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Auswahl der wissenschaftlichen Literatur zum Thema „Isotherm method 500“
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Zeitschriftenartikel zum Thema "Isotherm method 500"
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Yeo, In Hwan, Kyu Jae Hwang, Jae Hong An und Jong Ho Lee. „A Study on Heat Transfer Analysis and Experiment of Reinforced Concrete Columns Using 500°C Isotherm Method“. Advanced Materials Research 905 (April 2014): 249–53. http://dx.doi.org/10.4028/www.scientific.net/amr.905.249.
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This study aims to assess heat transfer analysis of RC columns and unstressed test by applying 500°C isotherm method, which is the strength deterioration estimation method of Eurocode, inorder to use it as basic data for fire engineering design. According to the heat transfer analysis and fire resistance experiment, it was decided an appropriate axial ratio of RC columns that have cross sections of 300 and 350 can be anticipated as 0.49 and 0.59.
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ARAÚJO, D. L., und G. D. C. PINTO. „Fire behavior of shallow prestressed hollow core slabs from computational modeling“. Revista IBRACON de Estruturas e Materiais 13, Nr. 2 (April 2020): 398–432. http://dx.doi.org/10.1590/s1983-41952020000200011.
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Abstract Prestressed hollow core slabs are one of the structural systems whose use has increased the most in recent years in Brazil due to its efficiency and versatility. They can be used in many types of structural systems, such as masonry, precast concrete, cast-in-place concrete and steel structures. However, there are few analytical models to evaluate the fire behavior of hollow core slabs. In a simplified way, the fire resistance is evaluated indirectly through the minimum distance of the surface in contact with fire to the reinforcement axis. In this paper, some numerical models in finite element software were developed to analyze the variation of temperature with fire exposure time of shallow hollow core slabs, focusing on the presence of voids in the transversal section of the slab. The 500 °C isotherm method applied to 20 cm high slabs confirmed the Standard Fire Resistance obtained from the tabular method. However, when applied to shallow prestressed hollow core slabs that are 16 cm high, the 500 °C isotherm method indicated that the Standard Fire Resistance of these slabs is lower than values obtained from tabular methods.
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SUAZNABAR, J. S., und V. P. SILVA. „Combined axial and flexural loads in short reinforced concrete columns in fire: ultimate limit state curves using 500 °C isotherm method“. Revista IBRACON de Estruturas e Materiais 11, Nr. 1 (Februar 2018): 163–82. http://dx.doi.org/10.1590/s1983-41952018000100009.
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Abstract Ultimate limit state curves of short reinforced concrete columns in fire situation are going to be presented in this paper. The authors created a code developed in Matlab. It makes a discretization of the cross sections of the columns and calculates the equilibrium integrals of them. The curves were plotted with the code considering the 500 °C isotherm method.
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Maciąg, Michał, und Szymon Spodzieja. „Designing reinforced concrete slabs under fire condition“. MATEC Web of Conferences 196 (2018): 02036. http://dx.doi.org/10.1051/matecconf/201819602036.
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In this article the capacity of reinforced concrete slabs of thickness larger than 15 cm was calculated with Isotherm 500 Method. For designed elements were analysed the support and span zone. There have been proposed tables for designers, on which basis it is possible to design slab of demanded fire capacity.
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Jaszczak, Bogusz, Mieczysław Kuczma und Wojciech Szymkuć. „Comparison of the load-bearing capacity of reinforced concrete columns under fire conditions using the method A, zone method and isotherm 500 method“. Fire Safety Journal 124 (September 2021): 103396. http://dx.doi.org/10.1016/j.firesaf.2021.103396.
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Dinh Du, Pham, Nguyen Trung Hieu, Thuy Chau To, Long Giang Bach, Mai Xuan Tinh, Tran Xuan Mau und Dinh Quang Khieu. „Aminopropyl Functionalised MCM-41: Synthesis and Application for Adsorption of Pb(II) and Cd(II)“. Advances in Materials Science and Engineering 2019 (19.02.2019): 1–15. http://dx.doi.org/10.1155/2019/8573451.
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This paper shows a comparison of porous properties of aminopropyl-MCM-41 materials functionalised via the direct and indirect methods. The obtained materials were characterised using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis-differential scanning calorimeter (TGA-DSC), adsorption/desorption isotherms of nitrogen, and Fourier-transfer infrared (FT-IR) spectroscopy. The results showed that the direct method provided the aminopropyl-MCM-41 material with well-ordered pores and high surface areas but with a lower quantity of grafted 3-aminopropyltriethoxysilane than the indirect method. To remove the organic template in the indirect method, solvent extraction with HCl/C2H5OH and calcination at 500°C were used, and the former gave a higher quantity of grafted 3-aminopropyltriethoxysilane in the resulting aminopropyl-MCM-41 materials. The experimental data were applied to the isotherm models of adsorption including Langmuir, Freundlich, Redlich–Peterson, and Sips either in the linear or nonlinear form. In order to avoid the bias of the determination coefficient and the error function method, the paired-samples t-test as an alternative method was first proposed to look for the most appropriate adsorption isotherms. The maximum adsorption capacity of Cd(II) and Pb(II) was 14.08 mg·g−1 and 64.21 mg·g−1, respectively. The mechanism of complexation and isoelectric interaction was suggested to explain the adsorption of Pb(II) and Cd(II) from aqueous solutions on aminopropyl functionalised MCM-41 in the range of pH from 2 to 9.
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Xu, Shun Jian, Guan Jun Qiao, Di Chen Li, Hong Jie Wang und Tian Jian Lu. „Using of Ethylene Glycol as Pore-Form Agent to Form Interconnected Mesopores in Carbonized Phenol Resin“. Materials Science Forum 569 (Januar 2008): 265–68. http://dx.doi.org/10.4028/www.scientific.net/msf.569.265.
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We used ethylene glycol as pore-forming agent to prepare porous carbon with interconnected pores derived from phenol–formaldehyde resin. The mixture of resins and glycol was by polymerization and pyrolysis monolithic material of porous carbon with interconnected mesopores and a narrow pore size range. The average pore size of the porous carbon obtained was 28.2 nm. The nitrogen adsorption isotherm for the porous carbon exhibited type IV isotherm, which corresponded to mesoporous adsorption. The method could endow porous carbon with BET surface area and pore volume about 500 m2/g and 0.607 cm3/g, respectively. The mesopores in porous carbon formed as a result of phase separation of resin-rich phase and glycol-rich phase at polymerization and remove of glycol-rich at subsequent pyrolysis.
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Romatschke, Ulrike. „Melting Layer Detection and Observation with the NCAR Airborne W-Band Radar“. Remote Sensing 13, Nr. 9 (24.04.2021): 1660. http://dx.doi.org/10.3390/rs13091660.
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A melting layer detection algorithm is developed for the NCAR 94 GHz airborne cloud radar (HIAPER CloudRadar, HCR). The detection method is based on maxima in the linear depolarization ratio and a discontinuity in the radial velocity field. A melting layer field is added to the radar data, which provides detected, interpolated, and estimated altitudes of the melting layer and the altitude of the 0 °C isotherm detected in model temperature data. The icing level is defined as the lowest melting layer, and the cloud data are flagged as either above (cold) or below (warm) the icing level. Analysis of the detected melting layer shows that the offset between the 0 °C isotherm and the actual melting layer varies with cloud type: in heavy convection sampled in the tropics, the melting layer is found up to 500 m below the 0 °C isotherm, while in shallow clouds, the offset is much smaller or sometimes vanishes completely. A relationship between the offset and the particle fall speed both above and below the melting layer is established. Special phenomena, such as a lowering of the melting layer towards the center of storms or split melting layers, were observed.
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Novakovic, Tatjana, Ljiljana Rozic, Srdjan Petrovic, Zorica Vukovic und Vera Dondur. „Pore surface fractal analysis of PEG and La(III)-doped mesoporous alumina obtained by the sol-gel method“. Journal of the Serbian Chemical Society 75, Nr. 6 (2010): 833–43. http://dx.doi.org/10.2298/jsc090922053n.
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Active porous alumina was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1200 ?C. The addition of lanthanum effectively inhibited the surface area loss of the aluminas. Fractal analysis from nitrogen adsorption isotherm was used to study the pore surface roughness of alumina samples with different chemical compositions (PEG, PEG and lanthanum) and calcinations conditions in terms of the surface fractal dimension, d. The Mahnke and M?gel (MM) model was used to determine the value of d of La(III)-doped alumina. Following the MM model, the d value of the activated aluminas increased as the calcination temperature increased from 500 to 700 ?C but decreased after calcination at 1000, 1100 and 1200 ?C. The addition of polyethylene glycol (PEG 5600) to the boehmite sol reduced the surface fractal of the activated alumina due to the heterogeneous distribution of the pores. With increasing La(III) concentration from 0.015 to 0.045 mol La(III)/mol Al(III), the d value of La-modified alumina samples decreased, indicating a smoother surface. The obtained PEG+La-doped boehmite sol can be used as a precursor dispersion for the deposition of mesoporous alumina coatings on stainless steel foil, by the spray pyrrolysis method.
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Putri, Fami Amalia, Nur Fala Hamadi, Ajeng Y. D. Lestari, Achmad Chafidz und Tintin Mutiara. „Potential of Modified Corn Cob (Zea mays L.) and Petai Hull (Parkia hassk) as New Biosorbent for Removal of Lead Waste“. Key Engineering Materials 783 (Oktober 2018): 126–31. http://dx.doi.org/10.4028/www.scientific.net/kem.783.126.
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Lead metal is one type of heavy metal that has high toxicity levels in the aquatic waste environment. The adsorption method is one of the alternatives in reducing heavy metal waste, by utilizing biosorbent. The purpose of this research is to study the process of making new biosorbent and to know the absorption of new biosorbent from corn cob (Zea mays L.) and petai hull (Parkia hassk) to dissolve lead metal waste (Pb). There are two types of biosorbents are ordinary (simplicia) biosorbents and modified biosorbents with nitric acid (HNO3). Synthetic waste is used in the form of Pb (II) metal ions from the Pb (NO3)2 solution using initial concentrations of 100, 200, 300, 400, and 500 mg / L. Biosorbents tested the concentration of metal ions with AAS and characterized using FTIR to determine functional groups. Maximum adsorption capacity was obtained by biosorbents D (simplicia) and H (HNO3) with Pb (II) adsorbed metal ion capacity of respectively 1.4175 mg/g and 2.230 mg/g at a concentration of 400 mg / l. The isotherm adsorption showed that the adsorption mechanism of Pb(II) ion fit for this study is seen from the values of R2 on C biosorbents is better with other adsorbents and respectively are followed Langmuir, Dubinin Radushkevich, Freundlich, and Langmuir isotherm adsorption.
Dissertationen zum Thema "Isotherm method 500"
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Santesson, Li. „Betongpelare och brand : En utvärdering av 500 °C isotermmetoden“. Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-25428.
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At the beginning of 2011, Sweden started using the European rules for structural design, the Eurocodes, instead of the previous national rules. In both the previous rules and the Eurocodes, it is possible to dimension concrete columns using tabled values. However, the required cross section measurements have increased considerably. Moreover, it is possible to dimension concrete columns using calculations, however, this is unusual. The development of a fire in a fire cell can be divided into the growth stage, the fully developed fire and the cooling phase. The duration of each phase, as well as the temperature, is dependent on a number of factors, e.g. the fire load, the size of openings and the geometry of the fire cell. In the Eurocodes there are standardized temperature-time curves that can be used in the dimensioning of a structural design, one of which is the standard temperature-time curve. The tabled values are based on this time-heat regime. When exposed to fire the strength of both concrete and reinforcements decreases. Regarding the reinforcement steel, the decrease is well documented. Concrete, however, is not a homogeneous material which makes the strength at elevated temperatures complex to determine. The dimensioning of concrete columns can be executed using tabled values. However, the objective of this report is a method called the 500 °C isotherm method. Using this method, concrete at temperatures above 500 °C is assumed not to contribute to the load bearing capacity. The residual cross-section retains its initial value of strength and modulus of elasticity. This results in a reduced cross-section. Subsequently, a reduced load bearing capacity is determined for the reinforcement steel due to the temperature. Thereafter, conventional calculation methods are used. The process of describing how the isotherm method should be implicated has been obstructed by the lack of explicit information in the Eurocodes. Furthermore, few people have knowledge about how the method should be used in practice. This has resulted in some assumptions based on logical arguments. A concrete column was evaluated for 60 and 90 minutes standard fire exposure to enable a comparison with the tabled values. The result showed that concrete columns can meet the requirements with a considerably smaller cross section. The calculated cross section measurements resulted in a value between the tabled values in the Eurocodes and those in the previous rules. Although the 500 °C isotherm method is the most simple of the simplified calculation methods, and the model in this report is limited to a circular, centrically loaded column, the method is complicated and time-consuming. It is therefore likely that it only will be used in special cases when the tabled values are inapplicable.Vid årsskiftet 2010-2011 övergick Sverige från nationell standard till de europeiska standarderna för konstruktion, Eurokoderna. I den europeiska standarden, precis som i den gamla, kan betongpelare förenklat branddimensioneras med hjälp av tabellvärden. Kraven på minsta tvärsnitt har dock blivit avsevärt större. Detta har varit blivit svårt att förena med önskemål från arkitekter. Det är även möjligt att branddimensionera betongpelare med beräkningar. Detta är dock ovanligt. Brandförloppet i en brandcell kan förenklat delas in i uppvärmning, fullt utvecklad brand och avsvalning. Tiden för de olika faserna, liksom temperaturen, påverkas av en mängd faktorer. Några av dessa är mängden brännbart material, hur stora öppningar som finns och brandcellens geometri. I Eurokoderna finns standardiserade brandförlopp som kan användas vid dimensionering. En av dessa kallas standardbrandkurvan. Tabellvärdena är baserade på standardbrandpåverkan. Vid branddimensionering används en annan lastkombination än vid normaltemperaturdimensionering. Denna lastkombination ger en lägre last än vid brottgränsdimensionering. Både betong och armeringsstål förlorar bärförmåga vid förhöjda temperaturer. För armeringsstål är denna reducering väl dokumenterad. För betong, som inte är ett homogent material, är hållfastheten svårare att beräkna. Betongpelare kan dimensioneras enligt tre metoder: Vedertagna och beprövade detaljlösningar (Tabellerade värden) Förenklade beräkningsmetoder Avancerade beräkningsmetoder Fokus i denna rapport ligger på en av de förenklade beräkningsmetoderna, 500 °C isotermmetoden. Den utgår från att betong som har en temperatur över 500 °C försummas, emedan betong med en temperatur under 500 °C antas ha sin fulla bärförmåga. Därefter beräknas en reducerad hållfasthet för armeringsstängerna utifrån den temperatur de uppnår. Dimensionering sker sedan enligt traditionella metoder. Arbetet med att beskriva hur isotermmetoden ska användas har försvårats av bristande information i Eurokoderna. Dessutom finns det få personer som känner till hur metoden ska användas i praktiken. Detta har resulterat i vissa antaganden som underbyggts av logiska resonemang. För att kunna jämföra isotermmetoden med tabellerade värden kontrollerades en pelare för 60 och 90 minuters standardbrandpåverkan (se Bilaga A). Resultatet visade att pelare kan klara kraven med mindre tvärsnitt än i tabellen. Vid dimensioneringen erhölls ett tvärsnitt som låg mellan de nya och de gamla kraven. 500 °C isotermmetoden är den enklaste av de förenklade beräkningsmetoderna för betongpelare. Detta innebär dock inte att den är enkel. Trots att modellen i denna rapport har avgränsats till centriskt belastade, cirkulära pelare är metoden tidskrävande. Troligt är därför att den bara kommer att användas vid speciella fall då tabellmetoden inte är tillämpbar.
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Lehoťák, Roman. „Návrh betonové konstrukce s ohledem na požární odolnost“. Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-444631.
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The diploma thesis deals with the analysis of internal forces and the design of the reinforcement of a reinforced concrete monolithic slab, a reinforcing wall and a column in the 1st floor of a dairy hall building. The fire resistance of selected structures was taken into account during dimensioning. The calculation of the internal forces was performed by the finite element method in Dlubal RFEM 5.24.
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Pivodová, Alena. „Návrh železobetonového objektu s ohledem na požadavky požární odolnosti“. Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392070.
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The diploma thesis deals with an analysis of internal forces of B4 reinforced construction of an office building. Analysis takes into account interaction with subsoil and when designing structural parts of the building, different requirements for fire resistance of a structure are taken into account. A Dlubal RFEM 5.17 program was used for finite element analysis, and model functionality verification was performer by using a summation of moments method. The thesis deals with the design and assessment of a point-supported slab, column, inner and external walls.
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Jindra, Daniel. „Stanovení požární odolnosti konstrukcí“. Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392030.
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Possibilities of modeling non-linear behavior of concrete within standard room temperatures and increased fire-load values using FEM software ANSYS are studied. Temperature dependences of material models are considered. Fire resistance of reinforced concrete and concrete-steel composite construction is analyzed. Fire loads are defined in accordance with relevant standards. Non-linear structural transient analyses are calculated after temperatures were determined by transient thermal analyses. Results obtained from analyses of simple reinforced concrete structure are compared with approach of isotherm 500 °C method.
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Löwe, Johannes [Verfasser], Gert [Akademischer Betreuer] Lube und Gerlind [Akademischer Betreuer] Plonka-Hoch. „Eine Finite-Elemente-Methode für nicht-isotherme inkompressible Strömungsprobleme / Johannes Löwe. Gutachter: Gert Lube ; Gerlind Plonka-Hoch. Betreuer: Gert Lube“. Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2011. http://d-nb.info/1043514961/34.
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Löwe, Johannes. „Eine Finite-Elemente-Methode für nicht-isotherme inkompressible Strömungsprobleme“. Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B3EE-B.
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Mentrup, Detlef. „Isothermal quantum dynamics: Investigations for the harmonic oscillator“. Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003052613.
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Thermostated time evolutions are on a firm ground and widely used in classical molecular dynamics (MD) simulations. Hamilton´s equations of motion are supplemented by time-dependent pseudofriction terms that convert the microcanonical isoenergetic time evolution into a canonical isothermal time evolution, thus permitting the calculation of canonical ensemble averages by time averaging. However, similar methods for quantum MD schemes are still lacking. Given the rich dynamical behavior of ultracold trapped quantum gases depending on the value of the s-wave scattering length, it is timely to investigate how classical thermostating methods can be combined with powerful approximate quantum dynamics schemes to deal with interacting quantum systems at finite temperature. In this work, the popular method of Nose and Hoover to create canonically distributed positions and momenta in classical MD simulations is generalized to a genuine quantum system of infinite dimensionality. We show that for the quantum harmonic oscillator, the equations of motion in terms of coherent states may be modified in a Nose-Hoover manner to mimic the coupling of the system to a thermal bath and create a quantum canonical ensemble. The method is developed initially for a single particle and then generalized to the case of an arbitrary number of identical quantum particles, involving entangled distribution functions. The resulting isothermal equations of motion for bosons and fermions contain additional terms leading to Bose-attraction and Pauli-blocking, respectively. Questions of ergodicity are discussed for different coupling schemes. In the many-particle case, the superiority of the Nose-Hoover technique to a Langevin approach is demonstrated. In addition, the work contains an investigation of the Grilli-Tosatti thermostating method applied to the harmonic oscillator, and calculations for quantum wavefunctions moving with a time-invariant shape in a harmonic potential.
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Dallmann, Helene. „Finite Element Methods with Local Projection Stabilization for Thermally Coupled Incompressible Flow“. Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0023-961A-9.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "Isotherm method 500"
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Liu, Qingqing, und Xiaoyan Li. „Study on Adsorption of U(VI) From Aqueous Solution by Activated MgO“. In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67922.
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The activated MgO was synthesized by microwave homo-precipitator method and characterized by SEM, EDS and FT-IR methods. It was used to adsorption of U(VI) from aqueous solution with batch system. The paper discussed the effect of pH, temperature, contact time, adsorbent dose and initial U(VI) concentration on the adsorption. The results showed that activated MgO has good adsorption capacity for U(VI), the removal rate and equilibrium adsorption capacity reached 83.5% and 84.04mg·g−1 at pH 5.0, 15mg dose and 313K,respectively. The adsorption kinetics of U(VI) onto activated MgO were better fitted with pseudo-second-order kinetic.The adsorption isotherm data were fitted well to Freundlich isotherm model.The thermodynamic parameters showed that the adsorption process is endothermic and spontaneous.
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Islam, A. K. M. Sadrul, M. Ruhul Amin, Shama F. Barna, Arafat A. Bhuiyan und M. H. Banna. „Mixed Convection and Entropy Generation Characteristics Inside a Porous Cavity With Viscous Dissipation Effect“. In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10883.
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This paper examines and explains two-dimensional, steady mixed convection flow in a porous square vented cavity. The interaction between the buoyancy stemming from one or more heated elements inside a microstructure filled vented enclosure and an imposed forced flow forms the topic of this investigation. Analysis has been carried out for two different boundary conditions. Initial investigations are carried out for walls of the enclosure being isothermal. A second stage of analysis is performed keeping only the left wall isothermal and other three walls adiabatic. Natural convection takes place due to temperature difference between the isothermal wall and the fluid. Forced convection condition is imposed by providing an inlet and a square vent inside the enclosure filled with fluid saturated porous medium. The mathematical model is developed using modified Darcy flow model and energy equation. Through the adaptation of the well known finite element method, solution to this numerical problem is obtained. Governing parameters chosen are Peclet Number (Pe), Rayleigh Number (Ra), Aspect ratio (AR) and the width of the inlet as a fraction of the width (I/W) of the enclosure. For detailed analysis different value of these parameters such as five Rayleigh Numbers (1, 50, 100, 500 and 1000) and seven different Peclet Numbers (0.1, 1, 5, 10, 20, 50 and 100) are considered. Effect of inlet to cavity width ratio is examined within the range 0.1 ≤ I/W ≤ 0.5 for a particular aspect ratio. The performance of the enclosure in both cases; are determined by flow visualization and by analyzing different parameters such as Bejan Number, Nusselt Number and Entropy Generation Number. Isotherms, streamlines show substantial variation in their pattern or magnitude. Average Nusselt number and average Bejan Number increases whereas Average energy flux density decreases with increasing I/W. These fluctuations also vary for different Rayleigh or Peclet numbers. The results for both the boundary conditions are also compared to find the most effective value of I/W.
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Yang, Yun, und Shimin Liu. „Quantification of Temperature-Dependent Sorption Kinetics in Shale Gas Reservoirs: Experiment and Theory“. In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205897-ms.
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Abstract A critical component of natural gas in organic-rich shales is adsorbed gas within organic matter. Quantification of adsorbed gas is essential for reliable estimates of gas-in-place in shale reservoirs. However, conventional high-pressure adsorption measurements for coal on the volumetric method are prone to error when applied to characterize sorption kinetics in shale-gas systems due to limited adsorption capacity and finer pores of shale matrix. An innovated laboratory apparatus and measurement procedures have been developed for accurate determination of the relatively small amount of adsorbed gas in the Marcellus shale sample. The custom-built volumetric apparatus is a differential unit composed of two identical single-sided units (one blank and one adsorption side) connected with a differential pressure transducer. The scale of the differential pressure transducer is ± 50 psi, a hundred-fold smaller than the absolute pressure transducer measuring to 5000 psi, leading to a significant increase in the accuracy of adsorption measurement. Methane adsorption isotherms on Marcellus shale are measured at 303, 313, 323 and 333 K with pressure up to 3000 psi. A fugacity-based Dubinin-Astakhov (D-A) isotherm is implemented to correct for the non-ideality and predict the temperature-dependence of supercritical gas sorption. The Marcellus shale studied displays generally linear correlations between adsorption capacity and pressure over the range of temperature and pressure investigated, indicating the presence of a solute gas component. It is noted that the condensed phase gas storage exists as the adsorbed gas on shale surface and dissolved gas in kerogen, where the solute gas amount is proportional to the partial pressure of that gas above the solution. To our best understanding, it is the first time to observe the contribution of dissolved gas to total gas storage. With adsorption potential being modeled by a temperature dependence expression, the D-A isotherm can successfully describe supercritical gas sorption for shale at multiple temperatures. Adsorption capacity remarkably decreases with temperature attributed to the isosteric heat of adsorption. Lastly, the wide applicability of the proposed fugacity-based D-A model is also tested for literature adsorption data on Woodford, Barnett, and Devonian shale. Overall, the fugacity-based D-A isotherm provides precise representations of the temperature-dependent gas adsorption on shales investigated in this work. The application of the proposed adsorption model allows predicting adsorption data at multiple temperatures based on the adsorption data collected at a single temperature. This study lays the foundation for accurate evaluation of gas storage in shale.
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Feng, Zhi-Gang, Samuel G. Musong und Efstathios E. Michaelides. „A Three Dimensional Immersed Boundary Method for Free Convection From Single Spheres and Aggregates“. In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21225.
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A novel numerical technique that utilizes a three-dimensional Immersed Boundary Method (IBM) to solve the thermal interactions between spherical particles in a fluid is developed. At first, the natural convection of an isolated isothermal sphere immersed in a viscous fluid is analyzed and a new correlation for the heat transfer rate from a single sphere is obtained for 0.5≤Pr≤200 and 0 ≤ Gr ≤500. Secondly, the free convection heat transfer rate of a pair of spheres (bi-sphere) and spherical clusters immersed in air (Pr=0.72) were investigated using this numerical technique. The interactions depend on the separation distance between the spheres. It was observed that an increase in the separation of two spheres in tandem or side-by-side within a certain range may enhance the average heat transfer rate, when the interparticle distance is more than five radii. The average heat transfer rate of a cluster of touching, identical spheres with the same Grashof number was found to decrease as the number of spheres increased in the cluster.
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Ellis, Fred V., und Sebastian Tordonato. „Calculation of Stress Relaxation Properties for 1CrMoV Bolt Material“. In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1939.
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Analytical life prediction methods have been developed for high temperature turbine and valve bolts. For 1CrMoV steel bolt material, long time creep-rupture and stress relaxation tests were performed at 450°C, 500°C, and 550°C by the National Research Institute for Metals of Japan. Based on analysis of their data, the isothermal creep behavior can be described using a power law: ε=Kσn(t)m+1 where ε is the creep strain, t is the time, σ is the stress, K, n, and m are material constants. The time power is a primarily a function of temperature, but also depends slightly on stress. To obtain the value for the time power typical of low stress, the creep equation constants were found in two steps. The time power was found using the lower stress data and a heat-centered type regression approach with the stress levels taking the place of the heats in the analysis. The heat constants were then calculated at all stress levels and regression performed to obtain the stress dependence. For comparison with the measured uniaxial stress relaxation properties, the relaxed stress as a function of time was calculated using the power law creep equation and a strain hardening flow rule. The calculated stress versus time curves were in good agreement with the measured at initial strain levels of 0.10%, 0.15%, and 0.20% for all temperatures except 500°C. At 500°C, good agreement was found using the creep properties typical of a stronger (within heat variation) material.
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Damian-Ascencio, Enrique A., Abel Hernandez-Guerrero, Cuauhtemoc Rubio-Arana und Gregory Kowalski. „Forced Convection Analysis in a Vertical Square Cavity With a Vortex Promoter“. In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38725.
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This paper presents a 2-D numerical study of the effect on the heat transfer from a promoter of turbulence in a vertical square cavity. The transient, turbulent flow simulation is for a fluid with a Prandtl number of 0.7 and constant properties. The thermal boundary conditions considered are isothermal cavity walls. In the analysis various aspect ratios and blockage fractions (10%, 25% and 50%) were examined at a constant Reynolds number (Re = 5000). The governing equations are solved using the LES (Large Eddy Simulation) method. The results demonstrate that increasing the channel blockage makes it more difficult to generate turbulence but increases the channel residence time of the fluid.
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Li, Zhihua, Jane Davidson und Susan Mantell. „Numerical Simulation of Flow Field and Heat Transfer of Streamlined Cylinders in Crossflow“. In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72024.
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The use of streamlined tubes to reduce pressure drop across polymer tube bundles is considered because of the relative ease of fabrication. The drag and convective heat transfer coefficients along the outer surface of lenticular and elliptical tubes with minor-to-major axis ratios of 0.3, 0.5, and 0.8 are determined numerically for cross-flow Reynolds numbers from 500 to 10,000. An isothermal surface is assumed. The two-dimensional, unsteady Navier-Stokes equations and energy equation are solved using the finite volume method. Laminar flow is assumed from the front stagnation point up to the point of separation. Turbulent flow in the wake is resolved using the shear stress transport k-omega model. Local heat transfer, pressure and friction coefficients as well as a total drag coefficient and average Nusselt number are presented. The results for streamlined tubes are compared to published data for circular and elliptical cylinders. Drag of the elliptical and lenticular cylinders is similar and lower than a circular cylinder. Reductions in drag may be increased by making the streamlined cylinders more slender. Over the range of Reynolds number considered, an elliptical cylinder with an axis ratio equal to 0.5 reduces pressure drop by 30 to 40 percent compared to that of a circular cylinder. The lenticular and elliptical geometries have nearly identical average of Nusselt number. The average Nusselt number of an elliptical or lenticular cylinder with axis ratio of 0.5 and 0.3 is 15 to 35% lower than that of a circular cylinder. A case study for an automotive radiator is presented to illustrate comparison of shaped and circular tubes in terms of both heat transfer and pressure drop.
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Dabbaghi, Hediyeh, Mohammadreza Nematollahi, Keyvan Safaei Baghbaderani, Parisa Bayatimalayeri und Mohammad Elahinia. „High-Temperature Oxidation Kinetics of Additively Manufactured NiTiHf“. In ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8449.
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Abstract NiTi-based high-temperature shape memory alloys (HTSMAs) such as NiTiHf have been utilized in a broad range of applications due to their high strength and work output, as well as, their ability to increase the transformation temperatures (TTs). Recently, additive manufacturing techniques (AM) have been widely used to fabricate complex shape memory alloy components without any major modifications or tooling and has paved the way to tailor the manufacturing and fabrications of microstructure and critical properties of their final parts. NiTi alloys properties such as transformation temperatures can be significantly altered due to oxidation, which can occur during the manufacturing process or post-processing. In this work, the oxidation behavior of Ni-rich NiTi20Hf shape memory alloys, which was fabricated by the selective laser melting (SLM) method, is evaluated. Thermogravimetric analysis (TGA) is used to assess the kinetic behavior of the oxidation at different temperature ranges of 500, 700, and 900 °C for 20 hours in the air. After oxidation, to evaluate the microstructure and chemical composition X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) was conducted. The isothermal oxidation kinetics of conventional NiTi20Hf alloys were studied, and the results were compared to AM samples. Results show a two-stage oxidation rate at which oxidation increased with the high rate at the initial stage. As the oxidation time increased, the oxidation rate gradually decreased. The oxidation behavior of NiTiHf alloys initially obeyed logarithmic rate law and then followed by parabolic rate law. SEM results showed the formation of a multi-layered oxide scale, including TiO2, NiTiO3, and Hf oxide.
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Chang, S. W., T. M. Liou und T. H. Lee. „Detailed Heat Transfer Distributions and Pressure Drop Measurements for a Rotating Parallelogram Channel With Radially Outward Flow“. In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45456.
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This experimental study examines the pressure drop coefficients (f) and the detailed Nusselt numbers (Nu) distributions over two opposite leading and trailing walls roughened by 45° ribs for a rotating parallelogram channel with radially outward flow. For the first time the isolated effects of Reynolds (Re), rotation (Ro) and buoyancy (Bu) numbers on local and area averaged Nusselt numbers (Nu and Nu) measured from the infrared thermography method were successfully examined at the parametric conditions of 5000≤Re≤15000, 0≤Ro≤0.3 and 0.001≤Bu≤0.23 for the single-pass parallelogram channel. A set of selected heat transfer data illustrates the Coriolis and rotating-buoyancy effects on the detailed Nu distributions and the area-averaged heat transfer performances of the rotating parallelogram channel. With the consideration of the f data generated at the isothermal conditions, the thermal performance factors (η) for this radially rotating channel were evaluated. The Nusselt numbers obtained from the leading and trailing walls of the rotating test channel fall in the respective ranges of 0.78–1.34 and 1.09–1.38 times of the stationary levels; while the η factors are in the range of 0.979–1.575 for the present test conditions.
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Simmons, Kathy, Stephen Hibberd, Yi Wang und Ian Care. „Numerical Study of the Two-Phase Air/Oil Flow Within an Aero-Engine Bearing Chamber Model Using a Coupled Lagrangian Droplet Tracking Method“. In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1568.
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Bearing chambers in an aero-engine are designed to provide specialised compartments where bearings may be supported to locate the shaft systems. The design of the bearing chambers, including sealing and oil system integration, is vital to the performance and reliability of aero-engines and hence it is of great significance to gain better understanding on the two-phase air/oil flow behaviour within the chambers. The physical phenomena occurring within the bearing chambers involve the interaction of turbulent airflow and oil in the form of jets, droplets and films. This paper reports two-way coupling CFD calculations for turbulent airflow and oil droplet motion in an aero-engine bearing chamber geometry in order to assess the influence of the interaction between airflow and oil droplets on the air flow and droplet impingement locations. In the CFD calculation the airflow is assumed to be incompressible and isothermal and the airflow motion is driven by rotating shafts and described by a standard k-ε turbulence model as implemented in the commercial CFD package CFX 4.2. The oil injected to the chamber is assumed to be in the form of discrete droplets and subsequent droplet motions are modelled using a Lagrangian tracking method. Turbulent dispersion and interaction between droplets are not included. The calculations are carried out at shaft speeds corresponding to a representative flight state with droplet diameters in the range of 1–500 microns. The CFD model of the bearing chamber used has a total cell number of 405,500 and the grid is constructed to ensure that the wall function formulation used at the boundaries for the turbulence model is valid. The boundary conditions within the chamber are specified by prescribing velocity conditions on chamber surfaces corresponding to the rotating components. The calculations are iterative; for the airflow, an additional source term, due to the drag forces from droplets, is added to the governing equations. The droplet trajectories are then simulated based on the updated airflow field. It is found that many major features of the airflow field obtained using the two-way coupling method are similar to those obtained using the simpler one-way coupling method. However, significant localised differences exist between the airflow fields obtained using the one-way and two-way coupling methods where the interaction of oil droplets with the airflow is more intense. There are localised regions in the vicinity of the oil injection where the oil droplet motion leads to an increased airflow speed. The motion of small droplets is differentially influenced by any change in airflow characteristics predicted using the two-way coupling method due to their small inertia and consequently the deposition characteristics of the small droplets are different. However, large droplets are less influenced by the modest change in the airflow and no significant difference is calculated in the deposition locations of oil droplets provided that droplet diameters larger than 100 microns are considered.