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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
371

Magnetohydrodynamics of the coreless induction furnace

Moore, Damien Jude January 1983 (has links)
No description available.
372

Sun seeking architecture : the relationship between passive solar energy and form

Brunkan, Robert Randall January 1978 (has links)
Thesis. 1978. M.Arch--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Bibliography: leaves 204-208. / by Robert R. Brunkan. / M.Arch
373

Heating and stability of Columbia Neutral Torus stellarator plasmas

Hammond, Kenneth January 2017 (has links)
This thesis describes physics research carried out at the Columbia Neutral Torus (CNT) stellarator after its adaptation from a non-neutral plasma experiment to a device relevant to magnetic fusion energy research. Results are presented in the areas of plasma heating and related topics (microwave-assisted plasma start-up, overdense heating, inversion of stellarator images), as well as to stellarator stability and related topics (high β, error fields). This thesis also describes the engineering improvements which enabled the said adaptation of CNT. The first step of that process involved the installation of a low-power, pulsed 2.45 GHz magnetron. In those initial experiments it was found that the simultaneous use of microwave start-up and of an emissive hot cathode resulted in non-linearly increased electron densities, implying a synergy between the two start-up methods. Then, a 10 kW, 2.45 GHz heating system was commissioned including a custom-designed transmission line and launch antenna. Highly overdense plasmas (a factor of 4 above the cutoff density) were obtained with this system, both for O-mode and X-mode polarization. The analysis of Langmuir probe profiles of density and temperature required the accurate mapping of the minor radius in the plasma, which motivated a study of CNT error fields. This resulted in a new numerical method for inferring coil misalignments from flux surface measurements. The improved knowledge of the actual magnetic field geometry of CNT permitted to develop and successfully apply an inversion technique to experimental plasma images. This technique (“onion peeling”) reconstructs radial emissivity profiles, and can be considered a 3D generalization of Abel inversion. Finally, simulations of high-β plasma equilibria in different CNT magnetic configurations indicate that (1) ballooning stability limits should be accessible at volume-averaged β as low as 0.9% and (2) ballooning-stable β values as high as 3.0% should be attainable with heating powers as low as 40-100 kW and 1-3 MW respectively, according to stellarator energy confinement scaling laws.
374

Elucidation of nonthermal effects of microwave irradiation on the unfolding pathways of [beta]-lactoglobulin and hemoglobin

Al-Jundi, Abdul Nasser January 2004 (has links)
No description available.
375

District heating to replace an electrical installation

Serra Ramon, Lourdes, Montañes Asenjo, Alba January 2009 (has links)
<p>This project has been developed at the company Gavlegardarna. The companyowns a large part of the buildings of Gävle and two of them are the objective ofthe project. Gavlegardana is highly concerned about the environment; for thisreason, they cooperate on the subject with the energy management from theirtechnical department.</p><p>Gävle is one of the Swedish cities where the DH (district heating) network isdistributed, arriving to most of the dwellings, industries and commercialbuildings. As DH uses environmentally friendly sources of energy,Gavlegardana is introducing it in its buildings.</p><p>Electrical radiators and boilers were installed in the buildings when the price ofelectricity was more affordable than nowadays. The price of the electricity canbe considered 1,23 SEK/kWh while the DH price is 0,45 SEK/kWh.</p><p>Consequently, this is another reason why the objective of the company at thepresent time is to replace electrical space heating systems by means of districtheating.</p><p>The energy balance of the buildings is analysed in order to study their currentenergy situation. This entails the consideration of heat gains and lossesinvolved. The heat gains of the building are the heat from solar radiation whicharrives at the building trough the windows, the heat internally generated (bypersons, lighting and other devices) and the heat supplied. The heat losses are composed by the transmission trough walls and windows, the infiltrations, the heat used for hot tap water and the ventilation losses.</p><p>An important part of the work required to calculate the energy balance hasconsisted of the collection and organization of all the data (areas, types ofmaterial, electrical devices, lighting, number of employees, opening hours...).This data comes from the drawings of the buildings provided by the companyand from the information gathered during the visits to the installation. In addition, the ventilation flows were measured in-situ using the tools provided by Theorells.</p><p>Gavle Energi, the DH distributor company, has been contacted in order to fixthe cost and other details related to the district heating connection. The heatexchanger models, selected from Palmat System AB, are TP20 for Building Aand TP10 for Building B. TP20 provides 100 kW of heating and 0,4 l/s of hot tap water and TP10 provides 50 kW and 0,31 l/s respectively. The capital cost is 187500 SEK which includes the heat exchangers and the connection cost.</p><p>As the secondary circuit is not currently installed because the existing system iscomposed by electrical radiators, the installation of the piping network in thebuilding has been designed. The radiators’ power is calculated taking intoaccount the need of heat in each room which is estimated as the transmissionlosses. This need of heat calculated is higher than the energy currently supplied which means that the thermal comfort is not achieved in all the rooms of the buildings.</p><p>In spite of using more energy for space heating, the change of heat sourceentails a lower energy cost per year. The selected radiators are from Epeconand the investment cost (including the installation) is 203671 SEK. The brand of the selected pipes is Broson and the investment cost of the total piping system is 66000 SEK.</p><p>The initial investment of the new installation is 457171 SEK, considering the DHconnection, heat exchangers, radiators and pipes. If the initial investment istotally paid in cash by the company the payback will be fulfilled in 6 years. Incase of borrowing the money from the bank (considering an interest rate of 5%), two possibilities can be considered: paying back the money in annual rates over 15 years or 30 years of maturity. The paybacks are 11 and 8 years respectively.</p><p>After designing the DH piping system in the buildings, estimating the total costs of the investment and studying the project’s feasibility by suggesting different payment options, some possible energy savings are recommended.</p><p> </p><p>The first of the options refers to the transmission losses trough the windowswhose values’ are considerably high. Using a glass with a lower U-value, theselosses can decrease until 66% (with triple glass windows). Consequently, thepower required for space heating can also be reduced until 26%.</p><p>Regarding the ventilation, rotating heat exchangers are currently used, whichentails the problem of smells mixture detected by the users of the buildings. By changing them with flat-plate heat exchangers, the problem is solved and the efficiency is increased from 66% to 85%. The new heat exchanger cost is340387 SEK and it has a payback of 10 years.</p>
376

Return temperature influence of a district heating network on the CHP plant production costs

Sallent, Roger January 2009 (has links)
<p><strong></strong>The aim of this Project is to study the influence of high return temperatures in district heating on the costs for heat and power production in a CHP plant.When the temperatures of the water coming back to the heating plant are so high, the overall performance of heat and power production is decreased and, consequently, also the production costs. Along the project, the influence of this temperature on the different parts of a CHP plant are analysed as well as the economical impact it has. At the same time, some general impacts on the entire network are mentioned.</p><p> </p><p>A real network is used in this project, and it is the net of district heating in Gävle (Sweden), and the most of the study is focus in its bigger combined heat and power production plant (CHP), called Johannes.</p>
377

Analysisof a DH system in Sörbyskolan : School placed in Gävle

Lopez, Carlos January 2008 (has links)
<p>Electricity and district heating are the most important energy carriers for the residential and service sector in Sweden. Today, district heating supplies about half of the total heating requirement of residential and commercial premises in Sweden. The aim of this paper is the analysis of the heating system of a school, placed in Gävle, Sweden. The heat is delivered to the school by a district heating network.</p><p>First of all, the Heat Balance must be done, with the purpose of obtain the best knowledge of the present situation in the school. The calculations about the transmission and ventilation losses and the internal heating generated have been showed. After this, the point of view has been focused on the district heating system itself. It is means, the distribution pipe system inside the school. The efficiency and accuracy of the net will be analysed and discussed.</p><p>Three possible ways to improve the net will be showed. The first of all is the most simple: just take the pipe system and try to reduce the waste heat, the heat losses; the second choice is to make a new connection to the district heating network, joining all the buildings with one connection for each building –five more- instead of only the connection that exists at the moment when this paper was written; the third option seems as a different model of the second, it is means to divide all the school in two bigger parts and make another connection to the district heating network with the purpose of dividing the heating system in two equal parts.</p><p>Thanks to the heat balance done in the school and in the district heating system, it is possible to know the waste of heat. Mainly, these losses are found in the district heating net. The amount of waste is around 17%, a really high amount of energy wasted, which must be reduced. According to the data of the company Gävle Energy, the waste in old buildings like the school which is under study in this paper, usually is between 15% and 20% of the supplied energy. So, this showed the accuracy of the method used to make this paper.</p><p>According to the possibilities of improvement, it will depend on the ultimate decision of the Gävle Fastigheter, company which owns the school, to choose the way that could be better for their own interest. However, in this paper the prices and possible pay-back times are showed, in order to provide better information.</p><p>Although the best solution has a total cost of 1750000 Swedish crowns (186289 €) and a pay-back time of 21 years –talking about making five new connections-, another cheaper possibility is also commented: improving the isolation of the pipe system, with a cost of 549000 SEK (58441 €) and a pay-back time near 7 years.</p>
378

Solar Water Heating in Dragash Municipality, Kosovo

Dahl Håkans, Mia January 2010 (has links)
<p>Water has been heated with the sun has almost as long as there have been humans, but itis not until recently that more advanced and effective solar water heating systems havebecome common, and they are still gaining ground. Through the years new systems andnew solar collectors have been developed. In Kosovo, however, not much attention hasbeen paid to replace fossil fuels with renewable energy sources and solar water heatingsystems is a new concept.The United Nations Development Programme (UNDP) in Kosovo is working on a projecton sustainable development in Dragash Municipality in southern Kosovo. A solar waterheating system has recently been installed at the hospital in Dragash, as part of the UNDPproject. The system is a pilot project, to see how well solar energy can be used in thisarea.The existing solar water heating system at the hospital in Dragash was examined andevaluated. The possibilities of using the fundamental principle of the solar water heatingsystem at the hospital on residential houses in Dragash were looked into. Six prototypesof average residential houses in the village of Brod and Dragash Town were created. Thesolar collector size and storage needed to meet the demands for the six house prototypeswere calculated. Information on the incoming solar irradiation for each hour of a year wasobtained from the online service SoDa Solar Radiation Data. The total annual incomingsolar radiation for one square meter was calculated.The environmental, social and economic effects of solar water heating in Dragash wereconsidered and discussed. Rough economic calculations were made on the effects ofinstallation of solar water heating systems.The solar water heating system at the hospital in Dragash is a good pilot project, and islikely to work satisfyingly. The annual output effect of the system is approximately 7 400kWh. The fundamental principle needs to be altered to work on residential houses. Thesolar collector needs to be of a cheaper kind, and the collector and storage tank can be ofsmaller dimensions.Solar water heating can contribute to Kosovo’s work toward sustainable environmental,social and economic development focusing on hot water supply. Kosovo has sufficientsolar radiation for solar water heating systems to work in a satisfactory way. The outputeffect for a solar water heating system in Dragash is around 390 kWh/(m2∙year) with atotal efficiency for the system of 30%. If the solar water heating system replaces heatingby electricity the annual savings can be 31 €/m2 solar collector. The biggest obstacles forthe use of solar energy are the public’s lack of knowledge on solar water heating andenvironmental problems connected to energy, as well as economy.The work done in this thesis is a good foundation for future research on solar energy inKosovo. It can be extended and elaborated with more thorough economic calculations,since economy is an important factor in the future for solar energy. Only roughcalculations were made in this thesis, since it has a technical approach. More extensiveresearch could also be done to evaluate the possibilities of using solar water heating forspace heating.</p> / <p>Varmvatten har värmts med hjälp av solen nästan så länge det funnits människor, men detär inte förrän nyligen som mer avancerade och effektivare solvärmesystem har blivitvanliga, och de blir allt vanligare. Genom åren har nya system och nya solfångareutvecklats. I Kosovo däremot har inte mycket uppmärksamhet ägnats åt att ersätta fossilabränslen med förnyelsebara energikällor, och solvärme är ett nytt koncept.FN:s utvecklingsprogram (UNDP) i Kosovo arbetar med ett projekt med målet hållbarutveckling i Dragash kommun i södra Kosovo. Ett solvärmesystem har nyligeninstallerats på sjukhuset i Dragash, som en del av UNDP:s projekt. Systemet är ettpilotprojekt för att se hur bra solenergi fungerar i det här området.Det befintliga solvärmesystemet på sjukhuset i Dragash undersöktes och utvärderades.Möjligheterna att använda grundprincipen för solvärmesystemet på sjukhuset påbostadshus i Dragash undersöktes. Sex prototyper för genomsnittliga hus i byn Brod och iDragash centrum togs fram. Solfångararean och ackumulatortanksvolymen som krävs föratt klara behoven för de sex husprototyperna beräknades. Information om solinstrålningenför varje hus erhölls från SoDa Solar Radiation Data. Den totala solinstrålningen på enkvadratmeter beräknades.De miljömässiga, sociala och ekonomiska effekterna av solvärme i Dragash diskuterades.Ekonomiska överslagsberäkningar gjordes på effekterna av installation av solvärme.Solvärmesystemet på sjukhuset i Dragash är ett bra pilotprojekt, och är sannolikt attfungera tillfredsställande. Den årliga energi som systemet kan ge kommer att vara ungefär7 400 kWh. Grundprincipen behöver ändras för att fungera på bostadshus. Solfångarnabehöver vara av en billigare typ, och storleken på solfångare och ackumulatortankbehöver vara mindre.Solvärme kan bidra till Kosovos arbete mot hållbar miljömässig, social och ekonomiskutveckling med fokus på varmvattenbehov. Kosovo har tillräcklig solinstrålning för attsolvärmesystem ska fungera tillfredsställande. Med en totalverkningsgrad på 30 % för ettsolvärmesystem kan systemet ge ungefär 390 kWh/(m2∙year). Om systemet ersätteruppvärmning med el kan de årliga besparingarna bli ungefär 31 €/m2 solfångare. Destörsta hindren för användning av solenergi är allmänhetens brist på kunskap om solvärmeoch miljöproblem kopplade till energi, samt ekonomi.Arbetet i detta examensarbete är en bra grund för fortsatta studier om solenergi i Kosovo.Arbetet kan vidgas och utvecklas med mer ingående ekonomiska beräkningar, eftersomekonomi är en viktig faktor i framtiden för solenergi. Endast överslagsberäkningar gjordesi detta examensarbete, eftersom det har ett tekniskt förhållningssätt. Mer omfattandestudier kan också göras för att utvärdera möjligheterna ätt använda solvärme föruppvärmning av bostäder.</p>
379

Maximum element temperature for Kanthal Super 1800S in flowing nitrogen atmosphere with low content of oxygen

Persson, Petter January 2010 (has links)
<p><strong>Abstract</strong></p><p>The behavior for MoSi<sub>2</sub> based high temperature heating elements for resistive heating has been examined in elevated temperature and low oxygen content environment. MoSi<sub>2</sub> spontaneously forms a protective SiO<sub>2</sub> scale at high temperature if the amount of oxygen in the ambient atmosphere is sufficient according to the following reaction:</p><p>5MoSi<sub>2</sub> + 7O<sub>2</sub>(g)  7SiO<sub>2</sub> + Mo<sub>5</sub>Si<sub>3</sub></p><p>If the oxygen content at a specific temperature is too low, SiO(g) is more stable than SiO<sub>2</sub> and the following reaction will occur instead:</p><p>2SiO<sub>2</sub>  2SiO(g) + O<sub>2</sub>(g)</p><p>Then surface will be Si-deplated and finally, the base material will be exposed. Si and Mo will oxidize and degas from the surface as SiO and MoO<sub>3</sub> with severe diameter reduction of the heating element as a result. It is therefore of high interest to find the relationship between the maximum element temperature and the oxygen content in the ambient atmosphere to be able to fully exploit the potential of the heating elements and also to aid and help diagnose customer complaints.</p><p> </p><p>After 14 full scale tests in a custom made atmospheric furnace, the following equation could be calculated:</p><p>p(O<sub>2</sub>) = 1.748·10<sup>0.01677·T·log(e)-10</sup></p><p>The equation gives the minimum oxygen content at a specified temperature. The equation is based on 100 hours tests at atmospheric pressure, gas flow rate of 4 liter per minute, varying temperature and varying oxygen content. Nitrogen has been used as carrier gas for the oxygen.</p>
380

Investigation of standard test procedures for integral storage solar domestic hot water systems /

Lindsay, Russell Charles, January 1983 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1983. / Vita. Abstract. Includes bibliographical references (leaves 80-82). Also available via the Internet.

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