Dissertations / Theses on the topic 'Heating modes'
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McGregor, Duncan Ekundayo. "Electron cyclotron heating and current drive using the electron Bernstein modes." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/212.
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Sinclair, Keith Ian. "Focussed microwave heating using degenerate and non-degenerate cavity modes." Thesis, Heriot-Watt University, 2009. http://hdl.handle.net/10399/2288.
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Microwave ovens have long been recognised as a means of reducing heating times versus conventional convection ovens. The principle design feature is based on the procurement of uniform heating within any material placed in the interior of the microwave cavity oven. Materials within the oven are subjected to a degree of heating dependent on their electromagnetic properties. For many applications, it is desirable to maintain control over the distribution of heat deposition. This can be achieved through focussing of the electromagnetic field within the cavity. Two new mechanisms are identified where an increased level of control over the heating pattern and its location could be advantageous. The research described within this thesis aims to improve heating selectivity in microwave cavity ovens by the identification and enhanced control of modal patterns in degenerate and non-degenerate resonators. This is achieved through the analysis of two novel oven arrangements. The first of these addresses the requirement for highly selective heating in hyperthermia treatment. It is demonstrated that proper selection of a forced degenerate mode set can lead to an enhancement in field focussing within the centre of the cavity through constructive and destructive interference of the fields in each mode pattern. It is found that a highly selective peak of field can be produced within the centre of a large cylindrical waveguide cavity for the purpose of hyperthermia treatment. The peak is produced using a quasi degenerate mode set excited at approximately 1:3GHz. The second example presents an open oven design for the curing of epoxy and encapsulant materials within the micro-electronics packaging industry. It is intended that the oven be placed on the arm of a precision alignment machine such that the curing and placement stages of production be combined, suggesting an increase in production efficiency. Two excitation schemes are presented based on the coupling of quasi degenerate mode sets through a wide frequency range and the excitation of a single high order mode enabling uniform field distribution for heating of encapsulant material and increased selective heating through spatial alignment of modal field peaks, respectively. Experimental results demonstrate the viability of the open-ended microwave oven for curing. Both proposed excitation methods within the open oven design are investigated with results presented. Optimisation of the heating fields is achieved through inclusion of lowloss materials within the oven. Curing of an encapsulant material covering a commercial chip package is achieved and the overall design validated.
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Клімук, Олександр Олександрович. "Оптимізація показників надійності, що визначаються тепловими режимами в блоці радіоелектронної апаратури." Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/23109.
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Структура й обсяг дипломної роботи
Магістерська дисертація: 101 c., 23 рис., 28 табл., 4 додатка, 13 джерел.
Актуальність теми. В процесі розробки конструкцій радіоелектронної апаратури постійно виникає необхідність розрахунку і аналізу тепловиділення, актуальним є оптимальні теплові параметри блоку РЕА.
Мета дослідження. Метою роботи є оптимізація показників надійності, що визначаються тепловими режимами в блоці РЕА.
Для реалізації поставленої мети були сформульовані такі завдання дослідження, що визначили логіку дослідження та його структуру: дослідити методи розрахунку температур в блоках РЕА; створити математичну модель теплообміну в блоці РЕА та за допомогою сучасної мови програмування розробити програмний продукт;
Об’єкт дослідження — температура комірок блоку РЕА.
Предмет дослідження — модель теплообміну в блоці РЕА
Методи дослідження: При вирішенні задач роботи застосовувались такі методи: математичне моделювання теплових процесів в РЕА, комп’ютерне моделювання в середовище Mathcad, комп’ютерне моделювання за допомогою мови програмування JavaScript.
Наукова новизна одержаних результатів. Наукова новизна полягає в розробці методики оптимізації розрахунку усереднених температур чарунок у блоці РЕА, створена програма, в порівняні з іншими САПР, дозволяє зменшити час розробки РЕА.
Практичне значення одержаних результатів роботи полягає в створенні програми, що може бути складовою у САПР блока РЕА з оптимальною компоновкою.Structure of the diploma Master dissertation: 101 p., 23 fig., 28 tabl. 4 aplication, 13 sources. Relevance of the topic. In the process of developing the design of radio-electronic equipment, there is a constant need for calculating and analyzing heat dissipation, the optimal thermal parameters of the unit of the radio electronic device are relevant The aim of the study The aim of the work is to optimize the reliability indicators determined by the thermal modes in the block of radio-electronic equipment. In order to achieve this goal, the following research objectives were formulated, which determined the logic of the research and its structure: to study the methods of calculating the temperatures in the blocks of the REA. Object of research: temperature of cells of the block of radio electronic equipment. Subject of research: Heat transfer model in the radio electronic equipment. Research methods: In solving problems of work, the following methods were used: the development of a mathematical model in the environment of Mathcad; development of a software product in the programming language JavaScript. Scientific novelty of the obtained results. The most significant scientific results of the master's thesis: is the development of a program for optimizing the calculation of the average temperatures of cells in the radio electronic equipment. block, which allows to reduce the time of development of the radio electronic equipment. in other CAD. The practical value of the results obtained is to create a program that can be part of the CAD of the REA unit with the optimal layout.
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Капітанюк, Микола Петрович. "Тепловий режим структурно-конструктивного модуля другого рівня та оптимізація розміщення чарунок для підвищення надійності." Master's thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/25847.
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Актуальність теми. В процесі розробки конструкцій радіоелектронної апаратури постійно виникає необхідність розрахунку і аналізу тепловиділення, актуальним є оптимальні теплові параметри блоку РЕА.
Мета дослідження. Метою роботи є оптимізація розміщення чарунок для підвищення надійності блоку.
Для реалізації поставленої мети були сформульовані такі завдання дослідження, що визначили логіку дослідження та його структуру: дослідити методи розрахунку температур в блоках РЕА; створити алгоритм оптимізації розміщення чарунок в блоці РЕА;
Об’єкт дослідження — температурне поле блоку РЕА.
Предмет дослідження — вплив розміщення чарунок на температурне поле блоку.
Методи дослідження: При вирішенні задач роботи застосовувались наступні методи: моделювання комп’ютерне моделювання теплових процесів в системі автоматизованого проектування SolidWorks Flow Simulation, перевірка роботи алгоритму за допомогою SolidWorks.
Наукова новизна одержаних результатів. Наукова новизна полягає в розробці методики оптимізації температури блоку РЕА, розроблений алгоритм, що дозволяє підвищити надійність блоку РЕА.
Практичне значення одержаних результатів роботи полягає в створенні алгоритму оптимізації розміщення чарунок, що може використовуватись для розробки більш надійних конструкцій РЕА.Relevance of the topic. In the process of developing the design of radio-electronic equipment, there is a constant need for calculating and analyzing heat dissipation, the optimal thermal parameters of the unit of the radio electronic device are relevant The aim of the study The purpose of the work is to optimize the placement of the cells for increasing the reliability of the block. To accomplish this goal, the following research objectives were formulated, which determined the logic of the research and its structure: investigate the methods of calculating the temperature in the blocks of the REA; to create algorithm of optimization of placement of cells in the REA block. Object of research: temperature of the block of radio electronic equipment. Subject of research: the influence of the placement of cells on the temperature field of the block. Research methods: The following methods were used to solve problems: simulation of computer simulation of thermal processes in the system of automated design of SolidWorks Flow Simulation, validation of the algorithm using SolidWorks. Scientific novelty of the obtained results. The scientific novelty is to develop a method for optimizing the temperature of the REA block, and an algorithm is developed that can increase the reliability of the REA block. The practical value of the results obtained is to create an optimization algorithm for placement of cells, which can be used to develop more reliable designs of REA.
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Song, Jingjing. "Restructured district heating price models and their impact on district heating users." Licentiate thesis, Mälardalens högskola, Framtidens energi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-34779.
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District heating (DH) is considered to be an efficient, environmentally friendly and cost-effective method for providing heat to buildings, since electricity is usually co-generated in biomass fuelled combined heat and power (CHP) plants. This gives it an important role in the mitigation of climate change. Swedish district heating companies are currently facing multiple challenges, and are in urgent need of new price models to increase transparency and maintain their competitiveness. This thesis describes a survey carried out to understand the structure of the present price models and subsequently proposes and compares two restructured price models with the most commonly used price model. This work also investigates the impact of restructured price models on users who would encounter a significant cost increase if the restructured price models were to be introduced. The district heating costs of different price models are compared with three alternative technical solutions. The results show that price models based on the consumption pattern of users can reflect district heating companies’ cost structure. Meanwhile, adopting a pricing strategy based on users’ consumption patterns increased the incentives to reduce the peak load. Consequently, users with high load factor (flat consecutive load curve) were able to reduce costs whereas users with low load factor (steep consecutive load curve) faced possible cost increases, when the load demand cost was changed to daily or hourly peak demand based methods. Further, the most economically preferable option for the invested district heating user was to combine district heating with direct electrical heating or with a ground source heat pump.Fjärrvärme anses som ett effektivt, miljövänligt och kostnadseffektivt sätt för att leverera värme eftersom kraftvärme blir vanligare i fjärrvärmesystem, där elektricitet produceras tillsammans med värme. Den spelar en viktig roll i att begränsa klimatförändringen. Svenska fjärrvärme företag står inför flera utmaningar nu för tiden, och är i akut behov av nya prismodeller för att öka öppenheten och behålla konkurrenskraften. I denna avhandling, genomfördes en undersökning för att ta reda på strukturen av de nuvarande prismodellerna. Därefter föreslogs två omstrukturerade prismodeller, vars påverkan på kostnaden av fjärrvärme konsument analyserades jämför med den nuvarande modellen. Detta arbete undersökte också effekten av omstrukturerade prismodeller på konsument som skulle drabbas på signifikant kostnadsökning i samband med införande prismodeller. Kostnaden av fjärrvärme under olika prismodeller har också jämförts med tre olika tekniska lösningar. Resultatet visade att prismodeller som baserar sig på konsuments förbrukningsprofil kunde återspegla fjärrvärme företagens kostnadsstruktur; Samtidigt medförde prissättningsstrategi baserad på användarens förbrukningsprofil högre incitament för att minska spetseffekt. Följaktligen kommer att konsumenter med stabila konsumtionsprofiler att spara kostnader, medan konsumenter med spetsiga konsumtionsprofiler kommer att drabbas av kostnadsökning. Och för den investerade fjärrvärme konsument, den ekonomiska bättre val var att kombinera fjärrvärme med elpanna eller bergvärmepump.
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Jones, Joshua Levi. "Development of an advanced stem heating model /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd231.pdf.
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Jones, Joshua L. "Development of an Advanced Stem Heating Model." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/88.
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A new one-dimensional heat conduction model for predicting stem heating during fires is presented. The model makes use of moisture and temperature dependent thermal properties for bark and wood. Also, the thermal aspects of the processes of bark swelling, desiccation, and devolatilization are treated in an approximate fashion. Simulation with a surface flux boundary condition requires that these phenomena be accounted for. Previous models have used temperature-time boundary conditions, which prevents them from being directly coupled to fire behavior models. This model uses a flux-time profile for its boundary condition, making it possible to eventually couple it to fire behavior models. Cambial mortality predictions are made through the incorporation of a cell mortality model. The model was developed and validated with laboratory experiments on four species.
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Bowness, Ruth. "Current sheets in the solar corona : formation, fragmentation and heating." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2081.
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In this thesis we investigate current sheets in the solar corona. The well known 1D model for the tearing mode instability is presented, before progressing to 2D where we introduce a non-uniform resistivity. The effect this has on growth rates is investigated and we find that the inclusion of the non-uniform term in η cause a decrease in the growth rate of the dominant mode. Analytical approximations and numerical simulations are then used to model current sheet formation by considering two distinct experiments. First, a magnetic field is sheared in two directions, perpendicular to each other. A twisted current layer is formed and we find that as we increase grid resolution, the maximum current increases, the width of the current layer decreases and the total current in the layer is approximately constant. This, together with the residual Lorentz force calculated, suggests that a current sheet is trying to form. The current layer then starts to fragment. By considering the parallel electric field and calculating the perpendicular vorticity, we find evidence of reconnection. The resulting temperatures easily reach the required coronal values. The second set of simulations carried out model an initially straight magnetic field which is stressed by elliptical boundary motions. A highly twisted current layer is formed and analysis of the energetics, current structures, magnetic field and the resulting temperatures is carried out. Results are similar in nature to that of the shearing experiment.
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Zhang, Lei. "Numerical modeling of induction assisted subsurface heating technology." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-theses/574.
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Nickel-based super alloys are widely employed in the aerospace industry due to their high- temperature strength and high corrosion resistance. Because of the special application, the superficial residual stress of the super alloy is mandatory to 100% compressive stress according to the Federal Aviation Administration (FAA) regulations. In manufacturing of nickel-based super alloy components, grinding processes are necessarily applied as the final material removal step for achieving the stringent tolerance and surface finish requirements. During the traditional grinding process of Nickel based alloy, due to the thermal effect, tensile residual stress might be generated on the surface of the alloy. It's critical to transfer the tensile residual stress to compressive one which benefits on the fatigue life of alloy. In the thesis, a novel technology is developed to generate the superficial compressive residual stress with the method of embed a subsurface heating layer inside the workpiece to regulate the distribution of temperature field very before mechanical process. The residual stress might be reduced much, even transfer to compressive stress after combining the thermal effect. The numerical model will be built in the thesis including the induction model, heat transfer model, grinding heat model. Effects of different parameters on final subsurface heating layer will be studied including the coil parameters, concentrator parameters, coolant parameters, feed rate and also electromagnetic field properties such as the skin effect, proximity effect and slot effect. The thesis creates a system combining induction heating and cooling processes to regulate the temperature distribution in subsurface area that will be used for further stress analysis.
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Holth, Erik. "Model Predictive Control of mixed solar and electric heating." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9106.
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In this report we will model a heat system consisting of a heat storage tank and an application. The heat storage tank is supplied by a heating element and heated water from a solar collector. The main objective of the heat system is to mainatian a reference temperature in the application (a house). Weather forecasts will be used as weather data affecting the heat system. We will assume that the weather forecasts and the actual weather will be the same. The heat sytem will consist of simplified nonlinear differential equations and be controlled by a model predictive controller (mpc). The mpc controller will use a linearized model of the nonlinear process. The average predicted outside temperature from the weather forecasts will be used as nominal value for the same temperature in the linearized model in the mpc controller. The mpc controller will measure some disturbances to make more efficient control. The most imortant disturbance will be the temperature of the water coming out of the solar collector, that will flow into the heat storage. By measuring this temperature, the mpc controller can apply it to its predictor and make sure that the power of the heating element in the heat storage is reduced when solar collector heated water is available. This is to make sure that the heat storage has enough capacity to receive the heated water from the solar collector, while still maintaining a reasonable temperature in the heat storage. Simulation with different weighting of the inputs in the mpc controller will show that heating element power consumption is influenced by these weights.
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Mogan, Jon Louis. "Transient billet heating model for a steel reheat furnace." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0007/MQ42668.pdf.
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Hill, Andrew D. C. "Mathematical models for the microwave heating of chilled food." Thesis, University of Bath, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438647.
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Öhrlund, Jack, and Catrin Östman. "DIGITALIZATION IS HEATING UP THE BUSINESS MODEL : A degree project regarding the impact of digitalization on a business model canvas within district heating." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-39808.
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The purpose of this degree project is to analyze and investigate how digitalization will affect business modeling in the district heating business. The chosen approach to this degree project was an iterative, abductive method, in order to always use a feedback-analysis and to keep the project open for new findings. The interviews were a mix of a structured method and a qualitative approach. With the structured method, the findings from the interviews were similar and regarding the research topic, and the qualitative approach in some open questions led to matters that otherwise would have been unnoticed. The interviews were performed via e-mail, phone and through personal interviews. This degree project concluded that digitalization has an impact on business modeling in district heating. Digitalization will affect some elements in a major way, for example key resources that will be characterized by digitalization. The findings from this work showed that a business model operating in district heating in a time of digitalization should focus on three main parts: economy, environment and easy visualization. An optimization tool should focus on delivering a value that consist of these three, and the remaining elements should together contribute to that value proposition.Syftet med detta examensarbete är att analysera och undersöka hur digitaliseringen kommer att påverka affärsmodellering inom fjärrvärmebranschen. Det valda tillvägagångssättet för detta examensarbete är en iterativ, abduktiv metod för att hela tiden återkoppla och hålla studien öppen för nya intryck. Intervjuerna är en kombination av strukturerad metod blandad med en kvalitativ ansats. Med den strukturerade metoden blir svaren inom samma ram samtidigt som den kvalitativa aspekten lockar fram svar som annars skulle passera obemärkta. Intervjuerna genomfördes via mail, telefon samt genom personliga intervjuer. Detta examensarbete drar slutsatsen att digitaliseringen kommer påverka affärsmodeller inom fjärrvärme. Digitaliseringen kommer påverka vissa element i större utsträckning som till exempel nyckelresurserser som kommer präglas av digitaliseringen. Upptäckterna från studien visar att en affärsmodell verksam inom fjärrvärme i en tid präglad av digitaliseringen ska fokusera på tre delar: ekonomi, miljö och lättförstådd visualisering. Ett optimeringsverktyg ska fokusera på att leverera ett värde som innehåller dem tre delarna och resterande element ska tillsammans bidra till det värdeerbjudandet.
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Adams, Jacob James. "A coupled electromagnetic-thermal model of heating during radiofrequency ablation." Connect to resource, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1191454972.
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Pangalos, Georg [Verfasser]. "Model-based Controller Design Methods for Heating Systems / Georg Pangalos." Berlin : Neopubli GmbH, 2016. http://d-nb.info/1103874276/34.
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Barreto, Sandoval Jose de Jesus. "Model studies of plasma heating in the continuous casting tundish." Thesis, Sheffield Hallam University, 1993. http://shura.shu.ac.uk/19322/.
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A room temperature water model of a tundish was design, constructed and operated. The model was equipped with a steam heating system that simulates that simulates the tundish plasma heating systems operated by some of the more modem continuous casting plants. Similarity between steam heating in the water model and plasma heating in the tundish has been established. A dimensionless criterion was developed to validate the simulation experiments and its represented by the plasma heating number. Using this similarity criterion plasma heating can be simulated by steam heating in an appropriately designed water model. A theoretical dispersion model has been formulated for the flow through the tundish and the parameters in this model determined from the results obtained from residence time distribution measurements. A conductivity method was used, a highly conducting species being injected at the inlet point and changes in conductivity monitored at the exit. Measurements were also made of the changes in temperature at the exit resulting both from changes in temperature of the inlet stream and from the use of steam heater system. A stable inverse heat conduction method has been developed in which the measured and estimated temperature are analysed in terms of a steady components of short duration. A finite difference method has been used to predict the effect on a thermocouple temperature of the deviatory components of the liquid steel temperature. The incorporation of these predictions into look-up tables has allowed an algorithm to be developed thet can deduce the current deviatory component of the steel temperature from the thermocouple response.
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Kamal, Majd. "Potential for low temperature district heating system : Integrating 4th generation district heating system with existing technology." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-35816.
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This project presents a feasibility study and an investigation of the potential for low temperature district heating system in Västerås. The investigation treats integrations possibilities for 4GDH (4th Generation District Heating) in Kungsängens area in Västerås, which is undergoing a large-scale building-up and construction. The study is conducted for the company Mälarenergi AB. The advantages of 4GDH technology are identified and analyzed, where energy effectiveness and economic benefits aspects were concluded. Problems with existing technology and higher cooling demand expectations drive 4GDH to be an interesting and necessary technology in the future. Four Different integration solutions between old and new networks are presented, analyzed and discussed. Quantitative analysis conducted where initial cost for the four technical solutions were estimated and compared. The results show that low temperature district heating could lead to reduction in the initial cost for the network by using PEX instead of steel as pipe material. The results show also that one solution using heat exchanger as exchange stations has the lowest cost between the four solutions. The results show that the cost for the retention flow that is linked with 4GDH stands for 20%-30% of the total cost. The importance of the retention flow pipe is investigated using two physical models in OpenModelica and Excel, where simulations were conducted. It is concluded that it is possible to provide Kungsängen area with low temperature district heating without having the retention flow pipe. Three parameters were identified to be critical which are, geographical placement of the consumers, pattern variation for the heat demand and heat systems installed inside consumer’s buildings. The results show also that it might be critical to have a variate and optimized supply temperature for the area, depending on the demand. The simulations of a fictive area that could present a future heat demand for Kungsängen area shows that a temperature of 55°C is satisfying during winter season where the demand is high and a temperature between 60-65°C must be available during spring/autumn seasons and specially during summer. The variation depends directly on the temperature drop through the supply pipes to the consumers. The temperature drop is directly linked with water velocity inside the pipes. The losses increase during summer nights when the heat demand is low which lead to low water velocities.
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Gerima, Kassaye. "Night Setback Identification of District Heating Substations." Thesis, Högskolan Dalarna, Mikrodataanalys, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:du-36071.
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Energy efficiency of district heating systems is of great interest to energy stakeholders. However, it is not uncommon that district heating systems fail to achieve the expected performance due to inappropriate operations. Night setback is one control strategy, which has been proved to be not a suitable setting for well-insulated modern buildings in terms of both economic and energy efficiency. Therefore, identification of a night setback control is vital to district heating companies to smoothly manage their heat energy distribution to their customers. This study is motivated to automate this identification process. The method used in this thesis is a Convolutional Neural Network(CNN) approach using the concept of transfer learning. 133 substations in Oslo are used in this case study to design a machine learning model that can identify a substation as night setback or non-night setback series. The results show that the proposed method can classify the substations with approximately 97% accuracy and 91% F1-score. This shows that the proposed method has a high potential to be deployed and used in practice to identify a night setback control in district heating substations.
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Kolenčíková, Jana. "Model teplárenské sítě." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417740.
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Subject of this thesis is district heating and heating network model design. Firstly, it de-scribes basic principles of heat supply and its elements. Secondly, computational model of heating network is created based on grid map of the network. The model contains proposed pipeline system and calculation of heat and pressure losses. Lastly, price map for heat con-sumption points, in dependence on heat losses, is presented.
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Woolnough, Steven James. "A study of Equatorial superrotation in a two-level model of the atmosphere." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363838.
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Aoun, Nadine. "Modeling and flexible predictive control of buildings space-heating demand in district heating systems." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC104.
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La gestion de la demande en chauffage des bâtiments raccordés à des réseaux de chaleur s'effectue classiquement au moyen d’une courbe de chauffe : lorsque la température extérieure chute, la température de départ de l’eau alimentant le circuit de chauffage interne est relevée. Ce mode de contrôle, appelé régulation par loi d’eau, présente des atouts en termes de simplicité et de robustesse, mais ne tient pas compte de l'inertie thermique du bâtiment et ne permet donc pas une modulation de sa demande. La modulation de la demande en chauffage se définit comme l'action de contrôle consistant à modifier de manière stratégique les conditions de confort thermique dans le cadre d’une optimisation énergétique et/ou économique. Il s’agit d’une brique essentielle du contrôle flexible qui envisage le déplacement des charges et l’effacement des pics pour une meilleure efficacité de production favorisant la pénétration des énergies renouvelables et de récupération.Ces travaux de thèse visent à développer une stratégie de contrôle prédictif et flexible de la demande en chauffage, applicable à grande échelle dans les réseaux de chaleur.Tout d'abord, un simulateur thermique dynamique de bâtiment résidentiel, équipé de radiateurs hydrauliques connectés à une sous-station de réseau de chaleur, est développé. Il permet de définir plusieurs cas d’études de bâtiments représentatifs du parc résidentiel français et constitue l’environnement expérimental virtuel de nos travaux de recherche. Ensuite, une méthodologie permettant d’obtenir un modèle orienté-contrôle et d’ordre réduit de bâtiment avec son système de chauffage est proposée. Elle commence par la définition de la structure du modèle en se basant sur des connaissances physiques, puis consiste en l'identification des paramètres par optimisation méta-heuristique à l'aide des données générées par le simulateur. L'approche d'identification paramétrique évalue la possibilité de réaliser cette tâche en ne s’appuyant que sur des données disponibles au niveau de la sous-station, notamment en s’interdisant d’utiliser des mesures de température intérieure au bâtiment, donnée à caractère personnel présumée indisponible à grande échelle pour des raisons techniques, économiques et juridiques. Enfin, la stratégie de contrôle prédictif est implémentée. Elle permet la planification de la température de départ de l'eau de chauffage en fonction des prévisions météorologiques et des prix de l’énergie. Le contrôleur flexible s’appuie sur un problème d’optimisation linéaire sous contraintes, selon le principe de l’horizon fuyant. Il incorpore les équations linéarisées du modèle d’ordre réduit et calcule le compromis optimal entre coûts énergétiques et inconfort thermique, le degré de flexibilité de la demande en chauffage étant défini par l’intermédiaire de paramètres de réglage dédiésIn District Heating Systems (DHSs), buildings Space-Heating (SH) demand management conventionally relies on a heating curve: when the outdoor temperature drops, the internal SH system supply water temperature is raised. This control mode, referred to as Weather-Compensation Control (WCC), offers widely recognized assets in terms of simplicity and robustness. However, WCC does not account for the building thermal inertia, and consequently, it does not allow modulation of its demand. SH demand modulation is the control action of strategically altering the indoor thermal comfort conditions within an energetic and/or economic optimization framework. It is a key measure in flexible demand control strategies, which seek loads shifting and peaks shaving to allow sustainable commitment of energy resources in favour of renewable power penetration and waste heat recovery.The work presented in this thesis aims at developing a flexible Model Predictive Control (MPC) strategy for SH demand, applicable at large scale in DHSs.Firstly, a thermal dynamic simulator of a residential building with a radiator SH circuit connected to a DHS substation is developed. It allows the definition of multiple case study buildings, well-representative of the french residential stock, and constitutes the virtual experimental environment for our research. Then, a methodology to obtain a control-oriented Reduced-Order Model (ROM) for the building and its SH system is proposed. It starts by defining the ROM structure based on physical knowledge, and proceeds to parameters identification by meta-heuristic optimization using data generated by the simulator. The parametric identification approach evaluates the possibility of carrying out this task by relying solely on data available at the substation level, refraining from using indoor temperature measurements, personal data assumed to be unavailable at large scale for technical, economic and legal reasons. Finally, MPC is implemented to schedule the SH supply water temperature as function of weather forecasts and energy price variations. The flexible controller is designed to solve a constrained linear optimization problem according to the receding horizon principle. It embeds the linearized ROM equations within the problem formulation and makes an optimal trade-off between energy consumption costs and thermal discomfort, the degree of flexibility to modulate SH demand being defined through dedicated tuning parameters
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Wu, Haijun Walker Paul N. "Numerical model for isobaric steam heating of initially saturated packed beds." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4300/index.html.
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Furtenback, Örjan. "Fuel substitution in district heating plants : CGE modeling with a forest resource /." Umeå : Sveriges lantbruksuniv, 2009. http://epsilon.slu.se/11862745.pdf.
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Uhrík, Patrik. "Implementace kogeneracni jednotky do siti "Smart Heating and Cooling Networks"." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318635.
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The aim of the Master‘s thesis was to create a computational model for integration of the cogeneration unit into the smart thermal network. For the better use of waste heat from the selected cogeneration unit MOTORGAS MGM250 during the summer period, the absorption circuit was dimensioned and the appropriate trigeneration computational model was formed. In the theoretical part, the function, operation and heat performance of the cogeneration unit as well as the suitability of the connection of the cogeneration unit with the absorption chiller during the summer period were described. In the practical part, the operational data of the Faculty of Mechanical Engineering of the Brno University of Technology and the theoretical performance data from created cogeneration and trigeneration computational models were compared. Based on this comparison, the conclusion about the suitability of use of both computational models was made.
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McCoy, Tammy Michelle. "Extension of the master sintering curve for constant heating rate modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22532.
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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Joe K. Cochran; Committee Co-Chair: Dr. Thomas H. Sanders; Committee Member: Dr. John Elton; Committee Member: Dr. Meilin Liu; Committee Member: Dr. Robert F. Speyer.
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Terril, Nathaniel D. "Field Simulation for the Microwave Heating of Thin Ceramic Fibers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36863.
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Microwave processing of ceramics has seen a growth in research and development efforts throughout the past decade. One area of interest is the exploration of improved heating control through experiments and numerical modeling. Controlled heating may be used to counteract non-uniform heating and avoid destructive phenomena such as cracking and thermal runaway. Thermal runaway is a potential problem in materials with temperature dependent dielectric properties. As the material absorbs electromagnetic energy, the temperature increases as does its ability to absorb more energy. Controlled processing of the material may be achieved by manipulating the applied field. The purpose of this research is to model the interaction of the EM-field with a thin ceramic fiber to investigate possible mechanisms that may affect the heating process. The fiber undergoes microwave heating in a single-mode resonant applicator. Maxwell's equations for the fields within the cavity are solved using mode-matching techniques taking into account the field interaction of the fiber and an arbitrarily shaped coupling aperture. Effects of varying the aperture shape on the field distribution are explored. The coupled nature of the electromagnetic solution with the material's temperature-dependent properties, including an analysis of non-uniform heating, is also discussed.Master of Science
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Johnston, Craig David. "Modelling chromospheric evaporation in response to coronal heating." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/14630.
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This thesis presents a new computationally efficient method for modelling the response of the solar corona to the release of energy. During impulsive heating events, the coronal temperature increases which leads to a downward heat flux into the transition region (TR). The plasma is unable to radiate this excess conductive heating and so the gas pressure increases locally. The resulting pressure gradient drives an upflow of dense material, creating an increase in the coronal density. This density increase is often called chromospheric evaporation. A process which is highly sensitive to the TR resolution in numerical simulations. If the resolution is not adequate, then the downward heat flux jumps over the TR and deposits the heat in the chromosphere, where it is radiated away. The outcome is that with an under-resolved TR, major errors occur in simulating the coronal density evolution. We address this problem by treating the lower transition region as a discontinuity that responds to changing coronal conditions through the imposition of a jump condition that is derived from an integrated form of energy conservation. In this thesis, it is shown that this method permits fast and accurate numerical solutions in both one-dimensional and multi-dimensional simulations. By modelling the TR with this appropriate jump condition, we remove the influence of poor numerical resolution and obtain the correct evaporative response to coronal heating, even when using resolutions that are compatible with multi-dimensional magnetohydrodynamic simulations.
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Florenz-Esnal, Julian. "Temperature prediction models and their application to the control of heating systems." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335130.
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Zabada, Shaker. "Analysis of heating expenditure in social housing : application of economic provisional models." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10181/document.
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Le travail mené dans cette thèse porte sur la consommation d’énergie, et plus particulièrement le chauffage dans le logement social. Il vise à (i) analyser l'influence des caractéristiques de bâtiments des indicateurs socio-économiques des occupants sur la consommation de chauffage et (ii) à développer des modèles numériques pour la prédiction de cette consommation. La recherche est basée sur des données fournies par le Lille Métropole Habitat, qui est en charge de la gestion d'un grand parc de logement social à Lille Métropole. La thèse comprend quatre parties. La première présente une analyse bibliographique, qui couvre le logement social en Europe, notamment en France, les facteurs qui affectent la consommation d'énergie dans le logement social et les politiques proposées pour les économies d'énergie dans ce secteur. La deuxième partie présente les données utilisées dans ce travail, qui ont été fournies par LMH. Ces données concernent un grand parc de logement social à Lille Métropole (Nord de la France). Elles comprennent les dépenses de chauffage, des caractéristiques des bâtiments et des indicateurs socio-économiques sur les occupants. La troisième partie présente une analyse de l'influence des caractéristiques des bâtiments (âge, DPE, superficie et nombre d'étages) et des paramètres socio-économiques des occupants (âge, situation matrimonial et revenues) sur la consommation de chauffage. La dernière partie présente l'élaboration des modèles de prévision des dépenses de chauffage dans le parc de LMH et l'utilisation de ces modèles pour la politique de rénovation. Deux méthodes sont utilisées: La Méthode des Moindres Carrés (OLS) et les Réseaux de Neurones ArtificieThe research conducted in this doctoral thesis concerns a major socio-economic issue, that of the heating consumption in social housing. It aims at understanding the influence of both building characteristics as well as socio-economic indicators on the heating consumption in this sector and the development of numerical models for the prediction of this consumption. The research is based on data provided by Lille Métropole Habitat, who is in charge of the management of a large social housing stock in Lille Metropolis. The thesis includes four parts. The first part presents a literature review which covers the social housing in Europe, in particular in France, the factors affecting the energy consumption in social housing, and policies proposed for the energy saving in this sector. The second part presents the data used in this work that are provided by LMH. The data concern a large social housing stock in Lille Metropolis (North of France). They include heating expenses as well as the buildings characteristics and some socio-economic indicators on the tenants. The third part presents analysis of the influence of both building characteristics (age, DPE, dwellings’ area, number of floors) and socio-economic parameters (tenants’ age, marital status and income) on the heating consumption. The last part presents the elaboration of prediction models for the heating expenses in the LMH housing stock and the use of these models to analyze the investment policy in the renovation of this stock. Two methods are used: the classical Ordinary Least Squares method (OLS) and the Artificial Neural Networks
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Petkov, Roumen Dimitrov. "High power switched mode magnetron power supply systems for industrial microwave heating applications." Thesis, Teesside University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259645.
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Sommer, Fabian. "Thermal insulation of high confinement mode with dominant electron heating in comparison to dominant ion heating and corresponding changes of torque input." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-162326.
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The ratio of heating power going to electrons and ions will undergo a transition from mixed electron and ion heating as it is in current fusion experiments to dominant electron heating in future experiments and reactors. In order to make valid projections towards future devices the connected changes in plasma response and performance are important to be study and understand: Do electron heated plasmas behave systematically different or is the change of heated species fully compensated by heat exchange from electrons to ions? How does particle transport influence the density profile? Is the energy confinement and the H-mode pedestal reduced with reduced torque input? Does the turbulent transport regime change fundamentally? The unique capabilities of the ECRH system at ASDEX Upgrade enable this change of heated species by replacing NBI with ECRH power and thereby offer the possibility to discuss these and other questions.
For low heating powers corresponding to high collisionalities the transition from mixed electron and ion heating to pure electron heating showed next to no degradation of the global plasma parameters and no change of the edge values of kinetic profiles. The electron density shows an increased central peaking with increased ECRH power. The central electron temperature stays constant while the ion temperature decreases slightly. The toroidal rotation decreases with reduced NBI fraction, but does not influence the profile stability. The power balance analysis shows a large energy transfer from electrons to ions, so that the electron heat flux approaches zero at the edge whereas the ion heat flux is independent of heating mix. The ion heat diffusivity exceeds the electron one.
For high power, low collisionality discharges global plasma parameters show a slight degradation with increasing electron heating. The density profile shows a strong peaking which remains unchanged when modifying the heating mix. The electron temperature profile is unchanged whereas the central ion temperature decreases significantly with increasing ECRH fraction. The relative contribution of the heat exchange is smaller so that the electrons still carry a substantial fraction of heat at the edge. The ion heat flux is still independent of the heating mix and the ion heat diffusivity exceeds the electron one.
The radial electrical field does not show any variation with changing heating mix. The analysis of the whole database of discharges shows a degradation of the ion temperature gradient with increasing Te/Ti and a steepening with increasing gradient of the toroidal rotation. These findings complement previous studies.
The electron density, and the electron and ion temperatures were modelled with a first principle code. The applied sawtooth model could reproduce the experimental observations. The profile shapes, the changing Te/Ti and the peaking of the density and temperature profiles agree very well with the experimental data. Linear gyrokinetic calculations found the ion temperature gradient mode to be the dominant candidate for heat transport. The investigations can explain the observed phenomena in the experiment, like the different degree of increase of ion heat flux or density peaking for various collisionalities.
The results presented in this work show a consistent picture of the observed phenomena and the understanding of the main underlying physics. They allow a correct implementation in the applied computer codes and a reliable prediction of the performance of future fusion devices.
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Abdel-Fattah, E., and H. Sugai. "Electron heating mode transition observed in a very high frequency capacitive discharge." American Institute of Physics, 2003. http://hdl.handle.net/2237/7247.
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Edwards, Christopher. "Sliding mode schemes using output information with application to heating plant problems." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34765.
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This thesis considers the problem of developing sliding mode output tracking controllers for uncertain systems when output information alone is available. Two different approaches to controller design are proposed. The first approach is an observer based scheme which utilizes integral action. A new framework is proposed for the design of a class of sliding mode observers. The attainment of a canonical form, which is central to the framework, is a necessary and sufficient condition for the existence of a class of observers insensitive to matched uncertainty. The results supersede previous work in this area which necessitated checking the validity of a structural constraint between the state space matrices of the system. A formal analysis is undertaken of the combined plant/observer dynamics obtained when using a sliding mode control law incorporating integral action. It is demonstrated that the combined system is quadratically stable, despite the presence of a class of bounded matched uncertainty. Furthermore, the control law and the observer system can be designed independently; in other words, the 'separation principle' for linear systems also holds for this class of uncertain system and controller/observer pair. The second approach considers an output feedback stabilization problem where the class of hyperplanes and control laws considered is restricted to those which require only output information. The analysis is performed in essentially the same framework as that developed for the sliding mode observer. It enables the class of systems considered by other workers in this field to be extended and provides a practical realizable controller which requires no additional assumptions. These results are used in a model-reference framework to obtain a tracking controller. Successful attempts to implement these new theoretical ideas on an experimental furnace at the Gas Research Centre at Loughborough are documented. A single-input single-output sliding mode scheme to control temperature is described. Details are given of a more ambitious, multivariable scheme to regulate both temperature and excess oxygen by the manipulation of the fuel and air flows.
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Mardaljevic, John. "Daylight simulation : validation, sky models and daylight coefficients." Thesis, De Montfort University, 1999. http://hdl.handle.net/2086/4180.
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Cordes, Brian G. "Modeling-based minimization of time-to-uniformity in microwave heating systems." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050607-202823/.
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Thesis (M.S.) -- Worcester Polytechnic Institute.Keywords: uniformity of heating; optimization; optimal process; modeling; microwave pulsing; microwave heating; FDTD method; coupled problem. Includes bibliographical references (leaves 50-59).
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Wang, Yu. "Using whey protein gel as a model food to study dielectric heating of salmon." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Fall2006/y_wang_121506.pdf.
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Pangalos, Georg [Verfasser], and Gerwald [Akademischer Betreuer] Lichtenberg. "Model-based controller design methods for heating systems / Georg Pangalos ; Betreuer: Gerwald Lichtenberg." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2016. http://d-nb.info/1117086380/34.
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PONCET, Thomas. "Future business model for district heating based on renewables in Ile-de-France." Thesis, KTH, Energiteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144184.
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District heating is an efficient way to integrate renewable energies in the energy mix. In the French region Ile-de-France, district heating and renewables have known strong developments for several years, and they are expected to grow much more in the future. The expansion of renewable energies depends partly on their competitiveness compared to fossil fuels, which is related to public subsidies, and on the spread of district heating networks in the region. Thus, it could be assess what is the future business model for district heating based on renewables in Ile-de-France. The data at the disposal of ADEME, the French agency for environment and renewable energies, show that district heating systems based on biomass could soon become more competitive than fossil fuels, whereas systems based on geothermal heat have fairly high costs. Yet, geothermal heat is more developed than biomass, and is expected to reach the targets set by the regional action plan for 2020, on the contrary to biomass. Though the increasing competitiveness of renewables will cut the necessity of public subsidies, the difficulty to reach some regional targets might mean that further actions should be implemented. From the energy operators’ point of view, the sector of district heating will surely grow considerably and therefore represent a large potential of development for those companies.
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Christensen, Samuel David. "A Model for Analyzing Heating and Cooling Demand for Atria Between Tall Buildings." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4211.
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The heating and air-conditioning energy demand of skyscrapers with atria between buildings is explored. Radiation, conduction, convection, and ventilation were evaluated to determine annual heating and cooling energy demands for a 100-building city located in Provo, Utah. Spreadsheets models were developed and calibrated with a computational fluid dynamics model. Three spreadsheet model cases were examined: a baseline no-atrium case, a conditioned atrium case, and an unconditioned atrium case. The energy demands and atrium temperatures were compared between the different cases. The research concludes that atria can be used between buildings to reduce the heating and cooling energy demands. The exposed surface area of the city was reduced by 73.7%. This resulted in a 49.7% reduction in heating and cooling energy consumption for the unconditioned atrium case and a 16.0% reduction in energy consumption for the conditioned atrium case.
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Brouns, Corine E. "A study of the multi-zone air movement model." Thesis, Coventry University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357221.
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McGurn, Sean J. T. "Application of heat transfer models to boiler fouling monitoring." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282256.
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Al, Shammeri Bashar Mohammed Flayyih. "A novel induction heating system using multilevel neutral point clamped inverter." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/8305.
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This thesis investigates a novel DC/AC resonant inverter of Induction Heating (IH) system presenting a Multilevel Neutral Point Clamped (MNPCI) topology, as a new part of power supply design. The main function of the prototype is to provide a maximum and steady state power transfer from converter to the resonant load tank, by achieving zero current switching (ZCS) with selecting the best design of load tank topology, and utilizing the advantage aspects of both the Voltage Fed Inverter (VFI) and Current Fed Inverter (CFI) kinds, therefore it can considered as a hybrid-inverter (HVCFI) category . The new design benefits from series resonant inverter design through using two bulk voltage source capacitors to feed a constant voltage delivery to the MNPCI inverter with half the DC rail voltage to decrease the switching losses and mitigate the over voltage surge occurred in inverter switches during operation which may cause damage when dealing with high power systems. Besides, the design profits from the resonant load topology of parallel resonant inverter, through using the LLC resonant load tank. The design gives the advantage of having an output current gain value of about Quality Factor (Q) times the inverter current and absorbs the parasitic components. On the contrary, decreasing inverter current means decreasing the switching frequency and thus, decreasing the switching losses of the system. This aspect increases the output power, which increases the heating efficiency. In order for the proposed system to be more reliable and matches the characteristics of IH process , the prototype is modelled with a variable LLC topology instead of fixed load parameters with achieving soft switching mode of ZCS and zero voltage switching (ZVS) at all load conditions and a tiny phase shift angle between output current and voltage, which might be neglected. To achieve the goal of reducing harmonic distortion, a new harmonic control modulation is introduced, by controlling the ON switching time to obtain minimum Total Harmonic Distortion (THD) content accompanied with optimum power for heating energy.
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Lanz, Jason E. "A Numerical Model for Thermal Effects in a Microwave Irradiated Catalyst Bed." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36604.
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Electromagnetic and heat transfer analysis is used to determine possibility of selective heating of nanometer-sized, metallic catalyst particles attached to a ceramic support through microwave irradiation. This analysis is incorporated into a macroscopic heat transfer model of a packed and fluidized catalyst bed heated by a microwave field to predict thermal effects associated with selective heating of the catalyst sites. The model shows a dependence on particle size and microwave frequency on the selective heating of the catalyst sites. The macroscopic thermal effects are shown to be small for a typical experiment. However, changing the support material and catalyst particle size are shown to distinguish the thermal effects associated with selective heating of the metallic catalysts.Master of Science
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Mascarenhas, Wilfred J. "An improved finite-element model for simulating microwave processing of polymers and polymer-composites in a cylindrical resonant cavity." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-08222009-040417/.
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Jackson, Mitchell L. "Modeling the microwave frequency permittivity of thermoplastic composite materials." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06232009-063055/.
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Sugai, H., I. Ghanashev, and K. Mizuno. "Transition of electron heating mode in a planar microwave discharge at low pressures." American Institute of Physics, 2000. http://hdl.handle.net/2237/7248.
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Löfås, Henrik. "Ionospheric modification by powerful HF-waves : Underdense F-region heating by X-Mode." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121898.
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Observations of modifications of the electron temperature in the F-region produced by powerful high-frequency waves transmitted in X-mode are presented. The experiments were performed during quiet nighttime conditions with low ionospheric densities so no reflections occurred. Nevertheless temperature enhancements of the order of 300-400K were obtained. The modifications found can be well described by the theory of Ohmic heating by the pump wave and both temporal and spatial changes are reproduced. A brief overview of several different experimental campaigns at EISCAT facilities in the period from October 2006 to February 2008 are also given pointing out some interesting features from the different experiments. The main focus is then on the campaign during October 2006 and modifications of the electron temperature in the F-region.
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Gallacher, Jonathan R. "The Influence of Season, Heating Mode and Slope Angle on Wildland Fire Behavior." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5691.
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Wildland fire behavior research in the last 100 years has largely focused on understanding the physical phenomena behind fire spread and on developing models that can predict fire behavior. Research advances in the areas of live-fuel combustion and combustion modeling have highlighted several weaknesses in the current approach to fire research. Some of those areas include poor characterization of solid fuels in combustion modeling, a lack of understanding of the dominant heat transfer mechanisms in fire spread, a lack of understanding regarding the theory of live-fuel combustion, and a lack of understanding regarding the behavior of flames near slopes. In this work, the physical properties, chemical properties and burning behavior of the foliage from ten live shrub and conifer fuels were measured throughout a one-year period. Burn experiments were performed using different heating modes, namely convection-only, radiation-only and combined convection and radiation. Models to predict the physical properties and burning behavior were developed and reported. The flame behavior and associated heat flux from fires near slopes were also measured. Several important conclusions are evident from analysis of the data, namely (1) seasonal variability of the measured physical properties was found to be adequately explained without the use of a seasonal parameter. (2) ignition and burning behavior cannot be described using single-parameter correlations similar to those used for dead fuels, (3) moisture content, sample mass, apparent density (broad-leaf species), surface area (broad-leaf), sample width (needle species) and stem diameter (needle) were identified as the most important predictors of fire behavior in live fuels, (4) volatiles content, ether extractives, and ash content were not significant predictors of fire behavior under the conditions studied, (5) broadleaf species experienced a significant increase in burning rate when convection and radiation were used together compared to convection alone while needle species showed no significant difference between convection-only and convection combined with radiation, (6) there is no practical difference between heating modes from the perspective of the solid—it is only the amount of energy absorbed and the resulting solid temperature that matter, and (7) a radiant flux of 50 kW m-2 alone was not sufficient to ignite the fuel sample under experimental conditions used in this research, (8) the average flame tilt angle at which the behavior of a flame near a slope deviated from the behavior of a flame on flat ground was between 20° and 40°, depending on the criteria used, and (9) the traditional view of safe separation distance for a safety zone as the distance from the flame base is inadequate for fires near slopes.
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Choi, Dong Chun. "A novel isolation curtain to reduce turbine ingress heating and an advanced model for honeycomb labyrinth seals." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3799.
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A combination of 3-D and 2-D computational fluid dynamics (CFD) modeling
as well as experimental testing of the labyrinth seal with hexagonal honeycomb cells on
the stator wall was performed. For the 3-D and 2-D CFD models, the hexagonal
honeycomb structure was modeled using the concept of the baffle (zero-thickness wall)
and the simplified 2-D fin, respectively. The 3-D model showed that even a small axial
change of the tooth (or honeycomb wall) location, or a small circumferential change of
the honeycomb wall location significantly affected the flow patterns and leakage
characteristics especially for small tooth tip clearance. Also, the local details of the flow
field were investigated.
The seven basic procedural steps to develop a 2-D axisymmetric honeycomb
labyrinth seal leakage model were shown. Clearly demonstrated for varying test
conditions was the 2-D model capability to predict the 3-D honeycomb labyrinth flow
that had been measured at different operating conditions from that used in developing the
2-D model. Specifically, the 2-D model showed very close agreement with measurements. In addition, the 2-D model greatly reduced the computer resource
requirement needed to obtain a solution of the 3-D honeycomb labyrinth seal leakage.
The novel and advanced strategy to reduce the turbine ingress heating, and thus
the coolant requirement, by injecting a Âcoolant isolation curtain was developed
numerically using a 3-D CFD model. The coolant isolation curtain was applied under the
nozzle guide vane platform for the forward cavity of a turbine stage. Specifically, the
isolation curtain serves to isolate the hot mainstream gas from the turbine outer region.
The effect of the geometry change, the outer cavity axial gap clearance, the
circumferential location of the injection curtain slot and the injection fluid angle on the
ingress heating was investigated. Adding the chamfer to the baseline design gave a
similar or higher maximum temperature T*
max than did the baseline design without
chamfer, but implementation of the injection curtain slot reduced substantially T*
max of
the outer region. In addition, a more desirable uniform adiabatic wall temperature
distribution along the outer rotor and stator surfaces was observed due to the presence of
the isolation curtain.
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Johnson, Nils. "Evaluation of ignition and self-heating risks in bio-char storage by numerical simulation." Thesis, Luleå tekniska universitet, Energivetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79246.
Full textAbstract:
The move from fossil fuels is getting more relevant throughout the globe, mainly for it getting more costly to emit CO$_2$. The steel industry is one of the biggest contributor of the CO$_2$ emissions, and is therefore very motivated to reduce their emissions. One way to reduce the emissions is to go from coal to bio-char as a reducing agent. BEST(Bio-energy and sustainable technologies) is a research institute in Austria, and have been tasked to do research on bio-char and what problems that may occur with changing from coal to bio-char. One problem with bio-char is that it is prone to self ignition. This project aims is to develop a numerical model that can simulate self heating within bio-char stockpiles. The tool will be for a one-dimensional case using Cartesian coordinates. The calculations are based on the SIMPLE algorithm for Navier-Stokes equations, which is widely used within CFD calculations. This tool has been used to do sensitivity analysis for multiple variables and parameter studies for kinetic parameters related to the oxidation that occurs when bio-char is exposed to oxygen. Results show that oxygen concentration is the limiting factor to how much heat is released within the bag during simulations. Results also show that the accurate descriptions of reaction schemes and their rate expressions is very important to get results that is in line with real world scenarios.