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1.
Evaluation of thermal and mechanical filler gas influence on honeycomb structures behaviour
Matej Vesenjak, Andreas Öchsner, Zoran Ren, 2007, izvirni znanstveni članek

Opis: In this paper the behavior of hexagonal honeycombs under dynamic in-plane loading is described. Additionally, the presence and influence of the filler gas inside the honeycomb cells is considered. Such structures are subjected to very large deformation during an impact, where the filler gas might strongly affect their behavior and the capability of deformational energy absorption, especially at very low relative densities. The purpose of this research was therefore to evaluate the influence of filler gas on the macroscopic cellular structure behavior under dynamic uniaxial loading conditions by means of computational simulations. The LS-DYNA code has been used for this purpose, where a fully coupled interaction between the honeycomb structure and the filler gas was simulated. Different relative densities, initial pore pressures and strain rates have been considered. The computational results clearly show the influence of the filler gas on the macroscopic behavior of analyzed honeycomb structures. Because of very large deformation of the cellular structure, the gas inside the cells is also enormously compressed which results in very high gas temperatures and contributes to increased crash energy absorption capability. The evaluated results are valuable for further research considering also the heat transfer in honeycomb structures and for investigations of variation of the base material mechanical properties due to increased gas temperatures under impact loading conditions.
Ključne besede: mechanics, cellular materials, honeycomb structure, gas filler, thermal properties, mechanical properties, dynamic loading, LS-DYNA, computational simulations
Objavljeno: 31.05.2012; Ogledov: 1037; Prenosov: 20
URL Povezava na celotno besedilo

2.
Calculation of the thermal conductivity of nanofluids containing nanoparticles and carbon nanotubes
Jurij Avsec, Maks Oblak, 2003, izvirni znanstveni članek

Opis: A mathematical model for the calculation of thermal conductivity of nanofluids containing nanoparticles and nanotubes on the basis of statistical mechanics is presented. This appears to be the first such attempt published in the scientific literature. We focus on the influence of the liquid layer structure around nanoparticles as the reason for enhancement of the thermal conductivity of nanofluids. Analytical results of both the current analysis and statistical mechanics are compared with experimental data reported in the scientific literature, which show good agreement.
Ključne besede: statistical thermodynamics, mathematical models, thermal conductivity, nanofluids, transport properties, statistical nano-mechanics
Objavljeno: 31.05.2012; Ogledov: 1139; Prenosov: 64
URL Povezava na celotno besedilo

3.
The calculation of thermal conductivity, viscosity and thermodynamic properties for nanofluids on the basis of statistical nanomechanics
Jurij Avsec, Maks Oblak, 2007, izvirni znanstveni članek

Opis: The paper features the mathematical model of calculation of thermophysical properties for nanofluids on the basis of statistical nanomechanics. Calculation of properties for nanofluids for real substances is possible by the classical and statistical mechanics. Classical mechanics has no insight into the microstructure of the substance. Statistical mechanics, on the other hand, calculates the properties of state on the basis of molecular motions in a space, and on the basis of the intermolecular interactions. The equations obtained by means of classical thermomechanics are empirical and apply only in the region under observation. The main drawback of classical thermomechanicsis that it lacks the insight into the substance of microstructure. Contrary to classical mechanics, statistical mechanics calculates the thermomechanic properties of state on the basis of intermolecular and intramolecular interactions between particles in the same system of molecules. It deals with the systems composed of a very large number of particles. The results of the analysis are compared with experimental data and show a relatively good agreement. The analytical results obtained by statistical mechanics are compared with the experimental data and show relatively good agreement.
Ključne besede: statistical thermodynamics, thermophysical properties, viscosity, thermal conductivity, thermodynamic properties, mathematical model, nanofluids, statistical nanomechanics
Objavljeno: 31.05.2012; Ogledov: 1322; Prenosov: 67
URL Povezava na celotno besedilo

4.
The combined analysis of phonon and electron heat transfer mechanism on thermal conductivity for nanofluids
Jurij Avsec, 2008, izvirni znanstveni članek

Opis: The paper features the mathematical model representing the analytical calculation of phonon and electron heat transfer analysis of thermal conductivity for nanofluids. The mathematical model was developed on the basis of statistical nanomechanics. We have made the detailed analysis of the influence of temperature dependence on thermal conductivity for nanofluids. On this basis are taken into account the influences such as formation of nanolayer around nanoparticles, the Brown motion of solid nanoparticles and influence of diffusive-ballistic heat transport. The analytical results obtained by statistical mechanics are compared with the experimental data and they show relatively good agreement.
Ključne besede: statistical nanomechanics, phonons, electron heat transfer, nanofluids, thermal conductivity, thermodynamic properties, mathematical model, statistical nanomechanics
Objavljeno: 31.05.2012; Ogledov: 1317; Prenosov: 67
URL Povezava na celotno besedilo

5.
Exergy analysis of a Brayton cycle with variable physical properties and variable composition of working substance
Marija Živić, Antun Galović, Jurij Avsec, Mario Holik, 2016, izvirni znanstveni članek

Opis: The exergy analysis of a Brayton cycle is performed in the paper. The four input variables: the ratio of the compressor exit and inlet pressures, the ratio of inlet temperature of gases in turbine and inlet temperature of air in compressor and the isentropic efficiencies of the compressor and turbine are analysed. The temperature ratio is varied in a way that the compressor inlet temperature of air is maintained constant, while the turbine inlet temperature of flue gases is varied from 900 to 1200°C. In the combustion chamber methane is completely combusted with excess air ratio which is determined by the temperature of flue gases at the turbine inlet. The analysis further includes variability of the molar heat capacities of air and flue gases with temperature and variability of their heat capacity ratios. The exergy destruction in turbine, compressor and combustion chamber and also total exergy efficiency of the cycle are considered in the analysis.
Ključne besede: Brayton cycle, variable physical properties, variable composition of working substance, maximum work output, maximum thermal efficiency
Objavljeno: 12.07.2017; Ogledov: 798; Prenosov: 178
.pdf Celotno besedilo (789,62 KB)
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6.
Thermal-mechanical sensory properties of hot-air welded textile transmission lines
Simona Jevšnik, Li Yi, Junyan Hu, Han Xiao, Wu Xinxing, Anthony Primentas, 2016, izvirni znanstveni članek

Opis: Hot air welding technology is one of the new promising techniques for integrating conductive yarns on or into fabrics, besides weaving, knitting, printing, coating or inserting conductive yarns by the sewing and/or embroidery processes. A new issue related to the introduction of hot air welding technology for making e-textile transmission lines, i.e., the mechanical-thermal sensory properties of hot air welded e-textile transmission lines, is investigated in this study. Fabric Touch Tester (FTT) was used to evaluate thermal, compressive and bending properties of hot air welded transmission lines. The results show that the bending of welded fabric increased after hot air welding in both warp and weft directions. Furthermore, the maximum thermal flux and thermal conductivity of welded specimens decreased in comparison to the substrate fabric.
Ključne besede: textile transmission lines, hot-air welding, fabric touch tester, conductive yarns, e-textile transmission lines, thermal properties
Objavljeno: 01.09.2017; Ogledov: 275; Prenosov: 197
.pdf Celotno besedilo (235,01 KB)
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7.
Ground-sourced energy wells for heating and cooling of buildings
Heinz Brandl, Dietmar Adam, Roman Markiewicz, 2006, izvirni znanstveni članek

Opis: 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.
Ključne besede: energy wells, energy foundations, geothermal geotechnics, geothermal heating/cooling, thermo-active structures, thermal ground properties, field testing
Objavljeno: 17.05.2018; Ogledov: 153; Prenosov: 58
.pdf Celotno besedilo (4,24 MB)
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