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CFD analysis of exothermic reactions in Al-Au nano multi-layered foils
Karlo Raić, Rebeka Rudolf, Primož Ternik, Zoran Žunič, Vojkan Lazić, Dragoslav Stamenković, Tatjana Tanasković, Ivan Anžel, 2011, original scientific article

Abstract: This work presents the possibility of numerical modelling using Computational Fluid Dynamics (CFD) in the field of nano-foils. The governing equations were solved using a Finite Volume Methodology (FVM). The computational domain was discretized using a uniform Cartesian grid with the appropriate mesh size along the x and y directions employing the corresponding number of grid points. The field variables were discretized at the cell centres and the spatial, as well as the time, derivatives were approximated using the second-order accurate numerical scheme. The time-evolution of the temperature and concentration fields, as well as the atomic diffusion coefficient, will be presented for the appropriate Al-Au nano-foil geometry and boundary conditions.
Keywords: Au-Al nano-foils, finite volume method, temperature transfer, concentration transfer
Published: 01.06.2012; Views: 993; Downloads: 59
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Rok Kopun, 2014, doctoral dissertation

Abstract: Optimization of heat transfer characteristics in automotive industries is one of the more important factors leading to reductions in fuel consumption and lower emissions values. Efficient heat treatment techniques, like immersion quenching, have been introduced in order to replace heavier metals with lower weight alloys (aluminum), which results in vehicle weight reduction and consequently improved fuel consumption and emission values. Immersion quenching is one of the more important heat treatment techniques introduced in automotive industries, where heat transfer plays a vital role in determining the structure and mechanical properties of the material (e.g. the cylinder head). This presented PhD thesis deals with the development and validation of improved computational methodology in order to simulate the heat transfer characteristics of the immersion quenching cooling process, as implemented within the commercial computational fluid dynamics (CFD) code AVL FIRE®. The boiling phase change process between the heated part and a sub-cooled liquid domain is handled by using the Eulerian multi-fluid modeling approach, where each phase is treated as interpenetrating continua. While for the fluid domain mass, momentum and energy equations are solved within the content of the multi-fluid modeling approach, where only the energy equation is solved to predict the thermal field within the solid region. Result comparisons between the measurements and corresponding numerical simulations using the variable Leidenfrost temperature with additional interfacial forces showed very good agreement. The comparisons were performed on an aluminum step-plate test piece with different thicknesses along its length and on a simplified aluminum cylinder head structure. The specimens were submerged within the liquid domain at different pool temperatures and different solid part orientations, where the solid temperature histories predicted by the numerical model correlated very well with the provided measurement data.
Keywords: CFD, Multiphase boiling, heat transfer, quenching, Leidenfrost temperature, interfacial forces, results comparison
Published: 14.08.2014; Views: 1081; Downloads: 139
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Analysis of two-stage high- temperature heat pump efficiency
Milovan Jotanović, G. Tadić, Jurij Krope, Darko Goričanec, 2012, original scientific article

Abstract: The paper shows the potential benefit of using low temperature heat sources with high temperature pumps. Two-stage heat pumps with flash unit and heat exchanger are described. To determine the characteristic parameters of the twoheat pumps a computer program was designed, with which we could determine the dependence of COP and compressor pressure ratios from evaporating temperature. An economic analysis of the justification of the use of heat pumps was made.
Keywords: heat transfer, high temperature heat pumps, computer programme, economic analysis
Published: 10.07.2015; Views: 704; Downloads: 28
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Optimal proportion of refrigerants in single- stage high-temperature heat pump
Milovan Jotanović, Mirko Miščević, Bojan Kulčar, Darko Goričanec, 2012, original scientific article

Abstract: The paper presents types of refrigerants with their characteristics for use insingle-stage high-temperature heat pump. A mathematical model is designed; based on the use of the modeling language GAMS a simulation of optimum mixtureproportions of two refrigerants was made, which allows for the heat pump to operate the most efficient. Software package Math Cad Professional wasused to make calculations of the characteristic properties of the heat pump.
Keywords: heat transfer, single-stage high temperature pump, refrigerant, simulation of effect
Published: 10.07.2015; Views: 458; Downloads: 24
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