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61.
On pipe diameter effects in surfactant drag-reducing pipe flows 总被引:3,自引:0,他引:3
Remarkable power saving in a fluid transport system is possible if the surfactant drag reduction technology is used. Application
of surfactant drag reduction to district heating and cooling systems has been investigated in the past. The establishment
of the scale-up law in drag-reducing pipe flows is one of the most important problems in this application. Main purpose of
this study is aimed to develop a reliable scale-up law in surfactant drag-reducing flows. As the basic data of surfactant
solutions, both non-Newtonian viscosity and viscoelasticity were experimentally determined. A turbulent eddy diffusivity model
based on the Maxwell model was employed to estimate the drag reduction of surfactant solutions. The predictions by the turbulence
model developed in this study with proper rheological characteristics of surfactant solutions has resulted in a reliable estimation
of the pipe diameter effect in surfactant drag-reducing flows over the pipe diameter range from 11 to 150mm.
Received: 30 June 1997 Accepted: 29 December 1997 相似文献
62.
Hiroshi?SuzukiEmail author Gerald?G.?Fuller Tomoe?Nakayama Hiromoto?Usui 《Rheologica Acta》2004,43(3):232-239
Development characteristics of dilute cationic surfactant solution flow have been studied through the measurements of the time characteristics of surfactant solution by birefringence experiments and of the streamwise mean velocity profiles of surfactant solution duct flow by a laser Doppler velocimetry system. For both experiments, the concentration of cationic surfactant (oleylbishydroxymethylethylammonium chloride: Ethoquad O/12) was kept constant at 1000 ppm and the molar ratio of the counter ion of sodium salicylate to the surfactants was at 1.5. From the birefringence experiments, dilute surfactant solution shows very long retardation time corresponding to micellar shear induced structure formation. This causes very slow flow development of surfactant solution in a duct. Even at the end of the test section with the distance of 112 times of hydraulic diameter form the inlet, the flow is not fully developed but still has the developing boundary layer characteristics on the duct wall. From the time characteristics and the boundary layer development, it is concluded that the entry length of 1000 to 2000 times hydraulic diameter is required for fully developed surfactant solution flow.List of abbreviations and symbols A1, A2 Coefficients for time constant fitting [-] - B Breadth of the test duct [m] - C1, C2 Coefficients for time constant fitting [-] - D Pipe diameter [m] - DH Hydraulic diameter [m] - g Impulse response function [Pa] - H Width of the test duct [m] - n Index of Bird-Carreau model [-] - Re Reynolds number (=UmDH/) - ReD Pipe Reynolds number (=UmD/) - Rex Streamwise distance Reynolds number (=U0x/) - T Absolute temperature [K] - t Time [s] - ta Retardation time [s] - tb Build-up time [s] - tx Relaxation time [s] - tx1, tx2 Relaxation time for double time constant fitting [s] - t Time constant in Bird-Carreau model [s] - U Time mean velocity [m/s] - Um Bulk mean velocity [m/s] - Umax Maximum velocity in a pipe [m/s] - U0 Main flow velocity [m/s] - u Friction velocity [m/s] - x, y Coordinates [m] -
Shear rate [s–1] -
Mean shear rate [s–1] - n Birefringence [-] - 99% boundary layer thickness [m] - Solution viscosity [Pa·s] - P, S Surfactant and solvent viscosity [Pa·s] - 0,
Zero and infinite viscosity of Bird-Carreau model [Pa·s] - Characteristic time in Maxwell model [s] - Water kinematic viscosity [m2/s] - Density [kg/m3] - Solution shear stress [Pa] - P, S Surfactant and solvent shear stress [Pa] - Time in convolution [s] 相似文献
63.
Hiroshi Suzuki Tetsu Itotagawa Yuli Setyo Indartono Hiromoto Usui Norihide Wada 《Rheologica Acta》2006,46(2):287-295
Rheological characteristics of trimethylolethane (TME) clathrate–hydrate slurry treated with drag-reducing surfactants were investigated. Friction coefficients and apparent viscosities were measured when the concentration of TME and its hydrate fraction treated with and without drag-reducing surfactants were changed in several steps. From the results, it is found that the surfactant addition causes effective drag reduction in a pipe flow when the hydrate fraction becomes high, while effective drag reduction disappears in the cases of low hydrate fraction. The results of viscosity measurements indicate that the TME molecules disturb the formation of shear-induced structures (SIS) causing drag reduction phenomena. To investigate this interaction between TME and surfactant micelles, the effect of TME concentration on viscosity and relaxation time of solutions was discussed. From this, it was found out that there exists a critical concentration of TME on the formation of SIS and that it becomes larger as shear rate increases. Thus, we conclude that this interaction between TME and micellar structures causes less drag reduction for the cases of low hydrate fraction, while the drag reduction appears in cases of high hydrate fraction because TME concentration in liquid phase becomes small. 相似文献
64.
Self‐Directed Orientation of Molecular Columns Based on n‐Type Hexaazatrinaphthylenes (HATNAs) for Electron Transport
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Xu‐Ying Liu Dr. Takayuki Usui Prof. Dr. Junichi Hanna 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(44):14207-14212
Self‐organizing n‐type hexaazatrinaphthylenes (HATNAs) with various bay‐located side chains have been synthesized. The HATNA derivatives are able to form long‐range molecular columns with self‐directed growth directions. In particular, alkyl‐substituted HATNAs showed in‐plane molecular columns with axes parallel to substrates, whereas the columnar orientation of the HATNAs with alkylethynyl or alkylthio groups strongly depended on the length of the introduced side chains. Interestingly, the derivative with octylthio chains exhibited out‐of‐plane molecular columns, in which electron mobility of up to 10?3 cm2 V?1 s?1 was determined through the time‐of‐flight technique, highlighting the fact that such molecular columns based on bay‐substituted HATNAs are promising n‐type semiconductors for device applications. 相似文献
65.
B. Monemar P.P. Paskov J.P. Bergman A.A. Toropov T.V. Shubina A. Usui 《Superlattices and Microstructures》2008,43(5-6):610
We report new data on the transient photoluminescence behaviour of free and donor bound excitons in high quality bulk GaN material grown by HVPE. With 266 nm photoexcitation the no-phonon free exciton has a short decay time, about 100 ps at 2 K, assigned to nonradiative surface recombination. The LO replicas of the free exciton have a much longer decay at 2 K, about 1.4 ns, believed to be a lower bound for the bulk radiative lifetimes of the free excitons at 2 K. The donor bound exciton no-phonon lines exhibit a rather short (about 300 ps) nonexponential decay at 2 K, which appears to be dominated by a scattering process. The corresponding LO replicas and the two-electron transitions have a much longer decay. From the latter, the lower bound of the radiative lifetime of the O- and Si-bound excitons are 1800 ps and 1100 ps, respectively. 相似文献
66.
A new criterion for the H-matrix property 总被引:3,自引:0,他引:3
Keiko Ojiro Hiroshi Niki Masataka Usui 《Journal of Computational and Applied Mathematics》2003,150(2):293-302
For many applications, it is very useful to know whether a matrix is an H-matrix or not. Recently, some iterative tests have been proposed for distinguishing H-matrix. In this paper, we propose a new method for being able to distinguish only a scalar times column vector. Numerical evidence for the effectiveness of the proposed algorithm is presented. 相似文献
67.
Imahori T Ojima H Yoshimura Y Takahata H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(34):10762-10771
An interesting acceleration effect of an allylic hydroxy group on ring-closing enyne metathesis has been found. Ring-closing enyne metathesis of terminal alkynes possessing an allylic hydroxy group proceeded smoothly without the ethylene atmosphere generally necessary to promote the reaction. The synthesis of (+)-isofagomine with the aid of this efficient reaction has been demonstrated. Mechanistic studies of the acceleration effect were also carried out. Results of NMR studies suggested that the reaction proceeded via an "ene-then-yne" pathway. Kinetic studies indicated switching of the rate-determining step as a consequence of the presence of an allylic hydroxy group. These results suggest acceleration of the reentry step of Ru-carbene species by the allylic hydroxy group. 相似文献
68.
The first palladium catalyst system that allows the direct allylation of indoles with allylic alcohols as substrates with water being the only byproduct is presented. The application of self-assembling ligands based on complementary hydrogen bonding was the key to success. 相似文献
69.
Dr. Masashi Hasegawa Dr. Yuki Nojima Prof. Dr. Yuya Nagata Prof. Dr. Kazuteru Usui Prof. Dr. Ken-ichi Sugiura Prof. Dr. Yasuhiro Mazaki 《European journal of organic chemistry》2023,26(36):e202300656
The synthesis, structure, and circularly polarized luminescence (CPL) of two types of shape-persistent [5]helicenes, hinged by a tethered (−OCH2CH2O−) or untethered (−OCH3) binaphthyl, are reported. The binaphthyl tethering system facilitated an effective Wittig ring-closure reaction in the synthesis of a macrocyclic precursor, which could be easily converted to the title compound via successive photocyclization. The tethered groups were replaced with untethered −OCH3 groups by treatment with BBr3 followed by methylation. Both compounds exhibited similar spectra, and their longest wavelength absorption band with a low intensity was attributed to the transition from HOMO to LUMO+1. These compounds exhibited CPL with higher dissymmetry factors glum values than unlocked helicenes. 相似文献
70.
Bleomycin-induced oxidative DNA damage under limited oxygen conditions results in the formation of the C4'-oxidized abasic site (1). We synthesized the oligodeoxynucleotides (ODN) 5, which contains 4'-o-nitrobenzyloxythymidine (3), and 6, which contains 2-nitrobenzyloxy-4'-methoxy-2'-deoxy-d-ribofuranoside (4), as the caged precursors of 7, an ODN containing 1, to study its reactivity with amines. Photoirradiation of the single- and double-stranded 5 led to the formation of 7. Uncaging of the duplex was faster and the yield of 7 was higher with the double-stranded than with the single-stranded ODN. It was suggested that a low dielectric environment of the o-nitrobenzyloxy group in the minor groove of the duplex might accelerate the uncaging rate. Similarly, 6 and its duplex yielded 7 by photoirradiation. However, the yields of 7 were lower than those of 5, and duplex formation slowed the uncaging rate. Reaction of the obtained 7 with an amine resulted in the formation of the lactam 2b in good yield in both single- and double-stranded forms, showing that amine modification of biomolecules by an ODN containing 1 is possible under physiologic conditions. 相似文献