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11.
Effects of Temperature-Dependent Viscosity on Forced Convection Inside a Porous Medium 总被引:1,自引:0,他引:1
Considering the exponential viscosity–temperature relation, effect of temperature-dependent viscosity on forced convection
of a liquid through a porous medium, bounded by isoflux parallel plates, is investigated numerically based on the general
model of momentum transfer. Local effects of viscosity variation on the distribution of velocity and temperature are analyzed.
Moreover, global aspects of the problem are investigated where corrections are proposed for total pressure drop and the fully
developed Nusselt number, in the form of out/in viscosity ratio. Results are obtained over a wide range of permeabilities
from clear (of solid material) fluid to very low permeability, where for constant properties one expects a nearly slug flow. 相似文献
12.
Two different approaches have been implemented to interpret the existing data in Merrikh and Lage (2005a, in: Pop, Ingham,
Transport Phenomena in Porous Media, Elsevier, Oxford) pertinent to the pore-scale simulation of natural convection in a laterally
heated square enclosure filled with a fluid bathing discrete, disconnected and conducting solid blocks. Mathematical analysis
of the problem based on the least squares method leads us to a Nu-Ra correlation with the solid-to-fluid thermal conductivity ratio and the porous medium permeability as the controlling parameters.
In this study, while the porosity is fixed, the permeability is varied by changing either the block size or the number of
blocks. Hence, three independent variables N, Ra, and κ being the number of blocks, Rayleigh number, and the conductivity ratio between the solid and the fluid, respectively,
affect the overall heat transfer process. Based on a simplified thermal resistance approach, an alternative correlation is
proposed to predict the Nusselt number as a function of the aforementioned parameters. Detailed analysis of the results and
the expected errors are presented. 相似文献
13.
Hooman Moradpour Mohsen Javaherian Ebrahim Namvar Amir Hadi Ziaie 《Entropy (Basel, Switzerland)》2022,24(6)
Relying on the quantum tunnelling concept and Maxwell–Boltzmann–Gibbs statistics, Gamow shows that the star-burning process happens at temperatures comparable to a critical value, called the Gamow temperature () and less than the prediction of the classical framework. In order to highlight the role of the equipartition theorem in the Gamow argument, a thermal length scale is defined, and then the effects of non-extensivity on the Gamow temperature have been investigated by focusing on the Tsallis and Kaniadakis statistics. The results attest that while the Gamow temperature decreases in the framework of Kaniadakis statistics, it can be bigger or smaller than when Tsallis statistics are employed. 相似文献
14.
Francesco Biccari Travis Hamilton Andrea Ristori Stefano Sanguinetti Sergio Bietti Massimo Gurioli Hooman Mohseni 《Particle & Particle Systems Characterization》2020,37(1):1900431
In recent years, dielectric microspheres have been used in conjunction with optical microscopes to beat the diffraction limit and to obtain superresolution imaging. The use of microspheres on quantum dots (QDs) is investigated, for the first time, to enhance the light coupling efficiency. The enhancement of the QD luminescence collection in terms of extraction and directionality is demonstrated, as well as the enhancement of spatial resolution. In particular, it is found that a dielectric microsphere, placed on top of an epitaxial QD, increases the collected radiant energy by about a factor of 42, when a low numerical aperture objective is used. Moreover, if two or more QDs are present below the microsphere, the modification of the far field emission pattern allows selective collection of the luminescence from a single QD by simply changing the collection angle. Dielectric microspheres present a simple and efficient tool to improve the QD spectroscopy, and potentially QD-based devices. 相似文献
15.
We show that solar axion conversion to photons in the Earth's magnetosphere can produce an x-ray flux, with average energy omega approximately 4 keV, which is measurable on the dark side of the Earth. The smallness of the Earth's magnetic field is compensated by a large magnetized volume. For axion masses m(a) less, similar10(-4) eV, a low-Earth-orbit x-ray detector with an effective area of 10(4) cm(2), pointed at the solar core, can probe the photon-axion coupling down to 10(-11) GeV-1, in 1 yr. Thus, the sensitivity of this new approach will be an order of magnitude beyond current laboratory limits. 相似文献
16.
Mohamed Abdel Salam Hooman Shadnia James S. Wright Robert Burk 《Journal of solution chemistry》2010,39(3):385-397
Multi-walled carbon nanotubes (MWCNTs) were chemically modified with octadecyl amine or polyethyleneglycol and then used as
solid phase adsorbents for the adsorption from aqueous solution of different polyhalogenated organic pollutants: pentachlorophenol,
2,4,5-trichlorophenol, 3,3′,4,4′-tetrachlorobiphenyl and 2,2′,5,5′-tetrabromobiphenyl from model aqueous solutions. The effects
of temperature were measured and thus the Gibbs energy, enthalpy, and entropy of adsorption were calculated. In general, the
Gibbs energy of adsorption was negative for the target analytes, indicating that adsorption was spontaneous at all temperatures.
On the other hand, the values of the enthalpy and entropy of adsorption were significantly dependent on the type of modified
MWCNTs as well as the analytes used. Computer modeling was used to simulate the adsorption process and calculate the Gibbs
energies of adsorption. The results showed moderate agreement with the experimentally determined values. 相似文献
17.
Karnel Hooman Mofid Gorji-Bandpy 《应用数学和力学(英文版)》2005,26(5):587
The effects of viscous dissipation on thermal entrance heat transfer in a parallel plate channel filled with a saturated porous medium, is investigated analytically on the basis of a Darcy model. The case of isothermal boundary is treated. The local and the bulk temperature distribution along with the Nusselt number in the thermal entrance region were found. The fully developed Nusselt number, independent of the Brinkman number, is found
to be 6. It is observed that neglecting the effects of viscous dissipation would lead to the well-known case of internal flows, with Nusselt number equal to 4.93. A finite difference numerical solution is also utilized. It is seen that the results of these two methods, analytical and numerical, are in good agreement. 相似文献
to be 6. It is observed that neglecting the effects of viscous dissipation would lead to the well-known case of internal flows, with Nusselt number equal to 4.93. A finite difference numerical solution is also utilized. It is seen that the results of these two methods, analytical and numerical, are in good agreement. 相似文献
18.
Fully developed forced convection inside a circular tube filled with saturated porous medium and with uniform heat flux at
the wall is investigated on the basis of a Brinkman–Forchheimer model. The matched asymptotic expansion method is applied
at small Darcy numbers. For large Darcy numbers, the solution for the Brinkman–Forchheimer momentum equation is found in terms
of an asymptotic expansion. Once the velocity distribution is determined, the energy equation is solved using the same asymptotic
technique. The results for the two limiting cases of clear fluid and Darcy flow conditions show good agreement with those
available in the literature. 相似文献
19.
Iain J. MacEwan Nicholas E. Glembotski Darryl D’Lima Won Bae Koichi Masuda Hooman H. Rashidi Loren K. Mell Mark Bydder 《Magnetic resonance imaging》2014
The purpose of this study was to evaluate a magnetic resonance imaging (MRI) technique for quantifying the proton density water fraction (PDWF) as a biomarker of bone marrow cellularity. Thirty-six human bone marrow specimens from 18 donors were excised and subjected to different measurements of tissue composition: PDWF quantification using a multiple gradient echo MRI technique, three biochemical assays (triglyceride, total lipid and water content) and a histological assessment of cellularity. Results showed a strong correlation between PDWF and bone marrow cellularity from histology (r = 0.72). A strong correlation was also found between PDWF and the biochemical assay of water content (r = 0.76). These results suggest the PDWF is a predictor of bone marrow cellularity in tissues and can provide a non-invasive assessment of bone marrow changes in clinical patients undergoing radiotherapy. 相似文献
20.
Elmira Kashani Nader Noroozi Pesyan Hamid Rashidnejad Ahmad Poursattar Marjani Hooman Yaghoobnejad Asl 《Journal of the Iranian Chemical Society》2017,14(10):2143-2156
Synthesis and characterization of novel polymeric organic–inorganic complex based on sodium 2,4-dioxo-6-aryl-3-oxa-bicyclo[3,1,0]hexane-1,5-dicarboxylate with three-dimensional hybrid networks were reported. The polymeric complex was crystallizing in the triclinic, space group P1. As determined by X-ray single-crystal analysis, in this compound each Na ion is coordinated by six O atoms: two from different carbonyl oxygen atom of carboxylic acid groups, two from bridged carbonyl oxygen atom of carboxylic acid groups, one from the carbonyl oxygen atom of cyclic anhydride and one from water molecule. The structure characterization was done by means of IR, 1H, 13C NMR, UV–Vis spectroscopies, Tg, flame photometry and X-ray crystallographic analysis. 相似文献