CFD Study on Supersonic Ejectors Used for Suction of Two Different Gases

2015 ◽  
Author(s):  
Mohsen Tavakol ◽  
Maziar Shafaee
Keyword(s):  
Numerical Simulation ◽  
Water Vapor ◽  
Mass Fraction ◽  
Pure Water ◽  
Variable Mass ◽  
Working Fluid ◽  
Gas Streams ◽  
Mass Fractions ◽  
Suction Flow ◽  
Different Gases

In ejector refrigeration cycles, ejector working fluids include various refrigerants with different properties. In some cases, ejector works with mixture of two different refrigerants; that each refrigerant have distinct properties. The purpose of this paper is to evaluate the performance of an ejector used for suction of a mixture of air and water vapor. In this regard, the ejector performance was numerically studied under the operating condition that a mixture of air and steam with variable mass fractions, were sucked into the ejector. With the help of numerical simulation, various conditions for two perfect gas streams of air and water vapor were investigated. Initially, the numerical simulation was carried out for the case that pure water vapor was considered as the working fluid of ejector. After validation of initial case with experimental data, numerical method was expanded for a specific case that, water vapor was considered as the working fluid of motive flow and a mixture of air and water vapor was considered for suction flow. Numerical simulations were done for different mass fraction of air and water vapor for suction flow mixture. Results indicated that, variations of the mass fraction of air in suction flow, leads to obvious changes in ejector performance. Also, it was observed that the increment of suction flow pressure, leads to increment of the ejector performance sensitivity to variations of suction flow mass fraction.

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.

scholarly journals The second law analysis of natural gas behavior within a vortex tube

2013 ◽  
Vol 17 (4) ◽  
pp. 1079-1092 ◽  
Author(s):  
Mahyar Kargaran ◽  
A. Arabkoohsar ◽  
S.J. Hagighat-Hosini ◽  
V. Farzaneh-Kord ◽  
Mahmood Farzaneh-Gord
Keyword(s):  
Natural Gas ◽  
Entropy Generation ◽  
Vortex Tube ◽  
Tube Length ◽  
Orifice Diameter ◽  
Working Fluid ◽  
Energy Separation ◽  
Second Law ◽  
Gas Streams ◽  
Mass Fractions

Vortex tube is a simple device without a moving part which is capable of separating hot and cold gas streams from a higher pressure inlet gas stream. The mechanism of energy separation has been investigated by several scientists and second law approach has emerged as an important tool for optimizing the vortex tube performance. Here, a thermodynamic model has been used to investigate vortex tube energy separation. Further, a method has been proposed for optimizing the vortex tube based on the rate of entropy generation obtained from experiments. Also, an experimental study has been carried out to investigate the effects of the hot tube length and cold orifice diameter on entropy generation within a vortex tube with natural gas as working fluid. A comparison has been made between air and natural gas as working fluids. The results show that the longest tube generates lowest entropy for NG. For air, it is middle tube which generates lowest entropy. Integration of entropy generation for all available cold mass fractions unveiled that an optimized value for hot tube length and cold orifice diameter is exist.

scholarly journals NUMERICAL SIMULATION OF THE SWIRLED FLOW OF WATER STEAM PLASMA WITH ALUMINUM MICROPARTICLES

2021 ◽  
Vol 6 (4) ◽  
pp. 25-34
Author(s):  
I. P. Zavershinskii ◽  
D. P. Porfirev
Keyword(s):  
Numerical Simulation ◽  
Water Vapor ◽  
Vortex Flow ◽  
Discharge Plasma ◽  
Pure Water ◽  
Kinetic Scheme ◽  
Molecular Complexes ◽  
Aluminum Particles ◽  
Water Steam ◽  
Heating Source

A study of the discharge plasma with a vortex flow of an argon + water vapor mixture with aluminum particles in a tube of a plasma vortex reactor (PVR) was carried out. The parameters of the discharge, plasma, and working flow in the PVR have been measured. Spectral methods were used to estimate the electron temperature, rotational and vibrational temperatures of excited molecular complexes, the temperature of metal clusters, and the electron density of plasma. A kinetic scheme is proposed for calculating the operating modes in a reactor using a water vapor discharge with aluminum particles. Numerical simulation of a vortex flow of pure water vapor with aluminum particles in the presence of a heating source is carried out.

scholarly journals Thermodynamic investigations of Zeotropic mixture of R290, R23 and R14 on three-stage auto refrigerating cascade system

2016 ◽  
Vol 20 (6) ◽  
pp. 2073-2086
Author(s):  
Mayilsamy Sivakumar ◽  
Periasamy Somasudaram
Keyword(s):  
Mass Fraction ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Cascade System ◽  
Environment Friendly ◽  
Mass Fractions ◽  
Zeotropic Mixture ◽  
Efficiency Defect ◽  
Low Temperature Refrigeration ◽  
System Operating

The zeotropic mixture of environment friendly refrigerants (hydrocarbons and hydrofluorocarbons) being the only alternatives for working fluid in low temperature refrigeration system. Hence, three-stage auto refrigerating cascade system was studied for the existence using four combinations of three-component zeotropic mixture of six different refrigerants. The exergy analysis confirmed the existence of three-stage auto refrigerating cascade system. The performances of the system like coefficient of performance, exergy lost, exergic efficiency, efficiency defect, and the evaporating temperature achieved were investigated for different mass fractions in order to verify the effect of mass fraction on them. In accordance with the environmental issues and the process of sustainable development, the three-component zeotropic mixture of R290/R23/R14 with the mass fraction of 0.218:0.346:0.436 was performing better and hence can be suggested as an alternative refrigerant for three-stage auto refrigerating cascade system operating at very low evaporating temperature in the range of ?97?C (176 K), at coefficient of performance of 0.253 and comparatively increased exergic efficiency up to 16.3% (58.5%).

Verification and Validation Studies for a Laminar Non-Premixed Methane/Air Flame

2006 ◽  
Author(s):  
S. Gokaltun ◽  
P. V. Skudarnov ◽  
C. X. Lin
Keyword(s):  
Experimental Data ◽  
Water Vapor ◽  
Mass Fraction ◽  
Numerical Solutions ◽  
Laminar Flame ◽  
Numerical Results ◽  
Verification And Validation ◽  
Reaction Products ◽  
Average Deviation ◽  
Mass Fractions

In this paper, verification and validation analysis for a nonpremixed methane/air laminar flame is presented. Numerical results were obtained using the finite volume method on structured grids. The verification of the numerical solutions was performed by using the Grid Convergence Index (GCI) and Richardson extrapolation techniques. A set of three different grids is used to calculate the error due to discretization where each grid was generated by doubling the number of cells in each direction of the coarser grid. The local value of GCI was used to calculate the observed order of convergence of the numerical method for local values of temperature and mass fractions of reaction products at various points along the flow domain. The largest error band at the finest grid solution was observed to be 4.6% for the static temperature, 0.5% for the mass fraction of methane and 2.9% for the mass fraction of water vapor. Finally the numerical results were validated with experimental data using the local measurements of temperature and species mass fractions. The results indicate that there is relatively good agreement between the present results and experimental data although a simple one-step reaction model was used for the methane/air combustion. The average deviation was found to be around 25%, 21% and 10% for temperature, methane mass fraction and water vapor mass fraction respectively.

Viscous Dissipation Effect of Liquid Flow in Microtubes

2008 ◽  
Author(s):  
Ning Guan ◽  
Zhigang Liu ◽  
Chengwu Zhang
Keyword(s):  
Numerical Simulation ◽  
Viscous Dissipation ◽  
Temperature Rise ◽  
Heating Temperature ◽  
Pure Water ◽  
Working Fluid ◽  
Ir Camera ◽  
Flow Through ◽  
New Criterion ◽  
D Model

Viscous dissipation effects on de-ionized ultra pure water flow through smooth quartz glass microtubes with different inner diameters are investigated numerically and experimentally as the Reynolds number varies in the range from 0 to 700. In present study, a 2-D model adapted to microtube is presented to analyze the viscous dissipation characteristic in microtube considering EDL effect. According to the numerical simulation results, a new criterion Vc demonstrating the law of the viscous dissipation in microtube is summed up in this paper. Based on the micro-area thermal-imaging technology and a series of correction tests, the viscous heating temperature rise in microtube can be exactly measured by an IR camera with a special magnifying lens. Moreover, the temperature rise of the working fluid resulted from the heat generated by the pump is also considered in present experiments. The experimental results are compared with predictions of the numerical simulation and the theoretical Vc correlation. The comparisons indicate that the experimental data are in accordance with numerical and theoretical results.

scholarly journals New Knowledge on the Performance of Supercritical Brayton Cycle with CO2-Based Mixtures

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1741 ◽  
Author(s):  
Aofang Yu ◽  
Wen Su ◽  
Li Zhao ◽  
Xinxing Lin ◽  
Naijun Zhou
Keyword(s):  
Mass Fraction ◽  
High Efficiency ◽  
Cycle Performance ◽  
Working Fluid ◽  
Temperature Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Critical Temperatures ◽  
Mass Fractions ◽  
Compressor Inlet

As one of the promising technologies to meet the increasing demand for electricity, supercritical CO2 (S-CO2) Brayton cycle has the characteristics of high efficiency, economic structure, and compact turbomachinery. These characteristics are closely related to the thermodynamic properties of working fluid. When CO2 is mixed with other gas, cycle parameters are determined by the constituent and the mass fraction of CO2. Therefore, in this contribution, a thermodynamic model is developed and validated for the recompression cycle. Seven types of CO2-based mixtures, namely CO2-Xe, CO2-Kr, CO2-O2, CO2-Ar, CO2-N2, CO2-Ne, and CO2-He, are employed. At different CO2 mass fractions, cycle parameters are determined under a fixed compressor inlet temperature, based on the maximization of cycle efficiency. Cycle performance and recuperators’ parameters are comprehensively compared for different CO2-based mixtures. Furthermore, in order to investigate the effect of compressor inlet temperature, cycle parameters of CO2-N2 are obtained under four different temperatures. From the obtained results, it can be concluded that, as the mass fraction of CO2 increases, different mixtures show different variations of cycle performance and recuperators’ parameters. In generally, the performance order of mixtures coincides with the descending or ascending order of corresponding critical temperatures. Performance curves of these considered mixtures locate between the curves of CO2-Xe and CO2-He. Meanwhile, the curves of CO2-O2 and CO2-N2 are always closed to each other at high CO2 mass fractions. In addition, with the increase of compressor inlet temperature, cycle performance decreases, and more heat transfer occurs in the recuperators.

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.

Numerical Simulation of Radon Atmospheric Dynamic Diffusion from a Flat Ground Uranium Tailings Impoundment

2013 ◽  
Vol 807-809 ◽  
pp. 628-631
Author(s):  
Xiao Yong Peng ◽  
Xin Zhang ◽  
Shuai Huang ◽  
Xu Sheng Chai ◽  
Lan Xia Guo
Keyword(s):  
Numerical Simulation ◽  
Mass Fraction ◽  
Space Distribution ◽  
Time And Space ◽  
Tailings Impoundment ◽  
Diffusion Characteristics ◽  
Atmospheric Dynamic ◽  
Uranium Tailings ◽  
Dynamic Diffusion ◽  
Flat Ground

with a flat ground uranium tailings impoundment as the object of the paper, CFD technology was used to study the atmospheric dynamic diffusion characteristics and the evolution of time and space distribution of radon in the uranium tailings impoundment. Results show that, within 1500m range of the leeward of uranium tailings impoundment the falling gradient of radon mass fraction improves with distance increases at the same moment, however the falling gradient flattens with the increase of time gradually; During the first 30 minutes, the radon mass fraction of tailings impoundment in the leeward direction has a larger growth gradient, then flattens out slowly, and stabilizes after 75 minutes.

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.

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