Academic literature on the topic 'Nanofluidik'
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Journal articles on the topic "Nanofluidik"
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Zhang, Li, and Xiaodong Chen. "“Gigantische” Energiegewinnung mittels Nanofluidik." Angewandte Chemie 125, no. 30 (June 17, 2013): 7792–94. http://dx.doi.org/10.1002/ange.201302707.
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Han, W. S., and S. H. Rhi. "Thermal characteristics of grooved heat pipe with hybrid nanofluids." Thermal Science 15, no. 1 (2011): 195–206. http://dx.doi.org/10.2298/tsci100209056h.
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In the present study, the specially designed grooved heat pipe charged with nanofluids was investigated in terms of various parameters such as heat transfer rate(50-300 W with 50 W interval), volume concentration(0.005%, 0.05%, 0.1%, and hybrid combinations), inclination(5?, 45?, 90?), cooling water temperature (1?C, 10?C, and 20?C), surface state, transient state and so on. Hybrid nanofluids with different volume concentration ratios with Ag-H2O and Al2O3-H2O were used as working fluids on a grooved heat pipe(GHP). Comparing with the pure water system, nanofluidic and hybrid nanofluidic system shows greater overall thermal resistance with increasing nano-particle concentration. Also hybrid nanofluids make the system deteriorate in terms of thermal resistance. The post nanofluid experimental data regarding GHP show that the heat transfer performance is similar to the results of nanofluid system. The thermal performance of a grooved heat pipe with nanofluids and hybrid nanofluids were varied with driving parameters but they led to worse system performance.
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Mohd Mokhtar, Nurul Afiqah, Hoe Guan Beh, and Kean Chuan Lee. "The Potential Application of MnZn Ferrite Nanofluids for Wettability Alteration and Oil-Water Interfacial Tension Reduction." Crystals 9, no. 12 (November 27, 2019): 626. http://dx.doi.org/10.3390/cryst9120626.
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Recently, a non-invasive method of injecting magnetic/dielectric nanofluids into the oil reservoir was used for oil recovery application. The use of magnetic nanofluids in Enhanced Oil Recovery (EOR) has been reported to improve oil recovery. It is believed that the magnetic properties of nanoparticles (NPs) have a direct influence on the viscosity and wettability of nanofluid, and on oil-water interfacial tension (IFT). Thus, Mn0.5Zn0.5Fe2O4 (MnZn) ferrites may be a good candidate to be used in nanofluids for wettability alteration and oil-water IFT reduction due to their excellent magnetic properties, such as a high initial permeability and low magnetic losses. Therefore, this work investigated the potential of MnZn ferrite NPs to alter viscosity, wettability, and oil-water IFT. MnZn Ferrite NPs have been synthesized by a sol-gel auto-combustion process. The effects of calcination temperature varying from 300 °C to 700 °C on the phase formation, microstructures such as surface morphology, and magnetic characterizations were studied. MnZn ferrite nanofluids were prepared using synthesized MnZn NPs that dispersed into brine along with sodium dodecylbenzenesulfonate (SDBS) as a dispersant, and their effects on the wettability and oil-water IFT were studied. X-ray diffraction (XRD) measurements revealed that MnZn ferrite calcined at 300 °C and 400 °C were single phase. The average crystallite size calculated through Scherrer’s equation differed from 32.0 to 87.96 nm. The results showed that the nanofluid with MnZn particles calcined at 300 °C is the best nanofluid in terms of IFT reduction and base nanofluid’s wettability alteration. Moreover, the overall results proved that nanofluid with MnZn ferrite NPs can alter the wettability of base nanofluid, oil-nanofluid IFT, and nanofluid viscosity. This study provides insights towards a better understanding of the potential application of MnZn Ferrite nanofluids to Wettability Alteration and IFT Reduction in Enhanced Oil Recovery.
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Shajahan, Mohamed Iqbal, Chockalingam Sundar Raj, Sambandan Arul, and Palanisamy Rathnakumar. "Heat transfer intensification of Zirconia/water nanofluid." JOURNAL OF ADVANCES IN CHEMISTRY 13 (January 9, 2017): 01–08. http://dx.doi.org/10.24297/jac.v13i1.4530.
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This paper investigated convective heat transfer and friction factor of ZrO2/H2O nanofluid through a circular pipe under laminar flow condition with constant heat flux. Nanofluid is prepared for 0.5, 0.75 and 1% volume concentrations with yttrium oxide surfactant. Nanofluid’s thermal conductivity and viscosity is measured by KD2 Pro thermal analyser and Brookfield viscometer respectively. Results showed that the thermal conductivity and viscosity increased with increase in particle volume concentration. These nanofluids are experimented in a forced convection system, first heat transfer characteristics of DI (Deionised) water under laminar flow in a copper tube measured, then three nanofluids are carried out the tests, results revealed that the enhanced Nusselt numbers of 21.09,28.05 and 35.73% at the 0.5, 0.75 and 1% volume concentrations, There is no excess penalty in pumping power and results showed less variations in friction factor for nanofluids comparatively with the base fluid DIWater.
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Bobbo, Sergio, Bernardo Buonomo, Oronzio Manca, Silvio Vigna, and Laura Fedele. "Analysis of the Parameters Required to Properly Define Nanofluids for Heat Transfer Applications." Fluids 6, no. 2 (February 2, 2021): 65. http://dx.doi.org/10.3390/fluids6020065.
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Nanofluids are obtained by dispersing nanoparticles and dispersant, when present, in a base fluid. Their properties, in particular their stability, however, are strictly related to several other parameters, knowledge of which is important to reproduce the nanofluids and correctly interpret their behavior. Due to this complexity, the results appear to be frequently unreliable, contradictory, not comparable and/or not repeatable, in particular for the scarcity of information on their preparation. Thus, it is essential to define what is the minimum amount of information necessary to fully describe the nanofluid, so as to ensure the possibility of reproduction of both their formulation and the measurements of their properties. In this paper, a literature analysis is performed to highlight what are the most important parameters necessary to describe the configuration of each nanofluid and their influence on the nanofluid’s properties. A case study is discussed, analyzing the information reported and the results obtained for the thermophysical properties of nanofluids formed by water and TiO2 nanoparticles. The aim is to highlight the differences in the amount of information given by the different authors and exemplify how results can be contradictory. A final discussion gives some suggestions on the minimum amount of information that should be given on a nanofluid to have the possibility to compare results obtained for similar nanofluids and to reproduce the same nanofluid in other laboratories.
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Suhaimi, Sabrina N., Abdul R. A. Rahman, Muhamad F. Md Din, Muhammad Zahir Hassan, Mohd Taufiq Ishak, and Mohd Taufik bin Jusoh. "A Review on Oil-Based Nanofluid as Next-Generation Insulation for Transformer Application." Journal of Nanomaterials 2020 (February 29, 2020): 1–17. http://dx.doi.org/10.1155/2020/2061343.
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Due to the increasing demand on developing good insulation, several researchers have performed experimental studies to prove the effectiveness and capabilities of transformer oil. This is done by suspending nanosized solid particles in the oil (nanofluid) for transformer applications. In brief, this paper presents a compilation of research studies which is divided into three parts. Part I discuss the preparation of the nanofluid which involves different types of nanomaterials, the optimal amount of concentrations, and applicable synthesisation methods for producing stably suspended nanofluids. In Part II, the nanofluid’s performances including the electrical breakdown voltages, impulse tests, and thermal and dielectric behaviour are reviewed in depth and compared. Part III emphasizes the limitation of nanofluids. Most researchers have agreed that appropriate concentrations of nanomaterials and the preparation method for nanofluids mainly affect the performance of nanofluids especially in terms of electrical properties. Meanwhile, types of nanomaterials and base oil also play a vital role in producing nanofluids as a better alternative transformer oil. However, among a few researchers, there are concerns regarding the issue of agglomeration and inconsistencies of findings that need to be resolved. Therefore, a few aspects must be taken into consideration to produce the next generation of high heat dissipation insulation.
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Sharifi, Amir Hossein, Iman Zahmatkesh, Fatemeh F. Bamoharram, Amir Hossein Shokouhi Tabrizi, Safieh Fazel Razavi, and Sara Saneinezhad. "Experimental Measurement of Thermophysical Properties of Alumina- MWCNTs/Salt–Water Hybrid Nanofluids." Current Nanoscience 16, no. 5 (October 5, 2020): 734–47. http://dx.doi.org/10.2174/1573413716666191218122600.
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Background: Hybrid nanofluids are considered as an extension of conventional nanofluids which are prepared through suspending two or more nanoparticles in the base fluids. Previous studies on hybrid nanofluids have measured their thermal conductivity overlooking other thermophysical properties such as viscosity and electrical conductivity. Objective: An experimental investigation is undertaken to measure thermal conductivity, viscosity, and electrical conductivity of a hybrid nanofluid prepared through dispersing alumina nanoparticles and multiwall carbon nanotubes in saltwater. These properties are the main important factors that must be assessed before performance analysis for industrial applications. Methods: The experimental data were collected for different values of the nanoparticle volume fraction, temperature, salt concentration, and pH value. Attention was paid to explore the consequences of these parameters on the nanofluid’s properties and to find optimal conditions to achieve the highest value of the thermal conductivity and the lowest values of the electrical conductivity and the viscosity. Results: The results demonstrate that although the impacts of the pH value and the nanoparticle volume fraction on the nanofluid’s thermophysical properties are not monotonic, optimal conditions for each of the properties are reachable. It is found that the inclusion of the salt in the base fluid may not change the thermal conductivity noticeably. However, a considerable reduction in the viscosity and substantial elevation in the electrical conductivity occur with an increase in the salt concentration. Conclusion: With the addition of salt to a base fluid, the thermophysical properties of a nanofluid can be controlled.
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Abdulwahid, Ammar Fakhir. "Experimental Investigation on the Multi-metallic Cu-Zn NanofluidsHeat Transfer Enhancement and Pressure Losses." Journal of University of Babylon for Engineering Sciences 26, no. 2 (January 1, 2018): 49–61. http://dx.doi.org/10.29196/jub.v26i2.381.
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Metallic nanofluidsare suspensions of metallic particles of nanometre size in base fluids. The combination of two kinds of metallic particles mixed at the same volume ratio is known as multi-metallic nanoparticles. These multiple metallic particles of nanometre size were suspended in deionized H2Ovia the use of ultrasonic vibratorsat varying volume fractions as well as variations in the ratios of metallic/metallic particles of nanometre size. In our study the dynamic viscosity, the nanofluid’s heat conductivities were determined for varying temperatures and volume fractions. The coefficient of thermal transmissionof the flowing nanofluid in the constant wall heat flux tube were determined experimentally in laminar condition. The results revealedhuge thermal transmission enhancement comparison to the base fluids. The pressure loses were illustrated for all nanofluids. The comparisons of the different metallic and multi-metallic types of the nanofluids were showed that Cu nanofluids have a greater coefficient ofthermal transmission compared with the Cu-Zn, Zn atequal volume fractions.
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Bakthavatchalam, Balaji, Khairul Habib, R. Saidur, Nagoor Basha Shaik, and Turnad Lenggo Ginta. "Analysis of Multiwalled Carbon Nanotubes Porosimetry And Their Thermal Conductivity with Ionic Liquid-Based Solvents." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 77, no. 2 (November 14, 2020): 63–75. http://dx.doi.org/10.37934/arfmts.77.2.6375.
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The suspension of nanoparticles with common heat transfer fluids like Ethylene glycol and water yields nanofluid exhibits superior thermal properties than their host fluids. Ionic liquids have the potential to demonstrate remarkable thermophysical properties (especially thermal conductivity) that ordinary nanofluids cannot achieve. On the other hand, the quantity and structure of nanoparticles porosity affects the nanofluid’s thermal conductivity considerably. Various investigations have revealed the improved thermophysical characteristicts of Multiwalled Carbon nanotubes (MWCNTs) nanofluids containing common solvents or base fluids. However, only limited studies are available on the impact of thermal conductivity in Ionic liquid-based nanofluids (Ionanofluids) owing to their high cost and viscosity. Ultrasonication technique is employed in preparing the three different Ionanofluids containing 0.5 Wt.% via the two-step method to achieve a greater stability and thermal conductivity without utilizing surfactants. Experimental investigations are performed to boost the thermal conductivity of MWCNT/Propylene glycol nanofluid using 1,3-dimethyl imidazolium dimethyl phosphate [Mmim][DMP], 1-ethyl-3-methyl imidazolium octyl sulfate [Emim][OSO4] and 1-ethyl-3-methyl imidazolium diethyl phosphate [Emim][DEP] at a temperature ranging from 295 K to 355 K. The acquired results illustrated that the thermal conductivity of MWCNT Ionanofluids incorporated with [Mmim][DMP], [Emim][OSO4] and [Emim][DEP] increased by 37.5%, 5% and 2% respectively. This unique class of Ionanofluids shows incredible capacity for use in high temperature applications as conventional heat transfer fluids.
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Lei, Lei. "Testing algorithm for heat transfer performance of nanofluid-filled heat pipe based on neural network." Open Physics 18, no. 1 (November 13, 2020): 751–60. http://dx.doi.org/10.1515/phys-2020-0170.
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AbstractTraditional testing algorithm based on pattern matching is impossible to effectively analyze the heat transfer performance of heat pipes filled with different concentrations of nanofluids, so the testing algorithm for heat transfer performance of a nanofluidic heat pipe based on neural network is proposed. Nanofluids are obtained by weighing, preparing, stirring, standing and shaking using dichotomy. Based on this, the heat transfer performance analysis model of the nanofluidic heat pipe based on artificial neural network is constructed, which is applied to the analysis of heat transfer performance of nanofluidic heat pipes to achieve accurate analysis. The experimental results show that the proposed algorithm can effectively analyze the heat transfer performance of heat pipes under different concentrations of nanofluids, and the heat transfer performance of heat pipes is best when the volume fraction of nanofluids is 0.15%.
Dissertations / Theses on the topic "Nanofluidik"
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Strobl, Christoph. "Mikro- und Nanofluidik auf piezoelektrischen Substraten." Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-37272.
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Henrich, Björn. "Partikelbasierte Simulationsmethoden in Pulvertechnologie und Nanofluidik." [S.l. : s.n.], 2007.
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Stöckle, Silke. "Thin liquid films with nanoparticles and rod-like ions as models for nanofluidics." Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4637/.
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With the rise of nanotechnology in the last decade, nanofluidics has been established as a research field and gained increased interest in science and industry. Natural aqueous nanofluidic systems are very complex, there is often a predominance of liquid interfaces or the fluid contains charged or differently shaped colloids. The effects, promoted by these additives, are far from being completely understood and interesting questions arise with regards to the confinement of such complex fluidic systems.
A systematic study of nanofluidic processes requires designing suitable experimental model nano – channels with required characteristics. The present work employed thin liquid films (TLFs) as experimental models. They have proven to be useful experimental tools because of their simple geometry, reproducible preparation, and controllable liquid interfaces. The thickness of the channels can be adjusted easily by the concentration of electrolyte in the film forming solution. This way, channel dimensions from 5 – 100 nm are possible, a high flexibility for an experimental system. TLFs have liquid IFs of different charge and properties and they offer the possibility to confine differently shaped ions and molecules to very small spaces, or to subject them to controlled forces. This makes the foam films a unique “device” available to obtain information about fluidic systems in nanometer dimensions.
The main goal of this thesis was to study nanofluidic processes using TLFs as models, or tools, and to subtract information about natural systems plus deepen the understanding on physical chemical conditions. The presented work showed that foam films can be used as experimental models to understand the behavior of liquids in nano – sized confinement.
In the first part of the thesis, we studied the process of thinning of thin liquid films stabilized with the non – ionic surfactant n – dodecyl – β – maltoside (β – C₁₂G₂) with primary interest in interfacial diffusion processes during the thinning process dependent on surfactant concentration 64. The surfactant concentration in the film forming solutions was varied at constant electrolyte (NaCl) concentration. The velocity of thinning was analyzed combining previously developed theoretical approaches. Qualitative information about the mobility of the surfactant molecules at the film surfaces was obtained. We found that above a certain limiting surfactant concentration the film surfaces were completely immobile and they behaved as non – deformable, which decelerated the thinning process. This follows the predictions for Reynolds flow of liquid between two non – deformable disks.
In the second part of the thesis, we designed a TLF nanofluidic system containing rod – like multivalent ions and compared this system to films containing monovalent ions. We presented first results which recognized for the first time the existence of an additional attractive force in the foam films based on the electrostatic interaction between rod – like ions and oppositely charged surfaces. We may speculate that this is an ion bridging component of the disjoining pressure. The results show that for films prepared in presence of spermidine the transformation of the thicker CF to the thinnest NBF is more probable as films prepared with NaCl at similar conditions of electrostatic interaction. This effect is not a result of specific adsorption of any of the ions at the fluid surfaces and it does not lead to any changes in the equilibrium properties of the CF and NBF. Our hypothesis was proven using the trivalent ion Y3+ which does not show ion bridging. The experimental results are compared to theoretical predictions and a quantitative agreement on the system’s energy gain for the change from CF to NBF could be obtained.
In the third part of the work, the behavior of nanoparticles in confinement was investigated with respect to their impact on the fluid flow velocity. The particles altered the flow velocity by an unexpected high amount, so that the resulting changes in the dynamic viscosity could not be explained by a realistic change of the fluid viscosity. Only aggregation, flocculation and plug formation can explain the experimental results. The particle systems in the presented thesis had a great impact on the film interfaces due to the stabilizer molecules present in the bulk solution.
Finally, the location of the particles with respect to their lateral and vertical arrangement in the film was studied with advanced reflectivity and scattering methods. Neutron Reflectometry studies were performed to investigate the location of nanoparticles in the TLF perpendicular to the IF. For the first time, we study TLFs using grazing incidence small angle X – ray scattering (GISAXS), which is a technique sensitive to the lateral arrangement of particles in confined volumes. This work provides preliminary data on a lateral ordering of particles in the film.Mit dem Heranwachsen der Nanotechnologie in den vergangenen zehn Jahren hat sich die Nanofluidik als Forschungsbereich etabliert und erfährt wachsende Aufmerksamkeit in der Wissenschaft, sowie auch in der Industrie. Im biomedizinischen Bereich, wo intrazelluläre Prozesse häufig komplexer, nanofluidischer Natur sind, wird sich vermehrt für ein detailliertes Verständnis von nanofluidischen Prozessen interessiert, z.B. für den Einfluss von Kolloiden verschiedenster Form oder elektrischer Ladung auf die Kanäle und auf das Fließverhalten oder die Auswirkungen der Einengung von Flüssigkeiten und Kolloiden in Nanometer Geometrien. In der vorliegenden Arbeit werden dünne flüssige Filme, hinsichtlich ihrer Funktion als nanofluidische Modelle untersucht. Im ersten Teil der Arbeit wurde die Fließgeschwindigkeit des Fluids aus dem dünnen Film, abhängig von der Konzentration der filmstabilisierenden Tensidmoleküle n – Dodecyl β – D – Maltoside ( β – C₁₂G₂) bei einer konstanten Elektrolytkonzentration von 0.2 mM NaCl untersucht. Mit einem theoretischen Modell konnte das Dünnungsverhalten nachgezeichnet werden. Es wurde eine kritische Tensidkonzentration gefunden, unter der die Oberflächen lateral mobil sind und über der sie sich wie fest verhalten. Dadurch konnten wir Aufschluss darüber erlangen, wie die Oberfläche des Films unter verschiedenen Bedingungen geschaffen ist, und das in Bezug zur Verteilungsdichte der Moleküle an den Oberflächen setzen. Im weiteren wurden komplexere, nanofluidische Systeme untersucht, wobei zum einen ~ 1 nm lange, stäbchenförmige, multivalent geladene Spermidin - Moleküle die punktförmigen Elektrolyte ersetzten. Es konnte eine deutliche Veränderung der Stabilität zwischen Filmen mit und ohne Stäbchen festgestellt werden. Die Filme, mit NaCl, blieben länger in dem metastabilen „Common Film“ (CF) Zustand als die Filme, die eine vergleichbare Konzentration von Spermidin Stäbchen beinhalteten. Die Ergebnisse deuteten auf eine zusätzliche Anziehungskraft durch Brückenbildung zwischen zwei geladenen Oberflächen durch gegensätzlich geladene Stäbchenförmige Moleküle hin. Es konnte gezeigt werden, dass dieser Effekt weder ein Ergebnis von spezifischer Ionenadsorption an die Filmoberfläche war, noch ein Unterschied in den Gleichgewichtszuständen von den Dicken der CFs und der Newton Black Films (NBFs) hervorrief, was auf die korrekte Annahme der Ionenstärke in der Lösung schließen ließ. Auch in Versuchen mit ebenfalls trivalenten Ionen YCl3 wurde festgestellt, dass kein vergleichbarer Überbrückungseffekt auftritt. Die Ergebnisse wurden mit theoretischen Simulationen verglichen und es wurde eine quantitative Übereinstimmung gefunden bezüglich der Größe des Systeminternen Energiegewinns durch den Überbrückungseffekt. Desweiteren wurde das Fließverhalten von Fluiden mit Kolloiden eingeengt in Nanometer Geometrien untersucht. Für zwei verschiedene Arten von Nanopartikeln (Fe3O4 stabilisiert mit Oleinsäure und polymerstabilisierte Goldpartikel) wurde eine Verlangsamung der Fließgeschwindigkeit festgestellt. Mit einem theoretischen Modell konnte das Fließverhalten nur für enorm erhöhte Viskositätswerte des Fluids erklärt werden. Die Viskositätserhöhung wurde mit Partikelaggregaten, die den Ausfluss behindern, erklärt und diskutiert, unter der Annahme eines nicht - Newtonischen Fließverhaltens der Dispersionen. Gleichermaßen wurde die strukturelle Anordnung der Partikel in den Filmen hinsichtlich ihrer vertikalen und lateralen Verteilung untersucht. In dieser Arbeit werden vorläufige Ergebnisse präsentiert, die noch weiteren Studien bedürfen. Mit Neutronenreflexion sollte die Anordnung der Partikel orthogonal zur Oberfläche im Film analysiert werden. Eine qualitative Analyse lässt schließen, dass bei einer höheren Konzentration von Partikeln in Lösung, sich auch eine erhöhte Konzentration von Partikeln im dünnen Film befindet. Leider konnten die Daten nicht hinsichtlich der Lage der Partikel analysiert werden. Zum ersten Mal wurden dünne flüssige Filme mit Kleinwinkelröntgenstreuung unter streifendem Einfall (GISAXS) analysiert. Mit Hilfe dieser Methode sollte eine laterale Anordnung der Partikel im Film untersucht werden. Es konnten erfolgreiche Messungen durchgeführt werden und mit Hilfe der rechnergestützten Analyse konnte eine Aussage gemacht werden, dass ~ 6 nm große Teilchen in ~ 43 nm Abstand sich im Film befinden. Die Aussage bezüglich der kleinen Teilchen könnte sich auf einzelne, kleinere Partikel beziehen, allerdings könnten auch die 43 nm eine relevante Strukturgröße darstellen, da es in der Dispersion gehäuft Aggregate mit dem Durchmesser in dem Größenbereich vorliegen. Zusammenfassend können sich mit dieser Arbeit die dünnen flüssigen Filme als eine wichtige Kernmethode der Untersuchung von nanofluidischen Prozessen, wie sie häufig in der Natur vorkommen, behaupten.
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Mutlu, Yavuz Selim [Verfasser]. "Entwicklung einer Fluid-Drossel aus porösen Keramiken zur Einstellung von Volumenströmen in der Nanofluidik / Yavuz Selim Mutlu." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2015. http://d-nb.info/1075025184/34.
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Haddad, Oriana. "Convection naturelle nanofluidique en cavité hémisphérique inclinée : approches numérique et expérimentale." Thesis, Paris 10, 2018. http://www.theses.fr/2018PA100091.
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Cette thèse, à la fois numérique et expérimentale, porte sur l’étude du transfert de chaleur par convection naturelle qui apparait au sein d’une cavité hémisphérique en régime stationnaire. L’enceinte est remplie d’eau ou de nanofluide de type eau / ZnO. La fraction volumique varie entre 0 (eau pure) et 10%. La coupole de la cavité est maintenue à température froide. Ce travail s’applique au domaine de l’ingénierie électronique et plus particulièrement au refroidissement des composants actifs de différentes formes. Trois géométries de sources de chaleur sont étudiées : la première est plane et circulaire (disque) et les suivantes, centrées sur le disque, de même surface d’échange, sont cubique et hémisphérique. L’angle d’inclinaison du disque varie entre 0 (coupole orientée vers le haut) et 180° (coupole orientée vers le bas) par rapport au plan horizontal. Les sources de chaleur génèrent des puissances qui conduisent à des Rayleigh importants. L’approche numérique est effectuée à l’aide de la méthode des volumes finis basée sur l’algorithme SIMPLE et un modèle monophasique. Pour chaque source active, le transfert de chaleur convectif est analysé et quantifié par l’intermédiaire d’une corrélation du type Nusselt-Rayleigh-Prandtl-angle d’inclinaison. D’un point de vue expérimental, la fabrication des sources de chaleur est minutieusement décrite étape par étape et le calcul du coefficient de transfert convectif moyen expérimental est détaillé. La comparaison mesures-corrélations remet en question l’efficacité du nanofluide en termes de refroidissementThis numerical and experimental thesis deals with natural convective heat transfer that occurs in a hemispherical cavity in steady state. The enclosure is filled with water or ZnO / water nanofluid. The volume fraction varies between 0% (pure water) and 10%. The coupola of the cavity is kept at a cold temperature. This work corresponds to the field of electronics and the cooling of different actives composants. Three active heating sources are studied: the first one is plane and circular (the disc) and the followings, centered on the disc with the same surface, are cubical and hemispherical. The tilted angle varies between 0 (dome facing upwards) and 180° (dome facing downwards) with respect to the horizontal plane. Heat sources generate important heat fluxes leading to high Rayleigh numbers values. Numerical approach is done by means of the volume control method based on the SIMPLE algorithm and using monophasic model. For each active source, the convective heat transfer is analyzed and quantified by means of a correlation of the Nusselt-Rayleig-Prandtl-tilt angle type. Experimentally, the heat sources are built step by step and the average convective heat transfer coefficient is calculated. The comparison measures-correlations questions on the cooling nanofluid’s efficiency
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Chen, Pin. "Amélioration de l'évaporation des gouttes à l'aide de nanoparticules et d'alcools." Thesis, Valenciennes, 2018. http://www.theses.fr/2018VALE0009/document.
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Au cours des dernières années, les exigences croissantes en matière de dissipation thermique à haut rendement pour la microélectronique, les engins spatiaux, les réacteurs nucléaires, etc., encouragent le développement d'échangeurs de chaleur de nouvelle génération. Le caloduc est l’un des équipements de refroidissement efficaces et potentiels. La plupart du transfert de masse et de chaleur se fait au niveau de la micro-région près de la ligne triple de contact (solide, liquide, vapeur), qui est essentielle à l'amélioration de la performance thermique du caloduc. Cette étude se concentre sur le processus d'évaporation de gouttes sessiles de deux nouveaux fluides de travail (solution binaire et nanofluide), qui possèdent une micro-région similaire à celle du caloduc. Le flux de Marangoni induit par le gradient de concentration et la conductivité thermique exceptionnelle devraient améliorer significativement le débit evaporé du mélange alcool-eau et du nanofluide de graphène, respectivement. Une combinaison de techniques acoustiques et infrarouges est développée pour suivre la variation de la concentration d'alcool pendant l'évaporation des gouttes des mélanges 1-butanol-eau et éthanol-eau. Selon l'observation du comportement d'évaporation à différentes températures du substrat, une série d'équations empiriques est suggérée pour prédire le taux d'évaporation de la solution binaire de 1-butanol-eau en considérant l'effet Marangoni thermal et solutal. De plus, l'effet de la PEGylation, de la concentration des nanoparticules et de la température du substrat sur l'évaporation de gouttes de graphène nanofluide est étudié par des méthodes microscopiques, optiques et infrarouges. Les résultats expérimentaux et l'analyse thermodynamique peuvent contribuer à la compréhension complète du mécanisme impliqué concernant les performances d'évaporation du nanofluide de graphèneIn recent years, increasing requirement in high efficient heat dissipation for micro-electronics, spacecraft, nuclear reactors etc., encourage the development of next generation heat exchanger. Heat pipe is one of potential effective cooling equipments and most of mass and heat transfer take place at micro-region near triple phase (solid, liquid, vapor) contact line of working fluid, which is essential to thermal performance improvement of heat pipe. This study focuses on the evaporation process of sessile droplets of two novel working fluids (binary solution and nanofluid), which possess similar micro-region to that in heat pipe. Concentration gradient induced Marangoni flow and exceptional thermal conductivity are expected to significantly enhance evaporation rate of alcohol-water mixture and graphene nanofluid, respectively. A combination of acoustic and infrared techniques is developed to track alcohol concentration variation during evaporation of 1-butanol and ethanol aqueous droplets. According to observation of evaporation behavior at different substrate temperature, a series of empirical equations is suggested to predict evaporation rate of 1-butanol-water binary solution droplet considering thermal and solutal Marangoni effect. In addition, the effect of PEGylation, nanoparticle concentration and substrate temperature on drop evaporation of graphene nanofluid are investigated by microscopic, optical and infrared methods. Experimental results and thermodynamic analysis can contribute to the full understanding of involved mechanism concerning evaporation performance of graphene nanofluid
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Cabral, Francismara Pires. "Estudo da ebulição convectiva de nanofluidos no interior de microcanais." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-16092013-163829/.
Full textAbstract:
Este trabalho trata do estudo teórico do ebulição convectiva de nanofluidos em canais de diâmetro reduzido (denominados de microcanais). Ele aborda, primeiramente, uma análise da literatura sobre a ebulição convectiva de fluidos convencionais em microcanais, na qual são discutidos critérios para a transição entre macro e microcanais e os padrões de escoamentos observados em canais de reduzido diâmetro. Métodos para a previsão das propriedades de transporte de nanofluidos foram levantados da literatura e estudos experimentais da convecção forçada, da ebulição nucleada e da ebulição convectiva de nanofluidos foram discutidos. Um método para a previsão do coeficiente de transferência de calor de nanofluidos em microcanais durante a ebulição convectiva foi proposto baseado em modelos convencionais da literatura ajustados para nanofluidos. O ajuste dos modelos convencionais foi realizado através de análise regressiva de dados experimentais para ebulição nucleada e convecção forçada de nanofluidos levantados da literatura, e da análise crítica de adimensionais que capturassem a influência das nanopartículas no processo de transferência de calor. De maneira geral o método proposto neste estudo apresenta concordância razoável com dados experimentais independentes, referente ao acréscimo do coeficiente de transferência de calor com o incremento da concentração volumétrica de nanopartículas. No entanto, a escassez de estudos experimentais sobre a ebulição convectiva de nanofluidos, especialmente em microcanais, impossibilitou uma análise mais aprofundada do método proposto.The present work aims the theoretical study of convective boiling of nanofluids in small diameter channels (called microchannel). It discusses an analysis of the literature on convective boiling of conventional fluids in microchannels which presents criteria for the transition between conventional and microchannels and the flow patterns observed in small diameter channels. Methods for predicting the transport properties of nanofluids were compiled from the literature and experimental studies of forced convection, nucleate boiling and convective boiling of nanofluids were discussed. A method for predicting the heat transfer coefficient of nanofluids in microchannels during convective boiling was proposed based on conventional models from literature adjusted to nanofluids. The conventional models fitting was performed by regression analysis of experimental data for nucleate boiling and forced convection of nanofluids compiled from the literature and by critical analysis of dimensionless numbers which enable to capture the influence of nanoparticles on heat transfer process. In general the proposed method in this work presents reasonable agreement with independent experimental data regarding the increase in heat transfer coefficient with increasing nanoparticles volume fraction. However the scarcity of experimental studies on the convective boiling of nanofluids, especially in microchannels, precluded further analysis of the proposed method.
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Rueda, García Daniel. "Development of novel electroactive nanofluids for flow cells." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670918.
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Flow cells are on their way to become a key player for electrical energy storage (EES) thanks to their suitability as load-levelling devices thus contributing to the development of smart grid and to offset the intermittency of renewable energy sources. Until recently flow cells have been limited to Redox Flow Batteries (RFB), where energy storage is given by the redox reactions of dissolved ions. Very recently, new types of “flowable” electrodes have been proposed making use of capacitive storage mechanism (Electrochemical Flow Capacitors or EFCs). Our group has been one of the pioneering labs in this type of novel flow cells based on electroactive nanofluids. The present thesis aimed at harnessing the activity of well-known electroactive species (quinones, graphene, polyoxometalates, LiFePO4) in novel electroactive nanofluids. An important part of our strategy has been the design of hybrid formulations and systems which could combine faradaic (redox) and capacitive (double-layer) storage mechanisms in order to improve the performance of the resulting flow cells.
We make an extended review and perspective of the electrochemical flow cell technology and their possible lines of evolution in the introduction of this thesis. With this we introduce the state of the art, the issues to solve and the different solutions proposed. Moreover, we also show our point of view and prospective for this technology and electrical energy storage in general.
In the chapter 4, the electrochemical fundamentals of quinones in lithium-organic electrolytes are studied. Quinones electrochemical mechanisms have been widely studied in aqueous media. In this work we study them in an organic electrolyte in an attempt to take advantage of the greater solubility and wider potential windows available in this media. We found and describe in detail several issues preventing the reversible functioning of quinones in Li+ organic electrolytes which in turn preclude their use in flow cells under those conditions.
Chapter 5 describes the synthesis, characterization and electrochemical performance of hybrid materials based on reduced graphene oxide (rGO) and polyoxometalates dispersed in an aqueous H2SO4 electrolyte in order to produce a nanofluid. These nanofluids feature low viscosity and show an ultrafast electrochemical
response. We demonstrated their functioning as energy storage fluids with full charge and discharge of all solid material dispersed.
In chapter 6 a new kind of rGO nanofluid is presented. Instead of using conventional surfactants, we dissolved an aromatic molecule able to stabilize rGO in an aqueous electrolyte. With this approach we achieved a great increase in the stability of the nanofluid. Furthermore, this new nanofluid also showed a great charge transfer capability, as demonstrated by its enabling of the redox activity of LiFePO4 nanoparticles. Thus, thanks to the presence of rGO in the nanofluid, electrons could reach the dispersed nanoparticles and thus be effectively and fully charged and discharged, something not possible in nanofluids containing only LiFePO4 nanoparticles.
Graphene synthesis has been also deeply studied as part of this thesis as is shown in the chapter 7. As a result, a new method for the production of graphene by electrochemical exfoliation of graphite has been developed and patented. The patent, a summary of the results obtained and the state of the art of the electrochemical exfoliation method of graphene are presented in this thesis as the last chapter describing research work carried out within the framework of this thesis.Las celdas de flujo van camino de convertirse en una pieza clave para el almacenamiento de energía eléctrica (EES) gracias a su idoneidad como dispositivos de nivelación de carga, contribuyendo así al desarrollo de una red inteligente que pueda compensar la intermitencia de las fuentes de energía renovables. Hasta hace poco, las celdas de flujo se habían limitado a las baterías de flujo redox (RFB), donde el almacenamiento de energía está dado por las reacciones redox de los iones disueltos. Muy recientemente, se han propuesto nuevos tipos de electrodos líquidos basados en un mecanismo de almacenamiento capacitivo (condensadores de flujo electroquímicos o EFC). Nuestro grupo ha sido uno de los laboratorios pioneros en este tipo de nuevas celdas de flujo basadas en nanofluidos electroactivos. La presente Tesis ha tenido como objetivo aprovechar la actividad de especies electroactivas bien conocidas (quinonas, grafeno, polioxometalatos, LiFePO4) en nuevos nanofluidos electroactivos. Una parte importante de nuestra estrategia ha sido el diseño de formulaciones y sistemas híbridos que pudieran combinar mecanismos de almacenamiento faradaico (redox) y capacitivo (doble capa) para mejorar el rendimiento de las celdas de flujo resultantes. En la introducción de esta tesis se ha realizado una revisión y perspectiva ampliadas de las tecnologías de celdas de flujo electroquímicas y sus posibles líneas de evolución. Con esto se presentan el estado del arte, los problemas a resolver y las diferentes soluciones propuestas para estas tecnologías. Además, también mostramos nuestro punto de vista y perspectivas para estas tecnologías y el almacenamiento de energía eléctrica en general. Por ello esta parte constituye la parte principal de la introducción y una parte fundamental de esta tesis para entender los objetivos, motivaciones y el trabajo realizado. En el capítulo 4 se estudiaron los fundamentos electroquímicos de las quinonas en electrolitos orgánicos con sal de litio. Los mecanismos electroquímicos de las quinonas se han descrito ampliamente en la bibliografía pero en medios acuosos. En este trabajo, los estudiamos en un electrolito orgánico en un intento de aprovechar la mayor solubilidad y las ventanas de potencial más amplias disponibles en este medio. Encontramos y describimos en detalle varios problemas que impiden el funcionamiento reversible de las quinonas en los electrolitos orgánicos con Li+ que, a su vez, impiden su uso en celdas de flujo en esas condiciones. En el capítulo 5 se describe la síntesis, caracterización y rendimiento electroquímico de materiales híbridos basados en óxido de grafeno reducido (rGO) y polioxometalatos dispersos en un electrolito acuoso (H2SO4) para producir un nanofluido. Estos nanofluidos presentan baja viscosidad y muestran una respuesta electroquímica ultrarrápida e hibrida, con contribución tanto capacitiva del rGO como faradaica de los polioxometalatos. Demostrando así su funcionamiento como fluidos de almacenamiento de energía con plena carga y descarga de todo el material sólido disperso. El sexto capítulo presenta un nuevo tipo de nanofluido basado en rGO. En lugar de usar tensioactivos convencionales como en el capítulo descrito anteriormente, disolvimos una molécula aromática capaz de estabilizar el rGO en un electrolito acuoso mediante interacciones de tipo π-π. Con este enfoque logramos un gran aumento en la estabilidad del nanofluido. Además, este nuevo nanofluido también mostró una gran capacidad de transferencia de carga, como lo demuestra el hecho de que permite que se produzca actividad redox de nanopartículas de LiFePO4 (sin recubrimento conductor) simplemente dispersas en el nanofluido. Por lo tanto, gracias a la presencia de rGO en el nanofluido, los electrones podrían alcanzar las nanopartículas dispersas y, por lo tanto, cargarse y descargarse de manera efectiva y completa, algo que no es posible en nanofluidos que contienen solo nanopartículas de LiFePO4. La síntesis de grafeno también se ha estudiado en profundidad en esta tesis tal y como se puede ver en el capítulo 7, dado que el objetivo final es producir materiales que se puedan usar en aplicaciones reales, asegurarse de que los materiales con los que se trabaja se pueden producir en cantidades grandes, mediante métodos escalables y elementos abundantes es también importante. Como resultado, se ha desarrollado y patentado un nuevo método para la producción de grafeno por exfoliación electroquímica de grafito. En esta tesis se presenta la patente, un resumen de los resultados obtenidos y el estado del arte del método de exfoliación electroquímica de grafeno. En esta tesis hemos demostrado el potencial de los nanofluidos en el almacenamiento de energía electroquímica. A partir de los resultados mostrados aquí, podemos inducir conclusiones generales importantes sobre los efectos extendidos de pequeñas cantidades de sólidos en todo el volumen del nanofluido. Hemos demostrado que las dispersiones estables de rGO en agua pueden transferir la carga a través de todo el volumen de nanofluidos, lo que hace que todo el nanofluido actúe como un electrodo supercondensador que almacena la carga a través de un mecanismo capacitivo. De hecho, el nanofluido acuoso rGO mostró una transferencia de carga extremadamente rápida, pudiendo realizar ciclos a 10V·s-1. Gracias a esta rápida transferencia de carga, pudimos cargar y descargar por completo nanopartículas activas redox dispersas de LiFePO4 y detectar claramente picos redox incluso a 25 mV·s-1. Además, al dopar el rGO con especies redox activas moleculares como los polioxometalatos, desarrollamos sistemas híbridos con potencia y capacidad mejoradas con respecto al nanofluido rGO puro. Finalmente, demostramos que los nanofluidos de rGO acuosos pueden mejorar su estabilidad al disolver una molécula aromática (DABA) capaz de estabilizar rGO mediante interacciones π-π manteniendo su buena conductividad eléctrica. Todo esto ha sido posible manteniendo la viscosidad de los nanofluidos desarrollados muy cerca de los disolventes originales, lo que facilitará su aplicación final en dispositivos de flujo real. Por otro lado, la baja concentración de nanopartículas de grafeno podría ser una desventaja para la aplicación de estos materiales en dispositivos de alta densidad de energía. Por lo tanto, aumentar la carga de nanopartículas electroactivas es un objetivo importante. En resumen, hemos diseñado y preparado nanofluidos basados en grafeno pero también en híbridos de grafeno. Hemos mostrado en esta descripción general cómo estos novedosos materiales de nanofluidos pueden presentar rendimientos sobresalientes incluso en el caso de sistemas muy diluidos. Hemos demostrado efectos no lineales, que conducen a propiedades notables con pequeñas cantidades de grafeno dispersas en los nanofluidos. Por lo tanto, nuestro trabajo subraya el sólido potencial de estos sistemas para el almacenamiento de energía.
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Haddad, Zoubida. "Instabilités thermoconvectives pour des fluides complexes." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4778.
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La controverse concernant les mécanismes proposés pour l’intensification de la conductivité thermique et de la forte augmentation de la viscosité suggère que les expériences avec des nanofluides bien dispersés et correctement caractérisés seraient intéressantes. Par conséquent, nous nous sommes fixés comme objectif la caractérisation de la conductivité thermique et la viscosité de deux nanofluides “eau-oxyde de silice“ et “eau-titanium“. Il a été observé que la conductivité thermique des deux nanofluides considérés concorde bien avec la théorie du milieu effectif, à savoir, le modèle de Maxwell, et ne montre aucune amélioration par rapport aux effets associés aux mécanismes proposés de l’intensification du transfert du nanofluide tels que le mouvement brownien ou l’effet de stratification. Pour confirmer ce résultat, nous avons également mesuré la conductivité thermique du nanofluide eau contenant une suspension de nanotubes de carbone NTC. Nous constatons que la conductivité thermique de ce nanofluide NTC est également en bon accord avec le modèle de Maxwell. Les disparités et les incohérences publiées par les différents groupes sur les résultats et modèles de la conductivité thermique ainsi que la viscosité du nanofluide se trouvent être principalement dues à la qualité du nanofluide telles que la stabilité colloïdale, la taille des particules, la formation des agrégats, etc… Par ailleurs, l’influence des incertitudes en raison de l’adoption de différents modèles sur le transfert de chaleur par convection naturelle a été étudiée. Il a été observé que les incertitudes dans les modèles prédictifs peuvent conduire à des évaluations erronées du transfert convectifThe controversy regarding the proposed mechanisms of the exceptionally enhanced thermal conductivity of nanofluids, as well as sharp increase of nanofluid viscosity suggest that systematic experiment with well dispersed and well characterized nanofluids are highly desired. Therefore, on the basis of this suggestion, thermal conductivity and viscosity of silica-water and titania-water nanofluids were measured. It was observed that the thermal conductivity of both nanofluids agrees well with the effective medium theory, i.e., Maxwell model, and does not show any enhancement due to effects associated with the proposed mechanisms of thermal energy transfer in nanofluids like Brownian motion or liquid layering. To support these results, the thermal conductivity of water based nanofluid containing carbon nanotubes was measured. It was found that that thermal conductivity of CNTs nanofluids agrees well with Maxwell model up to 1 vol.%. The inconsistencies in the reported thermal conductivity and dynamic viscosity from different research groups are found to be mainly due to the characterization of the nanofluid, including determination of colloidal stability and particle size, (i.e, aggregates size) within nanofluid. The influence of uncertainties due to adopting various formulas for the dynamic viscosity on natural convection heat transfer was investigated. It was observed that uncertainties in the predictive models for the effective thermal conductivity and dynamic viscosity of nanofluids, leads to erroneous evaluation of the convective heat transfer with nanofluids, and this acts as a brake on research in the area
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Rodríguez-Laguna, María del Rocío. "Heat transfer fluids: From fundamental aspects of graphene nanofluids at room temperature to molten salts formulations for solar-thermal conversion." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667803.
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Los fluidos de transferencia de calor, y en particular los nanofluidos, se pueden considerar un elemento esencial en diversos sectores industriales y su rendimiento es clave para una adecuada aplicación en tecnologías que van desde la gestión térmica y la refrigeración, a la generación de energía solar térmica y eléctrica mediante el uso de intercambiadores de calor. Estas industrias necesitan fluidos de transferencia de calor con un rango de temperatura del líquido más amplio y mejores prestaciones en la transferencia de calor que los fluidos convencionales. Todos los fluidos parecen beneficiarse de la dispersión de nanopartículas sólidas, tanto aquellos usados en aplicaciones de baja temperatura y temperatura ambiente, como aquellos que funden a más alta temperatura (p. ej. sales fundidas). La dispersión de nanopartículas conduce a la obtención de nanofluidos que con frecuencia presentan mejores conductividades térmicas y/o calores específicos en comparación con los fluidos base. Sin embargo hay algunas excepciones. En la bibliografía podemos encontrar resultados contradictorios acerca de la mejora de las propiedades térmicas en nanofluidos, lo cual hace que sea necesario un estudio de estos materiales en mayor profundidad. Por otra parte, la naturaleza líquida de estos materiales plantea un verdadero desafío, tanto desde el punto de vista experimental como en relación al marco conceptual.
El trabajo que se presenta en esta tesis ha abordado dos retos diferentes relacionados con los fluidos de transferencia de calor y los nanofluidos. En primer lugar, se llevó a cabo un estudio riguroso y sistemático de las propiedades térmicas, morfológicas, reológicas, de estabilidad, acústicas y vibracionales de nanofluidos de grafeno en disolventes orgánicos. Observamos un gran aumento de la conductividad térmica de hasta un 48% y un aumento del 18% en la capacidad calorífica de los nanofluidos de grafeno en N,N-dimetilacetamida (DMAc). También se observó una mejora significativa en los nanofluidos de grafeno en N,N-dimetilformamida (DMF) del orden del 25% y 12% para la conductividad térmica y la capacidad calorífica, respectivamente. El desplazamiento de varias bandas del espectro Raman de DMF y DMAc hacia altas frecuencias (máx. ~ 4 cm-1) al aumentar la concentración de grafeno, sugirió que éste tiene la capacidad de afectar a las moléculas de disolvente a larga distancia, en términos de energía vibracional. En paralelo, las simulaciones numéricas basadas en la teoría funcional de la densidad (DFT) y dinámica molecular (MD) mostraron una orientación paralela de DMF hacia el grafeno, favoreciendo la interacción π-π y contribuyendo a la modificación de los espectros de Raman. Además, se observó un orden local de las moléculas de DMF alrededor del grafeno, lo que sugiere que tanto este tipo especial de interacción como el orden local inducido pueden contribuir a la mejora de las propiedades térmicas del fluido. También se realizaron estudios similares en nanofluidos de grafeno disperso en 1-metil-2-pirrolidona, sin embargo, no se observó ninguna modificación de la conductividad térmica o de los espectros de Raman. Todas estas observaciones juntas sugieren que existe una correlación entre la modificación de los espectros vibracionales y el aumento de la conductividad térmica de los nanofluidos. En vista de los resultados, se discutieron y descartaron algunos de los mecanismos propuestos para explicar la mejora de la conductividad térmica en nanofluidos.
La segunda línea de investigación se centró en el desarrollo y caracterización de nuevas formulaciones de sales fundidas con baja temperatura de fusión y alta estabilidad térmica. Con este propósito, se sintetizaron dos nuevas formulaciones de seis componentes basadas en nitratos con una temperatura de fusión de 60-75 °C y una estabilidad térmica de aprox. 500 °C. Por otro lado, la complejidad de las muestras llevó a establecer una serie de métodos experimentales que se proponen para la detección del punto de fusión de estos materiales como una alternativa a la calorimetría convencional, estas técnicas son: espectroscopia Raman, técnica 3ω y transmisión óptica.Heat transfer fluids and nanofluids constitute an important element in the industry and their performance is key to the successful application in technologies that go from heat management and cooling to heat exchangers in thermal-solar energy and electricity generation. These industries demand heat transfer fluids with a wider liquid temperature range and better thermal performance than the conventional fluids. From low-temperature fluids to high-temperature molten salts, these fluids seem to benefit from the dispersion of solid nanoparticles, leading to nanofluids which frequently feature improved thermal conductivities and/or specific heats as compared with the bare fluids. However, there are some exceptions. Contradictory reports make it necessary to study these materials in greater depth than has been usual. Yet, the liquid nature of these materials poses a real challenge, both from the experimental point of view and from the conceptual framework. The work reported in this thesis has tackled two different challenges related to heat transfer fluids and nanofluids. In the first place, a careful and systematic study of thermal, morphological, rheological, stability, acoustic and vibrational properties of graphene-based nanofluids was carried out. We observed a huge increase of up to 48% in thermal conductivity and 18% in heat capacity of graphene-N,N-dimethylacetamide (DMAc) nanofluids. A significant enhancement was also observed in graphene-N,N-dimethylformamide (DMF) nanofluids of approximately 25% and 12% for thermal conductivity and heat capacity, respectively. The blue shift of several Raman bands (max. ~ 4 cm-1) with increasing graphene concentration in DMF and DMAc nanofluids suggested that graphene has the ability to affect solvent molecules at long-range, in terms of vibrational energy. In parallel, numerical simulations based on density functional theory (DFT) and molecular dynamics (MD) showed a parallel orientation of DMF towards graphene, favoring π–π stacking and contributing to the modification of the Raman spectra. Furthermore, a local order of DMF molecules around graphene was observed suggesting that both this special kind of interaction and the induced local order may contribute to the enhancement of the thermal properties of the fluid. Similar studies were also performed in graphene-N-methyl-2-pyrrolidinone nanofluids, however, no modification of the thermal conductivity or the Raman spectra was observed. All these observations together suggest that there is a correlation between the modification of the vibrational spectra and the increase in the thermal conductivity of the nanofluids. In light of these results, the mechanisms suggested in the literature to explain the enhancement of thermal conductivity in nanofluids were discussed and some of them were discarded. The second line of research focused on the development and characterization of novel molten salts formulations with low-melting temperature and high thermal stability. In this regard, two novel formulations of six components based on nitrates with a melting temperature of 60-75 °C and a thermal stability up to ~ 500 °C were synthesized. Moreover, the complexity of the samples led to establish a series of experimental methods which are proposed for the melting temperature detection of these materials as an alternative to conventional calorimetry. These methods are Raman spectroscopy, three-omega technique, and optical transmission.
Books on the topic "Nanofluidik"
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Mutlu, Yavuz Selim. Einstellung von Volumenströmen im Bereich der Nanofluidik. Wiesbaden: Springer Fachmedien Wiesbaden, 2016. http://dx.doi.org/10.1007/978-3-658-11356-8.
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Edel, Joshua, Aleksandar Ivanov, and MinJun Kim, eds. Nanofluidics. Cambridge: Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/9781849735230.
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Li, Zhigang. Nanofluidics. Boca Raton : Taylor & Francis, a CRC title, part of the Taylor &: CRC Press, 2018. http://dx.doi.org/10.1201/b22007.
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Michaelides, Efstathios E. Nanofluidics. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-05621-0.
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Edel, Joshua, and Andrew deMello, eds. Nanofluidics. Cambridge: Royal Society of Chemistry, 2008. http://dx.doi.org/10.1039/9781847558909.
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Prabhu, K. Narayan, ed. Nanofluids. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2012. http://dx.doi.org/10.1520/stp1567-eb.
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Kleinstreuer, Clement. Microfluidics and Nanofluidics. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118749890.
Full textBook chapters on the topic "Nanofluidik"
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Mutlu, Yavuz Selim. "Einleitung und Motivation." In Einstellung von Volumenströmen im Bereich der Nanofluidik, 1–16. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-11356-8_1.
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Mutlu, Yavuz Selim. "Methoden." In Einstellung von Volumenströmen im Bereich der Nanofluidik, 45–79. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-11356-8_3.
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Mutlu, Yavuz Selim. "Ergebnisse." In Einstellung von Volumenströmen im Bereich der Nanofluidik, 81–121. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-11356-8_4.
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Mutlu, Yavuz Selim. "Zusammenfassung, Diskussion und Ausblick." In Einstellung von Volumenströmen im Bereich der Nanofluidik, 123–42. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-11356-8_5.
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Mutlu, Yavuz Selim. "Grundlagen." In Einstellung von Volumenströmen im Bereich der Nanofluidik, 17–43. Wiesbaden: Springer Fachmedien Wiesbaden, 2015. http://dx.doi.org/10.1007/978-3-658-11356-8_2.
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Bhardwaj, Rashmi, and Saureesh Das. "Chaos in Nanofluidic Convection of CuO Nanofluid." In Industrial Mathematics and Complex Systems, 283–93. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-3758-0_20.
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Yoda, Minami, Jean-Luc Garden, Olivier Bourgeois, Aeraj Haque, Aloke Kumar, Hans Deyhle, Simone Hieber, et al. "Nanofluidic Channels." In Encyclopedia of Nanotechnology, 1543. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-90-481-9751-4_100499.
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Kim, Daejoong, Kilsung Kwon, Deok Han Kim, and Longnan Li. "Nanofluidic RED." In SpringerBriefs in Applied Sciences and Technology, 43–44. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-0314-2_6.
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Yoda, Minami, Jean-Luc Garden, Olivier Bourgeois, Aeraj Haque, Aloke Kumar, Hans Deyhle, Simone Hieber, et al. "Nanofluidics." In Encyclopedia of Nanotechnology, 1543. Dordrecht: Springer Netherlands, 2012. http://dx.doi.org/10.1007/978-90-481-9751-4_100500.
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Han, Jongyoon. "Nanofluidics." In Introduction to Nanoscale Science and Technology, 575–97. Boston, MA: Springer US, 2004. http://dx.doi.org/10.1007/1-4020-7757-2_24.
Full textConference papers on the topic "Nanofluidik"
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O’Hanley, Harry, Jacopo Buongiorno, Thomas McKrell, and Lin-wen Hu. "Measurement and Model Correlation of Specific Heat Capacity of Water-Based Nanofluids With Silica, Alumina and Copper Oxide Nanoparticles." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62054.
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Nanofluids are being considered for heat transfer applications. However, their thermo-physical properties are poorly known. Here we focus on nanofluid specific heat capacity. Currently, there exist two models to predict a nanofluid’s specific heat capacity as a function of nanoparticle concentration and material. Model I is a straight volume-weighted average; Model II is based on the assumption of thermal equilibrium between the particles and the surrounding fluid. These two models give significantly different predictions for a given system. Using differential scanning calorimetry, the specific heat capacities of water based silica, alumina, and copper oxide nanofluids were measured. Nanoparticle concentrations were varied between 5wt% and 50wt%. Test results were found to be in excellent agreement with Model II, while the predictions of Model I deviate very significantly from the data.
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Mu, Lijuan, Qunzhi Zhu, and Leilei Si. "Radiative Properties of Nanofluids and Performance of a Direct Solar Absorber Using Nanofluids." In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18402.
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Solar energy utilization is very important in the background of global warming and reduction of carbon dioxide emission. Solar air/water collectors are convenient to convert solar energy into heat. Compared with regular solar collectors, direct absorption solar absorbers are not common. However, nanofluids can be used in direct solar absorbers to improve their performances. The objective of this paper is to evaluate the potential of application of nanofluids in direct solar absorbers. Spectral transmittances of nanofluids within the solar spectrum have been measured by a customized spectrophotometer. A direct solar absorber has been built to use nanofluids as the working fluid and its performance has been experimentally investigated. It is found that the radiative properties of nanofluids deviate significantly from that of the base fluid. A remarkable amount of visible light can pass through the SiO2 nanofluid while solar radiation can hardly transmit through the TiO2 nanofluid and ZrC nanofluid. The ZrC nanofluid shows the highest solar absorbance among the studied nanofluids. The temperature increase rate of the nanofluid is faster than that of water when the liquid stagnant in the absorber is illuminated by solar radiation. Furthermore, the temperature differences between the inlet and outlet of the TiO2 nanofluid and ZrC nanofluid are higher than that of the SiO2 nanofluid at the same flow rate. This work is beneficial for the exploration of nanofluids in direct solar absorbers.
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Taylor, Robert A., Patrick E. Phelan, Ronald J. Adrian, Todd Otanicar, and Ravi S. Prasher. "Experimental Results for Light-Induced Boiling in Water-Based Graphite Nanoparticle Suspensions." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88176.
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One relatively simple subset of nanotechnology is nanofluids, obtained by the addition of nanoparticles to a conventional base fluid. The promise of nanofluids stems from the fact that at relatively small particle loading (typically <1% by volume) significant enhancement in thermal transport may be possible [1–3]. Since there are a wide variety of nanoparticle materials to choose from, nanofluidic systems can be tuned to fit a number of applications. This research focuses on direct thermal collection of light energy using highly absorptive nanofluids. Experimental tests are conducted using a 0.1% by volume graphite/water (30nm nominal particle diameter) nanofluid exposed to a 130 mW, 532 nm, continuous laser. A lens is placed between the laser and the fluid to achieve a high-energy flux (∼ 490 Wcm−2). Since initially over 99.9% of the light is absorbed in a path length of 0.1 mm, the irradiated portion of the base fluid collects enough energy to vaporize. Heuristic methods of analysis demonstrate this situation incorporates several interesting modes of heat transfer and fluid mechanics. These experiments also reveal the possibility for novel solar collectors in which the working fluid directly absorbs energy and undergoes phase change in a single step.
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Taylor, Robert, Sylvain Coulombe, Todd Otanicar, Patrick Phelan, Andrey Gunawan, Wei Lv, Gary Rosengarten, Ravi Prasher, and Himanshu Tyagi. "Critical Review of the Novel Applications and Uses of Nanofluids." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75189.
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Nanofluids — one simple product of the emerging world nanotechnology — where nanoparticles (nominally 1–100 nm in size) are mixed with conventional base fluids (water, oils, glycols, etc.). Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995 [1]. In the year 2010 alone there were nearly 500 research articles where the term nanofluid was used in the title, showing rapid growth from 2000 (12) and 2005 (78). Much of the first decade of nanofluid research was focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, convection coefficients). Recent research, however, has started to highlight how nanofluids might perform in a wide variety of other applications. These applications range from their use in nanomedicine [2] to their use as solar energy harvesting media [3]. By analyzing the available body of research to date, this article presents trends of where nanofluid research is headed and suggests which applications may benefit the most from employing nanofluids. Overall, this review summarizes the novel applications and uses of nanofluids while setting the stage for future nanofluid use in industry.
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He, Qinbo, Geni Yan, and Shuangfeng Wang. "Experimental Investigation on Solar Thermal Properties of Magnetic Nanofluids for Direct Absorption Solar Collector." In ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/mnhmt2016-6620.
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Nanofluids are found to have good optical and thermal properties as direct sunlight absorbers in solar collectors. In this article, Co-H2O nanofluids were prepared through two-step method. The photothermal properties of nanofluids were investigated under different magnetic field intensity. The effect of Co-H2O nanofluids on the efficiency of a direct absorption solar collector was also investigated experimentally. The experimental results show that the applied magnetic field can enhance the solar absorption ability of Co-H2O nanofluids, and has an optimal magnetic field intensity 30Gs. The highest temperature of Co-H2O nanofluid (0.04wt%, 30Gs) is increased up to 39.5% compared with deionized water. The maximum efficiency of direct absorption solar collector with Co-H2O nanofluid under 30Gs magnetic field (0.1wt%, 30nm) is increased up to 51.70% and 13.24% compared with water and Co-H2O nanofluid without magnetic field, respectively. The results indicate that the magnetic field has the potential to effectively improve the solar absorption capabilities of direct absorption solar collectors with magnetic nanofluids.
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Nnanna, A. G. Agwu, Tom Fistrovich, Kurt Malinski, and S. U. S. Choi. "Thermal Transport Phenomena in Buoyancy-Driven Nanofluids." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-62059.
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This paper presents an experimental investigation of the thermal transport phenomena in buoyancy-driven nanofluids. The experimental model for this study is a rectangular enclosure with differentially heated vertical walls and adiabatic horizontal walls. The nanofluids were confined within the enclosure. Simulations were performed to measure the transient and steady-state temperature response of the nanofluids to applied load. Experimental observation shows settling of the nanoparticle at low heat loads and a remixing of the nanofluid at higher loads. At high loads, the buoyancy force increased hence increasing the re-circulatory motion of the nanofluid. This may be one method of addressing the settling of nanoparticles in nanofluid. For natural convection in an enclosure, this paper shows that the thermal behavior of nanofluids is identical to pure fluids. Temperature data collected during the experiment were used to study the variation of Nusselt number with Rayleigh number.
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Xuan, Yimin, and Qiang Li. "Energy Transport Mechanisms in Nanofluids and Its Applications." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82154.
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Nanofluid is a solid-liquid mixture consisting of solid nanoparticles or nanofibers with sizes typically of 1–100 nm suspended in liquid. Thermal conductivity and heat transfer performance of nanofluids is superior to those of the original pure carrier fluids because the suspended nanoparticles remarkably improve energy exchange capability of the suspensions. In the present paper, the investigations efforts cover microscopic and mesoscaled approachs for the heat transfer enhancement mechanism of the nanofluid, flow and heat transfer mechanism and the relevant control methods of the magnetic fluid by suspending magnetic nanoparticles in base fluids, and some applications of nanofluid on a variety of thermal systems in order to understand energy transfer mechanism of nanofluids and guide future applications of nanofluids to thermal engineering.
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Kanjirakat, Anoop, Khalifa Taimour, Mohammed Al-Jubouri, Reza Sadr, and Mahmood Amani. "Viscosity Measurements of Nanofluids at Elevated Temperatures and Pressures." In ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icnmm2013-73103.
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Engineered colloidal suspensions of nano-sized particles (less than 100nm) dispersed in a base fluid (nanofluid), have shown potential for industrial cooling fluids due to their enhanced heat transfer characteristics. Understanding the rheological characteristics of these suspensions is vital while employing them for flow applications. The effect of temperature on the viscosity of nanofluids at atmospheric pressure is well documented in literatures; however, there are no available data for viscosity measurements of nanofluids at elevated pressure and temperature. In this work, rheological characteristics of oil based nanofluids at high pressures and temperatures, order of 100atm and 100 °C, respectively, are investigated. Nanofluid is prepared by dispersing commercially available SiO2 nanoparticles (∼20nm) in a highly refined paraffinic mineral oil (Therm Z-32, QALCO QATAR) which has wide applications for heat exchangers in oil industry. The rheological characteristics of both the base fluid and the nanofluid are measured using a High Pressure High Temperature (HPHT) viscometer. During experimentation, viscosity values are measured at pressures varying from 10MPa to 40MPa and temperatures ranging from 25°C to 170°C for nanofluid with mass concentrations of 3 percent. The viscosity values of nanofluids as well as base fluid are observed to increase with the increase in pressure. From the pressure coefficient values evaluated for basefluid and nanofluid, it is evident that the effect of pressure on nanofluid and basefluid was similar with no additional effect with respect to particle loading.
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Han, Jongyoon, and Harold G. Craighead. "From microfluidics to nanofluidics: DNA separation using nanofluidic entropic trap array device." In Micromachining and Microfabrication, edited by Carlos H. Mastrangelo and Holger Becker. SPIE, 2000. http://dx.doi.org/10.1117/12.395654.
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Ma, Xuehu, Fengmin Su, Zhong Lan, and Jiabin Chen. "Experimental Study on the Thermal Physical Properties of a CNTS-Ammonia Binary Nanofluid." In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52153.
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In this paper, carbon nanotubes—ammonia nanofluids (the binary nanofluids) have been prepared by two steps method. And the thermal conductivity, surface tension and kinetic viscosity of the binary nanofluid have been measured. The effects of the mass fraction of carbon nanotubes, the concentration of ammonia and temperature on the thermal physical properties of the binary nanofluid have been systematically studied. On the base, the effective thermal conductivities of the binary nanofluids have been calculated using the models in the literatures, and have been compared with the experimental values.
Reports on the topic "Nanofluidik"
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Ramsey, J. Michael. Nanofluidic Structures for Electrokinetic-Based Hydraulic Pumps. Office of Scientific and Technical Information (OSTI), June 2004. http://dx.doi.org/10.2172/839258.
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Gourley, Paul Lee, Anthony Eugene McDonald, and Judy K. Hendricks. Nanofluidic devices for rapid detection of virus particles. Office of Scientific and Technical Information (OSTI), January 2005. http://dx.doi.org/10.2172/921716.
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Pawel Keblinski. Fundamentals of Energy Transport in Nanofluids. Office of Scientific and Technical Information (OSTI), February 2007. http://dx.doi.org/10.2172/924115.
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Johnson, Drew W. Characterizations of Nanofluid Heat Transfer Enhancements. Fort Belvoir, VA: Defense Technical Information Center, September 2013. http://dx.doi.org/10.21236/ada590127.
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Fornasiero, Francesco. Unraveling the physics of nanofluidic phenomena at the single-molecule level. Office of Scientific and Technical Information (OSTI), October 2015. http://dx.doi.org/10.2172/1240944.
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Cropek, Donald M., Paul W. Bohn :In-Hyoung, Jonathan Sweedler, Yi Lu, Carla Swearingen, and Daryl Wernette. Metal Ion Sensor with Catalytic DNA in a Nanofluidic Intelligent Processor. Fort Belvoir, VA: Defense Technical Information Center, February 2005. http://dx.doi.org/10.21236/ada631384.
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Taborek, Peter. Nanoscale Heat Transfer Due to Near Field Radiation and Nanofluidic Flows. Fort Belvoir, VA: Defense Technical Information Center, July 2015. http://dx.doi.org/10.21236/ada625941.
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Globus, Tatiana, Aaron Moyer, Jerome Ferrance, Igor Sizov, and Tatyana Khromova. Development of a Biosensor Nanofluidic Platform for Integration with Terahertz Spectroscopic System. Fort Belvoir, VA: Defense Technical Information Center, January 2013. http://dx.doi.org/10.21236/ada587044.
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Gharagozloo, Patricia E., and Kenneth E. Goodson. Characterization and modeling of thermal diffusion and aggregation in nanofluids. Office of Scientific and Technical Information (OSTI), May 2010. http://dx.doi.org/10.2172/993305.
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Jeyashekar, Nigil S. Scanning Electron Microscope Studies on Aggregation Characteristics of Alumina Nanofluids. Fort Belvoir, VA: Defense Technical Information Center, August 2013. http://dx.doi.org/10.21236/ada602578.
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