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Fast single domain-subdomain BEM algorithm for 3D incompressible fluid flow and heat transfer
Jure Ravnik, Leopold Škerget, Zoran Žunič, 2009, original scientific article

Abstract: In this paper acceleration and computer memory reduction of an algorithm for the simulation of laminar viscous flows and heat transfer is presented. The algorithm solves the velocity-vorticity formulation of the incompressible Navier-Stokes equations in 3D. It is based on a combination of a subdomain boundary element method (BEM) and single domain BEM. The CPU time and storage requirements of the single domain BEM are reduced by implementing a fast multipole expansion method. The Laplace fundamental solution, which is used as a special weighting function in BEM, is expanded in terms of spherical harmonics. The computational domain and its boundary are recursively cut up forming a tree of clusters of boundary elements and domain cells. Data sparse representation is used in parts of the matrix, which correspond to boundary-domain clusters pairs that are admissible for expansion. Significant reduction of the complexity is achieved. The paper presents results of testing of the multipole expansion algorithm by exploring its effect on the accuracy of the solution and its influence on the non-linear convergence properties of the solver. Two 3D benchmark numerical examples are used: the lid-driven cavity and the onset of natural convection in a differentially heated enclosure.
Keywords: boundary element method, fast multipole method, fluid flow, heat transfer, velocity-vorticity fomulation
Published: 31.05.2012; Views: 1238; Downloads: 29
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Špela Valič, 2011, undergraduate thesis

Abstract: V diplomskem delu je podan primerjalni vpogled v nekatere evropske sisteme pridobitve lastninske pravice na premičnini od razpolagalno nesposobne osebe (a non domino). Tri od skupno petih obravnavanih sistemov pripadajo romanski pravni družini , zato bo težišče naloge usmerjeno v iskanje razlik, pa tudi skupnih imenovalcev ureditev germanskega in romanskega porekla. Med predstavljanjem teme, ki jo mnogi označujejo za »križišče obligacijskega in stvarnega prava« , se bom primarno osredotočila na obravnavo instituta a non domino, vendar je za njegovo učinkovito preučevanje potrebna tudi splošna predstavitev sistemov prenosa lastninske pravice v različnih pravnih redih. Zato bo v začetnih poglavjih vsake obravnavane ureditve kot tematsko izhodišče najprej opisana splošna pridobitev lastninske pravice, zatem pa še podrobnejša predstavitev pridobitve lastninske pravice na premičnini, kadar je odsvojitelj razpolagalno nesposobna oseba (t.i. »non domino«). Razvidno bo, da so si romanski in germanski sistemi glede prenosa lastninske pravice konceptualno precej različni, hkrati pa zaradi korekcij in izjem v vsakdanji praksi ne dajejo dramatično drugačnih oziroma nasprotujočih si rezultatov.
Keywords: a non domino, lastninska pravica, premičnina, razpolagalna nesposobnost, transfer lastnine, načelo nemo plus, romanski sistemi, Francija, Italija, Portugalska, Draft Common Frame of Reference.
Published: 23.09.2011; Views: 2356; Downloads: 377
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Influence of water scale on thermal flow losses of domestic appliances
Danijela Urbancl, Darko Goričanec, 2007, original scientific article

Abstract: Research results of how the precipitated water scale on heaters of small domestic appliances influences the consumption of electricity are presented. It shows that the majority of water scale samples are composed of aragonite, calcite and dolomite and that those components have an extraordinary low thermal conductivity. Also, the results show that at 2 mm thick deposit, depending on the chemical composition of water scale, the thermal flow is reduced for 10% to 40%; consequently, the consumption of electricity significantly increases.
Keywords: electricity, heat transfer, heat flow, heat exchanger, water scale
Published: 31.05.2012; Views: 1169; Downloads: 42
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Response functions and thermal influence for various multiple borehole configurations in ground coupled heat pump systems
Metka Pešl, Darko Goričanec, 2007, original scientific article

Abstract: Ground coupled heat pump (GCHP) utilizes the immense renewable storage capacity of the ground as a heat source or sink to provide space heating, cooling, and domestic hot water. GCHP systems are generally comprised of watersource heat pumps and ground heat exchangers (GHEs). Consisting of closedloop of pipes buried in boreholes, ground heat exchangers (GHEs) are devised for extraction or injection of thermal energy from/into the ground. Despite the low energy and lower maintenance benefits of ground-source heat pump systems, little work has been undertaken in detailed analysis. Many models, either numerical or analytical, have been proposed to analyze the thermal response of vertical heat exchangers that are used in ground coupled heat pump systems (GCHP). In both approaches, most of the models are valid after few hours of operation since they neglect the heat capacity of the borehole. In this paper, we present for three various multiple borehole configurations a comparison between g-functions, which will be calculated after an analytical model of final line source and g-functions, obtain with numerical model derived from the work of Eskilson. A case study is presented to show how the ground temperature changes with time for various multiple borehole configurations.
Keywords: geothermal heat exchanger, heat transfer, heat conduction, thermal influence
Published: 31.05.2012; Views: 1079; Downloads: 23
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Development of a mathematical model for the heat transfer of the system man - clothing - environment
Jelka Geršak, Milan Marčič, 2007, original scientific article

Abstract: The paper presents the development of a mathematical model of the heat transfer from the human body to the environment air that can be solved on a PC. The advantage of the presented heat transfer model is the ability of a fast evaluation of the heat transfer for various textile materials incorporated ino the clothing system under different ambient conditions.
Keywords: textiles, garment properties, heat transfer, mathematical model
Published: 31.05.2012; Views: 1331; Downloads: 46
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Determination of the process parameters relative influence on k[sub]La value using Taguchi design methodology
Marko Tramšek, Andreja Goršek, 2007, original scientific article

Abstract: This article describes experimental determination of the relative impact of significant process parameters that influence volumetric oxygen mass transfer coefficient (kLa) using Taguchi design methodology. For this purpose an automated RC1 reaction calorimeter (Mettler-Toledo), which was originally developed for chemical processes, was modified for the bioprocesses. Simple fermentation using Baker's yeast was studied to illustrate the design procedure. Orthogonal array L25 was selected for the proposed design and ANOVA method was used for recognizing the relative influence of the process parameters. Within the observed range of temperature (?), fermentation media volume (VFM), and yeast mass concentration (?Y), these process parameters were found to be unimportant compared to the volumetric air flow rate (qV,a) and rotational frequency of the stirrer (fm). The qV,a had a substantial effect on the kLa value (89.2 %) and the fm had just a small one (3.6 %), meanwhile the remain fraction to 100 % represents error. The results refer strictly to the selected case study. Anyhow, the proposed procedure shows that application of the Taguchi approach for analyzing the oxygen mass transfer based on the experimental data obtained from a highly-automated laboratory reactor appears to have potential usage in general biopharmaceutical process design.
Keywords: bioprocess parameters, mass transfer, volumetric oxygen mass transfer coefficient, process parameters, Taguchi method, analysis of variance
Published: 31.05.2012; Views: 1440; Downloads: 21
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