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Iskalni niz: "ključne besede" (cooling) .

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1.
A meshless numerical solution of thermo-mechanics of hot-rolled steel bars on a cooling bed
Gašper Vuga, Boštjan Mavrič, Umut Hanoglu, Božidar Šarler, 2023, objavljeni znanstveni prispevek na konferenci

Povzetek: After the continuous hot-rolling process, steel bars are immediately placed on the cooling bed. At the beginning of the cooling, the material is at high temperatures, and the yield strength is low. Due to thermal load, yield strength can be exceeded, and permanent plastic strains start accumulating, resulting in possible unwanted shape changes and residual stresses. The present paper aims to develop a thermo-mechanical model for studying and eliminating undesirable phenomena before the products leave the cooling bed. The governing equations are solved for the two-dimensional slice in a strong form, and a modified version of the radial basis function generated finite difference (RBF-FD) method [1]. The initial bar geometry is obtained from the existing meshless hot-rolling simulation system [2]. The thermal and mechanical models are one-way coupled, i.e. the temperature solution represents a driving force for the stress and strain solution. The temperature field is obtained with explicit propagation in time. The convective and radiative heat fluxes on the boundary are updated at each time step using the ray tracing procedure to determine the radiative heat flux. The mechanical part is solved by considering the small strain elasto-plasticity, where the isotropic von Mises temperature-dependent hardening is employed. The global system of nonlinear equations of the mechanical part is solved by the Newton-Raphson method. The closest point projection method is used to solve the constitutive relations. A sensitivity study is performed on the influence of cooling intensity on a rectangular steel bar’s temperature, stress and strain field. We defined the most influential factors for defect formation. For the first time, a novel meshless RBF-FD method is successfully used for solving such a complex industrial problem. The model will be perspectively upgraded from the slice to the three-dimensional model to enable also bending.
Ključne besede: cooling bed, steel bars, thermo-mechanics, strong form, meshless method
Objavljeno v DiRROS: 21.03.2024; Ogledov: 45; Prenosov: 28
.pdf Celotno besedilo (1,62 MB)
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2.
Influence of geology, hydrogeology, and climate on ground source heat pump distribution in Slovenia and selected European countries
Simona Adrinek, Mitja Janža, Rao Martand Singh, 2024, izvirni znanstveni članek

Povzetek: Shallow geothermal energy (SGE) is a renewable energy that could contribute to the decarbonatization of the heating and cooling sector. SGE is predominantly harnessed through ground source heat pump (GSHP) systems. The choice of which type of GSHP system depends on various factors. Understanding these factors is crucial for optimizing the efficiency of GSHP systems and fostering their implementation. In this paper, we have analysed the spatial distribution of GSHPs in Slovenia. We identified 1073 groundwater and 1122 ground-coupled heat pump systems with a total heat pump capacity of almost 30 MW. We quantitatively assessed the influence of geological, hydrogeological, and climate conditions on their spatial distribution. Using the χ2 test and information value method, we identified hydrogeological conditions as the most influential factor for the GSHP systems’ spatial distribution. We also performed the spatial analysis of geological and hydrogeological data in 22 European countries, including Slovenia. We collected the reported numbers of installed GSHP units in 2020 and were able to distinguish the shares of groundwater and ground-coupled heat pump systems for 12 of these countries. The analysis showed that ground-coupled heat pumps predominate in most countries, even if the natural conditions are favourable for groundwater heat pumps.
Ključne besede: shallow geothermal energy, renewable heating and cooling, ground-source heat pump, spatial distribution, natural condition
Objavljeno v DiRROS: 19.03.2024; Ogledov: 47; Prenosov: 17
.pdf Celotno besedilo (15,39 MB)

3.
A hybrid radial basis function-finite difference method for modelling two-dimensional thermo-elasto-plasticity : Application to cooling of hot-rolled steel bars on a cooling bed
Gašper Vuga, Boštjan Mavrič, Umut Hanoglu, Božidar Šarler, 2024, izvirni znanstveni članek

Povzetek: This paper represents Part 2 of the parallel paper Part 1, where the strong form hybrid RBF-FD method was developed for solving thermo-elasto-plastic problems. It addresses the industrial application of this novel meshless method to steel bars cooling on a cooling bed (CB) where the formation of residual stress is of primary interest. The study investigates the impact of the distance between the bars and the distance to the heat shield above the CB on radiative heat fluxes and, consequently, on thermo-mechanical response. The thermal model is solved on bars cross-section with a RBF-FD method where augmented polyharmonic splines are used for the local approximation. View factors, computed with a Monte-Carlo method, are included in radiative heat fluxes. The thermal solution is incrementally applied on a mechanical model that assumes a generalised plane strain state and captures bars bending. The study employs a hybrid RBF-FD method to resolve a nonlinear discontinuous mechanical problem successfully. The simulation of the process shows how different process parameters influence the thermo-mechanical response of the bars.
Ključne besede: steel bars, cooling bed, thermo-mechanical modelling, hybrid radial basis function, generated finite differences, residual stresses
Objavljeno v DiRROS: 28.02.2024; Ogledov: 70; Prenosov: 39
.pdf Celotno besedilo (8,55 MB)
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4.
Effect of the cooling regime on the mineralogy and reactivity of belite-sulfoaluminate clinkers
Sabina Dolenec, Katarina Šter, Maruša Mrak, Klara Žagar, Andrej Ipavec, Lea Žibret, 2020, izvirni znanstveni članek

Povzetek: This study investigated the influence of different cooling regimes on the microstructure and consequent reactivity of belite-sulfoaluminate clinkers. The cement clinkers were synthesized by incorporating secondary raw materials, such as titanogypsum and bottom ash, to the natural raw materials. Clinker phases were determined by Rietveld quantitative phase analysis, while the distribution morphology and the incorporation of substitute ions in the phases were characterized by scanning electron microscopy using energy-dispersive X-ray spectroscopy (SEM/EDS). Clinker reactivity was studied using isothermal calorimetry and was additionally investigated through compressive strength, which was determined for the cement prepared from the synthesized clinkers. X-ray diffraction analysis showed that, as well as the three main phases (belite, calcium sulfoaluminate, and ferrite), the clinkers contained additional minor phases (mayenite, gehlenite, arkanite, periclase, and perovskite), the ratios of which varied according to the cooling regime utilized. Microscopic observations indicated that the cooling regime also influenced the crystal size and morphology of the main phases, which consequently affected clinker reactivity. Furthermore, a smaller amount of substitute elements was incorporated in the main phases when cooling was slowed. Results showed that, in comparison to clinkers cooled at slower rates, air quenched clinkers reacted faster and exhibited a higher compressive strength at 7 days.
Ključne besede: clinkers, belite, calcium sulfoaluminate, cooling, microstructure, reactivity
Objavljeno v DiRROS: 20.12.2023; Ogledov: 145; Prenosov: 63
.pdf Celotno besedilo (4,18 MB)
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5.
Defining the fire decay and the cooling phase of post-flashover compartment fires
Andrea Lucherini, Jose L. Torero, 2023, izvirni znanstveni članek

Povzetek: The current research study discusses and characterises the fire decay and cooling phase of post-flashover compartment fires, as they are often mixed up despite their important heat transfer differences. The two pha- ses are defined according to the fire heat release rate time-history. The fire decay represents the phase in which the fire heat release rate decreases from the ventilation- or fuel-limited steady-state value of the fully-developed phase to fire extinguishment. This phase is highly influenced by the fuel characteristics, ranging from fast decays for hydrocarbon and liquid fuels to slow decays for charring cellulosic fuels (wood). Once the fuel is consumed, the compartment volume enters the cooling phase, where the cooling in the gas-phase and solid-phase happens with significantly different modes and characteristic times. The thermal boundary conditions at the structural elements are then defined according to physical characteristics and dynamics within the compartment. The research study also underlines how the existing performance-based methodologies lack explicit definitions of the decay and cooling phases and the corresponding thermal boundary conditions for the design of fire-safe struc- tural elements under realistic fire conditions.
Ključne besede: razpadanje ognja, hlajenje, izgorevanje, naravna izpostavljenost ognju, dinamika požara, požari v oddelkih, požarno inženirstvo, učinkovitost, požarna varnost, fire decay, cooling, burnout, natural fire exposure, fire dynamics, compartment fires, structural fire engineering, performance-based, fire safety
Objavljeno v DiRROS: 13.11.2023; Ogledov: 256; Prenosov: 119
.pdf Celotno besedilo (4,91 MB)
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7.
Odziv kambija navadne smreke (Picea abies) na ogrevanje in hlajenje debla
Jožica Gričar, Martin Zupančič, Katarina Čufar, Primož Oven, 2004, izvirni znanstveni članek

Povzetek: Proučili smo vpliv eksperimentalnega ogrevanja in hlajenja dela debla navadne smreke (Picea abies) na kambijevo aktivnost in celično diferenciacijo. Poskusasta potekala 30 dni; ogrevanje od 29.3.2004 do 3.5.2004, hlajenje pa od14.6.2004 do 20.7.2004. Vzorce floema, kambija in ksilema smo iz dreves odvzeli vsakih 10 dni, pripravili prečne prereze tkiv in preparate opazovali ssvetlobnim mikroskopom. Lokalno ogrevanje je po 10 dneh induciralo delitveno aktivnost kambija na floemsko stran, po 20 dneh pa tudi na ksilemsko. Po 30 dneh je pri ogrevanem vzorcu nastalo do 15 celic ranega lesa. V tem času se jeredna delitvena aktivnost kambija pri kontrolnem drevesu šele začela. Odziv kambija na hlajenje debla je bil manj izrazit. Anatomskih razlik med kontrolnim in hlajenim vzorcem po 10 in 20 dneh ni bilo. Po 30 dneh je pri hlajenem vzorcu začel nastajati kasni les, pri kontrolnem drevesu pa šele prehodni rani-kasni les. S poskusom smo demonstrirali, da je mogoče pri smrekiz umetnim ogrevanjem in hlajenjem debla vplivati na ksilo- in floemogenezo.
Ključne besede: navadna smreka, Picea abies, kambij, celična diferenciacija, ksilem, floem, ogrevanje, hlajenje, svetlobna mikroskopija, Norway spruce, cambium, cell differentiation, xylem, phloem, heating, cooling, light microscopy
Objavljeno v DiRROS: 12.07.2017; Ogledov: 4531; Prenosov: 2006
.pdf Celotno besedilo (1,85 MB)

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