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1
Robinson, Anthony James Judd R. L. "Bubble growth dynamics in boiling /." *McMaster only, 2003.
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2
Reinke, Peter. "Surface boiling of superheated liquid /." Zürich, 1996. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11598.
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3
Giannini, Leonardo. "Boiling Liquid Expanding Vapor Explosion of liquid hydrogen." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25472/.
Повний текст джерелаАнотація:
This thesis focuses on the modelling of liquid hydrogen Boiling Liquid Expanding Vapor Explosions (BLEVEs). This terminology identifies a catastrophic release of this unconventional fuel following the loss of its containment. The present work aims to enhance the knowledge on the consequences of such explosions, using the data collected from crucial experiments to validate the simulations. The consequence analysis of the "SH2IFT Project"
and the ”Bursting Tank Scenario” experimental BLEVEs is carried out simulating the explosions to verify the reliability of the implemented physical models.
To complete the modeling of the catastrophic rupture of liquid hydrogen (LH2) tanks, the combustion process is taken into account to describe the aftermath of the simulated accidents in terms of overpressure and impulse. Furthermore, it is also discussed the possible involvement of the endothermic reaction of the hydrogen para-isomer converting into its ortho-isomer form. In this way, a further validation and confrontation between the models currently used for conventional liquid fuels like propane and liquefied petroleum gas (LPG) is possible, adopting and adapting them to the specific case of a liquid hydrogen catastrophic release. So, it is possible to consider this thesis as divided in three major steps: the first one is the analysis of the physical explosions with the proposed models, the second one is the adaptation of such models to take hydrogen combustion into consideration and the third and last one is an analysis of the para-ortho reaction which may follow the explosion. At the end, a confrontation between the experimental data and the proposed calculations is carried out, underlining the aspects which still require further studies, experiments and documentation.
4
Barbone, Riccardo. "Explosive boiling of a depressurized volatile liquid." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23444.
Повний текст джерелаАнотація:
The explosive boiling that occurs when a volatile liquid is suddenly vented to the atmosphere has been investigated experimentally. Refrigerant 22 is used as the test liquid and is depressurized from an initial state of equilibrium using a bursting foil diaphragm. The competition between the rates of venting and vapor generation can lead to substantial repressurization within the vessel. The influence of vent area, quantity of liquid, initial pressure and pre-nucleation on the explosive boiling characteristics has been studied in a 260 ml Teflon-coated vessel as well as in a 75 ml glass tube. The amount of repressurization is found to be proportional to the pressure drop which determines the degree of superheat attained by the liquid. The time for repressurization is typically an order of magnitude larger than the time for the pressure drop. The repressurization in both vessels reaches a maximum value at an initial saturation vapor pressure of $ approx$2 MPa. The dependence of the repressurization on initial pressure observed experimentally is found to be consistent with the predictions of a semi-empirical correlation based on homogeneous nucleation theory. High-speed photography shows that the mode of boiling is dependent on the initial vapor pressure and the surface condition of the vessel walls. Heterogeneous boiling from the walls dominates in the Teflon-coated steel vessel. For initial vapor pressures less than $ approx$1 MPa, an evaporation wave propagates at $ approx$0.15 m/s from the free surface throughout the length of the glass tube. For higher initial vapor pressures the boiling mode in the glass tube becomes predominantly heterogeneous. Pre-nucleation with CO$ sb2$ within the refrigerant increases the boiling response by promoting heterogeneous boiling.
5
Ahmad, Hussain Hamed. "Boiling of immiscible systems over tube bundles." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/966.
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6
Talari, Kiran. "LIQUID CRYSTAL THERMOGRAPHY STUDIES IN WATER POOL BOILING AT SUBATMOSPHERIC PRESSURES." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3388.
Повний текст джерелаАнотація:
A pool boiling experimental facility has been designed and built to investigate nucleate pool boiling in water under sub atmospheric pressure. Liquid crystal thermography, a non intrusive technique, is used for the determination of surface temperature distributions. This technique uses encapsulated liquid crystals that reflect definite colors at specific temperatures and viewing angle. Design of the test section is important in this experimental study. Since a new TLC is required for every new set of test conditions, a permanently sealed test section is not an option. The real challenge is to design a leak proof test section which is flexible so that it can be taken apart easily. A plexiglass test section, including a top chamber with an internal volume of 60.9 x 60.9 x 66.4 mm and a bottom plate of 5.5mm thickness is designed and assembled together using quick grips. In the test section, water is boiled using 85.0mm x 16.0mm and 0.050mm thick Fecralloy® as the heating element. The TLC sheet is attached to the bottom plate and the heating element is placed on top of TLC so that the temperature distribution of the heating element during boiling can be interpreted from TLC. A camera system fast enough to capture the thermal response of the TLC and an arrangement to capture both hue of the TLC and growth of the bubble on the same frame has been designed and successfully used. This system allowed recording of position, size and shape of the bubble with synchronized surface temperature. In order to get hue vs. temperature relation, in-situ calibration of the TLC is performed for each test condition with the present experimental setup and lighting conditions. It is found that the calibration curve of the TLC at atmospheric pressure is different from the calibration curve of the same TLC at subatmospheric pressures. The maximum temperature difference between the two curves for the same hue is found to be only 0.6°C. The experiment is run at four different test conditions of subatmospheric pressure and low heat flux. It is run at system pressures of 6.2kPa (0.89Psi) and 8.0kPa (1.16Psi) with a constant heat flux of 1.88kW/m2 and 2.70kW/m2, and a constant heat flux of 2.70kW/m2, 3.662kW/m2 and 4.50 kW/m2 respectively. Analysis of nucleating surface temperatures using thermochromic liquid crystal technique is performed for these test conditions and the bubble dynamics is studied. The temperature distribution is quite varied in each case and the temperature is at its maximum value at the center of the bubble and it decreases radially from the center. The dry spot observed during the experiments indicates that the process of evaporation of the microlayer is dominant at subatmospheric pressures. It is observed that at very low pressure and heat flux the bubble growth is accompanied by the neck formation. Boiling parameters such as bubble frequency, bubble size and contact are also analyzed and a summary of these results for four different test conditions is presented and the relevant differences between the cases are discussed and the effect of increase in pressure and heat flux is noted.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
7
Aligoodarz, M. R. "Flow boiling heat transfer in a single narrow channel." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298767.
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8
Ament, David Lloyd. "Boiling heat transfer in thin liquid films with a wire mesh screen on the liquid surface." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19483.
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9
Gong, Shengjie. "An Experimental Study on Micro-Hydrodynamics of Evaporating/Boiling Liquid Film." Doctoral thesis, KTH, Kärnkraftsäkerhet, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50216.
Повний текст джерелаАнотація:
Study of liquid film dynamics is of significant importance to the understanding and control of various industrial processes that involve spray cooling (condensation), heating (boiling), coating, cleaning and lubrication. For instance, the critical heat flux (CHF) of boiling heat transfer is one of the key parameters ensuring the efficiency and safety of nuclear power plants under both operational and accident conditions, which occurs as the liquid layers (microlayer and macrolayer) near the heater wall lose their integrity. However, an experimental quantification of thin liquid film dynamics is not straightforward, since the measurement at micro-scale is a challenge, and further complicated by the chaotic nature of boiling process. The object of present study is to develop experimental methods for the diagnosis of liquid film dynamics, and to obtain data for the film instability under various conditions. A dedicated test facility was designed and constructed where micro conductive probes and confocal optical sensors were used to measure the thickness and dynamic characteristics of a thin liquid film on various heater surfaces, while a high speed camera was used to get visual observation. Extensive tests were performed to calibrate and verify the two thickness measuring systems. The micro conductive measuring system was proven to have a high reliability and repeatability with maximum system error less than 5µm, while the optical measuring system is capable of recording the film dynamics with spatial resolution of less than 1 mm. The simultaneous measurement on the same liquid film shows that the two techniques are in a good agreement with respect to accuracy, but the optical sensors have a much higher acquisition rate up to 30 kHz, which are more suitable for rapid process. The confocal optical sensors were therefore employed to measure the dynamic thickness of liquid films (ethanol, hexane and water) evaporating on various horizontal heater surfaces (aluminum, copper, silicon, stainless steel and titanium) to investigate the influences of heat flux, the surface and liquid properties on the film instability and the critical thickness. The critical thickness of water film evaporating on various surfaces was measured in the range of 60-150 mm, increasing with the increased contact angle or increased heat flux (evaporating rate) and also with the decreased thermal conductivity of the heater material. The data suggest the conjugate heat transfer nature of the evaporating liquid film dynamics at higher heat fluxes of interest to boiling and burnout. In the case of hexane on the aged titanium surface with contact angle of ~3o, the liquid film is found resilient to rupture, with film oscillations at relatively large amplitude ensuing as the averaged film thickness decreases below 15 µm. To interpret our experimental findings on liquid film evolution and its critical thickness at rupture, a theoretical analysis is also performed to analyze the dynamics of liquid films evaporating on heater surfaces. While the influences of liquid properties, heat flux, and thermal conductivity of heater surface are captured by the simulation of the lubrication theory, influence of the wettability is considered via a minimum free energy criterion. The thinning processes of the liquid films are generally captured by the simulation of the lubrication theory. For the case with ideally uniform heat flux over the heater surface, the instability of the liquid film occurs at the thickness level of tens micro meters, while for the case of non-uniform heating, the critical thicknesses for the film rupture are closer to the experimental data but still underestimated by the lubrication theory simulation. By introducing the minimum free energy criterion to considering the influence of surface wettability, the obtained critical thicknesses have a good agreement with the experimental ones for both titanium and copper surfaces, with a maximum deviation less than ±10%. The simulations also explain why the critical thickness on a copper surface is thinner than that on a titanium surface. It is because the good thermal conductivity of copper surface leads to uniform temperature distribution on the heat surface, which is responsible for the resilience of the liquid film to rupture. A silicon wafer with an artificial cavity fabricated by Micro Electronic Mechanical System (MEMS) technology was used as a heater to investigate the dynamics of a single bubble in both a thick and thin liquid layer under low heat flux (<60 kW/m2). The maximum departure diameter of an isolated bubble in a thick liquid film was measured to be 3.2 mm which is well predicted by the Fritz equation. However, in a thin liquid layer with its thickness less than the bubble departure diameter, the bubble was stuck on the heater surface with a dry spot beneath. A threshold thickness of the liquid film which enables the dry spot rewettable was obtained, and its value linearly increases with increasing heat flux. In addition, another test section was designed to achieve a constant liquid film flow on a titanium nano-heater surface which helps to successfully carry boiling in the liquid film from low heat flux until CHF. Again, the confocal optical sensor was employed to measure the dynamics of the liquid film on the heater surface under varied heat flux conditions. A statistical analysis of the measured thickness signals that emerge in a certain period indicates three distinct liquid film thickness ranges: 0~50 µm as microlayer, 50~500 µm as macrolayer, 500~2500 µm as bulk layer. With increasing heat flux, the bulk layer disappears, and then the macrolayer gradually decreases to ~105 µm, beyond which instability of the liquid film may lose its integrity and CHF occurs. In addition, the high-speed camera was applied to directly visualize and record the bubbles dynamics and liquid film evolution. Dry spots were observed under some bubbles occasionally from 313 kW/m2 until CHF with the maximum occupation fraction within 5%. A dry spot was rewetted either by liquid receding after the rupture of a bubble or by the liquid spreading from bubbles’ growth in the vicinity. This implies that the bubbles’ behavior (growth and rupture) and their interactions in particular are of paramount importance to the integrity of liquid film under nucleate boiling regime.QC 20111205
VR-2005-5729, MSWI
10
Glavin, Nicholas R. "Photonically Enhanced and Controlled Pool Boiling Heat Transfer." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343401685.
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11
Zhao, Donglin. "Liquid macro- and micro-mixing in sparged and boiling stirred tank reactors." Thesis, University of Surrey, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395548.
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12
Searle, Matthew Clark. "Thermal Transport at Superhydrophobic Surfaces in Impinging Liquid Jets, Natural Convection, and Pool Boiling." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7065.
Повний текст джерелаАнотація:
This dissertation focuses on the effects of superhydrophobic (SHPo) surfaces on thermal transport. The work is divided into two main categories: thermal transport without phase change and thermal transport with phase change. Thermal transport without phase change is the topic of four stand-alone chapters. Three address jet impingement at SHPo surfaces and the fourth considers natural convection at a vertical, SHPo wall. Thermal transport with phase change is the topic of a single stand-alone chapter exploring pool boiling at SHPo surfaces. Two chapters examining jet impingement present analytical models for thermal transport; one considered an isothermal wall and the other considered an isoflux wall. The chapter considering the isothermal scenario has been archivally published. Conclusions are presented for both models. The models indicated that the Nusselt number decreased dramatically as the temperature jump length increased. Further, the influence of radial position, jet Reynolds number, Prandtl number and isoflux versus isothermal heating become negligible as temperature jump length increased. The final chapter concerning jet impingement reports an experimental exploration of jet impingement at post patterned SHPo surfaces with varying microfeature pitch and cavity fraction. The empirical results show a decrease in Nusselt number relative to smooth hydrophobic surfaces for small pitch and cavity fraction and the isoflux model agrees well with this data when the ratio of temperature jump length to slip length is 3.1. At larger pitch and cavity fractions, the empirical results have higher Nusselt numbers than the SHPo surfaces with small pitch and cavity fraction but remain smaller than the smooth hydrophobic surface. We attribute this to the influence of small wetting regions. The chapter addressing natural convection presents an analytical model for buoyant flow at a vertical SHPo surface. The Nusselt number decreased dramatically as temperature jump length increased, with greater decrease occurring near the lower edge and at higher Rayleigh number. Thermal transport with phase change is the topic of the final stand-alone chapter concerning pool boiling, which has been archivally published. Surface heat flux as a function of surface superheat was reported for SHPo surfaces with rib and post patterning at varying microfeature pitch, cavity fraction, and microfeature height. Nucleate boiling is more suppressed on post patterned surfaces than rib patterned surfaces. At rib patterned surfaces, transition superheat decreases as cavity fraction increases. Increasing microfeature height modestly increases the transition superheat. Once stable film boiling is achieved, changes in surface microstructure negligibly influence thermal transport.
13
Wasekar, Vivek Mahadeorao. "Nucleate Pool Boiling Heat Transfer in Aqueous Surfactant Solutions." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin994964318.
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14
Hemmatian, Behrouz. "Contribution to the study of boiling liquid expanding vapor explosions and their mechanical effects." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/397646.
Повний текст джерелаАнотація:
Boiling Liquid Expanding Vapor Explosions keep occurring from time to time in process plants, storage areas and transportation by road or rail, often with severe effects. There is no doubt that a better knowledge of their main features will help in decreasing both their frequency and their consequences.
This is the main aim of this thesis: the analysis of the main causes of BLEVEs, the improvement in the prediction of their effects and consequences and, finally, the definition of simple measures to be applied in the management of emergencies associated to these events.
Historical analyses have been performed to determine the prevalence of BLEVEs among all major accidents in fixed plants and in the transportation of hazardous materials, as well as their main causes; the action of fire as domino effect escalation has also been studied, with special attention to the time to failure of a vessel in such a situation.
The different existing methodologies for the estimation of the peak overpressure are presented and compared, and the diverse uncertainty factors affecting the prediction of BLEVE mechanical effects are analyzed.
A new and relatively simple methodology has been proposed to predict the blast effects of these explosions, which allows a quick and accurate estimation. Finally, based on all these analyses, simple emergency management measures are proposed which could reduce significantly the consequences of BLEVEs on people.Encara avui, en plantes de procés, àrees d’emmagatzematge o en el transport per carretera o ferrocarril, de tant en tant es continuen produint les explosions anomenades BLEVE (Boiling Liquid Expanding Vapor Explosion, en català explosió del vapor en expansió d’un líquid bullent), sovint amb efectes molt severs. No hi ha cap mena de dubte que conèixer millor les principals característiques d’aquestes explosions permetrà reduir-ne tant la seva freqüència com les seves conseqüències. Aquesta és precisament la principal finalitat d’aquesta tesi: l’anàlisi de les causes principals de les BLEVEs, la millora en la predicció dels seus efectes i conseqüències i, finalment, la definició de mesures que siguin senzilles d’aplicar quan es produeixen emergències associades a aquest tipus d’esdeveniment. S’han dut a terme anàlisis històriques per a determinar la prevalença de les BLEVEs d’entre tots els accidents greus que es poden produir en instal·lacions fixes i durant el transport de mercaderies perilloses, així com també per a determinar-ne les causes principals. També s’ha analitzat l’acció que exerceix el foc com a element desencadenant d’efecte dominó, fent especial atenció al temps que trigarà un dipòsit en esclatar quan es veu sotmès a la seva acció. També es presenten i comparen les diverses metodologies existents per a l’estimació del pic de sobrepressió produït en una BLEVE, i s ¿analitzen els diversos factors d’incertesa que afecten la predicció dels efectes mecànics generats en una BLEVE. S’ha presentat una metodologia nova i relativament simple per predir els efectes d’aquest tipus d’explosions, que permet fer estimacions ràpides i acurades. Finalment, en base a totes aquestes anàlisis, s’han proposat mesures senzilles per a la gestió d’aquest tipus d’emergències que poden ajudar a reduir significativament les conseqüències de les BLEVEs sobre les persones.
15
Wang, Yuan. "Liquid-vapour phase change and multiphase flow heat transfer in single micro-channels using pure liquids and nano-fluids." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5752.
Повний текст джерелаАнотація:
Heat management in high thermal-density systems such as CPU chips, nuclear reactors and compact heat exchangers is confronting rising challenges due to ever more miniaturized and intensified processes. While searching for heat transfer enhancement, micro-channel flow boiling and the usage of high thermal potential fluids such as nanofluids are found to be efficient heat removal approaches. However, the limited understanding of micro-scale multiphase flows impedes wider applications of these techniques. In this thesis work, liquid-vapour phase change and multiphase flow heat transfer in micro-channels were experimentally investigated. Included are studies on the single phase friction, vapour dynamics, liquid meniscus evaporation, two-phase flow instabilities and heat transfer. An experimental system was built. Rectangular microchannels with different hydraulic diameters (571 μm, 762 μm and 1454 μm) and crosssectional aspect ratios were selected. Transparent heating was utilised by coating the micro-channels with a layer of tantalum on the outer surfaces. FC-72, n-pentane, ethanol, and ethanol-based Al2O3 nanofluids were used as working fluids. Pressures and temperatures at micro-channel inlet and outlet were acquired. Simultaneous visualisation and thermographic profiles were monitored. Single phase friction of pure liquids and nanofluids mostly showed good agreement with the conventional theory. The discrepancies were associated with hydrodynamic developing flow and the early transition to turbulent flow, but nanoparticle concentration showed minor impact. After boiling incipient, the single vapour bubble growth and flow regimes were investigated, exploring the influences of flow and thermal conditions as well as the micro-channel geometry on vapour dynamics. In addition, liquid meniscus evaporation as the main heat transfer approach at thin liquid films in micro-channels was studied particularly. Nanoparticles largely enhanced meniscus stability. Besides, flow instabilities were analyzed based on the pressure drop and channel surface temperature fluctuations as well as the synchronous visualization results. Moreover, study on flow boiling heat transfer was undertaken, the corresponding heat transfer characteristics were presented and the heat transfer mechanisms were elucidated. Furthermore, ten existing heat transfer correlations were assessed. A modified heat transfer correlation for high aspect ratio micro-channel flow boiling was proposed. The crucial role of liquid property and microchannel aspect-ratio on flow boiling heat transfer was highlighted.
16
Arumemi-Ikhide, Michael. "Boiling enhancement characteristics of an antifouling three-phase (vapour-liquid-solid) circulating fluidised bed heat exchanger." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/11509.
Повний текст джерелаАнотація:
Scale formation on heat transfer surfaces results in the build-up of deposits (products of heat and mass transfer processes) which act as additional thermal resistance, thereby leading to the degradation of equipment heat transfer performance. Under most conditions fouling is more severe during sub-cooled boiling heat transfer, mainly due to the mechanisms which govern the bubble formation and detachment process. Therefore in response, the current project aims to investigate the boiling enhancement characteristics and fouling mitigation potential of a three-phase (vapour-liquid-solid) circulating fluidised bed heat exchanger (CFBHX). The design of the three-phase boiling system is predicated on a combination of multiphase fluidisation and flow boiling heat transfer. Experiments are performed at atmospheric pressure, and distilled water is used as the working fluid. The three-phase test unit consist of a glass riser column with a minichannel of square cross sectional area 21.5 mm x 11mm, height 1000mm, fitted with an electrically heated cartridge heater rod of 8mm diameter x 730mm length. The set-up employs stainless steel particles as the solid phase. A systematic experimental study is made to understand the influence of particles and particle size on the boiling heat transfer behaviour of the three-phase CFBHX. The effect of operating parameters such as heat flux and superficial velocity are also investigated. In the riser column, the use of transparent glass walls is of major significance as it provides a means of observing, and studying (via the use of flow visualisation techniques) the complex multiphase flow system. Results from our experimental work show that higher heat transfer coefficients are achieved in (vapour-liquid-solid) three-phase flow boiling, compared with (vapour-liquid) two-phase flow boiling. The observed enhancement becomes more pronounced for progressively larger diameter particles. Based on both an analysis of the mechanisms governing three-phase boiling heat transfer, and the extension of existing two-phase flow boiling (and liquid-solid fluidised bed) heat transfer models, a boiling heat transfer correlation has been derived for the prediction of heat transfer in our vapour-liquid-solid circulating fluidised bed system. A favourable agreement between the derived three-phase boiling correlation and our empirically obtained results has also been duly demonstrated.
17
Guion, Alexandre Nicolas. "Modeling and simulation of liquid microlayer formation and evaporation in nucleate boiling using computational fluid dynamics." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112380.
Повний текст джерелаАнотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 243-252).
The transport of latent heat makes boiling one of the most efficient modes of heat transfer, allowing a wide range of systems to improve their thermal performance, from microelectronic devices to nuclear power plants. In particular, Boiling Water Reactors (BWR) use boiling as the primary mode of heat transfer in the reactor core to accommodate very high heat fluxes. In Pressurized Water Reactors (PWR) subcooled flow boiling can occur in hot sub-channels. As a bubble grows outside of a surface imperfection during nucleate boiling, viscous stresses at the wall can be strong enough to impede liquid motion and trap a thin liquid layer - referred to as microlayer, underneath the growing bubble. The contribution of microlayer evaporation to overall heat transfer and bubble growth can be large, in particular in the case of water1. In practice, numerical simulations of nucleate boiling resolve the macroscopic interface of the bubble and resort to subgrid models to account for the evaporation of the microlayer at the microscopic scale. The applicability of this subgrid modeling approach relies on the capacity to initialize the microlayer shape and extension, prior to its evaporation. However, existing models of microlayer formation are either physically incomplete2 or purely empirical3. In this work, we first confirm through a sensitivity study the need for accurate modeling of microlayer formation to initialize boiling simulations and to reproduce physical boiling dynamics (a). Then, we build the first generally applicable model for microlayer formation through direct computations of the hydrodynamics of bubble growth at the wall for a wide range of conditions and fluids, including water at 0.101MPa (lab experiments) and 15.5MPa (PWR), capillary numbers Ca [is element of] [0.001; 0.1], and contact angles [theta] [is element of] [10°; 90°] (b). In addition, we modify an existing experimental pool boiling setup to measure with unprecedented accuracy initial bubble growth rates needed to predict microlayer formation (c). Lastly, we develop a numerical procedure based on hydrodynamics theories to obtain mesh-independent results in moving contact line simulations for a wide range of contact angles and viscosity ratios (d). In particular, we use direct computations of the transition to a Landau-Levich-Derjaguin film in forced dewetting to inform the onset of microlayer formation in nucleate boiling. These contributions(a) (b) (c) (d) bridge a significant gap in our understanding of how boiling works and can be modeled at the microscopic scale, which represents a first step in designing surfaces with higher heat transfer performance and in building safer and more efficient energy systems.
by Alexandre Nicolas Guion.
Ph. D.
18
Joshua, Nihal E. "Direct Immersion Cooling Via Nucleate Boiling of HFE-7100 Dielectric Liquid on Hydrophobic and Hydrophilic Surfaces." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699916/.
Повний текст джерелаАнотація:
This study experimentally investigated the effect of hydrophobic and hydrophilic surfaces characteristics on nucleate boiling heat transfer performance for the application of direct immersion cooling of electronics. A dielectric liquid, HFE – 7100 was used as the working fluid in the saturated boiling tests. Twelve types of 1-cm2 copper heater samples, simulating high heat flux components, featured reference smooth copper surface, fully and patterned hydrophobic surface and fully and patterned hydrophilic surfaces. Hydrophobic samples were prepared by applying a thin Teflon coating following photolithography techniques, while the hydrophilic TiO2 thin films were made through a two step approach involving layer by layer self assembly and liquid phase deposition processes. Patterned surfaces had circular dots with sizes between 40 – 250 μm. Based on additional data, both hydrophobic and hydrophilic surfaces improved nucleate boiling performance that is evaluated in terms of boiling incipience, heat transfer coefficient and critical heat flux (CHF) level. The best results, considering the smooth copper surface as the reference, were achieved by the surfaces that have a mixture of hydrophobic/hydrophilic coatings, providing: (a) early transition to boiling regime and with eliminated temperature overshoot phenomena at boiling incipience, (b) up to 58.5% higher heat transfer coefficients, and (c) up to 47.4% higher CHF levels. The studied enhanced surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.
19
Turk, Ugur. "Boiling of highly wetting liquids in oscillatory flow." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306226.
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Fensin, Michael Lorne. "Optimum boiling water reactor fuel design strategies to enhance reactor shutdown by the standby liquid control system." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0005364.
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Pasek, Ari Darmawan. "Pool boiling on porous surfaces in cryogenic and refrigerant liquids." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315511.
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22
Vereen, Keon. "An experimental investigation on the dynamics of bubbles utilizing refrigerant R134a under pressurized flow boiling conditions." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4717.
Повний текст джерелаАнотація:
Flow boiling heat transfer allows for the dissipation of large amounts of heat. In this work, the effect of heat flux and pressure on flow boiling of liquid refrigerant R-134a is studied in a vertical thin channel. The experimental setup mimics a refrigeration cycle and specifically looks at the effect of pressure and wall heat flux on the departure size and bubble generation rate. The experimental setup consists of a closed loop which includes a vertical narrow rectangular channel and two synchronized high speed cameras for optical measurements at either sides of the channel. The setup is built to employ an accurate measurement technique to define wall temperatures of the representative flow boiling process. Instead of using thermocouples on the surface channel, the thermochromic liquid crystallography (TLC) technique is used to determine non-invasively the heater surface temperature at high temporal and spatial resolution. The TLC interval range is 30-50??C. The TLC is attached to a Fecralloy heating section. The high speed Prosilica cameras simultaneously capture, colored TLC images as well as bubble nucleation and departure at very high frame rates. Experiments on subcooled flow boiling heat transfer have been conducted with refrigerant R-134a under a mass flux range of 484.838 kg/m??s to 1212.1 kg/m??s. With the low mass flux, the wall heat flux ranged from 167.2 to 672.1 kW/m??, the inlet subcooling ranged from 0.35??C to 16.55??C, the system pressure ranged from 621 kPa to 1034 kPa. At high mass flux, the wall heat flux ranged from 329.8 kW/m?? to 744 kW/m??, the inlet subcooling from 0.16??C to 17.21??C, and the system pressure from 621 kPa to 1034 kPa. A parametric study was done by maintaining various input parameters constant. From the high speed images, bubble parameters such as size and frequency are calculated. Temperature contours are utilized to determine the surface wall temperature at specific points.; Sequential wall temperatures are traced over a short period of time to understand the cooling effects. The bubble propagation and coalescence are also visualized. Results show that bubble size and frequency increased with heat flux at any particular pressure. At higher pressure, the trend would be for the bubble size to decrease; however, the inlet subcooling and heat flux also affect bubble size. The bubble frequency is also seen to be affected by the inlet subcooling and the heat flux. Even though the inlet subcooling is maintained approximately constant, any slight decrease in subcooling increased bubble growth rate. Another trend that is observed is that at higher the heat flux, the bubble generation frequency is faster; however no specific trend is observed for wall superheat. With an increase in heat flux, the wall superheats are expected to increase; however, the localized nature of the nucleation activity sites is seen to affect the results. The variables are non-dimensionalized to note trends in parameters. In summary, the data analysis demonstrates that both heat flux and pressure significantly influence the bubble generation rate, size, propagation and coalescence.ID: 030646273; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.A.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 107-115).
M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Thermofluid Aerodynamics Systems Track
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Morgan, Nathaniel Ray. "A New Liquid-Vapor Phase Transition Technique for the Level Set Method." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6895.
Повний текст джерелаАнотація:
The level set method offers a simple and robust approach to modeling liquid-vapor interfaces that arise in boiling and condensing flows. The current liquid-vapor phase-transition techniques used with the level set method are not able to account for different thermal conductivities and specific heats in each respective phase, nor are they able to accurately account for latent heat absorption and release. This paper presents a new level set based technique for liquid-vapor phase-transition that accounts for different material properties in each respective phase, such as thermal conductivity and specific heat, while maintaining the interface at the saturation temperature. The phase-transition technique is built on the ghost fluid framework coupled with the standard level set method. A new technique is presented for constructing ghost nodes that implicitly captures the immersed boundary conditions and is second order accurate. The method is tested against analytical solutions, and it is used to model film boiling. The new phase-transition technique will greatly assist efforts to accurately capture the physics of boiling and condensing flows.
In addition to presenting a new phase transition technique, a coupled level set volume of fluid advection scheme is developed for phase transition flows. The new scheme resolves the mass loss problem associated with the level set method, and the method provides an easy way to accurately calculate the curvature of an interface, which can be difficult with the volume of fluid method. A film boiling simulation is performed to illustrate the superior performance of the coupled level set volume of fluid approach over the level set method and the volume of fluid method.
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Moghaddam, Saeed. "Microscale study of nucleation process in boiling of low-surface-tension liquids." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3878.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Bailey, Wendell O. S. "Applications of pool boiling heat transfer on modulated surfaces in organic liquids." Thesis, University of Southampton, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437112.
Повний текст джерела
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Прокопов, Максим Геннадійович, Максим Геннадьевич Прокопов, Maksym Hennadiiovych Prokopov, Валерій Миколайович Марченко, Валерий Николаевич Марченко та Valerii Mykolaiovych Marchenko. "Метод расчета показателей истечения вскипающей жидкости". Thesis, Издательство СумГУ, 2008. http://essuir.sumdu.edu.ua/handle/123456789/5734.
Повний текст джерелаАнотація:
Эффективность жидкостно-парового струйного термокомпрессора (СТК) в первую очередь определяется совершенством процессов истечения вскипающей жидкости и формирования рабочей струи влажного пара за выходным срезом активного сопла. В литературе приводится большое количество экспериментальных и теоретических исследований, посвященных изучению течения вскипающих потоков в расширяющихся каналах, но все они носят лишь описательный характер. Актуальным является создание метода расчета истечения вскипающей жидкости.
При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/5734
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Dietzel, Dirk [Verfasser], and Andreas [Akademischer Betreuer] Kronenburg. "Modeling and simulation of flash-boiling of cryogenic liquids / Dirk Dietzel ; Betreuer: Andreas Kronenburg." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1216505020/34.
Повний текст джерела
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Hama, Katsuhiko. "Film boiling heat transfer in various liquids under natural convection and forced convection conditions." Kyoto University, 2006. http://hdl.handle.net/2433/143793.
Повний текст джерела
29
Ge, Yang. "3D numerical study on droplet-solid collisions in the Leidenfrost regime." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1124291953.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxi, 225 p.; also includes graphics (some col.). Includes bibliographical references (p. 218-225). Available online via OhioLINK's ETD Center
30
Прокопов, Максим Геннадійович, Максим Геннадьевич Прокопов та Maksym Hennadiiovych Prokopov. "Теплофизическое моделирование рабочего процесса жидкостно-парового струйного компрессора". Thesis, Изд-во СумГУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/23679.
Повний текст джерелаАнотація:
У дисертаційній роботі наведені: теплофізична модель рідинно-
парового струминного компресора, результати аналізу
експериментальних досліджень закипаючих потоків рідини у каналах,
що розширюються, і проточній частині рідинний-парового
струминного компресора, опис формування трьох критичних режимів
течії і структурної інверсії потоку, характеристики компресора.
Представлена математична модель робочого процесу, яка
дозволяє визначати параметри і характеристики рідинно-парового
струминного компресора. Створена методика інженерного розрахунку
реалізована у вигляді розрахункової програми для ЕОМ і дозволяє
створити компресор з високими показниками ефективності.
При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/23679В диссертационной работе приведены: теплофизическая модель жидкостно-парового струйного компрессора, результаты анализа экспериментальных исследований вскипающих потоков жидкости в расширяющихся каналах и проточной части жидкостно-парового струйного компрессора, описание формирования трех критических режимов течения и структурной инверсии потока, характеристики компрессора. Представлена математическая модель рабочего процесса, которая позволяет определять параметры и характеристики жидкостно-парового струйного компрессора. Созданная методика инженерного расчета реализована в виде расчетной программы для ЭВМ и позволяет создать компрессор с высокими показателями эффективности. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/23679
The dissertation presents the results: thermophysical model of liquidsteam stream compressor, results of analysis of experimental researches of boiling up streams of liquid in the broadening ductings and running part of liquid-steam stream compressor, description of forming of three critical modes of flow and structural inversion of stream. The mathematical model of working process, which allows to determine parameters and descriptions of liquid-steam stream compressor, is presented. The created method of engineering calculation is realized as a calculation program for computer and allows to create a compressor highperformance efficiency, descriptions of compressor. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/23679
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Falleiro, Rafael Mauricio Matricarde. "Determinação experimental de dados de equilibrio liquido-vapor de misturas binarias de componentes de oleos vegetais atraves da calorimetria diferencial exploratoria." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267077.
Повний текст джерелаАнотація:
Orientadores: Maria Alvina Krahenbuhl, Antonio Jose de Almeida MeirellesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-13T05:54:13Z (GMT). No. of bitstreams: 1 Falleiro_RafaelMauricioMatricarde_M.pdf: 2025398 bytes, checksum: 267d9b60efd1dc4f0a2818661c23761d (MD5) Previous issue date: 2009
Resumo: Esse trabalho irá contribuir com alguns dados inéditos de equilíbrio líquido-vapor de compostos que constituem o biodiesel, pelo interesse imediato que este último tem despertado no mundo. Dados de Equilíbrio Líquido-Vapor (ELV) para três misturas binárias de ácidos graxos saturados foram medidos com sucesso através da Calorimetria Diferencial Exploratória (DSC). Esses dados são de grande interesse para as indústrias, principalmente as de biodiesel, já que processos como a cristalização ou a separação indesejada de componentes pode ser minimizada a partir do levantamento desses dados. Contudo, mudanças na célula de pressão do calorímetro e o uso de panelas herméticas com furo na tampa (f = 250 µm) foram necessárias para que a técnica analítica fosse possível de ser aplicada, apresentando precisão nos resultados, uso de pouca quantidade de amostra e menor tempo de operação. Foram determinados experimentalmente a 50 mmHg dados ELV dos seguintes sistemas: ácido mirístico (C14:0) + ácido palmítico (C16:0), ácido mirístico (C14:0) + ácido esteárico (C18:0), ácido palmítico (C16:0) + ácido esteárico (C18:0). Na pressão de 8 mmHg investigou-se o sistema ácido linoléico (C18:2) + ácido oléico (C18:1). Para estes quatro sistemas foram preparadas pequenas quantidades de amostras (2,5 a 4,5 mg) em diferentes composições cuja fração molar do componente mais volátil variara de 0 a 1,0 em intervalos de 0,1. Os coeficientes de fugacidade para os componentes da fase vapor foram calculados usando o método de Hayden e O'Connell (Fredenslund et al., 1977) e o coeficiente de atividade para a fase líquida foi correlacionado pelos modelos tradicionais de gE : NRTL (Renon and Prausnitz, 1968), UNIQUAC (Abrams and Prausnitz, 1975) e Wilson (Prausnitz et al., 1999). Os ajustes dos parâmetros foram então comparados afim de determinar quais dos ajustes representava melhor o ELV. A modelagem termodinâmica é importante para o desenvolvimento de equipamentos para a produção de biodiesel e fundamentais nos processos de purificação.
Abstract:This work will contribute to some unpublished data of phase equilibria of compounds that form the biodiesel, which arouses the interest immediately. Vapor-liquid equilibrium (VLE) data for three binary mixtures of saturated fatty acids have been successfully measured through differential scanning calorimetry (DSC). These data are of great interest to the industries mainly of biodiesel, since processes such as crystallization or separation of undesired components can be minimized from such data. However, changes in the calorimeter pressure cell and the use of hermetic pans with caps with holes (f = 250 µm) have been necessary so that this analytical technique was possible to be applied, showing accuracy in results, shorter sample quantity and operational time. The systems studied at 50 mmHg in this work were: myristic acid (C14:0) + palmitic acid (C16:0), myristic acid (C14:0) + stearic acid (C18:0) e palmitic acid (C16:0) + stearic acid (C18:0). The linoleic acid (C18:2) + oleic acid (C18:1) binary mixture was investigated in the pressure of 8 mmHg. The binary systems were prepared using small quantities (2.5 to 4.5 mg) of samples in different mole fractions varying between 0.0 and 1.0 in relation to the most volatile component of each diagram. The fugacity coefficients for the components in the vapor phase have been calculated using the Hayden and O'Connell's method (Fredenslund et al., 1977) and the activity coefficients for the liquid phase have been correlated to the traditional gE models: NRTL (Renon and Prausnitz, 1968), UNIQUAC (Abrams and Prausnitz, 1975) and Wilson (Prausnitz et al., 1999). The set of parameters were then compared in order to determine which adjustments would best represent the VLE. The thermodynamic modeling is important for the development of equipment for the biodiesel production and purification.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
32
Chassagnoux, Raphaël. "Etude des propriétés diélectriques de l'azote liquide et diphasique dans le cadre du limiteur de courant." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT104.
Повний текст джерелаАнотація:
L’interconnexion de plus en plus grande des réseaux électriques traditionnels AC et l’émergence de réseaux DC s’accompagne de courants de court circuit plus importants, et de contraintes plus fortes sur les disjoncteurs haute tension lors de la coupure du courant. L’une des solutions pour maitriser le courant de court circuit consiste à insérer un limiteur de courant en série sur les lignes haute tension. Parmi les technologies existantes, le limiteur de courant supraconducteur est un candidat idéal du point de vue du réseau, mais il fait face à de nombreuses contraintes de dimensionnement. Parmi elles, l’isolation électrique est particulièrement critique et très spécifique à cette application : milieu cryogénique (azote liquide à -196°C), rubans supraconducteurs générant des renforcements de champ électrique, et chauffage transitoire des rubans lors de la limitation de courant qui induit une forte ébullition de l’azote liquide.L’objectif de ce travail est de rassembler des données et des connaissances pour le dimensionnement de l’isolation des limiteurs de courant. Le cas d’étude d’un limiteur inséré sur une ligne électrique permet de mettre en évidence les principales contraintes que celui-ci subit durant son fonctionnement. Ces contraintes sont reproduites dans un dispositif expérimental associant cryogénie et haute tension. Les résultats expérimentaux incluent des mesures de tensions de claquage obtenues dans diverses conditions de tension (DC, choc impulsionnel) de pression (de 1 à 4 bar), et de température (de 65 à 77 K), de distance inter électrode (5 et 10 mm), avec et sans chauffage de l’électrode ruban. L’observation des phénomènes d’ébullition et de pré claquage met en évidence des phénomènes et paramètres nouveaux, et permet d’interpréter qualitativement les tensions de claquage observées. L’un des résultats importants de ces travaux est la mise en évidence de l’influence complexe et parfois délétère du sous refroidissement (diminution de la température ou augmentation de la pression) sur les tensions de claquage, liée à la variation de la taille des bulles d’azote gazeuxThe increasing number of interconnections in electrical networks and the massive integration of renewable energies nowadays comes with an increase of short circuit currents, and more constraints on high voltage circuit breaker during the current clearance. To solve this problem, a solution consists in inserting a fault current limiting device on electrical lines. Among the available technologies, the superconducting fault current limiter is ideal from the perspective of transmission system operator. However the design of this device is non-trivial, especially the electrical insulation, which is very specific to this apparatus: electrical insulation in a cryogenic environment (liquid nitrogen at - 196°C), superconducting tapes inducing electric field reinforcement, and strong transient heating generating numerous vapor bubbles.In this context, the aim of this work is to gather data and knowledge supporting the design of future superconducting fault current limiters. First, the case study of a fault current limiter model inserted on an electrical line allowed to deduce the main stresses on this device during its working sequence. These constraints are then reproduced within a high voltage cryostat. Experimental results gathered include breakdown voltages measured in various conditions of voltage type (DC or impulse voltage), pressure (from 1 to 4 bars), temperature (from 65 to 77 K), inter electrode gap (from 5 to 10 mm), with and without transient heating of the tape. The observation of boiling conditions and pre breakdown phenomena evidenced several new phenomena, and allowed to perform a qualitative interpretation of the breakdown voltages. An important result is the observation of the complex and sometimes adverse effect of subcooling (temperature decrease or pressure increase) on breakdown voltages, due to the variation of nitrogen bubbles size
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Kalaikadal, Deepak Saagar. "Investigation of Bubble Dynamics in Pure Liquids and Aqueous Surfactant / Polymer Solutions Under Adiabatic and Diabatic Conditions." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1525167893347615.
Повний текст джерела
34
Antariksawan, Anhar Riza. "Interaction thermique acier inoxydable fondu-eau sur l'installation SEIZIES : analyse et interprétation." Grenoble INPG, 1993. http://www.theses.fr/1993INPG0038.
Повний текст джерелаАнотація:
Le contact entre le jet d'eau et l'acier inoxydable fondu observe dans l'installation experimentale seizies provoque une pressurisation et une liberation de l'energie mecanique. On propose dans ce memoire une analyse et une interpretation de cette interaction a l'aide d'un modele thermodynamique et d'un modele parametrique. Les objectifs de ce travail sont: l'evaluation du terme source de l'interaction, a savoir l'energie reellement transmise dans l'interaction et celle transformee en travail mecanique et l'amelioration des connaissances sur l'interaction thermique metal fondu et notamment dans le cas d'une injection de l'eau sur le metal fondu. Les resultats importants sont: le travail mesure experimentalement est representatif du travail maximum liberable dans seizies, la masse d'acier participant a ete determine et certains mecanismes physiques ont ete valides
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Сафронова, Олена Олегівна. "Теплогідравлічні характеристики парогенератора ядерної енергетичної установки ГТ-МГР для виробництва електроенергії та водню". Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/23079.
Повний текст джерелаАнотація:
Магістерська дисертація складається зі вступу, трьох розділів, висновків. Загальний об’єм дисертації становить 101 сторінку, з них 88 сторінок основного тексту, 31 рисунок, 4 таблиці, список джерел з 37 найменувань.
Актуальність теми. Розвиток ядерної енергетики в даний час направлено на створення АЕС на базі екологічно чистих реакторів 4-го покоління. Однією з можливих концепцій таких реакторів є модульний гелієвий реактор, в якому в якості теплоносія використовується гелій. В даний час розробляються перспективні проекти створення газоохолоджувальних ЯЕУ 4-го покоління, які поєднують в собі виробництво електроенергії та водню методом високотемпературного електролізу пари, що здійснюється в високотемпературних парогенераторах. Найбільший інтерес у питанні моделювання парогенератора ЯЕУ представляє собою течія киплячої рідини в вертикальному каналі довільної форми. Тому пошук максимально можливої компактності конструкції при достатньому рівні міцності та високих теплогідравлічних характеристиках є актуальною проблемою.
Зв'язок роботи з науковими програмами, планами, темами. Науково-дослідна робота по темі дисертації проводилася по програмі спільних робіт з «Відділенням Цільової Підготовки «КПІ ім. Ігоря Сікорського» для НАНУ за напрямком №1.7.1.АХ.2 «Термогазодинаміка турбулентних потоків в обертових каналах високотемпературних енергетичних установок» від 02.01.2018 р., реєстраційний номер 0118Г000006.
Мета даної роботи − дослідження теплогідравлічних та геометричних параметрів парогенератора ГТ-МГР для виробництва електроенергії та водню, а також моделювання процесу теплообміну при кипінні рідини в вертикальній трубі.
Досягнення мети передбачає виконання таких завдань:
– Розробити математичну модель високотемпературного парогенератора ЯЕУ четвертого покоління з використанням гелію в якості первинного теплоносія з гвинтовими закрученими (змієвиковими) трубами.
– Змоделювати процес теплообміну при кипінні рідини.
– Дослідити структуру потоку та характерні режими теплообміну в вертикальній трубі.
– Реалізувати п'ять різних методів розрахунку теплообміну при кипінні у вертикальній трубі, заснованих на експериментальних кореляційних залежностях.
Об’єктом дослідження є теплогідравлічні процеси в парогенераторі ядерної енергетичної установки ГТ-МГР з гелієвим реактором для виробництва електроенергії та водню.
Предметом дослідження є закономірності та показники впливу на теплообмін і гідродинаміку від температури і тиску при кипінні рідини в теплообмінному елементі парогенератора.
Методи дослідження: При досліджуванні використовувався метод математичного моделювання за допомогою спеціалізованої програми «STEAMG» для теплового та гідравлічного розрахунку парогенератора.
Наукова новизна одержаних автором результатів полягає у наступному:
1. За допомогою спеціалізованої програми «STEAMG» було змодельовано процес теплообміну при кипінні рідини в вертикальній трубі.
2. Було визначено найбільш коректний з фізичної точки зору метод Чена для розрахунку теплообміну при русі двофазного потоку в каналі довільної форми.
3. Було отримано, що з ростом діаметра зовнішнього кожуха парогенератора в діапазоні D = 2,2…3,6 м відносні втрати тиску в холодному тракті парогенератора зростають на 7 % і знижуються зі збільшенням числа труб в трубному пучку на 11 %.
4. Відносні втрати тиску в гарячому тракті парогенератора невеликі і зменшуються з ростом діаметра зовнішнього кожуха і збільшенням числа труб в трубному пучку на 5 %.
5. З ростом діаметра зовнішнього кожуха парогенератора маса і об’єм теплопередавальних поверхонь парогенератора зростають на 10 % через зниження середньої швидкості первинного теплоносія, зниження значень коефіцієнта тепловіддачі і зростання потрібної довжини труб парогенератора.
6. В гарячому тракті значення коефіцієнта тепловіддачі при ηT = 0,925 на 15 % вище, ніж при ηT = 0,85.
Практичне значення даної роботи полягає в отриманні початкових даних для створення компактних високотемпературних теплообмінників ядерної енергетичної установки з гелієвим реактором по виробництву електроенергії та водню.
Апробація результатів роботи. Основні положення і результати роботи доповідались і обговорювались на конференції:
– ХVІ Науково практична конференція студентів аспірантів та молодих вчених «Теоретичні і прикладні проблеми фізики, математики та інформатики.», м. Київ, 2018 рThe Master's thesis consists of an introduction, three chapters, and conclusions. The total volume of the thesis is 101 pages, including 88 pages of the basic text, 31 figures, 4 tables, a list of references of 37 titles. Importance of scientific problem. The development of nuclear energy is currently aimed at the creation of a nuclear power plant based on the 4th generation environmentally friendly reactors. One of the possible concepts for such reactors is a modular helium reactor, in which helium is used as a coolant. Currently promising projects for the creation of gas-cooled UES of the 4th generation are being developed, which combine the production of electricity and hydrogen by high-temperature steam electrolysis, which is carried out in high-temperature steam generators. The greatest interest in the modeling of the steam generator EIEU is the flow of boiling fluid in a vertical channel of arbitrary shape. Therefore, finding the maximum possible compactness of the structure with sufficient strength and high thermo-hydraulic characteristics is an urgent problem. Relationship to scientific programs, plans and themes. The research work on the topic of the dissertation was conducted on the program of joint work with the "Department of Target Preparation" KPI them. Igor Sikorsky for the National Academy of Sciences of Ukraine in the direction №.1.7.1.AX.2 "Thermogasodynamics of turbulent flows in the rotary canals of high-temperature power plants" dated January 2, 2018, registration number 0118Г000006. The aim of this work is to study the thermohydraulic and geometrical parameters of the GT-MGG steam generator for the production of electricity and hydrogen, as well as to simulate the process of heat exchange during boiling liquid in a vertical pipe. Achieving the goal involves performing the following tasks: - To develop a mathematical model of the high-temperature steam generator EIEA of the fourth generation using helium as a primary coolant with spiral twisted (snake) pipes. - Modify the process of heat exchange with boiling liquids. - Explore the flow structure and characteristic heat transfer modes in the vertical pipe. - Realize five different methods of calculating heat transfer when boiling in a vertical pipe, based on experimental correlation dependencies. The object of research is the thermal-hydraulic processes in the steam generator of the nuclear power plant GT-MGR with a helium reactor for the production of electricity and hydrogen. The subject of research is the patterns and indicators of the effect on heat transfer and hydrodynamics from temperature and pressure at boiling liquid in the heat-exchange element of the steam generator. Research methodology: In the study, the method of mathematical modeling was used with the help of a specialized program "STEAMG" for thermal and hydraulic calculation of the steam generator. The scientific novelty of the results obtained by the author is as follows: 1. With the use of the STEAMG specialized program, the process of heat exchange during boiling liquid in a vertical pipe was simulated. 2. It was determined that the most correct from the physical point of view is the Chen method for calculating heat transfer in the movement of two-phase flow in a channel of arbitrary form. 3. It was found that with increasing diameter of the outer casing of the steam generator in the range D = 2,2…3,6 m relative pressure losses in the cold tract of the steam generator increase by 7% and decrease with an increase in the number of pipes in the tube bundle by 11%. 4. Relative pressure losses in the hot path of the steam generator are small and diminish with the growth of the diameter of the outer casing and the increase in the number of pipes in the tube bundle by 5%. 5. With the growth of the diameter of the outer casing of the steam generator, the mass and volume of the heat transfer surfaces of the steam generator increase by 10% due to the decrease in the average speed of the primary coolant, the decrease in the values of the coefficient of heat transfer and the growth of the required length of steam of the steam generator. 6. In the hot path, the value of the coefficient of heat transfer at ηT = 0,925 is 15% higher than at ηT = 0,85. The importance for practice of this work is to obtain the initial data for the creation of compact high-temperature heat exchangers of a nuclear power plant with a helium reactor for the production of electricity and hydrogen. Conferences. The main provisions and results of work were reported and discussed at the conference: - XVI Scientific and Practical Conference of Students of Postgraduate Students and Young Scientists "Theoretical and Applied Problems of Physics, Mathematics and Informatics.", Kyiv, 2018
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Kledy, Michel. "Développement d'une méthode de mesure des champs de vitesse et de température liquide en écoulement diphasique bouillant en conditions réacteurs ou simulantes." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI035.
Повний текст джерелаАнотація:
Ce travail de thèse constitue une contribution à la caractérisation des écoulements diphasiques bouillants convectifs à haute pression rencontrés dans les réacteurs à eau sous pression (REP) ou dans des conditions simulantes.La première partie présente un modèle bi-dimensionnel permettant de décrire le développement d'un écoulement bouillant dans une conduite circulaire (régime à bulle). La modélisation proposée est basée sur les équations locales stationnaires du mélange homogène fermées à l'aide d'un modèle de relaxation thermodynamique. Une confrontation des résultats avec les données expérimentales issues de la banque de donnée DEBORA a ensuite montré que si le modèle était capable de rendre compte de manière satisfaisante des résultats expérimentaux, les mécanismes de transport radiaux de la turbulence ainsi que de la vapeur étaient encore mal modélisés.La seconde partie de l'étude traite du développement de la thermo-anémométrie dans l'installation expérimentale DEBORA, afin de mesurer de manière colocalisée les champs de vitesse et de température liquide ainsi que le taux de vide en écoulement diphasique bouillant. La procédure expérimentale repose sur l'utilisation de sondes anémométriques classiques (sonde à film DANTEC@ 70 µm de diamètre, sonde à fil 2.5µm de 2.5 de diamètre) fonctionnant successivement à différentes surchauffes et pilotées à l'aide d'un anémomètre à courant constant. Des mesures ont d'abord été réalisées en écoulement monophasique chauffé, puis une procédure de discrimination phasique a été développée et a permis de fournir des premières mesures en écoulement bouillant. Ces dernières ont alors été comparées aux résultats du modèleThis study is a contribution to the comprehension of high pressure boiling flows relative to PWR.The first part exposes a two-dimensional unsteady state model in order to predict the development of a boiling flow in a circular pipe. The local mixture balanced equations are used with a relaxation model to close the vapor production rate (local homogeneous relaxation model). The results obtained from the comparison with the data bank DEBORA reveal a good qualitative agreement. Nerveless, the model is currently unable to correctly describe radial transports of turbulence and vapor fraction from the heated wall to the center of the pipe.The second part deals with the use of hot wire anemometry in experimental loop DEBORA to provide radial distributions of mean liquid velocity, mean liquid temperature and void fraction in a boiling flow. Classical hot wire probes are used (DANTEC@ hot film and hot wire probes) and are driven at different overheats using a constant current anemometer. Some measurements are first performed in single phase heated flows. Then, a phase identification procedure is developed, and some boiling flow measurements are obtained and compared with the model
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Witharana, Sanjeeva. "Boiling of refrigerants on enhanced surfaces and boiling of nanofluids." Licentiate thesis, KTH, Energy Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1589.
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Naylor, P. "Film boiling destabilisation." Thesis, University of Exeter, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370933.
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Doney, George Daniel. "Acoustic boiling detection." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28110.
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Huaiyu, Yang. "Crystallization of Parabens : Thermodynamics, Nucleation and Processing." Doctoral thesis, KTH, Teknisk strömningslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122228.
Повний текст джерелаАнотація:
In this work, the solubility of butyl paraben in 7 pure solvents and in 5 different ethanol-water mixtures has been determined from 1 ˚C to 50 ˚C. The solubility of ethyl paraben and propyl paraben in various solvents has been determined at 10 ˚C. The molar solubility of butyl paraben in pure solvents and its thermodynamic properties, measured by Differential Scanning Calorimetry, have been used to estimate the activity of the pure solid phase, and solution activity coefficients. More than 5000 nucleation experiments of ethyl paraben, propyl paraben and butyl paraben in ethyl acetate, acetone, methanol, ethanol, propanol and 70%, 90% ethanol aqueous solution have been performed. The induction time of each paraben has been determined at three different supersaturation levels in various solvents. The wide variation in induction time reveals the stochastic nature of nucleation. The solid-liquid interfacial energy, free energy of nucleation, nuclei critical radius and pre-exponential factor of parabens in these solvents have been determined according to the classical nucleation theory, and different methods of evaluation are compared. The interfacial energy of parabens in these solvents tends to increase with decreasing mole fraction solubility but the correlation is not very strong. The influence of solvent on nucleation of each paraben and nucleation behavior of parabens in each solvent is discussed. There is a trend in the data that the higher the boiling point of the solvent and the higher the melting point of the solute, the more difficult is the nucleation. This observation is paralleled by the fact that a metastable polymorph has a lower interfacial energy than the stable form, and that a solid compound with a higher melting point appears to have a higher solid-melt and solid-aqueous solution interfacial energy. It has been found that when a paraben is added to aqueous solutions with a certain proportion of ethanol, the solution separates into two immiscible liquid phases in equilibrium. The top layer is water-rich and the bottom layer is paraben-rich. The area in the ternary phase diagram of the liquid-liquid-phase separation region increases with increasing temperature. The area of the liquid-liquid-phase separation region decreases from butyl paraben, propyl paraben to ethyl paraben at the constant temperature. Cooling crystallization of solutions of different proportions of butyl paraben, water and ethanol have been carried out and recorded using the Focused Beam Reflectance Method, Particle Vision and Measurement, and in-situ Infrared Spectroscopy. The FBRM and IR curves and the PVM photos track the appearance of liquid-liquid phase separation and crystallization. The results suggest that the liquid-liquid phase separation has a negative influence on the crystal size distribution. The work illustrates how Process Analytical Technology (PAT) can be used to increase the understanding of complex crystallizations. By cooling crystallization of butyl paraben under conditions of liquid-liquid-phase separation, crystals consisting of a porous layer in between two solid layers have been produced. The outer layers are transparent and compact while the middle layer is full of pores. The thickness of the porous layer can reach more than half of the whole crystal. These sandwich crystals contain only one polymorph as determined by Confocal Raman Microscopy and single crystal X-Ray Diffraction. However, the middle layer material melts at lower temperature than outer layer material.QC 20130515
investigate nucleation and crystallization of drug-like organic molecules
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Giustini, Giovanni. "Microscopic modelling of boiling." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44077.
Повний текст джерелаАнотація:
One of the main thermal-hydraulic challenges of LWR modelling is the prediction of boiling phenomena. This thesis describes numerical and analytical studies aimed at modelling the heat transfer and hydrodynamics of a single steam bubble during nucleate boiling of water, aiming both to improve our current understanding of the phenomena - of the evaporation process itself, and of nucleate boiling heat transfer - and to improve our ability to predict such phenomena, at both single bubble and component scales. Analytical and CFD studies of bubble formation are described. These require accurate representations of evaporation from the liquid microlayer at the bubble base. This vaporization has been investigated from a molecular point of view, with modelling base on kinetic theory, and an apparent inconsistency in measurements of microlayer evaporation during bubble formation has been resolved, and an improved understanding of the molecular mechanism of phase-change thereby gained. The importance of including this improved representation of the evaporation process in single-bubble CFD simulations has been demonstrated. Aiming to improve the closure relations employed for component-scale CFD simulation of boiling flows, interface-tracking modelling of bubble growth and release has been used. Single-bubble interface-tracking models have been developed in an attempt to quantify the transient conduction ('quenching') component of nucleate boiling heat transfer, associated with bubble lift-off. These mechanistic models allowed detailed quantification of the complex physics associated with bubble growth, and with quenching of the dry area at the bubble base that takes place at bubble departure. A large discrepancy was observed between estimates of the quench heat transfer from these interface-tracking simulations, and that incorporated in the more approximate modelling embodied in the closure relations widely used in component scale CFD.
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Kew, Peter Arthur. "Boiling in narrow channels." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/748.
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Douglas, Zachary W. "Acoustically Enhanced Boiling Heat Transfer." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16325.
Повний текст джерелаАнотація:
An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.
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Athavale, Advait D. "EXPERIMENTAL STUDY OF SATURATED NUCLEATE POOL BOILING IN AQUEOUS POLYMERIC SOLUTIONS." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1314758640.
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Olayiwola, Nurudeen Oladipupo. "Boiling in Mini and Micro-Channels." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7148.
Повний текст джерелаАнотація:
Cooling systems that consist of mini-channels (hydraulic diameters in the 0.5 mm to 2.0 mm range) and micro-channels (hydraulic diameters in the 100 m-500 m range) can dispose of extremely large volumetric thermal loads that are well beyond the feasible operating range of conventional cooling methods. Mini/micro-channel systems that utilize boiling fluids are particularly useful due to the superiority of boiling heat transfer mode over single-phase flow convection. Although forced flow boiling in mini and micro-channels has been investigated by several research groups in the past, a verified and reliable predictive method is not yet available.
In this study, the capability of a large number of forced flow boiling heat transfer correlations for application to mini channels is examined by comparing their predictions with three experimental data sets. The data all represent recently-published experiments with mini-channels The tested correlations include well-established methods for forced-flow boiling in conventional boiling systems, as well as correlations recently proposed for mini-channels.
Based on these comparisons, the most accurate existing predictive methods for mini-channel boiling are identified. The deficiencies of the predictive methods and the potential causes that underlie these deficiencies are also discussed.
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Pascual, Christopher C. "EHD enhancement of nucleate pool boiling." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19027.
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Wen, Dongsheng. "Flow boiling heat transfer in microgeometries." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414305.
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Aziz, S. "Forced convection film boiling on spheres." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371536.
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Bentley, Thomas Keith. "Oscillatory behavior in boiling water reactors." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0003800.
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Sriraman, Sharan Ram. "Pool boiling on nano-finned surfaces." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2091.
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