contact freezing is challenging. Here we report an experimental method allowing to determine the temperature dependent ice nucleation probability of size selected aerosol particles. The method uses supercooled charged water droplets suspended in a laminar flow of air containing aerosol particles as contact freezing nuclei. The rate of droplet–particle collisions is calculated numerically with account for Coulomb attraction, drag force and induced dipole interaction between charged droplet and aerosol particles. The calculation is verified by direct counting of aerosol particles collected by a levitated droplet. By repeating the experiment on individual droplets for a sufficient number of times, we are able to reproduce the statistical freezing behavior of a large ensemble of supercooled droplets and measure the average rate of freezing events. The freezing rate is equal to the product of the droplet–particle collision rate and the probability of freezing on a single contact, the latter being a function of temperature, size and composition of the contact ice nuclei. Based on these observations, we show that for the types of particles investigated so far, contact freezing is the dominating freezing mechanism on the time scale of our experiment.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Lauber, Annika, Alexei Kiselev, Thomas Pander, Patricia Handmann und Thomas Leisner. „Secondary Ice Formation during Freezing of Levitated Droplets“. Journal of the Atmospheric Sciences 75, Nr. 8 (31.07.2018): 2815–26. http://dx.doi.org/10.1175/jas-d-18-0052.1.

Der volle Inhalt der Quelle

Annotation:

Abstract The formation of secondary ice in clouds, that is, ice particles that are created at temperatures above the limit for homogeneous freezing without the direct involvement of a heterogeneous ice nucleus, is one of the longest-standing puzzles in cloud physics. Here, we present comprehensive laboratory investigations on the formation of small ice particles upon the freezing of drizzle-sized cloud droplets levitated in an electrodynamic balance. Four different categories of secondary ice formation (bubble bursting, jetting, cracking, and breakup) could be detected, and their respective frequencies of occurrence as a function of temperature and droplet size are given. We find that bubble bursting occurs more often than droplet splitting. While we do not observe the shattering of droplets into many large fragments, we find that the average number of small secondary ice particles released during freezing is strongly dependent on droplet size and may well exceed unity for droplets larger than 300 μm in diameter. This leaves droplet fragmentation as an important secondary ice process effective at temperatures around −10°C in clouds where large drizzle droplets are present.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Svensson, E. A., C. Delval, P. von Hessberg, M. S. Johnson und J. B. C. Pettersson. „Freezing of water droplets colliding with kaolinite particles“. Atmospheric Chemistry and Physics 9, Nr. 13 (03.07.2009): 4295–300. http://dx.doi.org/10.5194/acp-9-4295-2009.

Der volle Inhalt der Quelle

Annotation:

Abstract. Contact freezing of single supercooled water droplets colliding with kaolinite dust particles has been investigated. The experiments were performed with droplets levitated in an electrodynamic balance at temperatures from 240 to 268 K. Under relatively dry conditions (when no water vapor was added) freezing was observed to occur below 249 K, while a freezing threshold of 267 K was observed when water vapor was added to the air in the chamber. The effect of relative humidity is attributed to an influence on the contact freezing process for the kaolinite-water droplet system, and it is not related to the lifetime of the droplets in the electrodynamic balance. Freezing probabilities per collision were derived assuming that collisions at the lowest temperature employed had a probability of unity. Mechanisms for contact freezing are briefly discussed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Chuah, Y. K., J. T. Lin und K. H. Yu. „An Experimental Study on the Heat Transfer of Traveling Airborne Water Droplets in Cold Environment“. Journal of Mechanics 32, Nr. 2 (Januar 2015): 219–25. http://dx.doi.org/10.1017/jmech.2015.84.

Der volle Inhalt der Quelle

Annotation:

AbstractThis paper presents experimental results on rapid freezing of water droplets injected into a low temperature environment. A heat balance method was applied to determine the ratio of the water droplets frozen at the collection after the airborne time. The experimental results show that rapid freezing of water droplets could be achieved within three seconds of airborne time. Droplet size distribution of the frozen water droplets after collection was estimated. Heat transfer during the airborne time was calculated with consideration of the droplet size distribution. At attempt was taken to compare the heat transfer obtained with some previous studies on heat transfer of spherical objects in air. The research results show that droplet size distribution is important for the prediction of heat transfer of water droplets traveling in air. The results presented in this study contribute to the understanding of heat transfer of water droplets injected into a low temperature air.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Alpert, P. A., und D. A. Knopf. „Analysis of isothermal and cooling rate dependent immersion freezing by a unifying stochastic ice nucleation model“. Atmospheric Chemistry and Physics Discussions 15, Nr. 9 (05.05.2015): 13109–66. http://dx.doi.org/10.5194/acpd-15-13109-2015.

Der volle Inhalt der Quelle

Annotation:

Abstract. Immersion freezing is an important ice nucleation pathway involved in the formation of cirrus and mixed-phase clouds. Laboratory immersion freezing experiments are necessary to determine the range in temperature (T) and relative humidity (RH) at which ice nucleation occurs and to quantify the associated nucleation kinetics. Typically, isothermal (applying a constant temperature) and cooling rate dependent immersion freezing experiments are conducted. In these experiments it is usually assumed that the droplets containing ice nuclei (IN) all have the same IN surface area (ISA), however the validity of this assumption or the impact it may have on analysis and interpretation of the experimental data is rarely questioned. A stochastic immersion freezing model based on first principles of statistics is presented, which accounts for variable ISA per droplet and uses physically observable parameters including the total number of droplets (Ntot) and the heterogeneous ice nucleation rate coefficient, Jhet(T). This model is applied to address if (i) a time and ISA dependent stochastic immersion freezing process can explain laboratory immersion freezing data for different experimental methods and (ii) the assumption that all droplets contain identical ISA is a valid conjecture with subsequent consequences for analysis and interpretation of immersion freezing. The simple stochastic model can reproduce the observed time and surface area dependence in immersion freezing experiments for a variety of methods such as: droplets on a cold-stage exposed to air or surrounded by an oil matrix, wind and acoustically levitated droplets, droplets in a continuous flow diffusion chamber (CFDC), the Leipzig aerosol cloud interaction simulator (LACIS), and the aerosol interaction and dynamics in the atmosphere (AIDA) cloud chamber. Observed time dependent isothermal frozen fractions exhibiting non-exponential behavior with time can be readily explained by this model considering varying ISA. An apparent cooling rate dependence ofJhet is explained by assuming identical ISA in each droplet. When accounting for ISA variability, the cooling rate dependence of ice nucleation kinetics vanishes as expected from classical nucleation theory. The model simulations allow for a quantitative experimental uncertainty analysis for parameters Ntot, T, RH, and the ISA variability. In an idealized cloud parcel model applying variability in ISAs for each droplet, the model predicts enhanced immersion freezing temperatures and greater ice crystal production compared to a case when ISAs are uniform in each droplet. The implications of our results for experimental analysis and interpretation of the immersion freezing process are discussed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Svensson, E. A., C. Delval, P. von Hessberg, M. S. Johnson und J. B. C. Pettersson. „Freezing of water droplets colliding with kaolinite particles“. Atmospheric Chemistry and Physics Discussions 9, Nr. 1 (27.01.2009): 2417–33. http://dx.doi.org/10.5194/acpd-9-2417-2009.

Der volle Inhalt der Quelle

Annotation:

Abstract. Contact freezing of single supercooled water droplets colliding with kaolinite dust particles has been investigated. The experiments were performed with droplets levitated in an electrodynamic balance at temperatures from 240 to 268 K. Under dry conditions freezing was observed to occur below 249 K, while a freezing threshold of 267 K was observed at high relative humidity. The effect of relative humidity is attributed to an influence on the contact freezing process for the kaolinite-water droplet system, and it is not related to the lifetime of the droplets in the electrodynamic balance. Freezing probabilities per collision were derived assuming that collisions at the lowest temperature employed had a probability of unity. The data recorded at high humidity should be most relevant to atmospheric conditions, and the results indicate that parameterizations currently used in modelling studies to describe freezing rates are appropriate for kaolinite aerosol particles. Mechanisms for contact freezing are briefly discussed.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Nagare, Baban, Claudia Marcolli, André Welti, Olaf Stetzer und Ulrike Lohmann. „Comparing contact and immersion freezing from continuous flow diffusion chambers“. Atmospheric Chemistry and Physics 16, Nr. 14 (19.07.2016): 8899–914. http://dx.doi.org/10.5194/acp-16-8899-2016.

Der volle Inhalt der Quelle

Annotation:

Abstract. Ice nucleating particles (INPs) in the atmosphere are responsible for glaciating cloud droplets between 237 and 273 K. Different mechanisms of heterogeneous ice nucleation can compete under mixed-phase cloud conditions. Contact freezing is considered relevant because higher ice nucleation temperatures than for immersion freezing for the same INPs were observed. It has limitations because its efficiency depends on the number of collisions between cloud droplets and INPs. To date, direct comparisons of contact and immersion freezing with the same INP, for similar residence times and concentrations, are lacking. This study compares immersion and contact freezing efficiencies of three different INPs. The contact freezing data were obtained with the ETH CoLlision Ice Nucleation CHamber (CLINCH) using 80 µm diameter droplets, which can interact with INPs for residence times of 2 and 4 s in the chamber. The contact freezing efficiency was calculated by estimating the number of collisions between droplets and particles. Theoretical formulations of collision efficiencies gave too high freezing efficiencies for all investigated INPs, namely AgI particles with 200 nm electrical mobility diameter, 400 and 800 nm diameter Arizona Test Dust (ATD) and kaolinite particles. Comparison of freezing efficiencies by contact and immersion freezing is therefore limited by the accuracy of collision efficiencies. The concentration of particles was 1000 cm−3 for ATD and kaolinite and 500, 1000, 2000 and 5000 cm−3 for AgI. For concentrations < 5000 cm−3, the droplets collect only one particle on average during their time in the chamber. For ATD and kaolinite particles, contact freezing efficiencies at 2 s residence time were smaller than at 4 s, which is in disagreement with a collisional contact freezing process but in accordance with immersion freezing or adhesion freezing. With “adhesion freezing”, we refer to a contact nucleation process that is enhanced compared to immersion freezing due to the position of the INP on the droplet, and we discriminate it from collisional contact freezing, which assumes an enhancement due to the collision of the particle with the droplet. For best comparison with contact freezing results, immersion freezing experiments of the same INPs were performed with the continuous flow diffusion chamber Immersion Mode Cooling chAmber–Zurich Ice Nucleation Chamber (IMCA–ZINC) for a 3 s residence time. In IMCA–ZINC, each INP is activated into a droplet in IMCA and provides its surface for ice nucleation in the ZINC chamber. The comparison of contact and immersion freezing results did not confirm a general enhancement of freezing efficiency for contact compared with immersion freezing experiments. For AgI particles the onset of heterogeneous freezing in CLINCH was even shifted to lower temperatures compared with IMCA–ZINC. For ATD, freezing efficiencies for contact and immersion freezing experiments were similar. For kaolinite particles, contact freezing became detectable at higher temperatures than immersion freezing. Using contact angle information between water and the INP, it is discussed how the position of the INP in or on the droplets may influence its ice nucleation activity.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Ettner, M., S. K. Mitra und S. Borrmann. „Heterogeneous freezing of single sulfuric acid solution droplets: laboratory experiments utilizing an acoustic levitator“. Atmospheric Chemistry and Physics 4, Nr. 7 (29.09.2004): 1925–32. http://dx.doi.org/10.5194/acp-4-1925-2004.

Der volle Inhalt der Quelle

Annotation:

Abstract. The heterogeneous freezing temperatures of single binary sulfuric acid solution droplets were measured in dependency of acid concentration down to temperatures as low as -50°C. In order to avoid influence of supporting substrates on the freezing characteristics, a new technique has been developed to suspend the droplet by means of an acoustic levitator. The droplets contained immersed particles of graphite, kaolin or montmorillonite in order to study the influence of the presence of such contamination on the freezing temperature. The radii of the suspended droplets spanned the range between 0.4 and 1.1mm and the concentration of the sulfuric acid solution varied between 5 and 14 weight percent. The presence of the particles in the solution raises the freezing temperature with respect to homogeneous freezing of these solution droplets. The pure solution droplets can be supercooled up to 40 degrees below the ice-acid solution thermodynamic equilibrium curve. Depending on the concentration of sulfuric acid and the nature of the impurity the polluted droplets froze between -11°C and -35°C. The new experimental set-up, combining a deep freezer with a movable ultrasonic levitator and suitable optics, proved to be a useful approach for such investigations on individual droplets.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Phillips, Vaughan T. J., Leo J. Donner und Stephen T. Garner. „Nucleation Processes in Deep Convection Simulated by a Cloud-System-Resolving Model with Double-Moment Bulk Microphysics“. Journal of the Atmospheric Sciences 64, Nr. 3 (01.03.2007): 738–61. http://dx.doi.org/10.1175/jas3869.1.

Der volle Inhalt der Quelle

Annotation:

Abstract A novel type of limited double-moment scheme for bulk microphysics is presented here for cloud-system-resolving models (CSRMs). It predicts the average size of cloud droplets and crystals, which is important for representing the radiative impact of clouds on the climate system. In this new scheme, there are interactive components for ice nuclei (IN) and cloud condensation nuclei (CCN). For cloud ice, the processes of primary ice nucleation, Hallett–Mossop (HM) multiplication of ice particles (secondary ice production), and homogeneous freezing of aerosols and droplets provide the source of ice number. The preferential evaporation of smaller droplets during homogeneous freezing of cloud liquid is represented for the first time. Primary and secondary (i.e., in cloud) droplet nucleation are also represented, by predicting the supersaturation as a function of the vertical velocity and local properties of cloud liquid. A linearized scheme predicts the supersaturation, explicitly predicting rates of condensation and vapor deposition onto liquid (cloud liquid, rain) and ice (cloud ice, snow, graupel) species. The predicted supersaturation becomes the input for most nucleation processes, including homogeneous aerosol freezing and secondary droplet activation. Comparison of the scheme with available aircraft and satellite data is performed for two cases of deep convection over the tropical western Pacific Ocean. Sensitivity tests are performed with respect to a range of nucleation processes. The HM process of ice particle multiplication has an important impact on the domain-wide ice concentration in the lower half of the mixed-phase region, especially when a lack of upper-level cirrus suppresses homogeneous freezing. Homogeneous freezing of droplets and, especially, aerosols is found to be the key control on number and sizes of cloud particles in the simulated cloud ensemble. Preferential evaporation of smaller droplets during homogeneous freezing produces a major impact on ice concentrations aloft. Aerosols originating from the remote free troposphere become activated in deep convective updrafts and produce most of the supercooled cloud droplets that freeze homogeneously aloft. Homogeneous aerosol freezing is found to occur only in widespread regions of weak ascent while homogeneous droplet freezing is restricted to deep convective updrafts. This means that homogeneous aerosol freezing can produce many more crystals than homogeneous droplet freezing, if conditions in the upper troposphere are favorable. These competing mechanisms of homogeneous freezing determine the overall response of the ice concentration to environmental CCN concentrations in the simulated cloud ensemble. The corresponding sensitivity with respect to environmental IN concentrations is much lower. Nevertheless, when extremely high concentrations of IN are applied, that are typical for plumes of desert dust, the supercooled cloud liquid is completely eliminated in the upper half of the mixed phase region. This shuts down the process of homogeneous droplet freezing.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Mehr Quellen

Dissertationen zum Thema "Freezing droplets"

Atkinson, James David. „Freezing of droplets under mixed-phase cloud conditions“. Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5858/.

Der volle Inhalt der Quelle

Annotation:

Mixed-phase clouds contain both liquid and ice particles. They have important roles in weather and climate and such clouds are thought to be responsible for a large proportion of precipitation. Their lifetime and precipitation rates are sensitive to the concentration of ice. This project focuses upon the formation of ice within clouds containing liquid droplets colder than 273 K. A new bench-top instrument has been developed to study ice nucleation in liquid droplets. Pure water droplets of sizes relevant to clouds in the lower atmosphere do not freeze homogeneously until temperatures below ~237 K are reached. However, literature measurements of nucleation rates are scattered over two kelvin and there is uncertainty over the actual mechanism of ice formation in small droplets. The freezing of droplets with diameters equivalent to ~4 – 17 μm has been observed. It was found that ice nucleation rates in the smallest droplets of this size range were consistent with nucleation due to the droplet surface, but that surface nucleation does not occur at fast enough rates to be significant in the majority of tropospheric clouds. Water droplets can be frozen at higher temperatures than relevant for homogeneous freezing due to the presence of a class of aerosol particles called ice nuclei. Field observations of ice crystal residues have shown that mineral dust particles are an important group of ice nuclei, and the ice nucleating ability of seven of the most common minerals found in atmospheric dust has been described. In comparison to the other minerals, it was found that the mineral K-feldspar is much more efficient at nucleating ice. To relate this result to the atmosphere, a global chemical and aerosol transport modelling study was performed. This study concluded that dust containing feldspar emitted from desert regions reaches all locations around the globe. At temperatures below ~255 K, the modelled concentration of feldspar is sufficient to explain field observations of ice nuclei concentrations.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Xiao, Ruiyang. „The Freezing of Highly Sub-cooled H2O/D2O Droplets“. The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211567463.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Xiao, Ruiyang. „The freezing of highly sub-cooled H₂O/D₂O droplets“. Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1211567463.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Bhola, Rabindra. „Impact and freezing of molten tin droplets on a solid surface“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28862.pdf.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Schwenke, George Kristian. „Analysis of the non-isothermal impaction-spreading and freezing of metal droplets“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39763.

Der volle Inhalt der Quelle

Annotation:

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.
Includes bibliographical references (leaves 113-119).
by George Kristian Schwenke.
M.S.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Amaya, Andrew J. „Freezing Supercooled Water Nanodroplets near ~225 K through Homogeneous and Heterogeneous Ice Nucleation“. The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511889157206238.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Hoffmann, Nadine [Verfasser], und Thomas [Akademischer Betreuer] Leisner. „Experimental Study on the Contact Freezing of Supercooled Micro-Droplets in Electrodynamic Balance / Nadine Hoffmann ; Betreuer: Thomas Leisner“. Heidelberg : Universitätsbibliothek Heidelberg, 2015. http://d-nb.info/1180396448/34.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Křepela, Radim. „Energetická náročnost výroby umělého sněhu“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443196.

Der volle Inhalt der Quelle

Annotation:

The presented diploma thesis informs about the origin, history, and benefits of technical snowmaking. It introduces what snow equipment consists of and what processes artificial snow is produced. It also shows the price of tons of snow produced from individual commercially available equipment. In the experimental part, the work deals with the calculation of droplet freezing for various input parameters of water, environment, and equipment. A sample calculation was performed for a falling water droplet from a snow lances. The droplet of discharged water was 0.3 mm in size and had a temperature of 2 ° C. The temperature of the environment was chosen to be -10 ° C. Furthermore, the trajectory of the droplet from a snow gun was determined. In the design, a specific snow pole was designed for the specified parameters, including the speed of the environment. The results were then compared with snow poles available on the market.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Karlsson, Linn. „A Numerical and Experimental Investigation of the Internal Flow of a Freezing Water Droplet“. Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17930.

Der volle Inhalt der Quelle

Annotation:

The overarching aim of this work is to study the freezing process of a single water droplet freezing on a cold surface, which is an interesting and important phenomenon with possible applications in many areas. Understanding the freezing process of a single water droplet is for example an important step when preventing unwanted icing, e.g. in the case of airplane wings and propellers, wind turbine rotor blades, and road surfaces.As a step in understanding the freezing process, the study specifically focuses on the internal flow in the droplet during the freezing process. To do this, the study combines the use of Computational Fluid Dynamics (CFD) to build a model of the freezing process and experimental methods, i.e. Particle Image Velocimetry (PIV) to validate the numerical results. Focus is to start with the heat- and mass transfer inside the droplet using simple geometries with a rigid boundary, not modelling the outside environment as the air and the cooling plate. These components will be incorporated in the model further on.Three papers will be included in the study. In Paper A the CFD model is created and tested on a simple 2D-geometry of a droplet. The numerical result is partially compared to experimental work found in literature. In Paper B the numerical model is developed even further and a more realistic geometry of a real droplet, although with rigid boundaries, is used. The numerical results are as for Paper A validated with experimental results found in literature. In Paper C the internal flow inside the droplet has been investigated experimentally to estimate the velocities in the water, so that in the future the results can be used to validate the numerical work.The results show that is possible to work with a very simple CFD model and still capture the main flow features and freezing characteristics in a freezing water droplet. In line with previous research, this study confirms that the natural convection induced by gravity is significant for the internal flow, as compared to conduction and effects of ice creation. If studying the freezing time the internal flow has little effect. However, when estimating the velocities in the water it is crucial. It can be seen that the gravity effects are most pronounced around the density maximum for water (at T = 4◦C). The experiments show that the method used to study the flow inside the droplet is a working method, and the velocities in the water has been estimated. The next step is to further develop the CFD model and validate the numerical work with the experimental results. An interesting next step is to incorporate a moving interface to capture the volume expansion during the phase change.

Godkänd; 2015; 20151020 (kainlr); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Linn Karlsson Ämne: Strömningslära/Fluid Mechanics Uppsats: A Numerical and Experimental Investigation of the Internal Flow of a Freezing Water Droplet Examinator: Professor Staffan Lundström, Institutionen för teknikvetenskap och matematik, Avdelning: Strömningslära och experimentell mekanik Luleå tekniska universitet Diskutant: Professor Alexander Kaplan, Institutionen för teknikvetenskap och matematik, Avdelning: Produkt- och produktionsutveckling Tid: Fredag 18 december, 2015 kl 09.00 Plats: E231, Luleå tekniska universitet

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Paukert, Marco [Verfasser], und C. [Akademischer Betreuer] Hoose. „Droplet freezing in clouds induced by mineral dust particles: Sensitivities of precipitation and radiation / Marco Paukert. Betreuer: C. Hoose“. Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1110969600/34.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Bücher zum Thema "Freezing droplets"

Bhola, Rabindra. Impact and freezing of molten tin droplets on a solid surface. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1999.

Den vollen Inhalt der Quelle finden

APA, Harvard, Vancouver, ISO und andere Zitierweisen

R, Miller Dean, Ide Robert F und United States. National Aeronautics and Space Administration., Hrsg. A study of large droplet ice accretion in the NASA Lewis IRT at near-freezing conditions; Pt. 2. [Washington, DC]: National Aeronautics and Space Administration, 1997.

Den vollen Inhalt der Quelle finden

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Buchteile zum Thema "Freezing droplets"

Chu, Fuqiang. „Dynamic Melting of Freezing Droplets on Superhydrophobic Surfaces“. In Springer Theses, 89–103. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-8493-0_5.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Tanner, F. X. „Droplet Freezing and Solidification“. In Handbook of Atomization and Sprays, 327–38. Boston, MA: Springer US, 2010. http://dx.doi.org/10.1007/978-1-4419-7264-4_16.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Fan, Zhouyou, Youtian Zhang, Sihui Wang und Wenli Gao. „2014 Problem 8: Freezing Droplets“. In International Young Physicists' Tournament, 83–99. WORLD SCIENTIFIC, 2016. http://dx.doi.org/10.1142/9789814740340_0007.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Whiteman, C. David. „Precipitation“. In Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0015.

Der volle Inhalt der Quelle

Annotation:

Precipitation is often the primary weather factor affecting outdoor activities. Precipitation that is of an unexpected type or intensity or that comes at an unexpected time or recurs more frequently than expected can disrupt both recreational and natural resource management plans. Heavy rain or snowfall can interfere with travel and threaten safety. Precipitation is water, whether in liquid or solid form, that falls from the atmosphere and reaches the ground. Table 8.1, adapted from Federal Meteorological Handbook No. 1 (National Weather Service, 1995), describes the different types of precipitation particles, collectively called hydrometeors. International guidelines for the reporting of precipitation do not include a category for sleet. Meteorologists in the United States use the term to describe tiny ice pellets that form when rain or partially melted snowflakes refreeze before reaching the ground. These particles bounce when they strike the ground and produce tapping sounds when they hit windows. Colloquial usage of the term, often used by the news media, coincides with British usage, which defines sleet as a mixture of rain and snow. Snow pellets, or graupel, are common in high mountain areas in summer. Graupel are low density particles (i.e., not solid ice) formed when a small ice particle (an ice crystal, snowflake, ice pellet, or small hailstone) falls through a cloud of supercooled (section 8.4) water droplets. The tiny droplets freeze as they impact the larger ice particle, building it into a rounded mass containing air inclusions (figure 8.1). This coating of granular ice particles is called rime, and the particle is said to be rimed. Graupel is usually produced in deep convective clouds that extend above the freezing level. Whereas graupel reaches the ground at high elevations, it usually melts to form rain before reaching the ground at lower elevations. As falling snow accumulates, a snowpack develops that can be described in terms of water content and density. The water content of snow is usually expressed as specific gravity, a number obtained in this application by dividing the water-depth equivalent of snow by the actual snow depth.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Konferenzberichte zum Thema "Freezing droplets"

Matsushima, Koji, und Yasuhiko H. Mori. „Freezing of supercooled water droplets impinging upon solid surfaces“. In International Heat Transfer Conference 12. Connecticut: Begellhouse, 2002. http://dx.doi.org/10.1615/ihtc12.2180.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Zhang, Zhi-Gang, Ken-Ichiro Sugiyama, Tadashi Narabayashi, Satoshi Nishimura und Izumi Kinosita. „Fragmentation of a Single and Continuous Molten Copper Droplets Penetrating a Sodium Pool“. In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89495.

Der volle Inhalt der Quelle

Annotation:

The progression of hypothetical core disruptive accidents in metal fuel cores is strongly affected by exclusion of molten metal fuel from the core region due to molten fuel-coolant interaction (FCI). As a basic study of FCI in metal fuel fast reactors, the present paper focuses on the fragmentation and the characteristics of the debris produced during a series of experiments of a single molten copper droplet from 1g to 5g and continuous droplets with a total mass from 16g to 26g, which penetrated a sodium pool at instantaneous contact interface temperatures from 1005 °C far below the freezing point: 1084°C to 1342°C. The results show that the mass median diameters (Dm) of different mass copper droplets both a single droplet and continuous ones penetrating a sodium pool differ very little, nearly the same when the instantaneous contact interface temperatures (Ti) are above the freezing point, and also the droplets are fragmented finely with their increasing Tis; but when Tis are below the freezing point, the Dms of different mass copper droplets scatter a little widely. These results basically show the fragmentation of molten fuel, which is important to assure the termination of accidents, is promising in the sodium space in the upper and lower plenums.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Graeber, Gustav, Thomas M. Schutzius, Hadi Eghlidi und Dimos Poulikakos. „Video: Surfaces that force freezing droplets to scrape themselves off“. In 70th Annual Meeting of the APS Division of Fluid Dynamics. American Physical Society, 2017. http://dx.doi.org/10.1103/aps.dfd.2017.gfm.v0078.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Raessi, Mehdi, Miranda Thiele und Behrooz Amirzadeh. „Computational Simulation of the Impact and Freezing of Micron-Size Water Droplets on Super-Hydrophobic Surfaces“. 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/ht2013-17749.

Der volle Inhalt der Quelle

Annotation:

We present a computational study on the dynamics and freezing of micron-size water droplets impinging onto super-hydrophobic surfaces, the temperatures of which are below the freezing point of water. Icing poses a great challenge for many industries. It is well known that increasing hydrophobicity can make a surface ice-phobic. Experiments show that millimeter size water drops landing on super-hydrophobic surfaces bounce off even when the surface temperature is well below the freezing point. However, it has been reported that the ice-phobicity feature of such surfaces can vanish due to frost formation on the surface, or when small micro-droplets begin to freeze and stick to the surface. Using an in-house, 3D, GPU-accelerated computational tool, we investigated the impact dynamics and freezing of a 40 μm water droplet impinging at 1.4 m/s onto two different super-hydrophobic surfaces chosen from [1]. The advancing and receding contact angles are 165° and 133°, respectively, on one surface, and 157° and 118°, respectively, on the other. The surface and initial droplet temperatures were varied from −25 to 25°C and from 0 to 25°C, respectively. On each surface a “transition” surface temperature was found, at which the drop behavior transitions from bouncing off the surface to sticking. The time between drop landing and bounce-off as well as the contact diameter between the stuck drop and the surface both increase with decreasing the surface temperature. The simulations also show that at some surface temperatures a thin ice layer forms during droplet spreading and then remelts as the droplet recoils.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Haque, Mohammad Rejaul, und Amy Rachel Betz. „Frost Formation on Aluminum and Hydrophobic Surfaces“. In ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icnmm2018-7609.

Der volle Inhalt der Quelle

Annotation:

Ice and frost formation on the surfaces of car windshield, airplanes, air-conditioning duct, transportation, refrigeration and other structures is of great interest due to its negative impact in the efficiency and reliability of the system. Frost formation is a complex and fascinating phenomenon. Frequent defrosting are required to remove the ice that causes economic losses. In order to delay the freezing phenomenon, hydrophobic surfaces (Al-H) were prepared using a very simple and low cost method by dip coating of Aluminum in Teflon© and FC - 40 solution at a ratio of 2:10. Later, the samples were placed on a freezing stage in a computer controlled environmental chamber. The freezing stage was held at a constant temperature of 265 ± 0.5 K. The environmental temperature was set to 295 ± 0.5 K and the relative humidity (RH) was set to 40% and 60% respectively. The samples were observed via optical microscopy from the top and videos of the freezing dynamics were captured. The time required for the whole surface to freeze was named as ‘Freezing time’ and is determined by investigating the consecutive images. The inter-droplet freezing wave propagation was accelerated via a frozen droplet/area and then propagates through the surface very quickly. Ice bridging was also seen for the frost propagation. However, the maximum freezing front propagation velocity was found for Al surfaces at 60% RH. At 40% RH, the Al surface required approximately 10 ± 1 minutes to freeze while the Al-H surface delay freezing until 15 ± 1 minutes. This is due to a slow rate of nucleation and also increased rate of coalescence. At 60% RH, both surface froze faster than 40% RH. The Al surface required 6.5 ± 1 minutes and the Al-H surface froze after 10 ± 1 minutes. The change in freezing kinetics, freezing time, the size of droplets at freezing, and the surface area covered at freezing are all related to the rate of coalescence of droplets. Again, the added thermal resistance of the coating and less water-surface contact area of the droplet to the cooled hydrophobic surface inhibited the growth rate resulting the freezing delay.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Blake, Joshua D., David S. Thompson, Dominik M. Raps und Tobias Strobl. „Simulating the Freezing of Supercooled Water Droplets Impacting a Cooled Substrate“. In 52nd Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-0928.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Yao, Yina, Cong Li, Zhenxiang Tao und Rui Yang. „Numerical Simulation of Water Droplet Freezing Process on Cold Surface“. In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71175.

Der volle Inhalt der Quelle

Annotation:

It is significant to clearly understand the freezing process of water droplets on a cold substrate for the prevention of ice accretion. In this study, a three-dimensional numerical model including an extended phase change method was developed on OpenFOAM platform to simulate the freezing of static water droplets on cooled solid substrates. The predicted freezing process was compared with numerical results obtained by others. Good agreements were obtained and our numerical model results in faster convergence compared to the traditional phase change method. The effects of surface wettability on freezing time and freezing velocity were numerically investigated. The results show that the freezing time presents a positive relationship with contact angle due to the smaller contact area with higher contact angle, which agrees well with the theoretical analysis. Besides, the empirical relation between freezing time and contact angle were obtained.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Karlsson, Linn, Anna-Lena Ljung und T. Staffan Lundstrom. „INFLUENCE OF INTERNAL NATURAL CONVECTION ON WATER DROPLETS FREEZING ON COLD SURFACES“. In Proceedings of CONV-14: International Symposium on Convective Heat and Mass Transfer. June 8 - 13, 2014, Kusadasi, Turkey. Connecticut: Begellhouse, 2014. http://dx.doi.org/10.1615/ichmt.2014.intsympconvheatmasstransf.110.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Raessi, Mehdi, und Rajkamal Sendha. „Effects of Heat Transfer on the Spreading and Freezing of Molten Droplets Impinging Onto Textured Surfaces: A Computational Study“. In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58166.

Der volle Inhalt der Quelle

Annotation:

We present our recent study on spreading and solidification of micro-droplets of alumina impacting onto patterned surfaces textured by micron-size obstacles. We employed an in-house, three-dimensional computational tool that solves the flow and energy equations and takes into account the solidification. We investigated the spreading dynamics, heat transfer, and solidification of the droplets as a function of the height and spacing of the obstacles as well as the impact velocity. The results show that, independent of the obstacle height, the droplet assumes a disk-shape geometry when the obstacles are either packed tightly or are very distanced. The results at intermediate obstacle spacings exhibit the most significant deformations, where the droplet develops long fingers. A quantitative relationship shows the collapse of the final spread diameter of the droplet normalized by the obstacle spacing when plotted against the spacing for different impact velocity as well as the obstacle height.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Blake, Joshua D., David S. Thompson, Dominik M. Raps, Tobias Strobl und Elmar Bonaccurso. „Effects of Surface Characteristics and Droplet Diameter on the Freezing of Supercooled Water Droplets Impacting a Cooled Substrate“. In 6th AIAA Atmospheric and Space Environments Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-2328.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Wir bieten Rabatte auf alle Premium-Pläne für Autoren, deren Werke in thematische Literatursammlungen aufgenommen wurden. Kontaktieren Sie uns, um einen einzigartigen Promo-Code zu erhalten!