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1.
Simulation of automotive air-conditioning system in 1D simulation software : diplomsko delo
Marko Copot, 2019, undergraduate thesis

Abstract: The development of state-of-the-art vehicles requires advanced simulations tools in heating, ventilation and air-conditioning (HVAC). The focus of this thesis is the construction of an automotive HVAC model, its calibration and the simulation of the behaviour of the HVAC model in various ambient conditions. The theoretical background of refrigeration system as part of the HVAC system is presented. The model is constructed with following components: compressor, condenser, throttling device, evaporator and battery chiller, which is a heat exchanger between coolant and refrigerant. The description and role of each component in the HVAC model is presented. All heat exchangers are calibrated, which is done with multiple simulations that have defined input data. The results are compared to experimental data. With addition of vehicle cabin with air recirculation, HVAC control logic is implemented. The behaviour of the system is simulated in defined environmental conditions. The results of the simulations are presented in graphs and tables.
Keywords: 1D simulations, air-conditioning, HVAC, calibration, thermodynamics, cooling
Published in DKUM: 23.09.2019; Views: 753; Downloads: 65
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2.
Ground-sourced energy wells for heating and cooling of buildings
Heinz Brandl, Dietmar Adam, Roman Markiewicz, 2006, original scientific article

Abstract: Energy wells are thermo-active elements for an economical extraction or storage of ground energy, similar to energy piles and other deep foundation elements also used as heat exchangers. Heating and/or cooling of buildings requires a primary and secondary thermo-active circuit, commonly connected by a heat pump. The paper gives several design aspects of energy wells which can be also used for the design of deep energy foundations. Thermal response tests have proved suitable for the in-situ determination of thermal ground properties required for an optimised design. Moreover, different systems of energy wells are discussed, and a comprehensive pilot research project is described.
Keywords: energy wells, energy foundations, geothermal geotechnics, geothermal heating/cooling, thermo-active structures, thermal ground properties, field testing
Published in DKUM: 17.05.2018; Views: 528; Downloads: 87
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3.
Cooling analysis of a light emitting diode automotive fog lamp
Matej Zadravec, Matjaž Ramšak, Jure Ravnik, Matjaž Hriberšek, Jernej Slanovec, 2017, original scientific article

Abstract: Efficiency of cooling fins inside of a light emitting diode fog lamp is studied using computational fluid dynamics. Diffusion in heat sink, natural convection and radiation are the main principles of the simulated heat transfer. The Navier-Stokes equations were solved by the computational fluid dynamics code, including Monte Carlo radiation model and no additional turbulence model was needed. The numerical simulation is tested using the existing lamp geometry and temperature measurements. The agreement is excellent inside of few degrees at all measured points. The main objective of the article is to determine the cooling effect of various heat sink parts. Based on performed simulations, some heat sink parts are found to be very ineffective. The geometry and heat sink modifications are proposed. While radiation influence is significant, compressible effects are found to be minor.
Keywords: heat transfer, cooling of electronic devices, cooling fins, light emitting diode automotive lamp, compressible flow
Published in DKUM: 07.07.2017; Views: 917; Downloads: 327
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4.
Weldability investigation steel P 91 by weld thermal cycle simulation
Marko Dunđer, Ivan Samardžić, Tomaž Vuherer, 2015, original scientific article

Abstract: This paper elaborates results of hardness and impact energy of thermal cycle simulated specimens of high-alloy steel P 91 and their dependence on cooling time from 800 to 500 °C. Results were obtained by measuring hardness HV 1 and by experimental testing of Charpy notched specimens. Metallographic analysis of samples was performed on scanning electronic microscope.
Keywords: welding, P 91, hardness, impact energy, cooling
Published in DKUM: 03.07.2017; Views: 1777; Downloads: 80
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5.
The microstructure and properties of materials at the fusion line
Vladimir Gliha, 2005, original scientific article

Abstract: In this paper, the formation of the HAZ that is caused by the thermal effects of welding is investigated from the theoretical and experimental points of view. Samples of the material found at the fusion line were prepared by simulating the thermal regimes that occur during welding. A number of CCT diagrams that are valid for the conditions during welding were designed, and the hardness and impact-toughness of the samples were measured. This information was then related to the results of metallographic examinations. The maximum temperature and the cooling rate of the applied thermal cycles were found to be decisive in terms of the properties of HAZ.
Keywords: welding, HAZ, thermal cycle, cooling rate, fusion line
Published in DKUM: 03.07.2017; Views: 1595; Downloads: 94
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6.
Impact energy analysis of quenched and tempered fine grain structural steel specimens after weld thermal cycle simulation
Marko Dunđer, Tomaž Vuherer, Ivan Samardžić, 2014, original scientific article

Abstract: The paper presents impact energy results of thermal cycle simulated specimens of quenched and tempered fine grain structural steel S960QL. These results are obtained by examining notched Charpy specimens. Upon performed metallographic analysis and measured hardness, total impact energy is separated into ductile and brittle components.
Keywords: quenched and tempered fine grain structural steel, welding thermal cycle, impact energy, cooling time t8/5
Published in DKUM: 03.07.2017; Views: 756; Downloads: 91
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7.
Effect of cooling rate on the microstructure of an Al94Mn2Be2Cu2 alloy
Tonica Bončina, Boštjan Markoli, Franc Zupanič, 2012, original scientific article

Abstract: In this study the effect of the cooling rate on the microstructure of Al94 Mn2 Be2 Cu2 alloy was investigated. The vacuum induction melted and cast alloy was exposed to different cooling rates. The slowest cooling rate was achieved by the DSC (10 K·min^−1), the moderate cooling rate succeeded by casting in the copper mould (≈1 000 K·s−1) and the rapid solidification was performed by melt spinning (up to 10^6 K·s^−1). The microstructure of the DSC-sample consisted of α-Al matrix, and several intermetallics: τ1-Al29 Mn6 Cu4 , Al4 Mn, θ-Al2 Cu and Be4 Al(Mn,Cu). The microstructures of the alloy at moderate and rapid cooling consisted of the α-Al matrix, i-phase and θ-Al2 Cu. Particles of i-phase and θ-Al2 Cu were much smaller and more uniformly distributed in melt-spun ribbons.
Keywords: Al-alloy, metallography, microstructure, cooling rate, solidification
Published in DKUM: 03.07.2017; Views: 544; Downloads: 74
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8.
Dependence of hardness and impact energy on cooling time Δt8/5 and temperature for S960QL
Ivan Samardžić, Marko Dunđer, Tomaž Vuherer, 2014, original scientific article

Abstract: The paper deals with research into dependence of hardness and impact energy of thermal cycle simulated specimens of fine-grained structural steel S960QL on cooling time from 800 to 500 °C and on tested temperature. Results were obtained by measuring hardness of HV 10 and by experimental testing of Charpy notched tubes on instrumented Charpy hammer. Total impact energy, initiation energy and fracture propagation energy needed for occurrence of fracture is also elaborated.
Keywords: structural steel, quenched hardness, impact energy, cooling time
Published in DKUM: 03.07.2017; Views: 673; Downloads: 83
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9.
The influence of cooling rate on the microstructure of an Al-Mn-Be alloy
Niko Rozman, Tonica Bončina, Ivan Anžel, Franc Zupanič, 2008, original scientific article

Abstract: In ternary Al-Mn-Be alloys a metastable quasicrystalline phase can form at relatively low cooling rates (≈ 100 K/s); however, besides the quasicrystalline phase other phases can also be present. We found that the investigated alloy is very prone to the formation of metastable phases, which are also quasicrystalline. Using different investigation methods we determined the type of phases, their shape, morphology, chemical composition and distribution. Special attention was given to the micro- and nano-sized quasicrystalline particles. When using slow cooling, Al10Mn3 and Be4AlMn were present; however, with a faster cooling rate a quasicrystal approximant and a quasicrystalline phase were formed.
Keywords: aluminium, quasicrystals, cooling rate, microstructure
Published in DKUM: 10.07.2015; Views: 1011; Downloads: 54
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10.
Energy saving cooling-unit for plastic moulding machine
Darko Lovrec, Vito Tič, 2011, original scientific article

Abstract: Compressed air is one of the major sources of energy consumption and also one of the most expensive types of energy. Consequently, special attention must be paid to its rational use. This is especially important in cases where compressed air is blowed into an "empty" space. All cleaning and cooling processes using compressed air are typical examples of such applications. They are the most wasteful consumers of compressed air. Measures to minimize air consumption in such cases are presented in the paper. The highly efficient cooling unit for plastic moulding machines has been designed and optimized based on CFD simulation, and then produced using RP/RM (Rapid Prototyping / Manufacturing) manufacturing technology. The developed and specially designed nozzle-system was used for cooling purposes during plastic canister manufacturing. The previously-used conventional cooling system had so far been recognized as the most wasteful compressed air consumer in the company. The newly-designed air-efficient cooling unit, with increased capacity for cooling air, allows for up to 50% energy savings regarding compressed air.
Keywords: compressed air, cooling, blow moulding machine
Published in DKUM: 10.07.2015; Views: 841; Downloads: 90
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