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51.
A. F. Borghesani 《Rheologica Acta》1985,24(2):189-197
A function correlating the relative viscosity of a suspension of solid particles in liquids to their concentration is derived here theoretically using only general thermodynamic ideas, with out any consideration of microscopic hydrodynamic models. This function (
r
= exp (1/2B
*
C
2)) has a great advantage over the many different functions proposed in literature, for it depends on a single parameter,B
*, and is therefore concise. To test the validity of this function, a least-squares regression analysis was undertaken of available data on the viscosity and concentration of suspensions of coal particles in fuel oil, which promise to be a useful alternative to fuel oil in the near future. The proposed function was found to accurately describe the concentration-dependent behaviour of the relative viscosity of these suspensions. Furthermore, an attempt was made to obtain information about the factors affecting the value ofB
*, however the results were only qualitative because of, among other things, the inaccuracy of the viscosity measurements in such highly viscous fluids.
shear viscosity of the suspension
-
0
shear viscosity of the Newtonian suspending medium
-
r
= /0
relative viscosity
-
solid volume concentration
-
c
solid weight concentration
-
m
maximum attainable volume concentration of solids
-
solid volume concentration at which the relative viscosity of the suspension becomes infinite
-
c
m
maximum attainable solid weight concentration
-
s
density of the solid phase
-
l
density of the liquid phase
-
m
density of the suspension
-
k
n
coefficients of theø-power series expansion of
r
- {
j
}
sets of parameters specifying the thermodynamic state of the solid phase of a suspension
-
T
absolute temperature (K)
-
f (c, T,
j)
formal expression for the relative variation of the viscosity with concentration = [1 / (/c)]
T,j
-
d
median size of the granulometric distribution
-
B
plastic or Bingham viscosity
-
K
consistency factor
-
n
flow index
-
g ([c
m
–c],T,
j
)
function including an asymptotic divergence asc tends toc
m
, formally describing the concentration dependent behaviour of the shear viscosity of a suspension
-
A (T,
j)
regression analysis parameters
-
B (T,
j)
regression analysis parameters
-
B
* (T,
j
)
regression analysis parameters 相似文献
52.
The present work concerns the study of the radial distribution of eddy viscosity and mixing length and their dependence upon the Reynolds number and the concentration of the solid phase in a non-Newtonian flow of a suspension of solid particles in a gas. The investigated systems have a pseudoplastic character and the deviation from Newtonian behaviour increases with an increase in the concentration of the dispersed phase. Relations are presented for the eddy viscosity and mixing length in the flow of pseudoplastic fluids. From the analysis of results it follows that the mixing length and eddy viscosity increases with an increase in the Reynolds number. In contrast, an increase in the concentration of the solid phase and consequently of the pseudoplasticity causes a decrease in the investigated quantities. The radial distribution of the mixing length and the eddy viscosity is characterized by a maximum, after which the investigated quantities vary only slightly. This enables the area of the core of the turbulent flow to be defined.
E
Non-dimensional eddy viscosity
-
K
fluid consistency defined by Ostwald-De Waele's formula (power law)
-
K
fluid consistency, eq. (12)
-
L
mixing length
-
L
t
non-dimensional mixing length
-
N
+
position parameter, eq. (3)
-
n
power-law index
-
n
+
Reichardt's position parameter, eq. (4)
-
n
slope of the dependence ln
w = f[ln (8w/D)]
-
R
pipe radius
-
r
radial distance from the pipe axis
-
Re=D W /µ
Reynolds number
-
U
+
non-dimensional local mean axial velocity, eq. (2)
-
u
* = w (/8)0.5
friction velocity
-
non-dimensional local mean axial velocity
-
local mean axial velocity
-
u
turbulence velocity component
-
mean axial velocity at pipe axis
-
w
average velocity over cross-section of pipe
-
loading ratio of solid to air, i.e. ratio of mass flow rates of solids to air
-
Y
m
+
=Rn u2–n /K 8n–1
non-dimensional distance of pipe centre from the wall
-
y
distance from pipe wall
-
y
+
non-dimensional distance from pipe wall, eq. (5)
-
friction factor
-
µ
L
laminar part of viscosity
-
µ
t
eddy viscosity
-
density
-
shear stress
-
w
shear stress on the wall 相似文献
53.
介绍了数字式有源磁悬浮的应用背景和数字式有源磁悬浮的工作原理、元件结构设计、力的计算方法。实验证明,采用数字式有源磁悬浮技术提高了陀螺仪的精度,对陀螺仪性能的提升起到了关键的作用。 相似文献
54.
An analytical solution is obtained for steady flow of Quemada-type fluids in a circular tube driven by a constant pressure gradient. Expressions are derived for velocity distribution and for volumetric flow rate as a function of pressure gradient or wall shear stress. 相似文献
55.
Fan Xijun 《Acta Mechanica Sinica》1992,8(4):295-306
The constitutive equation for a semiconcentrated fibre suspension in the Oldroyd-B fluid has been derived from a statistical
model of such a suspension by employing the molecular theory for polymeric liquids. To circumvent theoretical difficulties
in viscoelastic fluid mechanics, several simplified models are used to account for the interactions of fibres and polymer
molecules. Some of material functions are calculated in terms of the constitutive equation.
The project Supported by the University of Melbourne of Australia, the National Natural Science Foundation of China and Zhejiang
Province 相似文献
56.
Tobias Fieback Frieder DreisbachMarcus Petermann Roland SpanEckard Weidner 《Fluid Phase Equilibria》2011,301(2):217-224
A novel measuring method is presented here that allows sorption and solvation measurements near to different process conditions. Especially for the sorption kinetics it is important that the measuring conditions are similar to later applications. Particularly for high pressure sorption measurements this claim could not be fulfilled for most technical applications.The advantage of the measuring methods presented here is that solid bed samples in high pressure gravimetry can be measured under flow-through conditions in both directions and, for the first time in high pressure gravimetry, liquid samples can be measured under flow-through conditions. Especially for ionic liquids, of which a large variety of new substances with unknown sorption potentials have been synthesised in the last few years, this results in much shorter measuring times.The first measurements presented here show that the new system allows for measuring times around 26 times shorter for an ionic liquid. 相似文献
57.
The mobility of the microcapsules in saturated granular media was estimated on the basis of conventional breakthrough experiments in vertical columns packed with sands for various physical and chemical conditions. Four types of microcapsules have been tested, all of them were found to have reasonable mobility in clean quartz sand, but not in sandy soil. The immobility in the sandy soil was attributed to some production deficiencies in terms of shape, size and quality of the coating surface. The size of the microcapsules should be considerably smaller than those produced with an order of magnitude of a few micrometers. They should also be more spherical and with a smoother surface. The addition of a proper dispersant had stabilized the microcapsules suspension, and facilitated their transport in the sand. A major flow factor affecting microcapsules mobility is the water flux. The microcapsules should be applied at a high irrigation rate, which also implies a high water content in the soil profile. Considering solely the mobility aspect, it seems that the prospect for successful application of the new method for weed control is limited to granular soils with a high hydraulic conductivity at/or near saturation. However, for the time being the most limiting problem is the production of quality microcapsules with good physical and chemical properties. 相似文献
58.
Thioacids and thioamino acids were synthesized in excellent yields from readily available acyl benzotriazoles and sodium hydrosulfide in water at room temperature. The new methodology features mild reaction conditions, high yields, short reaction times, and does not involve the use of organic solvents or bases. The reaction is eco-friendly, and the workup procedure is simple and does not require chromatographic separation. 相似文献
59.
Yang Bai Xiang Yao Jiandong Wang Jin-Long Wang Si-Cheng Wu Shi-Ping Yang Wei-Shi Li 《Tetrahedron》2019,75(33):4676-4685
Fullerene-based organic solar cells are generally suffering from severe microstructure evolution occurring in their bulk heterojunction active layers and thus are extremely stable. To address it, four polymerizable C70 fullerene derivatives, [6,6]-phenyl-C71-ethyl acrylate (PC71EA), [6,6]-phenyl-C71-propyl acrylate (PC71PrA), [6,6]-phenyl-C71-butyl acrylate (PC71BA), and [6,6]-phenyl-C71-pentyl acrylate (PC71PeA), have been designed, synthesized, and investigated. These fullerene compounds have a molecular structure, shape and size very like the conventional C70 fullerene acceptor, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), and have been found no different in their light absorption, redox potentials, and frontier orbital energy levels. Using these fullerene acrylates individually as acceptor and poly(3-hexylthiophene) as donor, organic solar cells have been fabricated and gave optimal efficiencies ranging from 3.32% to 4.16%, comparable to PC71BM-based reference cells (4.06%). Owing to their acrylate functionality, these fullerene derivatives can turn into insoluble upon heating, and thus endow their solar cell devices much better thermostability than PC71BM-based reference cells. The best one, coming from PC71PeA devices, reported an optimal efficiency of 4.16%, and maintained 91.7% efficiency after heat treatment at 150 °C for 35 h. As a sharp contrast, the PC71BM reference cell dropped its optimal efficiency from 4.06% to 0.48% only after 5 h heat treatment. X-ray diffraction, optical and atomic force microscopy, and space-charge-limited current method have been carried out to understand active layer structure, morphology, and charge mobility change during heat treatment. 相似文献
60.
L.G. Prokhorov D.V. Koptsov M.S. Matiushechkina V.P. Mitrofanov K. Haughian J. Hough S. Rowan A.A. van Veggel P.G. Murray G.D. Hammond K. Tokmakov 《Physics letters. A》2018,382(33):2186-2191
Silicon optics suspended by silicon ribbons or silicon fibers and kept at low temperature are being considered, because of promising optical and mechanical properties, for the test masses of third generation interferometric gravitational-wave detectors. To interconnect the suspension elements the technique of hydroxide catalysis (or silicate) bonding can be used. In order to estimate the bond loss a tuning fork was fabricated from silicon ribbons, which were then silicate bonded. The temperature dependence of mechanical loss of this tuning fork was measured in the temperature range of 95–295 K. The ratio of the energy stored in the bond layer to the total energy of the tuning fork was calculated by numerical simulation. This provided an upper limit of the bond loss as a function of the temperature. It is at 123 K, a proposed operating temperature of cryogenically operating ground based interferometric gravitational-wave detectors. 相似文献