Дисертації з теми "Heat – Transmission Refrigerants Thermodynamics"
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Agarwal, Akhil. "Heat Transfer and Pressure Drop During Condensation of Refrigerants in Microchannels." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14129.
Повний текст джерелаWorm, Steven Lee. "Experimental measurement of heat transfer phenomena in a solid adsorbent." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/16487.
Повний текст джерелаFuller, Timothy Alan. "An analytical study of the performance characteristics of solid/vapor adsorption heat pumps." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/16961.
Повний текст джерелаLegodi, Annah Mokganyetji Kgotlelelo. "Analysis of heat transfer and thermal stability in a slab subjected to Arrhenius kinetics." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1250.
Повний текст джерелаDevelopment of safe storage for reactive combustible materials to prevent possible human and environmental hazards as well as ensure and enhance industrial safety can significantly benefit from mathematical modelling of systems. In the recent past, models with varying degrees of sophistication have been developed and applied to the problem of predicting thermal criticality conditions, temperature and concentration profiles of such system. In this thesis, a model showing the temperature history of an nth order exothermic oxidation reaction in a slab of combustible material with variable pre-exponential factor, taking the consumption of the reactant into account in the presence of a convective heating and oxygen exchange at the slab surface with the ambient is presented Both transient and steady state problems are tackled The critical regime separating the regions of explosive and non-explosive paths of a one step exothermic chemical reaction is determined The governing nonlinear partial differential equations are solved numerically by method of lines (MOL), with finite difference schemes used for the discretisation of the spatial derivatives. Moreover, both fourth order Runge-Kutta numerical integration coupled with shooting methods and perturbation techniques together with a special type of Hermite-Pade series summation and improvement method were employed to tackle the steady state problem. The crucial roles played by the boundary conditions in determining the location ofthe maximum heating were demonstrated. In chapter one, the relevant applications together with previous published work on the problem were highlighted The basic mathematical theory and equations needed to tackle the problem were derived in Chapter two. In chapter three, the transient model problem was formulated, analysed and discussed. The steady state problem was formulated and solved in Chapter four. Furtherwork and concluding remarks were highlighted in Chapter five.
Nicholas, Jack Robert. "Heat transfer for fusion power plant divertors." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:efedf39b-401b-418f-b510-386a512314a8.
Повний текст джерелаMi, Jian. "SiC Growth by Laser CVD and Process Analysis." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-04062006-135055/.
Повний текст джерелаLackey, W. Jack, Committee Chair ; Cochran, Joe K., Committee Member ; Danyluk, Steven, Committee Member ; Fedorov, Andrei G., Committee Member ; Rosen, David W., Committee Member ; Wang, Zhonglin, Committee Member.
Galand, Quentin. "Experimental investigation of the diffusive properties of ternary liquid systems." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209626.
Повний текст джерелаFor each of these techniques, experimental set-ups were designed, implemented and calibrated. The procedures for identifying the ternary diffusion coefficients from the measured compositions fields were studied in details.
The Open Ended Capillary Technique was applied under gravity condition to study isothermal diffusion binary and ternary systems. Difficulties related to a new procedure for interpreting the data collected at short times of the experiments are highlighted and its implication in the generalization of the technique for the study of multicomponent systems is discussed.
The Transient Interferometric Technique was used to perform an experimental study of three binary systems under gravity conditions. It was also applied for the investigation of ternary systems under microgravity condition in the frame of the DSC on SODI experiment, which took place aboard the International Space Station in 2011. The experimental results are reported and the analysis of the accuracy of the technique is presented. The TIT is the first technique ever providing accurate experimental measurements of the complete set of diffusion and thermodiffusion coefficients for ternary liquid systems.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Bright, Trevor James. "Non-fourier heat equations in solids analyzed from phonon statistics." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29710.
Повний текст джерелаCommittee Chair: Zhang, Zhuomin; Committee Member: Kumar, Satish; Committee Member: Peterson, G. P. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Ma, Zhiwen. "A combined differential and integral model for high temperature fuel cells." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15831.
Повний текст джерелаCross, Caleb Nathaniel. "Combustion heat release effects on asymmetric vortex shedding from bluff bodies." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42772.
Повний текст джерелаAndresen, Ulf Christian. "Supercritical Gas Cooling and Near-Critical-Pressure Condensation of Refrigerant Blends in Microchannels." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14503.
Повний текст джерелаMitra, Biswajit. "Supercritical gas cooling and condensation of refrigerant R410A at near-critical pressures." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-06142005-232427/.
Повний текст джерелаGarimella, Srinivas, Committee Chair ; Ghiaasiaan, S. Mostafa, Committee Member ; Graham, Samuel, Committee Member ; Breedveld, Victor, Committee Member ; Fuller,Tom, Committee Member.
Altalidi, Sulaiman Saleh. "Two-Phase Spray Cooling with HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics using Practical Enhanced Surfaces." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011876/.
Повний текст джерелаVereen, Keon. "An experimental investigation on the dynamics of bubbles utilizing refrigerant R134a under pressurized flow boiling conditions." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4717.
Повний текст джерелаID: 030646273; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.A.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 107-115).
M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Thermofluid Aerodynamics Systems Track
Schaffka, Flavia Tramontin Silveira. "Análise fluidodinâmica e térmica do processo de secagem de suspensão diluída em leito fluidizado." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2400.
Повний текст джерелаO presente trabalho teve como objetivo realizar um estudo do comportamento fluidodinâmico e térmico do processo de secagem de suspensão diluída em leito fluidizado gás-sólido. Para avaliar a estabilidade de fluidização, a fim de evitar a condição do fenômeno de defluidização, foi utilizada a análise espectral Gaussiana. Durante o processo de secagem, foi analisada a umidade relativa do ar, a umidade absoluta, eficiência de secagem e a força de secagem. Em relação ao comportamento térmico, foi analisado o coeficiente volumétrico de transferência de calor, avaliando a influência das condições experimentais. Os ensaios experimentais foram realizados em escala laboratorial utilizando-se uma coluna de acrílico de 0,11 m de diâmetro interno e 1,0 m de altura. Como material inerte, foram utilizadas esferas de alumínio e esferas de vidro, ambas com diâmetro médio de 1,55 mm. Foi utilizada uma suspensão de carbonato de cálcio com concentração de 9 e 15%. A vazão de atomização da suspensão foi de 11,0; 13,0 e 15,0 mL/min. Os resultados mostraram que a transição dos regimes de fluidização durante o processo de secagem de suspensão não pôde ser nitidamente identificada pela análise espectral Gaussiana. Adicionalmente, a concentração de carbonato de cálcio apresentou pouca influência no tempo para atingir a região de defluidização. A vazão de atomização da solução influenciou na estabilidade fluidodinâmica do leito. Em relação ao tipo de material inerte, as partículas de alumínio apresentaram melhores condições no processo de secagem do ponto de vista da fluidodinâmica. O coeficiente volumétrico médio de transferência de calor obtido foi de 1,76 kW/m³.K, não variando com o tipo da partícula inerte utilizado.
The objective of this study was to perform a study of the hydrodynamic and thermal behavior of the drying process of a dilute suspension in a gas-solid fluidized bed. To evaluate stability fluidization, in order to avoid the condition of the defluidization phenomenon, was utilized Gaussian spectral analysis, which is a technique based on pressure fluctuation measurements. During the drying process, was analyzed relative humidity, absolute humidity and a drying efficiency. In relation to the thermal behavior, the volumetric heat transfer coefficient was analyzed, evaluating the influence of experimental conditions. The experimental tests were carried out in laboratory scale using a Plexiglas column, with 0.11 m in inner diameter and 1.0 m in height. As inert material, aluminum beads and glass beads were used, both with mean diameter of 1.55 mm. It was used as suspension of calcium carbonate with a concentration of 9 and 15%. The atomization flow rates of the suspension were 11.0; 13.0 and 15.0 mL/min. The results showed that the transition of the fluidization regimes during the suspension drying process could not be clearly identified by Gaussian spectral analysis. Additionally, the solution concentration had little influence on the time to reach the defluidization region. The atomization flow of the solution influenced the fluid dynamic stability of the bed. As for the type of the inert material, the aluminum particles presented better conditions in the hydrodynamic of drying process. The average volumetric heat transfer coefficient was 1.76 kW/m³.K and it not changed with the type of inert particle used.
Au, Edwin C. F. "A computational scheme for calculating refrigerant properties & heat transfer in boiling tube flow." Thesis, 1999. http://hdl.handle.net/2440/120373.
Повний текст джерелаThesis (M.Eng.Sc.)--University of Adelaide, Dept. of Mechanical Engineering, 1999
"Condensing coefficients of the refrigerant mixture R-22/R-142b in smooth tubes and during enhanced heat transfer configurations." Thesis, 2009. http://hdl.handle.net/10210/1938.
Повний текст джерелаThe heating of water with hot-water heat pumps is extremely energy-efficient. With the refrigerant R-22 hot water temperatures of 60° C to 65° C are possible. However, these temperatures are low in comparison with the temperatures obtained from other methods of water heating, for instance electrical geysers. Should higher water temperatures be obtained, the applications of hot-water heat pumps will increase. This is possible by using a zeotropic refrigerant mixture as working fluid. A R-22 and R-142b zeotropic refrigerant mixture shows exceptional potential in achieving hot water temperatures. The condensing coefficients need to be predicted correctly to optimize the condenser design. Unfortunately, there is a lack of detailed literature available on condensing coefficients for the recommended mass fractions of R-22 with R-142b at condensing temperatures of 60° C or more. Micro-fin tubes perform outstanding in enhancing heat transfer and are widely used to save energy. Unfortunately, there is also a lack of detailed literature on condensing coefficient at the recommended mass fractions of R-22/R-142b refrigerant mixtures condensing in micro-fins, twisted tapes and high fins at temperatures of 60° C or more. In this study condensing coefficients of R-22 and the zeotropic refrigerant mixture R-22 with R-142b were obtained in smooth tubes at mass fractions of 90%/10%, 80%/20%, 70%/30%, 60%/40%, 50%/50%. The experimental data were used to evaluate some of the methods that are commonly used to predict condensing coefficients. Experiments were also conducted at the same zeotropic mass fractions, to compare three different methods of heat transfer enhancement to that of the smooth tubes namely: micro-fins, twisted tapes and high fins. All measurements were conducted at an isobaric inlet pressure of 2.43 MPa. The test sections consisted of a series of eight tubes with lengths of 1 603 mm. The smooth tubes had an inner diameter of 8.11 mm. With the R-22/R-142b zeotropic refrigerant mixture condensing in smooth tubes, it was observed in the sight glasses that a predominantly stratified wavy flow regime exists at low mass fluxes, from 40 kg/m2s to 350 kg/m2s. The refrigerant mass fraction decreased the condensing coefficient by up to a third on average from 100% R-22 to a 50%/50% mixture of R-22 with R142b. A predominantly annular flow regime was observed at mass fluxes of 350 kg/m2s and more. At this flow regime the condensing coefficients were not strongly influenced by the refrigerant mass fraction, decreasing only by 7% as the refrigerant mass fraction changed from 100% R-22 to a 50%/50% mixture of R-22 with R142b. When the experimental data were compared with three methods that are commonly used to predict condensing coefficients it was found that the flow pattern correlation of Dobson and Chato (1998) gave the best predictions for R-22. The Silver (1964) and Bell and Ghaly (1964) method gave the best predictions for the R-22/R-142b mixtures. When the three heat transfer enhancement methods were compared with smooth tubes it was found that micro-fins were more suitable as an enhancement method than twisted tubes or high fins. It was also found that the condensing coefficients and pressure drops decrease as the mass fractions of R-142b increases.
"Heat transfer performance during in-tube condensation in horizontal smooth, micro-fin and herringbone tubes." Thesis, 2008. http://hdl.handle.net/10210/1753.
Повний текст джерелаAn experimental investigation was conducted into the heat transfer characteristics of horizontal smooth, micro-fin and herringbone tubes during in-tube condensation. The study focused on the heat transfer coefficients of refrigerants R-22, R-134a and R-407C inside the three tubes. The herringbone tube results were compared to the smooth and micro-fin tube results. The average increase in the heat transfer coefficient when compared to the smooth tube was found to be as high as 322% with maximum values reaching 336%. When compared to the micro-fin tube, the average increase in heat transfer coefficient was found to be as high as 196% with maximum values reaching 215%. A new unified correlation was also developed to predict the heat transfer coefficients in a herringbone and micro-fin tube. The correlation predicted the semi-local heat transfer coefficients accurately with 96% and 89% of the data points falling in the ± 20% region for the herringbone and micro-fin tube respectively. The average heat transfer coefficients were also accurately predicted with all the data points for the herringbone tube and 83% of the data points for the micro-fin tube falling in the ± 20% region. The trend of the new correlation also fitted the data accurately and the conclusion was made that the correlation is accurate and could be used successfully in practice.
"Pressure drop during condensation inside smooth, helical micro-fin, and herringbone micro-fin tubest." Thesis, 2012. http://hdl.handle.net/10210/5410.
Повний текст джерелаSince the promulgation of the Montreal Protocol many refrigerants needed to be phased out. R-22, which is a widely used refrigerant in refrigeration systems, was one of these. Many replacements have been found throughout the years but very few have the same refrigeration capacity without being penalised by an increase in pressure drop. R-407C is one of the refrigerants having the potential to replace R-22 as it has the same theoretical coefficient of performance and has a lower global warming potential. However, due to its zeotropic characteristics there is a degradation in heat transfer during evaporation and condensation attributed to mass transfer resistance. Thus, augmentation techniques are needed not only to increase the heat capacity, but also to achieve an increase without incurring an excessive pressure drop. One approach to cope with this problem is to make use of the recently developed herringbone micro-fin tubes. Unfortunately very little data exists for refrigerants undergoing condensation inside herringbone micro-fin tubes. There is also little pressure drop information available for this type of tube. An experimental set-up was designed to determine the characteristics of this type of tube due to the scarcity of information. With the aid of current literature, various techniques were used to determine the pressure drops inside the herringbone micro-fin tube. One of these techniques was the use of the Kattan-Thome-Favrat flow regime map which helped to identify the flow patterns inside the tube. Knowledge of the type of flow occurring inside the tube helped to clarify the behaviour of the pressure drop relationships. The type of refrigerant being used also affected the behaviour of the pressure drop curves. A low-pressure refrigerant had a higher pressure drop due to the high vapour velocities achieved. Another cause for excessive pressure drop is the friction created by the high velocity vapour and condensate inside the tube. Many relationships for the friction factor exist and these are used to analyse the experimental data.The experimental facility comprised of a vapour compression loop and a water loop. The vapour compression loop consisted of a hermetically sealed compressor with a cooling capacity of 9.6 kW, a manually operated expansion valve and an evaporator. Three condensers were tested, namely a smooth tube, a helical micro-fin tube, and a herringbone micro-fin tube. The condensers were of the tube-in-tube type with the refrigerant flowing in the inner tube and the water in counter flow in the annulus. The hot water loop was used as a source for the evaporator and a cold loop as a heat sink for the condenser. Three refrigerants were tested, namely R-22, R-134a, and R-407C, all operating at a nominal saturation temperature of 40°C and at mass fluxes between 300 and 800 kg/m 2s. Accurate sensors and transducers were used to measure the temperatures, pressures, and mass flows at predefined points. Video cameras were attached to sight glasses to aid in the identification of the type of flow regime. Data were captured using a computerised data acquisition programme designed specifically for use with the experimental study. The experimental results showed that transition between the annular and intermittent flow regimes occurred at around 25% vapour quality for the herringbone micro-fin tube, as opposed to 30% for the helical micro-fin tube and 50% for the smooth tube. Pressure drops for the herringbone micro-fin tube were higher than those for the smooth tube but slightly lower than those for the helical micro-fin tube when using refrigerants R-22 and R-134a. The correlation of Liebenberg was modified for the pressure drops inside the herringbone micro-fin tube and gave a mean deviation of 12%. The efficiency ratio for the herringbone tube using R-22 was 1.85 and 1.69 when compared with the helical micro-fin and smooth tube respectively. For R-134 the efficiency ratio was 2.02 and 2.13 when compared with the helical micro-fin and smooth tube respectively, while for R-407C it was 1.58 and 1.26 for the two respectively. It was also concluded that R-407C could be used as a replacement refrigerant for R-22when used with a herringbone micro-fin tube.
"Flow patterns during refrigerant condensation in smooth and enhanced tubes." Thesis, 2009. http://hdl.handle.net/10210/1931.
Повний текст джерелаThe Montreal Protocol led to the phasing-out of ozone layer depleting refrigerants and replacing them with more environmentally friendly refrigerants, which in many cases caused heat transfer degradation in heat exchanger equipment. To make up for the heat transfer degradation, there was a need for the application of heat transfer enhancement techniques. One such technique is the use of micro-fin tubes as opposed to traditional smooth tubes. The purpose of this study is to develop a flow regime map for the condensation of R-22, R-407C and R-134a in a herringbone micro-fin tube. It was perceived that with the knowledge of flow patterns inside the tube and especially the annular-to-intermittent transition, it is possible to perform improved analyses of the heat transfer and pressure drop characteristics. Experimental and analytical work was performed to investigate the flow regimes during condensation of the refrigerants in smooth, helical micro-fin and herringbone micro-fin tubes at an average saturation temperature of 40oC, with mass fluxes ranging from 300 to 800 kg/m2s. Condensation occurred in tube-in-tube type condensers with cooling water flowing in the annulus and the refrigerant in the inner tubes. The condensers consisted of eight sub-sections to allow for the acquisition of sectional heat transfer and pressure data. Various criteria were considered in order to generate flow regime maps. The Thome flow regime transition criterion was used and complemented with visually-observed and photographic imaging, as well as the objective power spectral density distributions of the pressure signals of the condensing refrigerants. The observed flow regimes were mainly annular flow and intermittent flow. Stratified-wavy flow was observed at low mass fluxes and low vapour qualities. There were notable similarities in the flow pattern between the smooth and micro-fin tubes. However, the experimental results show that the transition from annular to intermittent flow regimes occurred at average vapour quality values of 0.26, 0.29 and 0.48 for the herringbone micro-fin, the helical micro-fin and smooth tubes respectively. The combined analyses assisted in adapting the helical micro-fin tube condensing flow pattern map, to ensure its application in accurately predicting herringbone micro-fin tube condensation. The new transition criterion effectively predicts the delay in transition from annular to intermittent flow for all three refrigerants, condensing in the herringbone micro-fin tube.
Liebenberg, Leon. "A unified prediction method for smooth and micro-fin tube condensation performance." Thesis, 2009. http://hdl.handle.net/10210/1939.
Повний текст джерелаKebonte, Shiko A. "Condensation heat transfer and pressure drop coefficients of R22/R142b in a water cooled helicaly coiled tube-in-tube heat exchanger." Thesis, 2012. http://hdl.handle.net/10210/6181.
Повний текст джерелаHeat transfer and pressure drop characteristics during in-tube condensation of nonazeotropic mixtures of R22/R142b in a smooth helically coiled copper tube with an inside diameter of 8.11 mm are investigated. The experimental results are compared with prediction from correlation. The coefficient of performance of.the heat pump built and used for experiments has been studied. The mass flux of the refrigerant was varied during the course of the experiments. At similar mass flow rate of fluids, the average heat transfer coefficients for mixtures were lower than those for pure refrigerant R22 used as reference for comparison. Also, the heat transfer coefficients of all the refrigerants increased with increasing mass flux.
Bluhm, Steven John. "Thermal performance of direct-contact water-air heat exchangers." Thesis, 2016. http://hdl.handle.net/10539/20857.
Повний текст джерелаThis work was carried out in response to the need for a simple engineering method for the thermal analysis of direct-contact air-water heat exchangers. A simple method of performance analysis is developed which is directly analogous and consistent with the fundamental approach used in conventional heat exchanger analysis and one in which the algebraic form of the overall equation and the grouping of each of the parameters are apparent. The range of conditions considered are air and water temperatures of between 0 and 50 DC and barometric pressures ranging from 80 to 120 kPa. The air conditions considered range from completely dry to completely satucated with water vapour. Both air cooling and water cooling processes are considered. [Abbreviated abstract. Open document to view full version]
Herron, Thomas G. "Design, modeling and performance of miniature reciprocating expander for a heat actuated heat pump." Thesis, 2004. http://hdl.handle.net/1957/31699.
Повний текст джерелаGraduation date: 2005
Visser, Coert Johannes. "Modelling heat and mass flow through packed pebble beds : a heterogeneous volume-averaged approach." Diss., 2008. http://hdl.handle.net/2263/27623.
Повний текст джерелаDissertation (MEng)--University of Pretoria, 2008.
Mechanical and Aeronautical Engineering
unrestricted
Sen, Biswanath. "Condensation Heat Transfer Of R-134A On Micro-Finned Tubes : An Experimental Study." Thesis, 2008. http://hdl.handle.net/2005/709.
Повний текст джерелаFitzpatrick, John Nathan. "Coupled thermal-fluid analysis with flowpath-cavity interaction in a gas turbine engine." Thesis, 2013. http://hdl.handle.net/1805/4441.
Повний текст джерелаThis study seeks to improve the understanding of inlet conditions of a large rotor-stator cavity in a turbofan engine, often referred to as the drive cone cavity (DCC). The inlet flow is better understood through a higher fidelity computational fluid dynamics (CFD) modeling of the inlet to the cavity, and a coupled finite element (FE) thermal to CFD fluid analysis of the cavity in order to accurately predict engine component temperatures. Accurately predicting temperature distribution in the cavity is important because temperatures directly affect the material properties including Young's modulus, yield strength, fatigue strength, creep properties. All of these properties directly affect the life of critical engine components. In addition, temperatures cause thermal expansion which changes clearances and in turn affects engine efficiency. The DCC is fed from the last stage of the high pressure compressor. One of its primary functions is to purge the air over the rotor wall to prevent it from overheating. Aero-thermal conditions within the DCC cavity are particularly challenging to predict due to the complex air flow and high heat transfer in the rotating component. Thus, in order to accurately predict metal temperatures a two-way coupled CFD-FE analysis is needed. Historically, when the cavity airflow is modeled for engine design purposes, the inlet condition has been over-simplified for the CFD analysis which impacts the results, particularly in the region around the compressor disc rim. The inlet is typically simplified by circumferentially averaging the velocity field at the inlet to the cavity which removes the effect of pressure wakes from the upstream rotor blades. The way in which these non-axisymmetric flow characteristics affect metal temperatures is not well understood. In addition, a constant air temperature scaled from a previous analysis is used as the simplified cavity inlet air temperature. Therefore, the objectives of this study are: (a) model the DCC cavity with a more physically representative inlet condition while coupling the solid thermal analysis and compressible air flow analysis that includes the fluid velocity, pressure, and temperature fields; (b) run a coupled analysis whose boundary conditions come from computational models, rather than thermocouple data; (c) validate the model using available experimental data; and (d) based on the validation, determine if the model can be used to predict air inlet and metal temperatures for new engine geometries. Verification with experimental results showed that the coupled analysis with the 3D no-bolt CFD model with predictive boundary conditions, over-predicted the HP6 offtake temperature by 16k. The maximum error was an over-prediction of 50k while the average error was 17k. The predictive model with 3D bolts also predicted cavity temperatures with an average error of 17k. For the two CFD models with predicted boundary conditions, the case without bolts performed better than the case with bolts. This is due to the flow errors caused by placing stationary bolts in a rotating reference frame. Therefore it is recommended that this type of analysis only be attempted for drive cone cavities with no bolts or shielded bolts.
Karimi, Abdullah. "Numerical study of hot jet ignition of hydrocarbon-air mixtures in a constant-volume combustor." Thesis, 2014. http://hdl.handle.net/1805/6249.
Повний текст джерелаIgnition of a combustible mixture by a transient jet of hot reactive gas is important for safety of mines, pre-chamber ignition in IC engines, detonation initiation, and in novel constant-volume combustors. The present work is a numerical study of the hot-jet ignition process in a long constant-volume combustor (CVC) that represents a wave-rotor channel. The mixing of hot jet with cold mixture in the main chamber is first studied using non-reacting simulations. The stationary and traversing hot jets of combustion products from a pre-chamber is injected through a converging nozzle into the main CVC chamber containing a premixed fuel-air mixture. Combustion in a two-dimensional analogue of the CVC chamber is modeled using global reaction mechanisms, skeletal mechanisms, and detailed reaction mechanisms for four hydrocarbon fuels: methane, propane, ethylene, and hydrogen. The jet and ignition behavior are compared with high-speed video images from a prior experiment. Hybrid turbulent-kinetic schemes using some skeletal reaction mechanisms and detailed mechanisms are good predictors of the experimental data. Shock-flame interaction is seen to significantly increase the overall reaction rate due to baroclinic vorticity generation, flame area increase, stirring of non-uniform density regions, the resulting mixing, and shock compression. The less easily ignitable methane mixture is found to show higher ignition delay time compared to slower initial reaction and greater dependence on shock interaction than propane and ethylene. The confined jet is observed to behave initially as a wall jet and later as a wall-impinging jet. The jet evolution, vortex structure and mixing behavior are significantly different for traversing jets, stationary centered jets, and near-wall jets. Production of unstable intermediate species like C2H4 and CH3 appears to depend significantly on the initial jet location while relatively stable species like OH are less sensitive. Inclusion of minor radical species in the hot-jet is observed to reduce the ignition delay by 0.2 ms for methane mixture in the main chamber. Reaction pathways analysis shows that ignition delay and combustion progress process are entirely different for hybrid turbulent-kinetic scheme and kinetics-only scheme.