Дисертації з теми "Cooling dynamics"
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1
Ryjkov, Vladimir Leonidovich. "Laser cooling and sympathetic cooling in a linear quadrupole rf trap." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1637.
Повний текст джерелаАнотація:
An investigation of the sympathetic cooling
method for the studies of large ultra-cold molecular ions in a quadrupole ion trap has been conducted.Molecular dynamics simulations are performed to study the rf heating mechanisms in the ion trap. The dependence of
rf heating rates on the ion temperature, trapping parameters,
and the number of ions is obtained. New rf heating mechanism
affecting ultra-cold ion clouds exposed to laser radiation is described.The saturation spectroscopy setup of the hyperfine spectra
of the molecular iodine has been built to provide an accurate frequency reference for the laser wavelength. This reference is used to obtain the fluorescence lineshapes of
the laser cooled Mg$^+$ ions under different trapping conditions.The ion temperatures are deduced from the measurements, and
the influence of the rf heating rates on the fluorescence lineshapes
is also discussed. Cooling of the heavy ($m=720$a.u.) fullerene ions to under 10K by the means of the sympathetic cooling by the Mg$^+$ ions($m=24$a.u.) is demonstrated. The single-photon imaging system has been developed and used to obtain the images of the Mg$^+$ ion crystal structures at mK temperatures.
2
Rogers, Chris. "Beam Dynamics in an Ionisation Cooling Channel." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499277.
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3
Sargison, Jane Elizabeth. "Development of a novel film cooling hole geometry." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365427.
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4
Dall'Olio, Giacomo. "CFD study of electric motor's cooling." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Знайти повний текст джерелаАнотація:
Nowadays electrification is one of the leading fields of engineering as it is seen as one of the key factors that can reduce environmental impact of human activities by reducing theirs polluting emissions. Mobility is the sector in which electric driven systems are diffusing the most. The search for performance in one of its main component, the electric motor, is therefore of fundamental importance in terms of efficiency and reliability of every electric driven applications. The optimization of thermal aspects covers a primary role and highly affect power consumption and lifetime of components. With this intent the use of CFD, Computational Fluid Dynamics, allows to exploit most of heat transfer aspects which concurs on thermal behavior both for design phase and performance estimations.
The work of this thesis investigates the cooling performances of the motor driving an electric vehicle made by Engines Engineering -EE- which is a company that projects motorbikes for thirds and is recently going to expand in the field of electric mobility. Beside the specific case studied, the methods can be extended to any component which require a thermal management as CFD tools are fundamental in a very wide spectrum of application in engineering.
5
Petters, Jonathan L. Clothiaux Eugene. "The impact of radiative heating and cooling on marine stratocumulus dynamics." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4602/index.html.
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6
Gudmundsson, Yngvi. "Performance evaluation of wet-cooling tower fills with computational fluid dynamics." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/19908.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: A wet-cooling tower fill performance evaluation model developed by Reuter is derived in Cartesian coordinates for a rectangular cooling tower and compared to cross- and counterflow Merkel, e-NTU and Poppe models. The models are compared by applying them to a range of experimental data measured in the cross- and counterflow wet-cooling tower test facility at Stellenbosch University. The Reuter model is found to effectively give the same results as the Poppe method for cross- and counterflow fill configuration as well as the Merkel and e-NTU method if the assumptions as made by Merkel are implemented. A second order upwind discretization method is applied to the Reuter model for increased accuracy and compared to solution methods generally used to solve cross- and counterflow Merkel and Poppe models. First order methods used to solve the Reuter model and crossflow Merkel and Poppe models are found to need cell sizes four times smaller than the second order method to obtain the same results. The Reuter model is successfully implemented in two- and three-dimensional ANSYS-Fluent® CFD models for under- and supersaturated air. Heat and mass transfer in the fill area is simulated with a user defined function that employs a second order upwind method. The two dimensional ANSYS-Fluent® model is verified by means of a programmed numerical model for crossflow, counterflow and cross-counterflow.
AFRIKAANSE OPSOMMING: ‘n Natkoeltoring model vir die evaluering van pakkings werkverrigting, wat deur Reuter ontwikkel is, word in Kartesiese koördinate afgelei vir ‘n reghoekige koeltoring en word vergelyk met kruis- en teenvloei Merkel, e-NTU en Poppe modelle. Die verskillende modelle word vergelyk deur hulle op ‘n reeks eksperimentele data toe te pas wat in die kruis- en teenvloei natkoeltoring toetsfasiliteit by die Universiteit van Stellenbosch gemeet is. Dit is bevind dat die Reuter model effektief dieselfde resultate gee as die Poppe model vir kruis- en teenvloei pakkingskonfigurasies sowel as die Merkel en e-NTU metode, indien dieselfde aannames wat deur Merkel gemaak is geїmplementeer word. ‘n Tweede orde “upwind” metode word op die Reuter model toegepas vir hoër akkuraatheid en word vergelyk met oplossingsmetodes wat gewoonlik gebruik word om kruis- en teenvloei Merkel en Poppe modelle op te los. Eerste orde metodes wat gebruik is om die Reuter model en kruisvloei Merkel en Poppe modelle op te los benodig rooster selle wat vier keer kleiner is as vir tweede orde metodes om dieselfde resultaat te verkry. Die Reuter model is suksesvol in twee- en driedimensionele ANSYS-Fluent® BVD (“CFD”) modelle geїmplementeer vir on- en oorversadigde lug. Warmte- en massaoordrag in die pakkingsgebied word gesimuleer mbv ‘n gebruiker gedefinieerde funksie (“user defined function”) wat van ‘n tweede orde numeriese metode gebruik maak. Die tweedimensionele ANSYS-Fluent® model word m.b.v. ‘n geprogrameerde numeriese model bevestig vir kruis-, teen- en kruis-teenvloei.
7
Khan, Jobaidur Rahman. "Fog Cooling, Wet Compression and Droplet Dynamics In Gas Turbine Compressors." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/908.
Повний текст джерелаАнотація:
During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.
8
Dunn, Josh W. "Stochastic models of atom-photon dynamics with applications to cooling quantum gases." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273696.
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Lippmann, Jan Frederik [Verfasser]. "Laser Cooling of Semiconductors: Ultrafast Carrier and Lattice Dynamics / Jan Frederik Lippmann." München : Verlag Dr. Hut, 2018. http://d-nb.info/1172581983/34.
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10
Johansson, Adam, and Jonas Gunnarsson. "Predicting Flow Dynamics of an Entire Engine Cooling System Using 3D CFD." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62763.
Повний текст джерелаАнотація:
A combustion engine generates a lot of heat which need to be cooled to prevent damages to the engine and the surrounding parts. If the cooling system can not provide enough cooling to keep the engine in a well defined range of temperatures performance and durability will decrease and emissions increase. It is also important that the cooling system do not over-cool the engine, since this may result in rough running, increased engine friction and an overall negative performance. The aim of this thesis work is to create a complete 3D digital model of the cooling system for the first generation VED4 HP with CFD in STAR-CCM+. The simulated results are compared to available experimental data for validation. Today the entire system is being modeled with 1D CFD. One of the selected components in the cooling system being model in 3D at Volvo Cars is the water jacket. The 3D CFD model depends on the 1D CFD model for the boundary conditions which is an ineffective and time consuming process, sending data back and forth between the models when making changes. A 3D CFD model is not only more accurate than the 1D CFD model, since it capture the 3D flow phenomenas but it also allows parts or areas to be studied in detail. A study of four different turbulence models is conducted on the water jacket and on an arbitrary pipe in the cooling system. A mesh study is carried on the water jacket, the same arbitrary pipe and on the thermostat, both for the opened and closed thermostat. These studies are done with regard to pressure drop only. The study yields a low Reynolds model with the k-ε v2f turbulence model gave the best results. There is a discrepancy between the simulated results and the experiments. Main reasons to this may be the difference in the geometry used in this thesis for the digital model and the geometry used for the experiments together with the inaccuracies in the experimental data. The overall deviation is larger for a case with closed thermostat than for a case with an open thermostat. With the correct geometry and more accurate experimental data the simulations should be a close representation of reality.
11
Vera, Vidal Camila Constanza. "Analysis of cooling effects and non-Newtonian rheology on lava flow dynamics." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/169867.
Повний текст джерелаАнотація:
Tesis para optar al grado de Doctor en Ciencias, Mención GeologíaMemoria para optar al título de Geóloga
La actividad volcanica representa una gran amenaza para la propiedad privada, comunidades y habitantes ubicados en las cercanias de centros volcanicos. La volcanologia y mecanica de fluidos se utilizan en conjunto con el fin de estudiar la evolucion de los flujos de lava. Nos enfocamos en el estudio de flujos de lava simples y viscosos, de composiciones andesitica hasta riolitica, para determinar la relevancia de la evolucion reologica del flujo en tiempos de emplazamiento, distancias, y proporciones finales. Los experimentos analogos han sido una herramienta util en previos estudios de flujos de lava. Para este trabajo se caracterizo el manjar, un derivado de la leche, para utilizarlo como material analogo de lava viscosa con una reologia dependiente de la temperatura. Los experimentos simularon un flujo no confinado simple sobre una superficie inclinada, en el Laboratorio de Volcanologia Experimental del Laboratoire de Magmas et Volcans, Clermont-Ferrand, Francia. Un total de 33 experimentos de extrusiones puntuales sobre una superficie inclinada, con caudales desde 1 $ (cc/s) $ a 25 $ (cc/s) $, con inclinaciones entre 10$^\circ$ - 15$^\circ$, y diferentes temperaturas iniciales desde ambiente hasta 71\textcelsius{}. Cada experimento fue grabado con camara visual y camara termica, con los cuales se pudo obtener la evolucion termica y las distancias en el tiempo a las que avanzaba cada flujo. Se utilizo python para obtener la base de datos de temperatura, y bibliotecas especificas para manejar, procesar y visualizar datos, tales com matplotlib, scipy y pandas. Los resultados indican que la formacion de una pseudo corteza en los flujos de manjar que estan sujetos a enfriamiento, controlan las distintas dimensiones y tiempos de emplazamiento obtenidos para los flujos estudiados, mientras que los cambios de pendiente tambien juegan un rol importante en estos resultados. La existencia de esta pseudo corteza esta basada en la perdida de agua presente en el manjar, asi como tambien en la buena correlacion existente que muestra el numero de Graetz con las diferentes dimensiones obtenidas, que dependen de la tasa efusiva, la escala de tiempo de extrusion, y por ende el desarrollo de esta corteza obtenida segun estimaciones basadas en la difusividad termica del material. Mayores caudales presentan flujos mas anchos con menores espesores, mientras que menores caudales se desarrollan de manera vertical, teniendo menor expansion areal y mayores espesores. Mayores pendientes resultan en flujos que se desarrollan principalmente pendiente abajo, con distancias de $ X_{min} $ e $ Y_{max} $ menores. Por otro lado, la comparacion entre flujos sujetos a enfriamiento versus flujos en condiciones isotermales, tambien apoyan la teoria de existencia de una pseudo corteza que controla la dinamica de flujo. Los modelos DEM realizados presentan caracteristicas similares a las presentes en flujos de lava, con zonas de menor espesor cerca del punto extrusivo, seguido por un posible canal central entre estructuras tipo levee que culminan en un frente de flujo de gran espesor, presentando la mayor potencia del flujo. Este frente de flujo inflado, consideramos que es evidencia de que existe una pseudo corteza que contiene material con mayor movilidad en su interior. Los perfiles de temperatura de termocuplas y FLIR, tambien muestran como existe un perfil termal vertical en los flujos, con altas temperaturas en porciones internas luego de que todo el material ya ha sido extruido, mientras la superficie del flujo presenta menores temperaturas.
12
Maletzke, Fabian. "Investigation Of The Influence Of Geometrical Parameters On Heat Transfer In Matrix Cooling : A Computational Fluid Dynamics Approach." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-177185.
Повний текст джерелаАнотація:
Modern gas turbine blades and vanes are operated at temperatures above their material’s melting point. Active external and internal cooling are therefore necessary to reach acceptable lifetimes. One possible internal cooling method is called matrix cooling, where a matrix of intersecting cooling air channels is integrated into a blade or vane. To further increase the efficiency of gas turbines, the amount of cooling air must be reduced. Therefore it is necessary that heat transfer inside a cooling matrix is well understood. In the first part of the thesis, a methodology for estimating heat transfer in the flow of matrix cooling channels was established using Computational Fluid Dynamics. Two four-equation RANS turbulence models based on the k-ε turbulence model showed a good correlation with experimental results, while the k-ω SST model underpredicted the heat transfer significantly. For all turbulence models, the heat transfer showed high sensitivity towards changes in the numerical setup. For the k-ω SST turbulence model, the mesh requirements were deemed too computationally expensive and it was excluded from further investigations. As the second part of the thesis, a parameter study was conducted investigating the influence of several geometric parameters on the heat transfer in a cooling matrix. The matrix was simplified as a channel flow interacting with multiple crossing flows. The highest enhancement in heat transfer was seen with changes in taper ratio, aspect ratio and matrix angle. Compared to smooth pipe flow, an increase in heat transfer of up to 60% was observed. Rounded edges of the cooling channels showed a significant influence on the heat transfer as well. In contrast, no influence of the wall thickness on the heat transfer was observed. While no direct validation is possible, the base case and the parameter sweeps show a good correlation with similar cases found in the literature.
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Gerty, Donavon R. "Fluidic driven cooling of electronic hardware." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31722.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Glezer, Ari; Committee Member: Alben, Silas; Committee Member: Joshi, Yogendra; Committee Member: Smith, Marc; Committee Member: Webster, Donald. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Tran, Nghia Trong Van. "Film cooling with wake passing applied to an annular endwall." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4582.
Повний текст джерелаАнотація:
Advancement in turbine technology has far reaching effects on today's society and environment. With more than 90% of electricity and 100% of commercial air transport being produced by the usage of gas turbine, any advancement in turbine technology can have an impact on fuel used, pollutants and carbon dioxide emitted to the environment. Within the turbine engine, fully understanding film cooling is critical to reliability of a turbine engine. Film cooling is an efficient way to protect the engine surface from the extremely hot incoming gas, which is at a temperature much higher than allowable temperature of even the most advanced super alloy used in turbine. Film cooling performance is affected by many factors: geometrical factors and as well as flow conditions. In most of the film cooling literature, film effectiveness has been used as criterion to judge and/or compare between film cooling designs. Film uniformity is also a critical factor, since it determines how well the coolant spread out downstream to protect the hot-gas-path surface of a gas turbine engine. Even after consideration of all geometrical factors and flow conditions, the film effectiveness is still affected by the stator-rotor interaction, in particular by the moving wakes produced by upstream airfoils. A complete analysis of end wall film cooling inside turbine is required to fully understand the phenomena. This full analysis is almost impossible in the academic arena. Therefore, a simplified but critical experimental rig and computational fluid model were designed to capture the effect of wake on film cooling inside an annular test section. The moving wakes are created by rotating a wheel with 12 spokes or rods with a variable speed motor. Thus changing the motor speed will alter the wake passing frequency. This design is an advancement over most previous studies in rectangular duct, which cannot simulate wakes in an annular passage as in an engine.; This rig also includes film injection that allows study of impact of moving wakes on film cooling. This wake is a simplified representation of the trailing edge created by an upstream airfoil. An annulus with 30?? pitch test section is considered in this study. This experimental rig is based on an existing flat plate film cooling (BFC) rig that has been validated in the past. Measurement of velocity profiles within the moving wake downstream from the wake generator is used to validate the CFD rotating wake model. The open literature on film cooling and past experiments performed in the laboratory validated the CFD film cooling model. With these validations completed, the full CFD model predicts the wake and film cooling interaction. Nine CFD cases were considered by varying the film cooling blowing ratio and the wake Strouhal number. The results indicated that wakes highly enhance film cooling effectiveness near film cooling holes and degrades the film blanket downstream of the film injection, at the moment of wake passing. However, the time-averaged film cooling effectiveness is more or less the same with or without wake.ID: 029049607; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.E.)--University of Central Florida, 2010.; Includes bibliographical references (p. 118-123).
M.S.M.E.
Masters
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
15
Rathsman, Karin. "Modeling of Electron Cooling : Theory, Data and Applications." Doctoral thesis, Uppsala universitet, Kärnfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-129686.
Повний текст джерелаАнотація:
The Vlasov technique is used to model the electron cooling force. Limitations of the applicability of the method is obtained by considering the perturbations of the electron plasma. Analytical expressions of the electron cooling force, valid beyond the Coulomb logarithm approximation, are derived and compared to numerical calculations using adaptive Monte Carlo integration. The calculated longitudinal cooling force is verified with measurements in CELSIUS. Transverse damping rates of betatron oscillations for a nonlinear cooling force is explored. Experimental data of the transverse monochromatic instability is used to determine the rms angular spread due to solenoid field imperfections in CELSIUS. The result, θrms= 0.16 ± 0.02 mrad, is in agreement with the longitudinal cooling force measurements. This verifies the internal consistency of the model and shows that the transverse and longitudinal cooling force components have different velocity dependences. Simulations of electron cooling with applications to HESR show that the momentum reso- lution ∆p/p smaller than 10−5 is feasible, as needed for the charmonium spectroscopy in the experimental program of PANDA. By deflecting the electron beam angle to make use of the monochromatic instability, a reasonable overlap between the circulating antiproton beam and the internal target can be maintained. The simulations also indicate that the cooling time is considerably shorter than expected.
16
Schlesinger, Daniel. "Molecular structure and dynamics of liquid water : Simulations complementing experiments." Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-120808.
Повний текст джерелаАнотація:
Water is abundant on earth and in the atmosphere and the most crucial liquid for life as we know it. It has been subject to rather intense research since more than a century and still holds secrets about its molecular structure and dynamics, particularly in the supercooled state, i. e. the metastable liquid below its melting point. This thesis is concerned with different aspects of water and is written from a theoretical perspective. Simulation techniques are used to study structures and processes on the molecular level and to interpret experimental results. The evaporation kinetics of tiny water droplets is investigated in simulations with focus on the cooling process associated with evaporation. The temperature evolution of nanometer-sized droplets evaporating in vacuum is well described by the Knudsen theory of evaporation. The principle of evaporative cooling is used in experiments to rapidly cool water droplets to extremely low temperatures where water transforms into a highly structured low-density liquid in a continuous and accelerated fashion. For water at ambient conditions, a structural standard is established in form of a high precision radial distribution function as a result of x-ray diffraction experiments and simulations. Recent data even reveal intermediate range molecular correlations to distances of up to 17 Å in the bulk liquid. The barium fluoride (111) crystal surface has been suggested to be a template for ice formation because its surface lattice parameter almost coincides with that of the basal plane of hexagonal ice. Instead, water at the interface shows structural signatures of a high-density liquid at ambient and even at supercooled conditions. Inelastic neutron scattering experiments have shown a feature in the vibrational spectra of supercooled confined and protein hydration water which is connected to the so-called Boson peak of amorphous materials. We find a similar feature in simulations of bulk supercooled water and its emergence is associated with the transformation into a low-density liquid upon cooling.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.
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Boufadel, George Fadlo. "Dynamic thermal response of buildings resulting from heating and cooling interruptions." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/74757.
Повний текст джерелаАнотація:
Transient modelling of heat fluxes and temperatures in structures was conducted to examine the effect of various characteristics on the temperature response during unusual operating and extreme weather conditions. The analytical model was validated using published experimental data and numerical results from well-known computer codes.
The effect of including radiation heat transfer between interior surfaces, using the Mean Radiative Temperature method, on the temperature response was investigated and found to be negligible for a typical commercial building and a house during winter and summer power outages.
The effect of thermal mass in the interior and exterior walls on the inside temperature drift after an HVAC system cutoff or a power outage was presented. The inside air temperature response curve is presented for different wall (exterior or interior) constructions of buildings. The effect of insulation position in exterior walls was also shown for several R values. The effect of exterior wall emissivity, sky temperature, outside vertical convective coefficient, furnishings, and ground temperature on the interior temperature response during winter and summer power outages were examined for buildings.
The effect of infiltration on the temperature drift in buildings was investigated during winter and summer power outages. Restarting the HVAC after the power outage was examined during both seasons for typical buildings.
Outside temperature profiles exceeding the 97.5 design temperature criterion were used to study the effect of extreme weather on the interior temperature of buildings with the HVAC system operating.Ph. D.
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Yata, Vishnu Vardhan Reddy. "Investigation of Spray Cooling Schemes for Dynamic Thermal Management." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984153/.
Повний текст джерелаАнотація:
This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 μm thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and ~10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2 - 5 ml/cm².s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.
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Backman, Björn. "Future Upgrades of the LHC Beam Screen Cooling System." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7727.
Повний текст джерелаАнотація:
The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used.
There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon.
For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used.
When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is.
For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.
20
Wang, Yong. "Microfluidic technology for integrated thermal management: micromachined synthetic jet." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5438.
Повний текст джерела
21
Carson, Robert J. "Critical heat flux for a heated surface impacted by a stream of liquid droplets." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/19579.
Повний текст джерела
22
Forbes, Richard M. "Numerical model parametrization of ice microphysics and the impact of evaporative cooling on frontal dynamics." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397748.
Повний текст джерела
23
Aljohani, Faraj Jaber R. "Improving Cooling Effectiveness in Air-Cooled Data Centres: Analysis and Assessment using Computational Fluid Dynamics." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75227.
Повний текст джерелаАнотація:
Datacentre efficiency becomes increasingly important as demand for IT infrastructure grows. This thesis presents detailed Computational Fluid Dynamics analyses of flow and heat transfer within typical raised floor datacentres. Compared with previous studies, greater understanding of the unsteady flow and heat transfer in datacentres resulted from using Scale-Adaptive turbulence modelling instead of a RANS approach. This led to a novel rack-level sub-cooler design, which was shown to allow higher volumetric heat generation rates within datacentres.
24
Orhan, Omer Emre. "Numerical Investigation On Cooling Of Small Form Factor Computer Cases." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608160/index.pdf.
Повний текст джерелаАнотація:
In this study, cooling of small form factor computer is numerically investigated.
The numerical model is analyzed using a commercial computational fluid
dynamics software Icepak&trade. The effects of grid selection, discretization schemes and turbulence models are discussed and presented. In addition, physical phenomena like recirculation and relaminarization are addressed briefly. For a comparison with the computational fluid dynamics results, an experiment is conducted and some temperature measurements are obtained from critical locations inside the chassis.The computational results were found to be in good agreement with the experimental ones.
25
Miller, Mark W. "Heat transfer in a coupled impingement-effusion cooling system." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4807.
Повний текст джерелаАнотація:
The efficiency of air-breathing gas turbine engines improves as the combustion temperature increases. Therefore, modern gas turbines operate at temperatures greater than the melting temperature of hot-gas-path components, and cooling must be introduced in order to maintain mechanical integrity of those components. Two highly effective techniques used in modern designs for this purpose are impingement cooling and use of coolant film on hot-gas-path surface introduced through discrete film or effusion holes. In this study, these two mechanisms are coupled into a single prototype cooling system. The heat transfer capability of this system is experimentally determined for a variety of different geometries and coolant flow rates. This study utilizes Temperature Sensitive Paint (TSP) in order to measure temperature distribution over a surface, which allowed for local impingement Nusselt number, film cooling effectiveness, and film cooling heat transfer enhancement profiles to be obtained. In addition to providing quantitative heat transfer data, this method allowed for qualitative investigation of the flow behavior near the test surface. Impinging jet-to-target-plate spacing was varied over a large range, including several tall impingement scenarios outside the published limits. Additionally, both in-line and staggered effusion arrangements were studied, and results for normal injection were compared to full coverage film cooling with inclined- and compound-angle injection. Effects of impingement and effusion cooling were combined to determine the overall cooling effectiveness of the system. It is shown that low impingement heights produce the highest Nusselt number, and that large jet-to-jet spacing reduces coolant flow rate while maintaining moderate to high heat transfer rates. Staggered effusion configurations exhibit superior performance to in-line configurations, as jet interference is reduced and surface area coverage is improved. Coolant to mainstream flow mass flux ratios greater than unity result in jet blow-off and reduced effectiveness. The convective heat transfer coefficient on the film cooled surface is higher than a similar surface without coolant injection due to the generation of turbulence associated with jet-cross flow interaction.ID: 030646180; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; .; Thesis (M.S.M.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 171-176).
M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Thermo-Fluids Track
26
Virdi, Amandeep Singh. "Aero-thermal performance and enhanced internal cooling of unshrouded turbine blade tips." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:62c3e94a-a1ff-47a8-bb81-e870b0013f11.
Повний текст джерелаАнотація:
The tips of unshrouded, high-pressure turbine blades are prone to significantly high heat loads. The gap between the tip and over-tip casing is the root cause of undesirable over-tip leakage flow that is directly responsible for high thermal material degradation and is a major source of aerodynamic loss within a turbine. Both must be minimised for the safe working and improved performance of future gas-turbines. A joint experimental and numerical study is presented to understand and characterise the heat transfer and aerodynamics of unshrouded blade tips. The investigation is undertaken with the use of a squealer or cavity tip design, known for offering the best overall compromise between the tip aerodynamics, heat transfer and mechanical stress. Since there is a lack of understanding of these tips at engine-realistic conditions, the present study comprises of a detailed analysis using a high-speed linear cascade and computational simulations. The aero-thermal performance is studied to provide a better insight into the behaviour of squealer tips, the effects of casing movement and tip cooling. The linear cascade environment has proved beneficial for its offering of spatially-resolved data maps and its ability to validate computational results. Due to the unknown tip gap height within an entire engine cycle, the effects of gap height are assessed. The squealer's aero-thermal performance has been shown to be linked with the gap height, and qualitative different trends in heat transfer are established between low-speed and high-speed tip flow regimes. To the author's knowledge, the present work is the first of its kind, providing comprehensive aero-thermal experimental research and a dataset for a squealer tip at engine-representative transonic conditions. It is also unique in terms of conducting direct and systematic validations of a major industrial computational fluid dynamics method for aero-thermal performance prediction of squealer tips at enginerepresentative transonic conditions. Finally, after recognising the highest heat loads are found on the squealer rims, a novel shaped squealer tip has been investigated to help improve the thermal performance of the squealer with a goal to improve its durability. It has been discovered that a seven percent reduction in tip temperature can be achieved through incorporating a shaped squealer and maximising the internal cooling performance.
27
Selva, Francesco. "Seismic performance of rooftop cooling towers in buildings." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4884/.
Повний текст джерелаАнотація:
Negli ultimi anni la ricerca ha fatto grandi passi avanti riguardo ai metodi di progetto e realizzazione delle strutture portanti degli edifici, a tal punto da renderle fortemente sicure sotto tutti i punti di vista. La nuova frontiera della ricerca sta quindi virando su aspetti che non erano mai stati in primo piano finora: gli elementi non-strutturali. Considerati fino ad oggi semplicemente carico accessorio, ci si rende sempre più conto della loro capacità di influire sui comportamenti delle strutture e sulla sicurezza di chi le occupa. Da qui nasce l’esigenza di questo grande progetto chiamato BNCs (Building Non-structural Component System), ideato dall’Università della California - San Diego e sponsorizzato dalle maggiori industrie impegnate nel campo delle costruzioni. Questo progetto, a cui ho preso parte, ha effettuato test su tavola vibrante di un edificio di cinque piani in scala reale, completamente arredato ed allestito dei più svariati elementi non-strutturali. Lo scopo della tesi in questione, ovviamente, riguarda l’identificazione strutturale e la verifica della sicurezza di uno di questi elementi non-strutturali: precisamente la torre di raffreddamento posta sul tetto dell’edificio (del peso di circa 3 tonnellate). Partendo da una verifica delle regole e calcoli di progetto, si è passato ad una fase di test sismici ed ispezioni post-test della torre stessa, infine tramite l’analisi dei dati raccolti durante i test e si è arrivati alla stesura di conclusioni.
28
Reuter, Hanno Carl Rudolf. "Performance evaluation of natural draught cooling towers with anisotropic fills." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5440.
Повний текст джерелаАнотація:
Thesis (PhD) -- University of Stellenbosch, 2010.ENGLISH ABSTRACT: In the design of a modern natural draught wet-cooling tower (NDWCT), structural and performance characteristics must be considered. Air flow distortions and resistances must be minimised to achieve optimal cooling which requires that the cooling towers must be modelled two-dimensionally and ultimately threedimensionally to be optimised. CFD models in literature are found to be limited to counterflow cooling towers packed with film fill, which is porous in one direction only and generally has a high pressure drop, as well as purely crossflow cooling towers packed with splash fill. This simplifies the analysis considerably as the effects of flow separation at the air inlet are minimised and fill performance is determined using the method of analysis originally employed to determine the fill performance characteristics from test data. Many counterflow cooling towers are, however, packed with trickle and splash fills which have anisotropic flow resistances, which means the fills are porous in all flow directions and thus air flow can be oblique through the fill, particularly near the cooling tower air inlet. This provides a challenge since available fill test facilities and subsequently fill performance characteristics are limited to purely counter- and crossflow configuration. In this thesis, a CFD model is developed to predict the performance of NDWCTs with any type of spray, fill and rain zone configuration, using the commercial code FLUENT®. This model can be used to investigate the effects of different: atmospheric temperature and humidity profiles, air inlet and outlet geometries, air inlet heights, rain zone drop size distributions, spray zone performance characteristics, variations in radial water loading and fill depth, and fill configurations or combinations on cooling tower performance, for optimisation purposes. Furthermore the effects of damage or removal of fill in annular sections and boiler flue gas discharge in the centre of the tower can be investigated. The CFD modelling of NDWCTs presents various options and challenges, which needed to be understood and evaluated systematically prior to the development of a CFD model for a complete cooling tower. The main areas that were investigated are: spray and rain zone performance modelling by means of an Euler-Lagrangian model; modelling of air flow patterns and flow losses; modelling of fill performance for oblique air flow; modelling of air pressure and temperature profiles outside and inside the cooling tower. The final CFD results for the NDWCT are validated by means of corresponding one-dimensional computational model data and it is found that the performance of typical NDWCTs can be enhanced significantly by including protruding platforms or roundings at the air inlet, reducing the mean drop size in the rain zone, radially varying the fill depth and reducing the air inlet height.
AFRIKAANSE OPSOMMING: By die ontwerp van ‘n moderne natuurlike trek nat koeltoring (NTNK), moet strukturele en werkverrigtings eienskappe in ag geneem word. Wanverdeelde lugvloei en vloeiweerstande moet geminimaliseer word om optimale verkoeling te bewerkstellig, wat vereis dat die koeltorings twee-dimensioneel en uiteindelik driedimensioneel gemodelleer moet word om hulle te kan optimeer. Dit is gevind dat berekeningsvloeidinamika (BVD of “CFD” in engels) modelle in die literatuur, beperk is tot teenvloei koeltorings gepak met film tipe pakking, wat net in een vloeirigting poreus is en boonop gewoonlik ook ‘n hoë drukval het, sowel as suiwer dwarsvloei koeltorings met spatpakking. Hierdie vergemaklik die analise aansienlik omdat die effekte van vloeiwegbreking by die luginlaat verklein word en die pakking se werkverrigtingsvermoë bereken kan word met die analise metode wat oorspronklik gebruik is om die pakkingseienskappe vanaf toets data te bepaal. Baie teenvloei koeltorings het egter drup- (“trickle”) of spatpakkings met anisotropiese vloeiweerstand, wat beteken dat die pakking poreus is in alle vloeirigtings en dat die lug dus skuins deur die pakking kan vloei, veral naby die koeltoring se lug inlaat. Hierdie verskaf ‘n uitdaging aangesien beskikbare pakking toetsfasiliteite, en dus ook pakking karakteristieke, beperk is tot suiwer teenvloei en dwarsvloei konfigurasie. ‘n BVD model word in hierdie tesis ontwikkel wat die werkverrigtingsvermoë van NTNK’s kan voorspel vir enige sproei, pakking en reënsone konfigurasie deur van die kommersiële sagteware FLUENT® gebruik te maak. Hierdie model kan gebruik word om die effekte van verskillende: atmosferiese temperatuur- en humiditeitsprofiele, lug inlaat en uitlaat geometrië, lug inlaat hoogtes, reënsone druppelgrootteverdelings, sproeisone werkverrigtingskarakteristieke, variasie in radiale waterbelading en pakking hoogte, en pakking konfigurasies of kombinasies op koeltoringvermoë te ondersoek vir optimerings doeleindes. Verder kan die effekte van beskadiging of verwydering van pakking in annulêre segmente, en insluiting van ‘n stoomketel skoorsteen in die middel van die toring ondersoek word. Die BVD modellering van NTNK bied verskeie moontlikhede en uitdagings, wat eers verstaan en sistematies ondersoek moes word, voordat ‘n BVD model van ‘n algehele NTNK ontwikkel kon word. Die hoof areas wat ondersoek is, is: sproeien reënsone modellering mbv ‘n Euler-Lagrange model; modellering van lugvloeipatrone en vloeiverliese; modellering van pakking verrigting vir skuins lugvloeie; modellering van lugdruk- en temperatuurprofiele buite en binne in die koeltoring. Die BVD resultate word mbv van data van ‘n ooreenstemmende eendimensionele berekeningsmodel bevestig en dit is bevind dat die werkverrigting van ‘n tipiese NTNK beduidend verbeter kan word deur: platforms wat uitstaan of rondings by die luginlaat te installeer, die duppelgrootte in die reënsone te verklein, die pakkingshoogte radiaal te verander, en die luginlaathoogte te verlaag.
29
Ravi, Bharath Viswanath. "Heat Transfer Performance Improvement Technologies for Hot Gas Path Components in Gas Turbines." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71352.
Повний текст джерелаАнотація:
In the past few decades, the operating temperatures of gas turbine engines have increased significantly with a view towards increasing the overall thermal efficiency and specific power output. As a result of increased turbine inlet temperatures, the hot gas path components downstream of the combustor section are subjected to high heat loads. Though materials with improved temperature capabilities are used in the construction of the hot gas path components, in order to ensure safe and durable operation, the hot gas path components are additionally supplemented with thermal barrier coatings (TBCs) and sophisticated cooling techniques. The present study focusses on two aspects of gas turbine cooling, namely augmented internal cooling and external film cooling.
One of the commonly used methods for cooling the vanes involves passing coolant air bled from the compressor through serpentine passages inside the airfoils. The walls of the internal cooling passages are usually roughened with turbulence promoters like ribs to enhance heat transfer. Though the ribs help in augmenting the heat transfer, they have an associated pressure penalty as well. Therefore, it is important to study the thermal-hydraulic performance of ribbed internal cooling passages. The first section of the thesis deals with the numerical investigation of flow and heat transfer characteristics in a ribbed two-pass channel. Four different rib shapes- 45° angled, V-shaped, W-shaped and M-shaped, were studied. This study further aims at exploring the performance of different rib-shapes at a large rib pitch-to-height ratio (p/e=16) which has potential applications in land-based gas turbines operating at high Reynolds numbers. Detailed flow and heat transfer analysis have been presented to illustrate how the innate flow physics associated with the bend region and the different rib shapes contribute to heat transfer enhancement in the two-pass channel. The bend-induced secondary flows were observed to significantly affect the flow and heat transfer distribution in the 2nd pass. The thermal-hydraulic performance of V-shaped and 45° angled ribs were better than W-shaped and M-shaped ribs.
The second section of the study deals with the analysis of film cooling performance of different hole configurations on the endwall upstream of a first stage nozzle guide vane. The flow along the endwall of the airfoils is highly complex, dominated by 3-dimensional secondary flows. The presence of complex secondary flows makes the cooling of the airfoil endwalls challenging. These secondary flows strongly influence endwall film cooling and the associated heat transfer. In this study, three different cooling configurations- slot, cylindrical holes and tripod holes were studied. Steady-state experiments were conducted in a low speed, linear cascade wind tunnel. The adiabatic film cooling effectiveness on the endwall was computed based on the spatially resolved temperature data obtained from the infrared camera. The effect of mass flow ratio on the film cooling performance of the different configurations was also explored. For all the configurations, the coolant jets were unable to overcome the strong secondary flows inside the passage at low mass flow ratios. However, the coolant jets were observed to provide much better film coverage at higher mass flow ratios. In case of cylindrical ejection, the effectiveness values were observed to be very low which could be because of jet lift-off. The effectiveness of tripod ejection was comparable to slot ejection at mass flow ratios between 0.5-1.5, while at higher mass flow ratios, slot ejection was observed to outperform tripod ejection.Master of Science
30
Ozturk, Emre. "Cfd Analyses Of Heat Sinks For Cpu Cooling With Fluent." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605700/index.pdf.
Повний текст джерелаАнотація:
In this study, forced cooling of heat sinks mounted on CPU&rsquos was investigated. Heat sink effectiveness, effect of turbulence models, effect of radiation heat transfer and different heat sink geometries were numerically analyzed by commercially available computational fluid dynamics softwares Icepak and Fluent. The numerical results were compared with the experimental data and they were in good agreement. Conjugate heat transfer is simulated for all the electronic cards and packages by solving Navier-Stokes equations. Grid independent, well converged and well posed models were run and the results were compared. The best heat sink geometry is selected and it is modified in order to have lower maximum temperature distribution in the heat sink.
31
Storm, Heinrich Claude. "CFD investigation of flow in and around a natural draft cooling tower." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4353.
Повний текст джерелаАнотація:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Cooling tower inlet losses and effective flow diameter under no crosswind conditions and the pressure distribution around a circular cylinder subjected to a crosswind are modelled using CFD. The CFD model used to evaluate the inlet losses is validated with data measured in an experimental cooling tower sector model and data obtained from literature. The effect of different inlet geometries on the inlet loss coefficient and the effective diameter are investigated in order to improve cooling tower inlet designs. CFD models are developed to investigate the pressure distribution around infinite and finite circular cylinders. The infinite cylinder is modelled with a smooth surface and a rough surface so that the results can be compared to experimental data from literature. Ultimately a finite cylinder model with a rough surface is developed and the results are compared to experimental data from literature.
AFRIKAANSE OPSOMMING: Koeltoring inlaatverlies en effektiewe vloei deursnit onder geen teenwind toestande en die drukverdeling rondom ‘n sirkelvormige silinder, onderworpe aan ‘n teenwind, word gemodelleer deur gebruik te maak van “CFD”. Die “CFD” model wat gebruik word om die inlaatverlies te evalueer is gevalideer met data verkry vanaf ‘n eksperimentele koeltoring sektor model. Verder word die “CFD” model gebruik in ‘n ondersoek om te bebaal wat die effek is van verskillende inlaat geometrieë op die inlaat verlies koeffisiënt en die effektiewe diameter sodat die inlaat geometrie van koeltorings verbeter kan word. ‘n “CFD” model word dan ontwikkel om die druk verdeling rondom ‘n sirkelvormige silinder te ondersoek. Die silinder word as oneindig gesimuleer met ‘n glade en ruwe wand sodat die resultate vergelyk kan word met eksperimentele data verkry vanaf literatuur. Die afdeling word afgesluit deur die silinder as eindig met ‘n ruwe wand te simuleer en dan word die resultate vergelyk met eksperimentele data verkry vanaf literatuur.
32
Huisamen, Ewan. "A thermo-hydraulic model that represents the current configuration of the SAFARI-1 secondary cooling system." Diss., University of Pretoria, 2005. http://hdl.handle.net/2263/66205.
Повний текст джерелаАнотація:
This document focuses on the procedure and results of creating a thermohydraulic model of the secondary cooling system of the SAFARI-1 research reactor at the Pelindaba facility of the South African Nuclear Energy Corporation (Necsa) to the west of Pretoria, South Africa. The secondary cooling system is an open recirculating cooling system that comprises an array of parallel-coupled heat exchangers between the primary systems and the main heat sink system, which consists of multiple counterflow-induced draught cooling towers. The original construction of the reactor was a turnkey installation, with no theoretical/technical support or verifiability. The design baseline is therefore not available and it is necessary to reverse-engineer a system that could be modelled and characterised. For the nuclear operator, it is essential to be able to make predictions and systematically implement modifications to improve system performance, such as to understand and modify the control system. Another objective is to identify the critical performance areas of the thermohydraulic system or to determine whether the cooling capacity of the secondary system meets the optimum original design characteristics. The approach was to perform a comprehensive one-dimensional modelling of all the available physical components, which was followed by using existing performance data to verify the accuracy and validity of the developed model. Where performance data is not available, separate analysis through computational fluid dynamics (CFD) modelling is performed to generate the required inputs. The results yielded a model that is accurate within 10%. This is acceptable when compared to the variation within the supplied data, generated and assumed alternatives, and when considering the compounding effect of the large amount of interdependent components, each with their own characteristics and associated performance uncertainties. The model pointed to potential problems within the current system, which comprised either an obstruction in a certain component or faulty measuring equipment. Furthermore, it was found that the current spray nozzles in the cooling towers are underutilised. It should be possible to use the current cooling tower arrangement to support a similar second reactor, although slight modifications would be required to ensure that the current system is not operated beyond its current limits. The interdependent nature of two parallel systems and the variability of the conditions that currently exist would require a similar analysis as the current model to determine the viability of using the existing cooling towers for an additional reactor.Dissertation (MEng)--University of Pretoria, 2015.
Mechanical and Aeronautical Engineering
MEng
Unrestricted
33
Olakoyejo, O. T. (Olabode Thomas). "Geometric optimisation of conjugate heat transfer in cooling channels with different cross-sectional shapes." Thesis, University of Pretoria, 2012. http://hdl.handle.net/2263/25484.
Повний текст джерелаАнотація:
In modern heat transfer, shape and geometric optimisation are new considerations in the evaluation of thermal performance. In this research, we employed constructal theory and design to present three-dimensional theoretical and numerical solutions of conjugate forced convection heat transfer in heat generating devices with cooling channels of different cross-sectional shapes. In recent times, geometric configurations of cooling channel have been found to play an important role in thermal performance. Therefore, an efficient ways of optimally designing these cooling channels shapes is required. Experimentation has been extensively used in the past to understand the behaviour of heat removals from devices. In this research, the shapes of the cooling channels and the configurations of heat-generating devices were analytically and numerically studied to minimise thermal resistance and thus illustrate cooling performance under various design conditions. The cooling channels of five different cross-sectional shapes were studied: Circular, square, rectangular, isosceles right triangular and equilateral triangular. They were uniformly packed and arranged to form larger constructs. The theoretical analysis is presented and developed using the intersection of asymptotes method. This proves the existence of an optimal geometry of parallel channels of different cross-sectional shapes that penetrate and cool a volume with uniformly distributed internal heat generation and heat flux, thus minimising the global thermal resistance. A three-dimensional finite volume-based numerical model was used to analyse the heat transfer characteristics of the cross-sectional shapes of various cooling channels. The numerical computational fluid dynamics (CFD) package recently provided a more cost-effective and less time-consuming means of achieving the same objective. However, in order to achieve optimal design solutions using CFD, the thermal designers have to be well experienced and carry out a number of trial-and-error simulations. Unfortunately, this can not always guarantee an accurate optimal design solution. In this thesis a mathematical optimisation algorithm (a leapfrog optimisation program and DYNAMIC-Q algorithm) coupled with numerical CFD was employed and incorporated into the finite volume solver, –FLUENT, and grid (geometry and mesh) generation package, – GAMBIT to search and identify the optimal design variables at which the system would perform optimally for greater efficiency and better accuracy. The algorithm was also specifically designed to handle constraint problems where the objective and constraint functions were expensive to evaluate. The automated process was applied to different design cases of cooling channels shapes. These cooling channels were embedded in a highly conductive solid and the peak temperature was minimised. The trend and performance of all the cooling channel shapes cases studied were compared analytically and numerically. It was concluded that an optimal design can be achieved with a combination of CFD and mathematical optimisation. Furthermore, a geometric optimisation of cooling channels in the forced convection of a vascularised material (with a localised self-cooling property subjected to a heat flux) was also considered. A square configuration was studied with different porosities. Analytical and numerical solutions were provided. This gradient-based optimisation algorithm coupled with CFD was used to determine numerically the optimal geometry that gave the lowest thermal resistance. This optimiser adequately handled the numerical objective function obtained from numerical simulations of the fluid flow and heat transfer. The numerical results obtained were in good agreement with results obtained in the approximate solutions based on scale analyses at optimal geometry dimensions. The approximate dimensionless global thermal resistance predicted the trend obtained in the numerical results. This shows that there were unique optimal design variables (geometries) for a given applied dimensionless pressure number for fixed porosity. The results also showed that the material property had a significant influence on the performance of the cooling channel. Therefore, when designing the cooling structure of vascularised material, the internal and external geometries of the structure, material properties and pump power requirements would be very important parameters to be considered in achieving efficient and optimal designs for the best performance. Finally, this research investigated a three-dimensional geometric optimisation of conjugate cooling channels in forced convection with an internal heat generation within the solid for an array of cooling channels. Three different flow orientations based on constructal theory were studied numerically- firstly, an array of channels with parallel flow; secondly, an array of channels in which flow of every second row was in a counter direction and finally, an array of channels in which the flow direction in every channel was opposite to that of previous channel. The geometric configurations and flow orientations were optimised in such a way that the peak temperature was minimised subject to the constraint of fixed global volume of solid material. The optimisation algorithm coupled with CFD was also used to determine numerically the optimal geometry that gave the lowest thermal resistance. The use of the optimisation algorithm coupled with the computational fluid dynamics package; render the numerical results more robust with respect to the selection of optimal structure geometries, internal configurations of the flow channels and dimensionless pressure difference.Thesis (PhD(Eng))--University of Pretoria, 2012.
Mechanical and Aeronautical Engineering
unrestricted
34
BROCKMAN, TRACY. "Dynamics of Cooling and Plagioclase Crystallization in a Feeder Dike of the Columbia River Flood Basalt Group." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1213234666.
Повний текст джерела
35
Messana, Michael R. "Heat transfer to an accelerated stream of droplets impinging onto a heated surface." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15950.
Повний текст джерела
36
Burger, Abri Andre Spies. "Numerical analysis of flow around infinite and finite cylinders at trans-critical Reynolds numbers with and without surface roughness." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97053.
Повний текст джерелаАнотація:
Thesis (MEng)--Stellenbosch University, 2015.ENGLISH ABSTRACT: This thesis investigates the flow field and pressure distributions around cylinders at trans-critical Reynolds numbers using the k-ε Realizable turbulence model. A steady state 2-D and 3-D Fluent® model is successfully developed to evaluate the effects of changing various modelling parameters on the static pressure distribution around an infinite and finite cylinder. These parameters include surface roughness, cylinder rotation and air viscosity at the cylinder surface. The subsequent results obtained are compared to each other and to data trends from literature as well as measured experimental results and are found to be in good agreement. In addition a method for calibrating all developed methods based on their shear stress curves over a flat plate model is also successfully developed. The main objective is to find an appropriate single parameter which can be used for the rigorous adjustment of the pressure distribution around a cooling tower, which will allow for improved sensitivity analysis and modelling of cooling tower performance under wind conditions with and without meridional ribs located on the outer shell surface.
AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die vloeiveld en druk verdelings rondom silinders by trans-kritiese Reynolds getalle deur gebruik te maak van die k-ε Realizable turbulensie model. ‘n Bestendige toestand 2-D en 3-D Fluent® model is suksesvol ontwikkel om die uitwerking van die verandering van verskeie model parameters op die statiese druk verdeling rondom ‘n oneindige en eindige silinder te evalueer. Die laasgenoemde parameters sluit in oppervlak grofheid, silinder rotasie en lug viskositeit by die silinder wand. Die daaropeenvolgende resultate wat verkry word, word met data tendense uit die literatuur asook gemete data vanuit eksperimente vergelyk en goeie ooreenkoms i.t.v die data tendense is gevind. Verder is ‘n metode vir die suksesvolle kalibrasie van die ontwikkelde numeriese tegnieke ontwikkel. Die laasgenoemde kalibrasie metode is gebaseer op die vergelyking van skuifspanning kurwes vir vloei oor ‘n plat plaat model. Die hoofdoel van die navorsing is om ‘n geskikte enkele parameter te vind wat gebruik kan word vir die effektiewe aanpassing van die druk verdeling rondom ‘n koeltoring wat sal lei tot verbeterde sensitiwiteits analise en modellering van koeltoring verrigting onder wind toestande met en sonder meridionale ribbes geleë op die buitenste dop oppervlak.
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Peterson, Blair A. "A Study of Blockage due to Ingested Airborne Particulate in a Simulated Double-Wall Turbine Internal Cooling Passage." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429738411.
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Wilson, Scott E. "Investigation of Copper Foam Coldplates as a High Heat Flux Electronics Cooling Solution." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6944.
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Compact heat exchangers such as porous foam coldplates have great potential as a high heat flux cooling solution for electronics due to their large surface area to volume ratio and tortuous coolant path. The focus of this work was the development of unit cell modeling techniques for predicting the performance of coldplates with porous foam in the coolant path.
Multiple computational fluid dynamics (CFD) models which predict porous foam coldplate pressure drop and heat transfer performance were constructed and compared to gain insight into how to best translate the foam microstructure into unit cell model geometry. Unit cell modeling in this study was realized by applying periodic boundary conditions to the coolant entrance and exit faces of a representative unit cell. A parametric study was also undertaken which evaluated dissimilar geometry translation recommendations from the literature. The use of an effective thermal conductivity for a representative orthogonal lattice of rectangular ligaments was compared to a porosity-matching technique of a similar lattice. Model accuracy was evaluated using experimental test data collected from a porous copper foam coldplate using deionized water as coolant. The compact heat exchanger testing facility which was designed and constructed for this investigation was shown to be capable of performing tests with coolant flow rates up to 300 mL/min and heat fluxes up to 290 W/cm2. The greatest technical challenge of the testing facility design proved to be the method of applying the heat flux across a 1 cm2 contact area. Based on the computational modeling results and experimental test data, porous foam modeling recommendations and porous foam coldplate design suggestions were generated.
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Shrivastava, Saurabh K. "Cooling analysis of data centers CFD modeling and real-time calculators /." Diss., Online access via UMI:, 2008.
Знайти повний текст джерелаАнотація:
Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2008.Includes bibliographical references.
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JImenez, Lopez Carlos. "Performance analysis and validation of high-temperature cooling panels in passive geothermal system." Thesis, KTH, Hållbara byggnader, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247915.
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High Temperature Cooling, HTC, is a thermal conditioning strategy, which aims to reducemixing and transfer heat losses. Cooling capacity strongly depends on heat transfer coefficientsand offers a great response and several advantages in terms of efficiency and sustainability.Among the advantages, there is evidence that HTC offers an increment of energy efficiency ofHVAC systems, provision of healthier and more comfortable indoor climate and provide widepotentials for the applications of renewable. This principle leads to a higher energy efficiency ofwater-based radiant cooling systems.This paper intends to focus on the research of the thermal capacity and performance of a newalternative. This is where Cooling Radiant Ceiling Panels, CRCP, becomes a major innovationwithin the sector and begin to take on certain relevance. The cooling capacity curve of thisparticular CRCP panels has been only measured in an idealized room environment according toDIN EN 14240. Thus, further studies of this key parameter through climate chamber testingand Computational Fluid Dynamics simulations, CFD, are necessary. CFD particularly focuseson fluids in motion, their behavior and their influences in complex processes such as heat transfer.The fluid motion can be described through fundamental mathematical equations and it isbecoming widely used within the building sector.Two different cases are going to be investigated. The first case will determine the mostoptimal peripheral gap to enhance cooling performance through Natural Convection, NC. Thisstudy states the existence of a peripheral gap around the panels has proven to be inefficientin terms of enhancing natural convection in the climate chamber. The second case is aboutcalculating the cooling capacity as a function of the internal heat loads. The cooling capacity ofthe CRCP panels followed an expected behavior. The R-squared factor of the linear regressionwas found to be 0.986, hence, it does not affect the performance of the CRCP panels dependingon the inclusion of the IHLs.This thesis provides the necessary information for the implementation of CRCP panels anddifferent possible operating environments, including considerations, limitations and recommendationsfor future implementation of this strategy.
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Montazeri, Mohammad. "Strain Engineering of the Band Structure and Picosecond Carrier Dynamics of Single Semiconductor Nanowires Probed by Modulated Rayleigh Scattering Microscopy." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367946034.
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Nambisan, Jayadev. "EXPERIMENTAL STUDY ON PRESSURE LOSSES IN ADDITIVELY MANUFACTURED AND MACHINED ORIFICES : A rectangular geometry of additively manufactured MA 247 orice and a circular geometry ofmachined AW-6082 T6 orifice study." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170131.
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Gas turbine components for cooling purposes including other unique and complex three-dimensional designs could be made explicitly possible through additive manufacturing using SLM technology in contrary to the conventional machining processes. Nevertheless, the surface roughness and subsequently the friction factor governs thepressure drop in these components implicitly, thus, influencing the secondary air flow system of a gas turbine. Research studies to understand and predict flow behaviours through especially AM parts are still in a budding stage, and thus, in this scope of thesis, the same has been attempted through experimentation to quantifypressure losses in additively manufactured rectangular orices. With the purpose of a brief analogy, a set of aluminium circular samples were also tested which were manufactured by the conventional process of machining. A total of 9 rectangular MA247 samples of different lengths and hydraulic diameters were tested as continuation to the ongoing research at Siemens Industrial Turbomachinery AB and further on to that, 5 Aluminium Alloy- AW-6082 T6 material samples of circular geometry with varying lengths were tested. The on-going research focuses on the additively manufactured geometries for both rectangular and circular, and hence, the data for circular orifices were used to draw a comparison with its Aluminium counterpart. Pressure losses here were described using the coefficient of discharge and the investigations on roughness were by calculating Darcy frictional factor and Colebrooks equation. Classical theories such as the boundary layer theory, Hagen's power law, Ward-Smith's theory for vena contracta and other works by previous researchers were used to validate the results. The coefficient of discharge could be deployed to restrict and measure the mass flow in the secondary air systems, whereas the results from the calculated frictional factors could be held to simulate the flow distribution in cooling geometries.E-presentation via Zoom due to the pandemic.
Part of the on-going research on pressure loss study for Gas Turbine cooling purposes by Siemens Energy
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Tang, Brian M. T. "Unshrouded turbine blade tip heat transfer and film cooling." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:f8479e89-9cd1-4aa7-b5c8-8068ad80de54.
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This thesis presents a joint computational and experimental investigation into the heat transfer to unshrouded turbine blade tips suitable for use in high bypass ratio, large civil aviation turbofan engines. Both the heat transfer to the blade tip and the over-tip leakage flow over the blade tip are characterised, as each has a profound influence on overall engine efficiency. The study is divided into two sections; in the first, computational simulations of a very large scale, low speed linear cascade with a flat blade tip were conducted. These simulations were validated against experimental data collected by Palafox (2006). A thorough assessment of turbulence models and minimum meshing requirements was performed. The standard k-ω and standard k-ϵ turbulence models significantly overpredicted the turbulence levels within the tip gap. The other models were very similar in performance; the SST k-ω and realisable k-ϵ models were found to be the most suitable for the flow environment. The second section documents the development and testing of a novel hybrid blade tip design, the squealet tip, which seeks to combine the known benefits of winglet and double squealer tips. The development of the external geometry was performed primarily through engine-representative CFD simulations at a range of tip gaps from 0.45% to 1.34% blade chord. The squealet tip was found to have a similar aerodynamic sensitivity to tip clearance as a baseline double squealer tip, with a tip gap efficiency exchange rate of 2.03, although this was 18% greater than the alternative winglet tip. The squealet tip displayed higher predicted stage efficiency than the winglet tip over the majority of the range of tip clearances investigated, however. The overall heat load was reduced by 14% compared with the winglet tip but increased by 28% over the double squealer tip, primarily due to the change in wetted surface area. The predicted local heat transfer coefficients were similar across all geometries. A realistic internal cooling plenum and an array of blade tip cooling holes were subsequently added to the squealet tip geometry and the cooling configuration refined by the selective sealing of cooling holes. Film cooling performance was largely assessed by the predicted adiabatic wall temperature distributions. A viable cooling scheme which reduced the cooling air requirement by 38% was achieved, compared to the initial case which had all cooling holes open. This was associated with just a 7% increase in blade tip heat flux and no penalty in peak temperature on the blade tip. Film cooling air ejected from holes on the blade suction side was swept away from the blade tip region, making the squealet rim at the crown of the blade particularly challenging to cool. It was demonstrated that this region could be cooled effectively by ballistic cooling from holes located on the blade tip cavity floor, although this was expensive in terms of the mass flow rate of cooling air required. The computational results were reinforced with experimental data collected in a transonic linear cascade. Downstream aerodynamic loss measurements were taken for a linearised version of the squealet tip design without cooling at nominal tip gaps of 0.45%, 0.89% and 1.34% blade chord, which was compared to similar data taken by O’Dowd (2010) for flat and winglet tips. The squealet was seen to have a similar aerodynamic loss to the flat tip and a reduced loss compared with the winglet tip. Full surface heat transfer measurements were taken for the uncooled squealet tip, at tip gaps of 0.89% and 1.34% blade chord, and for two configurations of the cooled squealet tip, at a tip clearance of 0.89% blade chord. The qualitative similarity between the measured heat transfer distributions and the those predicted by the engine-representative CFD simulations was good. A CFD simulation of the uncooled linear cascade environment at the 1.34% blade chord tip clearance was performed using a single blade with translationally periodic boundary conditions. The predicted size of the over-tip leakage vortex was smaller than had been measured, resulting in a large underprediction in the magnitude of the downstream area-averaged aerodynamic loss. The magnitudes of the predicted blade tip Nusselt number distribution were similar to those produced by the engine-representative CFD simulations and lower than that measured experimentally. Differences in the shape of the Nusselt number distribution were observed in the vicinity of regions of separated and reattaching flow, but other salient features were replicated in the computational data. The squealet tip has been shown to be a promising, viable unshrouded blade tip design with an aerodynamic performance similar to the double squealer tip but is more amenable to film cooling. It is significantly lighter than a winglet tip and incurs a reduced thermal load. The squealet tip design can now be developed into a blade tip geometry for use in real engines to provide an alternative to shrouded turbine blades and current unshrouded blade tip designs. A commercial CFD solver, Fluent 6.3, was shown to capture blade tip heat transfer and over-tip leakage flow sufficiently well to be a useful design guide. However, the sensitivity of the flow structure (and hence, heat transfer) in the forward part of the blade tip cavity suggests that physical testing cannot be eliminated from the design process entirely.
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Durham, Michael Glenn. "COMPARISON OF SQUARE-HOLE AND ROUND-HOLE FILM COOLING: A COMPUTATIONAL STUDY." Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4390.
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Film cooling is a method used to protect surfaces exposed to high-temperature flows such as those that exist in gas turbines. It involves the injection of secondary fluid (at a lower temperature than that of the main flow) that covers the surface to be protected. This injection is through holes that can have various shapes; simple shapes such as those with a straight circular (by drilling) or straight square (by EDM) cross-section are relatively easy and inexpensive to create. Immediately downstream of the exit of a film cooling hole, a so-called horseshoe vortex structure consisting of a pair of counter-rotating vortices is formed. This vortex formation has an effect on the distribution of film coolant over the surface being protected. The fluid dynamics of these vortices is dependent upon the shape of the film cooling holes, and therefore so is the film coolant coverage which determines the film cooling effectiveness distribution and also has an effect on the heat transfer coefficient distribution. Differences in horseshoe vortex structures and in resultant effectiveness distributions are shown for circular and square hole cases for blowing ratios of 0.33, 0.50, 0.67, 1.00, and 1.33. The film cooling effectiveness values obtained are compared with experimental and computational data of Yuen and Martinez-Botas (2003a) and Walters and Leylek (1997). It was found that in the main flow portion of the domain immediately downstream of the cooling hole exit, there is greater lateral separation between the vortices in the horseshoe vortex pair for the case of the square hole. This was found to result in the square hole providing greater centerline film cooling effectiveness immediately downstream of the hole and better lateral film coolant coverage far downstream of the hole.M.S.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical, Materials and Aerospace Engineering
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Meyer, Adriaan Jacobus. "Steam jet ejector cooling powered by low grade waste or solar heat." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2012.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2006.A small scale steam jet ejector experimental setup was designed and manufactured. This ejector setup is of an open loop configuration and the boiler can operate in the temperature range of Tb = 85 °C to 140 °C. The typical evaporator liquid temperatures range from Te = 5 °C t o 10 °C while the typical water cooled condenser presure ranges from Pc = 1 . 70 kPa t o 5. 63 kPa (Tc = 15 °C to 35 °C). The boiler is powered by by two 4kW electric elements, while a 3kW electric element simulates the cooling load in the evaporator. The electric elements are controlled by means of variacs. The function ...
Centre for Renewable and Sustainable Energy Studies
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Ongkodjojo, Ong Andojo. "Electrohydrodynamic Microfabricated Ionic Wind Pumps for Electronics Cooling Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1354638816.
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Tran, Lucky. "Development of Full Surface Transient Thermochromic Liquid Crystal Technique for Internal Cooling Channels." Master's thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6371.
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Proper design of high performance industrial heat transfer equipment relies on accurate knowledge and prediction of the thermal boundary conditions. In order to enhance the overall gas turbine efficiency, advancements in cooling technology for gas turbines and related applications are continuously investigated to increase the turbine inlet temperature without compromising the durability of the materials used.
For detailed design, local distributions are needed in addition to bulk quantities. Detailed local distributions require advanced experimental techniques whereas they are readily available using numerical tools. Numerical predictions using a computational fluid dynamics approach with popular turbulence models are benchmarked against a semi-empirical correlation for the friction in a circular channel with repeated-rib roughness to demonstrate some shortcomings of the models used. Numerical predictions varied widely depending on the turbulence modelling approach used. The need for a compatible experimental dataset to accompany numerical simulations was discussed.
An exact, closed-form analytical solution to the enhanced lumped capacitance model is derived. The temperature evolution in a representative 2D turbulated surface is simulated using Fluent to validate the model and its exact solution. A case including an interface contact resistance was included as well as various rib sizes to test the validity of the model over a range of conditions. The analysis was extended to the inter-rib region to investigate the extent and magnitude of the influence of the metallic rib features on the apparent heat transfer coefficients in the inter-rib region. It was found that the thermal contamination is limited only to the regions closest to the base of the rib feature.
An experimental setup was developed, capable of measuring the local heat transfer distributions on all four channel walls of a rectangular channel (with aspect ratios between 1 and 5) at Reynolds numbers up to 150,000. The setup utilizes a transient thermochromic liquid crystals technique using narrow band crystals and a four camera setup. The setup is used to test a square channel with ribs applied to one wall. Using the transient thermochromic liquid crystals technique and applying it underneath high conductivity, metallic surface features, it is possible to calculate the heat transfer coefficient using a lumped heat capacitance approach. The enhanced lumped capacitance model is used to account for heat conduction into the substrate material. Rohacell and aluminum ribs adhered to the surface were used to tandem to validate the hybrid technique against the standard technique. Local data was also used to investigate the effect of thermal contamination. Thermal contamination observed empirically was more optimistic than numerical predictions.
Traditional transient thermochromic liquid crystals technique utilizes the time-to-arrival of the peak intensity of the green color signal. The technique has been extended to utilize both the red and green color signals, increasing the throughput by recovering unused data while also allowing for a reduction in the experimental uncertainty of the calculated heat transfer coefficient. The over-determined system was solved using an un-weighted least squares approach. Uncertainty analysis of the multi-color technique demonstrated its superior performance over the single-color technique. The multi-color technique has the advantage of improved experimental uncertainty while being easy to implement.M.S.M.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering; Thermo-Fluids Track
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Reding, Brian D. II. "Tubular and Sector Heat Pipes with Interconnected Branches for Gas Turbine and/or Compressor Cooling." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/969.
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Designing turbines for either aerospace or power production is a daunting task for any heat transfer scientist or engineer. Turbine designers are continuously pursuing better ways to convert the stored chemical energy in the fuel into useful work with maximum efficiency. Based on thermodynamic principles, one way to improve thermal efficiency is to increase the turbine inlet pressure and temperature. Generally, the inlet temperature may exceed the capabilities of standard materials for safe and long-life operation of the turbine. Next generation propulsion systems, whether for new supersonic transport or for improving existing aviation transport, will require more aggressive cooling system for many hot-gas-path components of the turbine. Heat pipe technology offers a possible cooling technique for the structures exposed to the high heat fluxes. Hence, the objective of this dissertation is to develop new radially rotating heat pipe systems that integrate multiple rotating miniature heat pipes with a common reservoir for a more effective and practical solution to turbine or compressor cooling.
In this dissertation, two radially rotating miniature heat pipes and two sector heat pipes are analyzed and studied by utilizing suitable fluid flow and heat transfer modeling along with experimental tests. Analytical solutions for the film thickness and the lengthwise vapor temperature distribution for a single heat pipe are derived. Experimental tests on single radially rotating miniature heat pipes and sector heat pipes are undertaken with different important parameters and the manner in which these parameters affect heat pipe operation.
Analytical and experimental studies have proven that the radially rotating miniature heat pipes have an incredibly high effective thermal conductance and an enormous heat transfer capability. Concurrently, the heat pipe has an uncomplicated structure and relatively low manufacturing costs. The heat pipe can also resist strong vibrations and is well suited for a high temperature environment. Hence, the heat pipes with a common reservoir make incorporation of heat pipes into turbo-machinery much more feasible and cost effective.
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Weiß, Frank-Peter. "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28406.
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Die Veranstaltung widmete sich mit der Borverdünnung in Druckwasserreaktoren bzw. mit der Verstopfung der Sumpfansaugsiebe durch freigesetztes Isolationsmaterial schwerpunktmäßig zwei Themen der Reaktorsicherheit, die auch in aktuellen Aufsichtsverfahren eine Rolle spielen. Eingebettet in den internationalen Kontext wollten die Veranstalter die sicherheitstechnische Bedeutung dieser Themen für die deutschen Anlagen beleuchten und die Auswirkungen auf die zu erbringenden Sicherheitsnachweise und den Anlagenbetrieb darstellen. Dabei kamen Gutachter, Vertreter der Forschung, Hersteller und Betreiber gleichermaßen zu Wort. Der Fachtag sollte den Teilnehmern aber insbesondere vermitteln, welche Beiträge die privat und öffentlich finanzierte Reaktorsicherheitsforschung zur Aufklärung der jeweiligen Ereignisabläufe und ihrer sicherheitstechnischen Bedeutung geleistet hat. In diesem Forschungskontext spielen, auch international, die Methoden der so genannten Computational Fluid Dynamics (CFD) eine zunehmende Rolle. Deshalb widmete sich eine Sitzung den Grundlagen, Möglichkeiten und Grenzen von CFD-Methoden. Dabei wurden u.a. Anwendungen zur Borvermischung und zum Verhalten von Mineralwolle im Sumpf präsentiert.
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Weiß, Frank-Peter. "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland." Forschungszentrum Rossendorf, 2006. https://hzdr.qucosa.de/id/qucosa%3A21667.
Повний текст джерелаАнотація:
Die Veranstaltung widmete sich mit der Borverdünnung in Druckwasserreaktoren bzw. mit der Verstopfung der Sumpfansaugsiebe durch freigesetztes Isolationsmaterial schwerpunktmäßig zwei Themen der Reaktorsicherheit, die auch in aktuellen Aufsichtsverfahren eine Rolle spielen. Eingebettet in den internationalen Kontext wollten die Veranstalter die sicherheitstechnische Bedeutung dieser Themen für die deutschen Anlagen beleuchten und die Auswirkungen auf die zu erbringenden Sicherheitsnachweise und den Anlagenbetrieb darstellen. Dabei kamen Gutachter, Vertreter der Forschung, Hersteller und Betreiber gleichermaßen zu Wort. Der Fachtag sollte den Teilnehmern aber insbesondere vermitteln, welche Beiträge die privat und öffentlich finanzierte Reaktorsicherheitsforschung zur Aufklärung der jeweiligen Ereignisabläufe und ihrer sicherheitstechnischen Bedeutung geleistet hat. In diesem Forschungskontext spielen, auch international, die Methoden der so genannten Computational Fluid Dynamics (CFD) eine zunehmende Rolle. Deshalb widmete sich eine Sitzung den Grundlagen, Möglichkeiten und Grenzen von CFD-Methoden. Dabei wurden u.a. Anwendungen zur Borvermischung und zum Verhalten von Mineralwolle im Sumpf präsentiert.