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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.
11

Numerical Simulation of the Non-Uniformity of Cross Flow over Helical Tube Bundles / Numerisk simulering av ojämnheter i tvärflödet över spiralformade rörbuntar

Ma, Anxiang January 2024 (has links)
Helical tube bundles are usually used in the steam generator (SG) of High-Temperature Gas-Cooled Reactors (HTGRs) as the heat transfer area. The helical tube bundle is composed of multiple-layer helically coiled tubes, which are fixed by multiple sets of supporting structures. There are ideal flow paths separated by different layers of helical tubes. The velocity non-uniformity for different flow paths will affect the heat transfer tube temperature and the outlet steam temperature uniformity of different tube layers. In the shell side of the SG, turbulent cross flow over helical tube bundles are complicated and difficult to predict due to reverse pressure gradient and boundary layer separation. Due to the huge amount of computation resources consumption, there are few numerical simulation studies on the non-uniformity of cross flow over large-volume helical tube bundles.Two cases, namely the flow past a circular cylinder and cross flow over in-line tube bundles, are simulated to validate if Partially-Averaged Navier-Stokes (PANS) model is suitable for simulations of cross flow over helical tube bundles. The simulation results of k-ω SST PANS model are well agree with the average and local experimental data. Therefore, k-ω SST PANS model is used to investigate the influences of the supporting structure and helical diameter on the non-uniformity of cross flow over ideal helical tube bundles. The helix angle of helical tube bundle is neglected. The computational domain consists of 5 rows of helically coiled tubes in the streamwise direction. Periodic boundary conditions are used for the inlet and outlet to reduce the consumption of computing resources.For cross flow over helical tube bundles, there exists significant circumferential and radial velocities, which means there are secondary flows in the plane perpendicular to the streamwise direction. The radial velocity is about 16% of the streamwise velocity. Due to the presence of secondary flow, cross flow over individual tube is inclined, and the inclination direction changes at different circumferential positions. At the same circumferential position, the flow inclination direction is the same along the streamwise direction and radial direction. For helical tube bundles, the ratio of the blocking area to the flow area (blocking area ratio) of the inner, outer and middle flow paths are different. The blocking area ratio of the inner flow path is large, and the blocking area ratio of the outer flow path is small, resulting in non-uniform velocity distribution in different flow paths.Cross flow over helical tube bundles with three helical diameters (inner wall radius Ri is 0.02 m, 0.14 m and 0.26 m, respectively) are simulated. For small helical diameter tube bundle (Ri = 0.02 m), the maximum streamwise velocity non-uniformity is 16.6%. For tube bundles with middle and large helical diameters (Ri = 0.14 m and 0.26 m), the maximum streamwise velocity non-uniformity is 6.7% and 5.8%, respectively. The results show that the flow non-uniformity becomes more obvious for small helical diameter.The supporting structures results in more complex secondary flows. The secondary flows far from the supporting structures are larger than those in the region near the supporting structures. The supporting structures causes the blocking area ratio of inner, outer and middle flow paths vary with the helical diameter, and the blocking area ratio non-uniformity is larger than that without supporting structures. In the presence of supporting structures, the maximum streamwise velocity non-uniformities of small, middle and large helical diameter tube bundles are 22.0%, 8.8% and 6.3%, respectively. The effect of supporting structures on the flow non-uniformity increases as the helical diameter decreases. / Spiralformade rörknippen används vanligtvis i ånggeneratorn (SG) i gaskylda högtemperaturreaktorer (HTGR) som värmeöverföringsområde. Det spiralformade rörknippet består av flerskikts spiralformade rör, som är fixerade av flera uppsättningar stödkonstruktioner. Det finns idealiska flödesvägar åtskilda av olika lager av spiralformade rör. Hastighetsojämnheten för olika flödesvägar kommer att påverka värmeöverföringsrörets temperatur och utloppsångans temperaturlikformighet för olika rörskikt. På skalsidan av SG är turbulent tvärflöde över spiralformade rörknippen komplicerade och svåra att förutsäga på grund av omvänd tryckgradient och gränsskiktsseparation. På grund av den enorma förbrukningen av beräkningsresurser finns det få numeriska simuleringsstudier om ojämnheten i tvärflödet över spiralformade rörknippen med stora volymer.Två fall, nämligen flödet förbi en cirkulär cylinder och korsflödet över in-line rörknippen, simuleras för att validera om PANS-modellen (Partially-Averaged Navier-Stokes) är lämplig för simuleringar av tvärflöde över spiralformade rörknippen. Simuleringsresultaten för k-ω SST PANS-modellen stämmer väl överens med genomsnittliga och lokala experimentella data. Därför används k-ω SST PANS-modellen för att undersöka påverkan av stödstrukturen och spiraldiametern på ojämnheten i tvärflödet över ideala spiralformade rörknippen. Helixvinkeln för spiralformad rörbunt försummas. Beräkningsdomänen består av 5 rader spiralformade rör i strömriktningen. Periodiska randvillkor används för inlopp och utlopp för att minska förbrukningen av datorresurser.För tvärflöde över spiralformade rörknippen finns det signifikanta perifera och radiella hastigheter, vilket innebär att det finns sekundära flöden i planet vinkelrätt mot strömriktningen. Den radiella hastigheten är cirka 16 % av den strömvisa hastigheten. På grund av närvaron av sekundärt flöde lutar tvärflödet över enskilda rör och lutningsriktningen ändras vid olika omkretspositioner. Vid samma perifera position är flödesinklinationsriktningen densamma längs strömriktningen och radiell riktning. För spiralformade rörknippen är förhållandet mellan blockeringsarean och flödesarean (blockeringsareaförhållandet) för de inre, yttre och mellersta flödesvägarna olika. Blockeringsareaförhållandet för den inre flödesvägen är stort och blockeringsareaförhållandet för den yttre flödesvägen är litet, vilket resulterar i ojämn hastighetsfördelning i olika flödesvägar.Tvärflöde över spiralformade rörknippen med tre spiralformade diametrar (innerväggsradien Ri är 0,02 m, 0,14 m respektive 0,26 m) simuleras. För rörknippe med liten spiraldiameter (Ri = 0,02 m) är den maximala strömhastighetsolikformigheten 16,6 %. För rörknippen med mellersta och stora spiralformade diametrar (Ri = 0,14 m och 0,26 m) är den maximala strömhastighetsolikformigheten 6,7 % respektive 5,8 %. Resultaten visar att flödesojämnheten blir mer uppenbar för små spiralformade diametrar.De bärande strukturerna resulterar i mer komplexa sekundärflöden. Sekundärflödena långt från stödkonstruktionerna är större än de i området nära stödkonstruktionerna. De bärande strukturerna gör att blockeringsareaförhållandet för inre, yttre och mellersta flödesvägar varierar med den spiralformade diametern, och blockeringsareaförhållandets ojämnhet är större än utan stödkonstruktioner. I närvaro av stödkonstruktioner är de maximala strömhastighetsojämnheterna för små, mellersta och stora spiralformade rörknippen 22,0 %, 8,8 % respektive 6,3 %. Effekten av stödkonstruktioner på flödesojämnheten ökar när den spiralformade diametern minskar.
12

Železobetonová konstrukce / The reinforced concrete structure of elementary school

Benešová, Lenka January 2018 (has links)
The diploma thesis is focused on the design and evaluation of the concrete monolithic ceiling slab in the shape of semicircular ring, ribs lining this plate and skylights. The result is static calculation and drawing documentation.
13

Pavilon botanické zahrady v Brně / The Botanical Pavillion in Brno

Rusoňová, Nikola January 2015 (has links)
Master´s thesis describes the design and check of the construction of botanical pavillion in Brno. The structure has an elliptical ground plan with dimensions 34 x 20 m, height of 9 m. The supporting structure consists of 16 support curved ribs which are braced at the top of the elliptical steel ring. Between the ribs are inserted purlins which support the perimeter cladding. The supporting structure is designed as an alternative system as girders of glued laminated timber and as system of steel truss girders.
14

Sportovní hala / Sports hall

Štelc, Martin January 2015 (has links)
This diploma thesis deals with the design expertise and supporting structures the single-roof sports hall for locality Brno. The ground plan dimensions are 42 x 72 m and ground clearance of about eight meters. Two variants are processed and selected variant is elaborated in detail. The sports hall is designed for most sports played indoors. In a static calculation are designed and assessed the main load-bearing elements such as truss glued laminated timber, wooden purlins, columns, girts and bracing. The work includes drawings.
15

Statika atypického RD / Statics of an atypical family house

Bartoň, Jakub January 2022 (has links)
The diploma thesis deals with a desing and assessment a prestressed ceiling structure above a family house with a vegetated roof. The creation of the static model was analyzed by the SCIA Engineer program.
16

Untersuchungen zu Trageigenschaften von plattenförmigen Betonleichtbauelementen in Kreuz-Kanal-Technologie

Jäger, Wolfram 21 July 2022 (has links)
Die Herstellung von Stahlbeton erfordert einen hohen Energie- und Ressourceneinsatz, vor allem im Bereich der Zement- und Stahlproduktion. Stahlbetonbauteile sind gekennzeichnet durch hohe Traglasten, aber auch durch hohe Eigengewichte. Bei Beanspruchung auf Biegung wird Beton eigentlich nur im Bereich der Druckzone und zum Schutz der Bewehrung in der Zugzone benötigt. Dem können sich bisher platten- oder scheibenförmige Bauteile nicht anpassen. Der Beton wird über den gesamten Querschnitt eingesetzt. Natürlich wird er dabei auch zur Übertragung der Schubkräfte zwischen Druck- und Zugzone benötigt. Setzt man ihn über den vollen Querschnitt ein, bringt er einen hohen Anteil an Eigenlast in das Tragmodell ein und damit wird ein Teil der Tragfähigkeit durch die Eigenlast aufgebraucht. [Aus: Motivation und Ziel] / The production of reinforced concrete requires a high input of energy and resources, especially in the area of cement and steel production. Reinforced concrete components are characterised by high load-bearing capacities but also by high dead weights. When stressed in bending, concrete is actually only needed in the compression zone and to protect the reinforcement in the tension zone. Until now, slab or wall-shaped components have not been able to adapt to this. The concrete is used over the entire crosssection. Of course, it is also needed to transmit the shear forces between the compression and tension zones. If it is used over the full cross-section, it introduces a high proportion of dead load into the load-bearing model and thus part of the load-bearing capacity is used up by the dead load.
17

Návrh a kalkulace cen vybraných stropních konstrukcí / Design and calculation of prices of selected ceiling structures

Chmelařová, Kateřina January 2018 (has links)
This final thesis discuss about design, calculation and efficient choice of ceiling construction. The goal is to optimize the design of the building in order to minimize construction and operation costs, to meet the required purpose and to meet a certain quality standard. The effort to achieve this goal is based on the theory that a family house may not be designed in a single design system. In the practical part, three types of ceiling construction are designed for the selected RD. The result of the study is to determine the most appropriate option for a family house using value analysis and budget price.
18

Sportovně rehabilitační středisko / Sports and Rehabilitation Center

Langenberger, Adam January 2013 (has links)
This master´s thesis elaborates a project documentation of sports rehabilitation center in Brno–Bystrc. The building object is four-storeyed and a partial basement. On the basement floor there is a pool with sauna, gym and fitness with support to assist for all activities offered. On the ground floor there is an entrance, reception for accommodation, restaurant and kitchen for the restaurant. The 2nd overground floors is determined by the rehabilitation clinic. On the grand and overground floor are designed sanitary appliances for the restaurant and patient surgeries. There are projected 9 apartments for weekend accommodation. Apartments allow access to the terrace. Foundations are made strip foundations. The building object is bricked and insulated with ventilated facades. Load bearing structure of the roof create roof trusses.
19

Montovaná konstrukce ze železobetonu / Prefabricated concrete structure

Šimon, Jan January 2014 (has links)
The master thesis is about a design of supporting structure of prefabricated skeleton hall. The major part of a design are an internal trasverse and longitudinal frames, which contents roof reinforce concrete truss, columns, beam and ceiling joists. All the load acting to the bearing structure is transferred to the prefabricate footing made of reinforce concrete. Other parts of the bulding are not solved in this thesis. The content of the thesis consists of an assembly drawing of parts of the skeleton and the static calculation according to the actual international standards. The output of each static calculation is drawing of a shape of part and its reinforcement.
20

Začleňování fotovoltaických elektráren do elektrizační soustavy / Integration of Photovoltaic Power Plants in the Electricity System

Michl, Pavel January 2010 (has links)
The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.

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