Triple-Choking Model for Ejector

2010 ◽  
Vol 2 (2) ◽  
Author(s):  
J. Sargolzaei ◽  
M. R. Pirzadi Jahromi ◽  
E. Saljoughi
Keyword(s):  
Theoretical Models ◽  
Mixing Efficiency ◽  
Governing Equations ◽  
Critical Mode ◽  
Cross Sectional ◽  
New Approach ◽  
Mode Operation ◽  
Operation Conditions ◽  
Mixing Chamber ◽  
Good Agreement

In this study, a 1D analysis has been presented for the prediction of ejector performance at critical mode operation. The new triple-choking model has been developed using the governing equations of the compressible fluids and thermodynamics properties based on the frictional adiabatic fluid study. A new approach has been introduced to consider the frictional effects on the mixing efficiencies by extending the 1D ejector theory. A very good agreement has been reported for the R141b and steam experimental data at critical mode operation. Furthermore, simulated results have been compared with some of the recent theoretical models. In addition, the influence of operation conditions on the ejector performance and the required cross-sectional area of the mixing chamber has been showed. Finally, the influence of the operation conditions (such as generator, condenser, and evaporator temperatures) and the size of ejector on the mixing efficiency have been studied.

scholarly journals Study on the Expansion of Primary Flow for the Mixing Uniformity in the Two-Phase Ejector

2021 ◽  
Vol 2097 (1) ◽  
pp. 012012
Author(s):  
Lixing Zheng ◽  
Hongwei Hu ◽  
Changning Mi
Keyword(s):  
Secondary Flow ◽  
Optimization Design ◽  
Entropy Change ◽  
Mixing Efficiency ◽  
Primary Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Thermodynamic Entropy ◽  
Mixing Chamber ◽  
Flow Pressure

Abstract The expansion of primary flow in the suction chamber of the CO2 two-phase ejector is investigated and its influences on the mixing characteristics are analyzed. An ejector model is developed, by constructing differential equations for mass, momentum and energy then get the governing equation. In the suction chamber, the expansion of primary flow and the compression of secondary flow are modeled along the flow path. Based on the constant-pressure mixing theory, the pressure equilibrium positions of two stream (namely at the inlet and inside of mixing chamber, respectively) are considered. The mass and energy transfer in the mixing chamber were analyzed by using the double-flow model formulation. The ejector performance parameters are obtained for the different operation conditions, and the distributions of temperature and velocity of two streams in the mixing chamber are presented. The simulation results showed the influence of primary flow expansion on the pressure lift ratio was relatively obvious, and the larger expansion distance was helpful to improve the mixing efficiency and decrease the thermodynamic entropy change during the mixing. Moreover, the temperature of secondary flow for lower primary flow pressure presented larger descent rates at the initial of mixing. This work is helpful for the improvement of ejector theoretical model and the optimization design.

scholarly journals A New Approach for the Solution of Three-Dimensional Magnetohydrodynamic Rotating Flow over a Shrinking Sheet

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
S. S. Motsa ◽  
S. Shateyi
Keyword(s):  
Three Dimensional ◽  
Rotating Flow ◽  
Shrinking Sheet ◽  
Analysis Method ◽  
Governing Equations ◽  
New Approach ◽  
Homotopy Analysis ◽  
Stress Variations ◽  
Spectral Homotopy Analysis Method ◽  
Good Agreement

The numerical solution of magnetohydrodynamic (MHD) and rotating flow over a porous shrinking sheet is obtained by the new approach known as spectral homotopy analysis method (SHAM). Using a similarity transformation, the governing equations for the momentum are reduced to a set of ordinary differential equations and are solved by the SHAM approach to determine velocity distributions and shear stress variations for different governing parameters. The SHAM results are analysed and validated against numerical results obtained using MATLAB's built-inbvp4croutine, and good agreement is observed.

Investment Shocks and Asset Prices: An Investment-Based Approach

2019 ◽  
Vol 55 (8) ◽  
pp. 2665-2699
Author(s):  
Lorenzo Garlappi ◽  
Zhongzhi Song
Keyword(s):  
Measurement Errors ◽  
Asset Prices ◽  
Simulation Analysis ◽  
Simulated Data ◽  
Theoretical Models ◽  
Cross Sectional ◽  
New Approach ◽  
Economic Mechanism ◽  
Growth Firms ◽  
Specific Technology

We propose a new approach, based on investment data, to determine firms’ return exposure to investment-specific technology (IST) shocks. When applied to U.S. data, we find that, in contrast to the pattern estimated from empirical IST proxies, value firms have higher exposure to IST shocks than growth firms. When applied to simulated data from existing theoretical models, our approach reveals that existing empirical findings may result from measurement errors in the IST proxies. Importantly, our simulation analysis uncovers the key role played by investment data in determining the economic mechanism through which IST shocks affect cross-sectional asset prices.

Longitudinal Impact of Cylindrical Shells With Discontinuous Cross-Sectional Area

1972 ◽  
Vol 39 (4) ◽  
pp. 1005-1010 ◽  
Author(s):  
R. W. Mortimer ◽  
J. L. Rose ◽  
A. Blum
Keyword(s):  
Cylindrical Shells ◽  
Cross Sectional Area ◽  
Experimental Results ◽  
Longitudinal Impact ◽  
Sectional Area ◽  
Governing Equations ◽  
Cross Sectional ◽  
Inertia Effects ◽  
Stress Ratios ◽  
Good Agreement

The reflections and transmissions of longitudinal strain pulses in cylindrical shells having cross-sectional area discontinuities are studied both analytically and experimentally. Three different theories were used to analyze this problem: the first, termed “bending” theory, includes the transverse shear, radial inertia, and rotary inertia effects; the second is based on a modified “membrane” theory; the last is derived from the “uniaxial” theory. Solutions were obtained by solving each of the three systems of governing equations by the method of characteristics. The longitudinal and circumferential incident, reflected, and transmitted strain pulses calculated from the bending and membrane theories are shown to be in good agreement with the experimental results, whereas the uniaxial comparisons are poor. In addition, the calculated reflected and transmitted stress ratios are in good agreement with the experimental results; the ratios obtained from the uniaxial theory are shown to be generally inadequate.

Enhancement of Mixing in a Micro TAS by Micro-Bubble Emission Boiling

2007 ◽  
Author(s):  
H. Kato ◽  
T. Kimura ◽  
K. Yamazaki ◽  
M. Yamaguchi
Keyword(s):  
Heat Flux ◽  
Nucleate Boiling ◽  
Mixing Efficiency ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Heat ◽  
Two Fluids ◽  
Maximum Heat Flux ◽  
Mixing Chamber ◽  
Micro Bubble

The mixing of two fluids is important in enhancing chemical reactions in a micro TAS. Some devices or methods are needed to enhance the mixing, because the Reynolds number is very low, on the order of 1. In the present research, we studied the possibility of using micro-bubble emission boiling. A heater made of a platinum wire of 30 micrometer was installed in a Y-shaped micro-channel whose cross sectional area was 2 mm × 0.5 mm. The heater was directly powered by electric current up to 1.5 A. The maximum heat flux was 7.47 MW/m2, which was well above the burnout heat flux. The subcool was 80 degrees and the velocity of fluid (colored water) was changed from 0.5 to 2.0 mm/s. When micro-bubble emission boiling occurred, the mixing was improved drastically. The mixing efficiency reached above 90% at v = 2.0 mm/s and q = 7.47MW/m2. In contrast, the mixing efficiency was poor in the case of normal nucleate boiling. The effect of the mixing chamber was also examined.

scholarly journals A Numerical Study of Sub-Millisecond Integrated Mix-and-Inject Microfluidic Devices for Sample Delivery at Synchrotron and XFELs

2021 ◽  
Vol 11 (8) ◽  
pp. 3404
Author(s):  
Majid Hejazian ◽  
Eugeniu Balaur ◽  
Brian Abbey
Keyword(s):  
Molecular Dynamics ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Liquid Jets ◽  
Mixing Efficiency ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Time Required

Microfluidic devices which integrate both rapid mixing and liquid jetting for sample delivery are an emerging solution for studying molecular dynamics via X-ray diffraction. Here we use finite element modelling to investigate the efficiency and time-resolution achievable using microfluidic mixers within the parameter range required for producing stable liquid jets. Three-dimensional simulations, validated by experimental data, are used to determine the velocity and concentration distribution within these devices. The results show that by adopting a serpentine geometry, it is possible to induce chaotic mixing, which effectively reduces the time required to achieve a homogeneous mixture for sample delivery. Further, we investigate the effect of flow rate and the mixer microchannel size on the mixing efficiency and minimum time required for complete mixing of the two solutions whilst maintaining a stable jet. In general, we find that the smaller the cross-sectional area of the mixer microchannel, the shorter the time needed to achieve homogeneous mixing for a given flow rate. The results of these simulations will form the basis for optimised designs enabling the study of molecular dynamics occurring on millisecond timescales using integrated mix-and-inject microfluidic devices.

scholarly journals 3D-Volume Rendering of the Pelvis with Emphasis on Paraurethral Structures Based on MRI Scans and Comparisons between 3D Slicer and OsiriX®

2021 ◽  
Vol 45 (3) ◽  
Author(s):  
C. M. Durnea ◽  
S. Siddiqi ◽  
D. Nazarian ◽  
G. Munneke ◽  
P. M. Sedgwick ◽  
...  
Keyword(s):  
Image Processing ◽  
Secondary Analysis ◽  
Three Dimensional ◽  
3D Models ◽  
Clinical Role ◽  
Cross Sectional ◽  
3D Slicer ◽  
Mri Scans ◽  
3D Volume ◽  
Good Agreement

AbstractThe feasibility of rendering three dimensional (3D) pelvic models of vaginal, urethral and paraurethral lesions from 2D MRI has been demonstrated previously. To quantitatively compare 3D models using two different image processing applications: 3D Slicer and OsiriX. Secondary analysis and processing of five MRI scan based image sets from female patients aged 29–43 years old with vaginal or paraurethral lesions. Cross sectional image sets were used to create 3D models of the pelvic structures with 3D Slicer and OsiriX image processing applications. The linear dimensions of the models created using the two different methods were compared using Bland-Altman plots. The comparisons demonstrated good agreement between measurements from the two applications. The two data sets obtained from different image processing methods demonstrated good agreement. Both 3D Slicer and OsiriX can be used interchangeably and produce almost similar results. The clinical role of this investigation modality remains to be further evaluated.

scholarly journals A NEW APPROACH TO DYNAMIC FINITE-SIZE SCALING

2003 ◽  
Vol 14 (07) ◽  
pp. 945-954 ◽  
Author(s):  
MEHMET DİLAVER ◽  
SEMRA GÜNDÜÇ ◽  
MERAL AYDIN ◽  
YİĞİT GÜNDÜÇ
Keyword(s):  
Three Dimensional ◽  
Finite Size ◽  
Taylor Series Expansion ◽  
Scaling Behavior ◽  
Dynamic Scaling ◽  
Finite Size Scaling ◽  
New Approach ◽  
Size Scaling ◽  
Dynamic Exponent ◽  
Good Agreement

In this work we have considered the Taylor series expansion of the dynamic scaling relation of the magnetization with respect to small initial magnetization values in order to study the dynamic scaling behavior of two- and three-dimensional Ising models. We have used the literature values of the critical exponents and of the new dynamic exponent x0 to observe the dynamic finite-size scaling behavior of the time evolution of the magnetization during early stages of the Monte Carlo simulation. For the three-dimensional Ising model we have also presented that this method opens the possibility of calculating z and x0 separately. Our results show good agreement with the literature values. Measurements done on lattices with different sizes seem to give very good scaling.

Back calculation of parent austenite orientation using a clustering approach

2013 ◽  
Vol 46 (1) ◽  
pp. 210-215 ◽  
Author(s):  
V. Tari ◽  
A. D. Rollett ◽  
H. Beladi
Keyword(s):  
Face Centered Cubic ◽  
Orientation Relationships ◽  
New Approach ◽  
Austenite Grain ◽  
Parent Orientation ◽  
Back Calculation ◽  
Clustering Approach ◽  
Face Centered ◽  
Parent Austenite ◽  
Good Agreement

A new approach is presented for calculating the parent orientation from sets of variants of orientations produced by phase transformation. The parent austenite orientation is determined using the orientations of bainite variants that transformed from a single parent austenite grain. In this approach, the five known orientation relationships are used to back transform each observed bainite variant to all their potential face-centered-cubic (f.c.c.) parent orientations. A set of potential f.c.c. orientations has one representative from each bainite variant, and each set is assembled on the basis of minimum mutual misorientation. The set of back-transformed orientations with the minimum summation of mutual misorientation angle (SMMA) is selected as the most probable parent (austenite) orientation. The availability of multiple sets permits a confidence index to be calculated from the best and next best fits to a parent orientation. The results show good agreement between the measured parent austenite orientation and the calculated parent orientation having minimum SMMA.

On the Influence of a Heat Treat for an Aluminizing Progress Based on Al Microparticles Slurry for Model Ni and Ni20Cr. Experimental and Theoretical Approaches.

2012 ◽  
Vol 323-325 ◽  
pp. 373-379 ◽  
Author(s):  
B. Rannou ◽  
M. Mollard ◽  
B. Bouchaud ◽  
J. Balmain ◽  
G. Bonnet ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Substrate Surface ◽  
Single Step ◽  
Alloying Element ◽  
Aluminum Particles ◽  
New Approach ◽  
Theoretical Approaches ◽  
Barrier Coating ◽  
Coating Characteristics ◽  
Good Agreement

The use of thermal barrier coating systems allows superalloys to withstand higher operating temperatures in aeroengine turbines. Aiming at providing oxidation protection to such substrates, an aluminum-rich layer is deposited to form the α-Al2O3scale over which a ceramic layer (i.e. YSZ layer) is applied to provide thermal insulation. A new approach is now being investigated within the FP7 European project « PARTICOAT », in which a single step process is employed by applying micro-sized aluminum particles. The particles are mixed in a binder and deposited by brushing or spraying on the substrate surface. During a heat treatment, the particles sinter and oxidize to form a top coat composed of hollow con-joint alumina spheres and simultaneously, an Al-rich diffusion zone is formed in the substrate. For a better understanding of the diffusion / growth processes, preliminary tests were carried out on pure nickel and Ni20Cr model alloys prior to further application on commercial superalloys. The effect of the heat treatment on the coating characteristics (number of layers, thickness, composition, homogeneity, etc.) was particularly investigated to emphasize the mechanisms of diffusion governing the growth of the coatings. The establishment of the diffused layers occurred very readily even at intermediate temperatures (650 and 700°C). However, the layers formed did not match perfectly with the thermodynamic modeling because of the quick incorporation of Ni into molten Al at intermediate temperatures (650°C). In contrast, at higher temperatures (700 and 1100°C) the phases predicted by Thermocalc are in good agreement with the observed thickness of the diffused layers. The incorporation of Cr as an alloying element restrained Al ingress by segregation of Cr even at very low temperatures aluminizing temperatures (625°C).

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