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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.
21

Návrh roštového kotle s přirozenou cirkulací na spalování RDF / Design of steam boiler with grate firing burning RDF

Basov, Mykhailo January 2017 (has links)
This thesis deals with a project of steam boiler to combustion of refused-derived fuel. Considering the required fuel and output parameters of the steam was made the thermal calculation of boiler with it design and an individual calculation of heat exchange surfaces; hydrodynamic and aerodynamic calculations of the steam boiler.
22

Náhrada trubkových výměníků tepla v CFD výpočtech proudění / Simplified modelling of tube bank heat exchanger in CFD

Cacková, Tereza January 2020 (has links)
The master thesis deals with the replacement of heat exchanger surfaces during simulations in the ANSYS Fluent. The aim of this work is to find a simplified model of the heat exchanger usable for flow simulations in large process and energy units, where it is not possible to model the entire heat exchanger in detail. The calculation procedures are applied to „tube bank” heat exchanger. The master thesis is divided into three parts. First part deals with pressure losses. The "porous zone" approach is used as a replacement for the heat exchanger surface. In the second part, the heat transfer by convection and conduction through the heat exchanger is replaced by the "Heat Exchanger" module. The third part examines the influence of material properties, heat source and fixed temperatures on incident radiation. All calculations resulting from the methods are performed using a script that prepares the output data in format suitable for insertion into ANSYS Fluent. A simplification, which faithfully replaces a fully modeled heat exchanger, has been found in all three parts of the thesis.
23

Odloučení dopravního vzduchu surovinové moučky / Severance of raw material flour transportation air

Brzobohatý, Lukáš January 2013 (has links)
The dissertation is focused on the applied technical and economic analysis of the influence separation of transport air from raw meal on the economy clinker/cement production, in specific cement production. The analysis is performed on the basis of a detailed understanding and analysis of the function of each component of the technology of cement production, which are affected by separation of transport air from raw meal, mainly the dosing and preheat system of the raw meal. The results of the analysis show a significant effect (impact) separation of transport air on the production costs.
24

Řešení inverzních úloh v oblasti výměníků hmoty a tepla / Solutions of inverse problems in the area of material and heat exchangers

Kůdelová, Tereza January 2014 (has links)
This master’s thesis deals with the dynamic behaviour of the heat exchangers which is described by a system of differential equations. In this connection, it contains general informations about heat transfer, heat exchangers and their arrangements. The main aim of this thesis is to solve the inverse problem of the antiparallel arrangement and discuss the question of the controllability, observability and identifiability of its parameters.
25

Design and Development of Solar Thermal Propulsion SystemWith PCM as Thermal Energy Storage Medium

Vommina, Naga Sree Sumanvitha 07 August 2023 (has links)
No description available.
26

Dimensioning study of EPR2 fuel pool cooling system / Dimensioneringsstudie av EPR2 bränslebassäng kylsystem

Rubler, Thomas January 2023 (has links)
The PTR system allows the EPR2 fuel pool to be cooled. The evacuation of the residual power fromthe pool is ensured by several heat exchangers and pumps, which have to be dimensioned in order to meetdifferent requirements.In order to dimension them, the worst-case scenario of the components must first be determined.Sensitivity to external conditions and efficiency studies enable to propose a heat exchanger design tomeet the requirements. A parametric study then allows to study more precisely the influence of thegeometry of the exchanger on the heat transfer. This allows to guide the conception of a CFD study ofthe design on the Comsol software in order to validate it. The proposed design can then be integratedinto the PTR cooling train. The train is modeled with FloMaster, in order to compute the head losses inthe hydraulic system and to propose a pump altimetry preventing cavitation.The dimensioning case of the exchangers corresponds to the operating case of the PTR trains duringunit shutdown, while the scenario that facilitates cavitation corresponds to the boiling of the fuel pool.The temperature of the cold source RRI is a sensitive data for the operation of the exchangers. In addition,the placement of the baffles and the space between the tubes play a determining role in the heat removal.It was difficult to construct the desired exchanger geometry in CFD. A compromise model was thusidentified and studied in CFD. The FloMaster study showed that the pressure drop in the PTR network isabout 15.5 mCE at the considered flow rate. Cavitation in a main train is not a problem if the pumps arelowered by at least 1.8 meters from the pool suction point.The sizing study therefore allowed us to propose a heat exchanger design close to the specifications,but this could not be precisely studied in CFD. The pressure drop study allowed to propose a pumpaltimetry preventing cavitation. / PTR-systemet gör det möjligt att kyla bränslebassängen i EPR2. Evakueringen av den återstående energin frånfrån bassängen säkerställs av flera värmeväxlare och pumpar, som måste dimensioneras för att uppfyllaolika krav.För att kunna dimensionera dem måste man först fastställa det värsta tänkbara scenariot för komponenterna.Känslighet för yttre förhållanden och effektivitetsstudier gör det möjligt att föreslå en värmeväxlardesign somuppfyller kraven. En parametrisk studie gör det sedan möjligt att mer exakt studera påverkan avväxlarens geometri har på värmeöverföringen. Detta gör det möjligt att vägleda utformningen av en CFD-studie avav konstruktionen i programvaran Comsol för att validera den. Den föreslagna konstruktionen kan sedan integrerasi PTR-kyltåget. Tåget modelleras med FloMaster, för att beräkna huvudförlusterna ihydraulsystemet och för att föreslå en pumphöjdmätning som förhindrar kavitation.Dimensioneringsfallet för växlarna motsvarar driftsfallet för PTR-tågen under driftavställning avenhetens avstängning, medan det scenario som underlättar kavitation motsvarar kokning av bränslebassängen.Temperaturen hos den kalla källan RRI är en känslig uppgift för driften av växlarna. Dessutom måsteplaceringen av bafflarna och utrymmet mellan rören en avgörande roll för värmeavledningen.Det var svårt att konstruera den önskade växlargeometrin i CFD. En kompromissmodell identifierades därföridentifierades och studerades i CFD. FloMaster-studien visade att tryckfallet i PTR-nätverket ärcirka 15,5 mCE vid det aktuella flödet. Kavitation i ett huvudtåg är inte ett problem om pumparna ärsänks med minst 1,8 meter från poolens sugpunkt.Dimensioneringsstudien gjorde det därför möjligt för oss att föreslå en värmeväxlardesign som ligger nära specifikationerna,men detta kunde inte studeras exakt i CFD. Tryckfallsstudien gjorde det möjligt att föreslå en pumpaltimetri som förhindrar kavitation.
27

Prestanda hos värmeväxlande system : Undersökning och utvärdering av värmeväxlare för medicinskt bruk / Performance of Heat Exchange System : Investigation and Evaluation of Heat Exchangers for Medical Use

Weman, Sara January 2022 (has links)
Detta examensarbete har genomförts på uppdrag av företaget Sangair i syfte att bidra med kunskap i deras utveckling av en produkt ämnad att behandla sepsis med hjälp av ozon. Sepsis är en av de ledande dödsorsakerna i världen och behandlas idag primärt med antibiotika. På grund av den ökade antibiotikaresistensen efterfrågas nya behandlingsmetoder. Ozon har bakteriedödande egenskaper och det finns goda indikationer på att ozonterapier kan komma att bli ett komplement till antibiotikabehandlingar. För att ozon ska lösas in väl i blod krävs låga temperaturer. Blod kan kylas utanför kroppen med hjälp av värmeväxlare som har till uppgift att överföra värme mellan två fluider. Målet för examensarbetet var att undersöka två värmeväxlare, CSC14 och BCD Vanguard från tillverkaren Sorin Group för att utvärdera deras kapacitet att kyla blod till temperaturer lägre än 12 °C. Som en del i målet undersöks värmeväxlarnas effektivitet i flödesintervallet 80–150 ml/min, samt förhållandet mellan den önskade temperaturen och den uppnådda temperaturen i processen.  Arbetet utfördes primärt genom flertalet tester där ett system med värmeväxlare kopplades upp. Vid genomförandet av testerna användes mjölk för att simulera blodets egenskaper. Inställningen för kylaren var den parameter som hade störst påverkan på temperaturen som mjölken kunde kylas till. Skillnaden mellan den önskade och den uppmätta temperaturen var större ju närmre 0 °C kylartemperaturen kom. Testerna visade att CSC14 inte fungerar optimalt vid låga flödeshastigheter och därför ansågs denna inte lämplig för vidare tester. BCD Vanguard har en god effektivitet inom flödesintervallet där effektiviteten ökar med flödeshastigheten. / This thesis work was carried out on behalf of the company Sangair with the purpose of contributing to their product development where they are designing a medical device for treating sepsis using ozone. Sepsis is one of the leading causes of death worldwide and is primarily treated using antibiotics. Due to the increase in antibiotic resistant bacteria new treatment methods must be developed. Ozone is bactericidal and may serve as a complement to antibiotic treatments. The solubility of ozone in blood increases with decreasing temperatures. Heat exchangers, which transfer heat between two fluids, can be used to cool the blood outside the human body.  The goal for this thesis work was to investigate two heat exchangers, CSC14 and BCD Vanguard, both manufactured by Sorin Group. The objective was to evaluate their respective capacity to cool blood to temperatures below 12 °C. The efficiency of the heat exchangers for flow rates ranging from 80—150 ml/min and the relationship between the desired temperature and the actual temperature were evaluated.  Multiple tests were performed with heat exchangers connected in a simple system. Milk was used to simulate the properties of blood. The settings of the cooling unit had the greatest effect on the achieved cooling. Differences between the desired and the measured temperature were greater the closer to 0 °C the cooler was set. The test unveiled that CSC14 does not perform well at low flow rates and thus no further testing was done using that heat exchanger. The BCD Vanguard was shown to have a high efficiency in the desired interval with performance increasing with increasing flow rates.
28

Investigation of the correlation of fracture frequency and electric resistivity in impact craters in crystalline rocks

Bäckström, Ann January 2004 (has links)
<p>Impact craters are formed when a large meteorite or comethits the Earth. At the impact a shock wave is released causingabundant fracturing in the surrounding bedrock. This type offracturing is intense and occurs throughout a very large volume(>100 km<sup>3</sup>) of the bedrock. Fractures of this type have beenobserved in deep drilling, to 5 km depth, in thePuchezh-Katunki Impact Crater. At theses depths the ambienttemperature is high. Thus impact structures are candidates forpotential heat-exchange sources for extraction of geothermalenergy.</p><p>There is a relation between fracture intensity and electricresistivity in bedrock predominated by impact-generatedfractures. In crystalline bedrock changes in electricresistivity is mainly due to fracturing which is the mainsource of porosity in these rocks. Electric resistivity methodsare highly sensitivity to porosity. Furthermore highfracture-intensities have generally been associated with lowelectric resistivity. Electro-magnetic methods like Very LowFrequency Resistivity (VLF-R) and Magnetotellurics (MT) canindirectly measure electric resistivity to relatively largedepths in the bedrock.</p><p>This study will quantify the relationship between fractureintensity and electric resistivity which can be used as aprospecting tool for geothermal energy resources at largedepth.</p><p>To meet that end, a method for fracture mapping on outcropsin Swedish terrain and a method to calculate thethree-dimensional fracture frequency from two-dimensionalfracture data has been developed. The fracture traces measuredin two dimensions on outcrops are assumed to represent avertical surface and must be converted to a three-dimensionalmeasure of the fracture frequency per unit volume. Spacing, dipand trace length of fractures have been accounted for. Thebiases associated with the mapping method have also beenaccounted for (II).</p><p>The correlation between impact-induced fracturing andelectric resistivity in crystalline rocks in the Lockne Areashows that the extent of impact fracturing in crystalline rockscan be measured with electro-magnetic or electric techniques.In addition the electric resistivity of crystalline basementand impact generated Tandsby Breccia from the Lockne Craterwere determined (I).</p><p>The relation between fracture frequency and electricresistivity in fresh water conditions using the VLF-R method isestablished from data collected from both two drill holes andfrom numerous outcrops in the Björkö region. Apreliminary quantification of the fracture frequency has beenmade. The MT resistivity models, related to the two drillholes, show that porosity and mineral-conductivity variationsof the bedrock affect this relation more than the salinityvariations in the bore-hole fluid. Further research is neededto establish a firm relation between fracture frequency,salinity of rock fluid, conductivity and porosity in order tovalidate the MT resistivity models (III).</p><p><b>Keywords:</b>Electric resistivity, Fracture frequency,Impact generated fractures, Electro-magnetic techniques, VLF-Rmethod, MT method, Window-mapping technique, Three-dimensionalfracture calculations, heat-exchange structure, geothermalenergy.</p>
29

Kvantitativ analys av organiska syror i kylvätska / Quantitative analysis of organic acids in engine coolant

Henriksson, Emma, Holm, Martin January 2017 (has links)
Volvo Cars är ett välkänt företag som säljer bilar över hela världen. Idag skickar Volvo Cars sin kylvätska till leverantörer för analys. Processen är komplicerad och tar mycket tid. Det finns ett intresse hos Volvo Cars att själva kunna analysera kylvätskan. För att kunna göra detta krävs det att en metod som de kan använda för att analysera kylvätskan utvecklas. Examensarbetet syftar till att utveckla en metod som gör det möjligt att analysera koncentrationen av organiska syror i Volvos kylvätska. Analysen ska göras med hjälp av en High Performance Liquid Chromatography - HPLC. De organiska syrorna är inhibitorer som skyddar material i motorn från korrosion när det kommer i kontakt med kylvätskan. Metoden utvecklas i flera steg, det är viktigt att veta hur olika organiska syror kan analyseras med en HPLC. HPLC-analyser är mycket beroende av de intrumentella inställningarna. Inställningarna som ändrar när metoden utvecklas är pH, typ av kolonn, våglängd på detektorn, flödeshastighet i kolonnen, injektionsvolymen, sammansättning av eluent (lösningsmedel) och analystid. Kalibreringskurvor konstrueras för att sedan kunna användas i fortsatta studier. Tre av fem organiska syror som skulle analyseras var möjliga att analysera med två olika metoder. Den enda skillnaden mellan metoderna var våglängden på detektorn. En av de organiska syrorna hade en mer linjär kalibreringskurva vid en högre våglängd. / Volvo Cars is a well-known company and they are selling their cars all over the world. Today, Volvo Cars send their engine coolant to the supplier of engine coolant for analysis. This process is complicated and takes a lot of time. It is in the interest of Volvo Cars to be able to analyze the engine coolant themselves. In order to do that, a method where they can analyze the engine coolant must be developed. This exam work aim to develop a method where it is possible to analyze the concentration of organic acids in Volvo´s engine coolant with a High Performance Liquid Chromatography - HPLC. The organic acids are inhibitors that protect the materials in the engine from corrosion when in contact with the engine coolant. The method is developed in several steps. First it is important to know how different organic acids could be analyzed with an HPLC. HPLC-analysis is very dependent of the instrumental parameters. The parameters you change when developing a method are pH, kind of column, wavelength of the detector, kind of detector, flow rate in the column, injections volume, composition of the eluent (solvent) and, analysis time. Calibration curves are created and could be used as a reference in further analysis. Three of the five organic acids that were supposed to be analyzed were possible to analyze. Three organic acids were analyzed with one method and the two remaining organic acids with another method. The only difference between the methods is the wavelengths of the detector.
30

Rayonnement acoustique d'une structure périodique de type batterie à ailettes : Application aux pompes à chaleur / Acoustic radiation of a periodic structure of finned-coil type : Application to heat pumps

Gosse, Guillaume 20 November 2012 (has links)
La prédiction du bruit émis par les unités extérieures des pompes à chaleur, provenant en partie des batteries à ailettes, constitue un enjeu industriel important. L’obstacle majeur réside dans l’impossibilité de réaliser le calcul acoustique d’une batterie à ailettes avec les outils de simulation classiques (Éléments Finis de Frontière) à cause du trop grand nombre d’éléments nécessaires (près de 600 ailettes par mètre). Cette thèse a pour objectif d’exploiter la périodicité des batteries à ailettes afin de pouvoir calculer leur bruit rayonné à partir du rayonnement d’une seule ailette. La propagation des vibrations est décrite sous la forme d’une décomposition en ondes, autorisant la réalisation séparée des calculs pour chaque onde. Le déplacement en tout point de la structure est calculé à partir du déplacement d’un seul élément unitaire, obtenu par la Méthode des Éléments Finis (FEM). Un élément unitaire acoustique est spécialement défini, comprenant des baffles rigides destinés à représenter l’influence des autres ailettes de la structure. Le rayonnement de cet élément est calculé pour chaque onde en utilisant la méthode des Éléments Finis de Frontière (BEM), puis dupliqué spatialement en tenant compte de la nature propagative des différentes ondes. Pour chaque structure étudiée, la comparaison avec le calcul direct de la structure complète montre une très bonne concordance avec des temps de calcul fortement réduits. L’influence de plusieurs paramètres sur le comportement de la structure a également été identifiée, mettant ainsi en évidence certains phénomènes particuliers propres aux structures périodiques. Dans la dernière partie de cette thèse, une validation expérimentale de l’approche périodique est proposée. Les résultats numériques sont comparables aux mesures vibratoires et acoustiques réalisées sur les batteries à ailettes. / The prediction of noise from outdoor units of heat pumps, partly coming from finned coils, is an important industrial issue. The major obstacle to the study of finned coils lies in the inability to perform the acoustic calculation with classic simulation tools (Boundary Element Method) because of the huge number of required elements (about 600 fins per meter). The goal of this thesis is to exploit the periodicity of finned coils in order to calculate the total noise radiated from the radiation of a single fin, and thus get rid of the number of fins composing the structure. The vibrations propagation is described as a wave decomposition, allowing the realization of separate calculations for each wave. The displacement at any point of the structure is calculated from the displacement of a single unit element, obtained with the Finite Element Method (FEM). An acoustic unit element is especially defined, comprising rigid baffles representing the influence of other fins of the structure. The radiation of this component is calculated for each wave using the Boundary Element Method (BEM), then spatially duplicated taking into account the propagation of the different waves. For each considered structure, a comparison with the direct calculation of the complete structure shows very good agreement with greatly reduced computation times. The influence of several parameters on the behaviour of the structure was also identified, thus highlighting some particular phenomena specific to periodic structures. In the last part of this thesis, an experimental validation of the periodic approach is proposed. Numerical results are close to vibratory and acoustic measurements done on the finned coils.

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