scholarly journals A Hidden Anomaly in the Binary Mixture Natural Convection Subject to Flux Boundary Conditions

Physics ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 144-159
Author(s):  
Peter Vadasz
Keyword(s):  
Natural Convection ◽  
Binary Mixture ◽  
Boundary Conditions ◽  
Mass Fraction ◽  
Solute Concentration ◽  
Flux Boundary Conditions ◽  
Mass Fractions ◽  
Low Mass ◽  
Thermodiffusion Coefficient ◽  
Solid Walls

The problem of natural convection in a binary mixture subject to realistic boundary conditions of imposed zero mass flux on the solid walls shows solutions that might lead to unrealistic negative values of the mass fraction (or solute concentration). This anomaly is being investigated in this paper, and a possible way of addressing it is suggested via a mass-fraction-dependent thermodiffusion coefficient that can have negative values in regions of low mass fractions.

A technique for uranium and plutonium determination using coulometric potentiostatic facility UPK-19 for analysis of mixed-oxide fuel

2020 ◽  
Vol 86 (12) ◽  
pp. 15-22
Author(s):  
N. A. Bulayev ◽  
E. V. Chukhlantseva ◽  
O. V. Starovoytova ◽  
A. A. Tarasenko
Keyword(s):  
Acid Solution ◽  
Mass Fraction ◽  
Background Electrolyte ◽  
Stable State ◽  
Sulfamic Acid ◽  
Oxide Fuel ◽  
Oxidation Current ◽  
Mox Fuel ◽  
Mass Fractions ◽  
Uranium Plutonium

The content of uranium and plutonium is the main characteristic of mixed uranium-plutonium oxide fuel, which is strictly controlled and has a very narrow range of the permissible values. We focused on developing a technique for measuring mass fractions of uranium and plutonium by controlled potential coulometry using a coulometric unit UPK-19 in set with a R-40Kh potentiostat-galvanostat. Under conditions of sealed enclosures, a special design of the support stand which minimized the effect of fluctuations in ambient conditions on the signal stability was developed. Optimal conditions for coulometric determination of plutonium and uranium mass fractions were specified. The sulfuric acid solution with a molar concentration of 0.5 mol/dm3 was used as a medium. Lead ions were introduced into the background electrolyte to decrease the minimum voltage of hydrogen reduction to –190 mV. The addition of aluminum nitride reduced the effect of fluoride ions participating as a catalyst in dissolving MOX fuel samples, and the interfering effect of nitrite ions was eliminated by introducing a sulfamic acid solution into the cell. The total content of uranium and plutonium was determined by evaluation of the amount of electricity consumed at the stage of uranium and plutonium co-oxidation. Plutonium content was measured at the potentials, at which uranium remains in the stable state, which makes it possible to subtract the contribution of plutonium oxidation current from the total oxidation current. The error characteristics of the developed measurement technique were evaluated using the standard sample method and the real MOX fuel pellets. The error limits match the requirements set out in the specifications for MOX fuel. The technique for measuring mass fractions of uranium and plutonium in uranium-plutonium oxide nuclear fuel was certified. The relative measurement error of the mass fraction of plutonium and uranium was ±0.0070 and ±0.0095, respectively. The relative error of the ratio of the plutonium mass fraction to the sum of mass fractions of uranium and plutonium was ±0.0085.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

Numerical and Experimental Investigation Into the Effects of Nanoparticle Mass Fraction and Bubble Size on Boiling Heat Transfer of TiO2–Water Nanofluid

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Cong Qi ◽  
Yongliang Wan ◽  
Lin Liang ◽  
Zhonghao Rao ◽  
Yimin Li
Keyword(s):  
Heat Transfer ◽  
Bubble Size ◽  
Boiling Heat Transfer ◽  
Mass Fraction ◽  
Experimental Methods ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fractions ◽  
Boiling Heat Transfer Coefficient ◽  
Bubble Sizes

Considering mass transfer and energy transfer between liquid phase and vapor phase, a mixture model for boiling heat transfer of nanofluid is established. In addition, an experimental installation of boiling heat transfer is built. The boiling heat transfer of TiO2–water nanofluid is investigated by numerical and experimental methods, respectively. Thermal conductivity, viscosity, and boiling bubble size of TiO2–water nanofluid are experimentally investigated, and the effects of different nanoparticle mass fractions, bubble sizes and superheat on boiling heat transfer are also discussed. It is found that the boiling bubble size in TiO2–water nanofluid is only one-third of that in de-ionized water. It is also found that there is a critical nanoparticle mass fraction (wt.% = 2%) between enhancement and degradation for TiO2–water nanofluid. Compared with water, nanofluid enhances the boiling heat transfer coefficient by 77.7% when the nanoparticle mass fraction is lower than 2%, while it reduces the boiling heat transfer by 30.3% when the nanoparticle mass fraction is higher than 2%. The boiling heat transfer coefficients increase with the superheat for water and nanofluid. A mathematic correlation between heat flux and superheat is obtained in this paper.

scholarly journals Cosmological simulations of low-mass galaxies: some potential issues

2010 ◽  
Vol 6 (S270) ◽  
pp. 503-506
Author(s):  
Pedro Colín ◽  
Vladimir Avila-Reese ◽  
Octavio Valenzuela
Keyword(s):  
Star Formation ◽  
Adaptive Mesh Refinement ◽  
Mass Fraction ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Mesh Refinement ◽  
Adaptive Mesh ◽  
Stellar Mass ◽  
The Galaxy ◽  
Low Mass

AbstractCosmological Adaptive Mesh Refinement simulations are used to study the specific star formation rate (sSFR=SSF/Ms) history and the stellar mass fraction, fs=Ms/MT, of small galaxies, total masses MT between few × 1010 M⊙ to few ×1011 M⊙. Our results are compared with recent observational inferences that show the so-called “downsizing in sSFR” phenomenon: the less massive the galaxy, the higher on average is its sSFR, a trend seen at least since z ~ 1. The simulations are not able to reproduce this phenomenon, in particular the high inferred values of sSFR, as well as the low values of fs constrained from observations. The effects of resolution and sub-grid physics on the SFR and fs of galaxies are discussed.

Effect of CeO2 addition on microstructure and tribological characteristics of laser cladded Cu10Al–MoS2 coating under oil lubrication

2021 ◽  
pp. 146442072110309
Author(s):  
Shao Lifan ◽  
Ge Yuan ◽  
Kong Dejun
Keyword(s):  
Abrasive Wear ◽  
Wear Mechanism ◽  
Mass Fraction ◽  
Friction Reduction ◽  
Depth Of Field ◽  
Oil Lubrication ◽  
Wear Properties ◽  
Fatigue Wear ◽  
Wear Rates ◽  
Mass Fractions

In order to improve the friction and wear properties of Cu10Al–MoS2 coating, the addition of CeO2 is one of the present research hot spots. In this work, Cu10Al–MoS2 coatings with different CeO2 mass fractions were successfully fabricated on Q235 steel using a laser cladding. The microstructure and phase compositions of obtained coatings were analyzed using an ultra-depth of field microscope and X-ray diffraction, respectively. The friction-wear test was carried out under oil lubrication using a ball-on-disk wear tester, and the effects of CeO2 mass fraction on the microstructure, hardness, and friction-wear properties were studied, and the wear mechanism was also discussed. The results show that the laser cladded Cu10Al–MoS2 coatings with the different CeO2 mass fractions were mainly composed of Cu9Al4, Cu, AlFe3, Ni, MoS2, and CeO2 phases. The Vickers-hardness (HV) of Cu10Al–8MoS2–3CeO2, Cu10Al–8MoS2–6CeO2, and Cu10Al–8MoS2–9CeO2 coatings was 418, 445, and 457 HV0.3, respectively, which indicates an increase in hardness with the increase of CeO2 mass fraction. The average coefficients of friction (COF) and wear rates decrease with the increase of CeO2 mass fraction, presenting the outstanding friction reduction and wear resistance performances. The wear mechanism of Cu10Al–MoS2 coatings is changed from abrasive wear with slight fatigue wear to abrasive wear with the increase of CeO2 mass fraction.

Boundary conditions for Maxwell fields in Kerr-AdS spacetimes

2016 ◽  
Vol 25 (09) ◽  
pp. 1641011 ◽  
Author(s):  
Mengjie Wang
Keyword(s):  
Black Holes ◽  
Angular Momentum ◽  
Boundary Conditions ◽  
Energy Flux ◽  
Momentum Flux ◽  
De Sitter ◽  
Perturbative Methods ◽  
Flux Boundary Conditions ◽  
Maxwell Fields ◽  
New Type

Perturbative methods are useful to study the interaction between black holes and test fields. The equation for a perturbation itself, however, is not complete to study such a composed system if we do not assign physically relevant boundary conditions. Recently we have proposed a new type of boundary conditions for Maxwell fields in Kerr-anti-de Sitter (Kerr-AdS) spacetimes, from the viewpoint that the AdS boundary may be regarded as a perfectly reflecting mirror, in the sense that energy flux vanishes asymptotically. In this paper, we prove explicitly that a vanishing energy flux leads to a vanishing angular momentum flux. Thus, these boundary conditions may be dubbed as vanishing flux boundary conditions.

Three-dimensional flow of Powell–Eyring nanofluid with heat and mass flux boundary conditions

2016 ◽  
Vol 25 (7) ◽  
pp. 074701 ◽  
Author(s):  
Tasawar Hayat ◽  
Ikram Ullah ◽  
Taseer Muhammad ◽  
Ahmed Alsaedi ◽  
Sabir Ali Shehzad
Keyword(s):  
Boundary Conditions ◽  
Mass Flux ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Flux Boundary Conditions
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