scholarly journals A Review on Process and Practices in Operation and Design Modification of Ejectors

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 409
Author(s):  
Ravi Koirala ◽  
Quoc Linh Ve ◽  
Baoshan Zhu ◽  
Kiao Inthavong ◽  
Abhijit Date
Keyword(s):  
Influencing Factor ◽  
Internal Flow ◽  
Water Desalination ◽  
Domestic Water ◽  
Design Modification ◽  
Mixing Chamber ◽  
Primary Water ◽  
Design Selection ◽  
Vacuum Generation ◽  
The One

This work reviews the current operational condition and activities on design modification for different applications of ejectors. Ejectors being a simple mechanical system capable of performing multiple fluid related functions (vacuum generation, pumping, mixing, condensing and heat exchanging), have been an essential part of several industrial processes. Two areas have been emphasized; internal flow and application-based modifications in components of ejectors. The geometry and inlet flow conditions were found to be the prime influencing factor of its performance. The objective and application-based modifications were performed on the primary nozzle, secondary nozzle, mixing chamber, throat and diffuser. The resultant performance was found to be dependent on operational condition and fluid type. This emphasizes the requirement of application-based design selection of the technology. In addition, the flow dynamics of condensing, non-condensing, particle and slurry flow has been studied based on available literatures. The one-point final objective is to identify the usability of primary water jet ejectors for active vapor transport and condensation, to replace vacuum pump and condenser in compact domestic water desalination system.

Investigation of the natural ventilation of wind catchers with different geometries in arid region houses

2020 ◽  
Vol 14 (3) ◽  
pp. 7109-7124
Author(s):  
Nasreddine Sakhri ◽  
Younes Menni ◽  
Houari Ameur ◽  
Ali J. Chamkha ◽  
Noureddine Kaid ◽  
...  
Keyword(s):  
Arid Region ◽  
Natural Ventilation ◽  
Reduction Rate ◽  
Internal Flow ◽  
Climatic Conditions ◽  
Maximum Pressure ◽  
Ventilation Technique ◽  
Window Position ◽  
The One ◽  
Flow Velocities

The wind catcher or wind tower is a natural ventilation technique that has been employed in the Middle East region and still until nowadays. The present paper aims to study the effect of the one-sided position of a wind catcher device against the ventilated space or building geometry and its natural ventilation performance. Four models based on the traditional design of a one-sided wind catcher are studied and compared. The study is achieved under the climatic conditions of the South-west of Algeria (arid region). The obtained results showed that the front and Takhtabush’s models were able to create the maximum pressure difference (ΔP) between the windward and leeward of the tower-house system. Internal airflow velocities increased with the increase of wind speed in all studied models. For example, at Vwind = 2 m/s, the internal flow velocities were 1.7, 1.8, 1.3, and 2.5 m/s for model 1, 2, 3, and 4, respectively. However, at Vwind = 6 m/s, the internal flow velocities were 5.6, 5.5, 2.5, and 7 m/s for model 1, 2, 3, and 4, respectively. The higher internal airflow velocities are given by Takhtabush, traditional, front and middle tower models, respectively, with a reduction rate between the tower outlet and occupied space by 72, 42, 36, and 33% for the middle tower, Takhtabush, traditional tower, and the front model tower, respectively. This reduction is due to the due to internal flow resistance. The third part of the study investigates the effect of window (exist opening) position on the opposite wall. The upper, middle and lower window positions are studied and compared. The air stagnation or recirculation zone inside the ventilated space reduced from 55% with the lower window to 46% for the middle window and reached 35% for the upper window position. The Front and Takhtabush models for the one-sided wind catcher with an upper window position are highly recommended for the wind-driven natural ventilation in residential houses that are located in arid regions.

scholarly journals Outdoor Physical Activity During the First Wave of the COVID-19 Pandemic. A Comparative Analysis of Government Restrictions in Italy, France, and Germany

2021 ◽  
Vol 9 ◽  
Author(s):  
Enrico Michelini ◽  
Nico Bortoletto ◽  
Alessandro Porrovecchio
Keyword(s):  
Physical Activity ◽  
Health Systems ◽  
Qualitative Content Analysis ◽  
Influencing Factor ◽  
National Level ◽  
Scientific Discourse ◽  
The Other ◽  
Risky Behaviour ◽  
Health Politics ◽  
The One

Introduction: Mandated restrictions on outdoor physical activity (PA) during the coronavirus pandemic disrupted the lifeworld of millions of people and led to a contradictory situation. On the one hand, PA was perceived as risky behaviour, as it might facilitate transmission of the virus. On the other hand, while taking precautions, regular PA was an important tool to promote the population's health during the lockdown.Methods: This paper examines the differences in government restrictions on PA in France, Germany, and Italy during the first wave of the COVID-19 pandemic. We draw on techniques of qualitative content analysis and apply a critical theoretical framework to assess the countries' restrictions on PA.Results: Our analysis shows that the restrictions on PA varied in the three countries, in all three countries. This variance is attributed both to differences in the timing and severity of the pandemic in the countries analysed, as well as to the divergence in the relationships between the countries' sport and health systems.Conclusion: At the national level, the variance in restrictions on PA reflect the differences in the spread of the coronavirus and in the health systems' understanding of and approach to PA. The global scientific discourse on the pandemic represents a further key influencing factor. The management of the coronavirus pandemic has demonstrated that the extreme complexity of societies in terms of public health, politics, and the economy pose challenges and unsolvable contradictions.

scholarly journals Long-term Results for the BacJac Interspinous Device in Lumbar Spine Degenerative Disease

2018 ◽  
Vol 80 (01) ◽  
pp. 003-007 ◽  
Author(s):  
Aldo Spallone ◽  
Luigi Lavorato ◽  
Daniele Belvisi
Keyword(s):  
Lumbar Spine ◽  
Influencing Factor ◽  
Relevant Literature ◽  
Long Term Results ◽  
Surgical Technology ◽  
Disability Scale ◽  
Interspinous Device ◽  
Satisfactory Outcome ◽  
The One

Objective To evaluate the long-term results of using the BacJac interspinous device (Pioneer Surgical Technology Inc.) in a series of patients with degenerative lumbar spine disease. Methods Forty-one patients undergoing lumbar surgery with implantation of a BacJac device from 2009 to 2012 were enrolled in the present study. Patients were evaluated using the Oswestry Disability Scale (ODI). Results Although all patients showed a significant improvement of the ODI score immediately after surgery, only 41% of patients showed a satisfactory outcome. We observed worse results in the patients operated on at the L3–L4 level and in whom the device was implanted in a segment different from the one where surgical decompression had been performed. Weight gain in the months after surgery was also a poor outcome-influencing factor. Conclusions This study confirms what is already suggested in the relevant literature regarding the long-term inefficacy of the so-called dynamic stabilization devices.

scholarly journals Numerical and Experimental Study on the Internal Flow of the Venturi Injector

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 64 ◽  
Author(s):  
Hao Li ◽  
Hong Li ◽  
Xiuqiao Huang ◽  
Qibiao Han ◽  
Ye Yuan ◽  
...  
Keyword(s):  
Energy Loss ◽  
Internal Flow ◽  
Hydraulic Performance ◽  
Mixing Process ◽  
Cavitation Model ◽  
Precise Control ◽  
Mixing Chamber ◽  
Numerical Simulation Methods ◽  
The Stability ◽  
Good Agreement

To study the appropriate numerical simulation methods for venturi injectors, including the investigation of the hydraulic performance, mixing process, and the flowing law of the two internal fluids, simulations and experiments were conducted in this study. In the simulations part, the cavitation model based on the standard k–ε turbulence and mixture models was added, after convergence of the calculations. The results revealed that the cavitation model has good agreement with the experiment. However, huge deviations occurred between the experimental results and the ones from the calculation when not considering the cavitation model after cavitation. Thus, it is inferred that the cavitation model can exactly predict the hydraulic performance of a venturi injector. In addition, the cavitation is a crucial factor affecting the hydraulic performance of a venturi injector. The cavitation can ensure the stability of the fertilizer absorption of the venturi injector and can realize the precise control of fertilization by the venturi injector, although it affects the flow stability and causes energy loss. Moreover, this study found that the mixing chamber and throat are the main areas of energy loss. Furthermore, we observed that the internal flow of the venturi injector results in the majority of mixing taking place at the diffusion and outlet sections.

scholarly journals Effect of Inlet Geometry on Fan Performance and Flow Field in a Half-Ducted Propeller Fan

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Pin Liu ◽  
Norimasa Shiomi ◽  
Yoichi Kinoue ◽  
Ying-zi Jin ◽  
Toshiaki Setoguchi
Keyword(s):  
Flow Field ◽  
Flow Measurement ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Internal Flow ◽  
Fan Performance ◽  
Ducted Propeller ◽  
Inlet Geometry ◽  
Blade Tip ◽  
The One

In order to clarify the effect of rotor inlet geometry of half-ducted propeller fan on performance and velocity fields at rotor outlet, the experimental investigation was carried out using a hotwire anemometer. Three types of inlet geometry were tested. The first type is the one that the rotor blade tip is fully covered by a casing. The second is that the front one-third part of blade tip is opened and the rest is covered. The third is that the front two-thirds are opened and the rest is covered. Fan test and internal flow measurement at rotor outlet were conducted about three types of inlet geometry. At the internal flow measurement, a single slant hotwire probe was used and a periodical multisampling technique was adopted to obtain the three-dimensional velocity distributions. From the results of fan test, the pressure-rise characteristic drops at high flowrate region and the stall point shifts to high flowrate region, when the opened area of blade tip increases. From the results of velocity distributions at rotor outlet, the region with high axial velocity moves to radial inwards, the circumferential velocity near blade tip becomes high, and the flow field turns to radial outward, when the opened area increases.

Kinetic Study of the Low Temperature Internal Oxidation of Nickel Based Model Alloys Exposed to PWR Primary Water

2008 ◽  
Vol 595-598 ◽  
pp. 449-462 ◽  
Author(s):  
Benoît Ter-Ovanessian ◽  
Julien Deleume ◽  
Jean Marc Cloué ◽  
Eric Andrieu
Keyword(s):  
Ternary Alloys ◽  
Pressurized Water Reactor ◽  
Oxide Interface ◽  
Intergranular Stress Corrosion ◽  
Pressurized Water ◽  
Free Oxygen ◽  
Primary Water ◽  
Nickel Base ◽  
The One ◽  
Intergranular Stress Corrosion Cracking

Two Ni-Fe-Cr ternary alloys have been oxidized in simulated pressurized water reactor primary water at 360°C for 1000 h. The chemical composition of those alloys were chosen in order to be representative of the one of chromium depleted areas under the oxide scale of industrial alloys (e.g. alloy 600) exposed in the same conditions. The resulting oxidized structures (corrosion scale and underlying metal) were characterized using complementary analytical methods (FEG-SEM, TEM, SIMS, optical microscopy). On the one hand, the characterized external oxide layer is very close to the one observed on industrial nickel-base alloys, hence validating the use of such model alloys. On the other hand, both free oxygen and oxides have been detected at grain boundaries several micrometers under the metal/oxide interface. Implications of such a finding on the involved transport mechanisms for oxygen and the intergranular stress corrosion cracking resistance of nickel-base alloys are then discussed.

Pumping Speed Measurement of the Rotary Vane Vacuum Pump by Using Numerical and Experimental Approaches

2014 ◽  
Author(s):  
M. Nadeem Azam ◽  
M. Umar ◽  
M. Maqsood ◽  
Imran Akhtar ◽  
Imran Aziz
Keyword(s):  
Internal Flow ◽  
Vacuum Pump ◽  
Assessment System ◽  
Navier Stokes ◽  
Vane Pump ◽  
Navier Stokes Equation ◽  
Time Shape ◽  
Experimental Approaches ◽  
Computational Fluid Dynamics Cfd ◽  
The One

Pumping speed is the main performance parameter of a vacuum pump. In the present work, pumping speed for a three-vane rotary vacuum pump is quantified using both experimental and numerical approaches. The numerical methodology assumes continuum flow (Knudsen number < 0.1), thus allowing the use of Navier Stokes equation. Commercial computational fluid dynamics (CFD) solver i.e. Fluent, is used to discretize the governing equations. Moving / dynamic mesh technique is used for the internal flow volumes of the pump to reproduce the change-in-time shape. Complete process starting from the CAD modeling to CFD simulations is discussed in detail. The adopted approaches are generic and can be used to find the pumping speed of any other rotary vane vacuum pump. The vane pump is also tested using an assessment system, which is constructed according to DIN28432 standard. Results of experimentally measured pumping speed are in good agreement with the one computed numerically.

scholarly journals Introductory Fluid Mechanics taught using a carburetor

2017 ◽  
Author(s):  
Andrew Trivett ◽  
Andrew Milne ◽  
Cecile Devaud ◽  
Tyler Gallant
Keyword(s):  
Fluid Mechanics ◽  
Mechanical Engineering ◽  
Engineering Students ◽  
Gasoline Engine ◽  
Internal Flow ◽  
Momentum Conservation ◽  
Design Modification ◽  
Conservation Of Energy ◽  
Basic Fluid ◽  
Control Volumes

The typical fluid mechanics introduction in mechanical engineering covers basic fluid statics, forces on submerged bodies, control volumes, continuity, conservation of momentum, conservation of energy, Reynolds' transport theorem, internal and external flows. Students often struggle with the basic concepts and how they might apply to a real system.In the winter of 2015, a new set of open-ended labs were created for  mechanical engineering students. Teams of 3 or 4 students in a third-year class of 110 were each given a small engine, and removed the carburetors. The series of labs had them discover some of the principles within the  small carburetor from a single-cylinder 4-stroke gasoline engine. Students were asked to explore and explain how the carburetor worked, and then progressed through a set of hands-on labs culminating with a design modification and performance measurement of a real carburetor. At each stage, the students applied principles of fluid statics, control volumes,  internal flow losses, and external flow drag to the physical device.The paper will describe the specific activities, and track the evolution of refinements to the experience through three implementations of the same course by three different instructors. Student feedback and measured evidence of learning will be reported to help justify the evolution of the  activity. The scalability of the activity will be discussed.

Internal Flow in Vacuum Ejector Using Water Table

2007 ◽  
Author(s):  
Naoya Kurahashi ◽  
Masaki Endo ◽  
Junjiro Iwamoto
Keyword(s):  
Flow Field ◽  
Water Table ◽  
Internal Flow ◽  
Vacuum Pressure ◽  
Maximum Performance ◽  
Optimum Performance ◽  
Mixing Chamber ◽  
Hydraulic Analogy

The purpose of this study elucidates a structure of internal flow in vacuum ejector. The vacuum ejector is used as a part of automatic conveyance systems, in which precision parts or foods are handled utilizing vacuum pressure from the ejector. So far, the vacuum ejector has been designed mostly by experience and the internal flow in vacuum ejector is not well analyzed. The flow field of ejector is so small that conventional measurements can not be employed and it is difficult to obtain the detailed information. Thus, the flow in the ejector is simulated on water table using hydraulic analogy. In this paper, to obtain optimum performance of the ejector, we examined the different ejector models with parameters, such as the nozzle width and the distance between nozzle and inlet of mixing chamber. As a result, it is shown that maximum performance is obtained for the ejector model with the nozzle width of 40mm, the mixing chamber width of 100mm and the port size of 40mm.

A Detailed Loss Analysis Methodology for Centrifugal Compressors

2021 ◽  
Author(s):  
Luying Zhang ◽  
Loukia Kritioti ◽  
Peng Wang ◽  
Jiangnan Zhang ◽  
Mehrdad Zangeneh
Keyword(s):  
Flow Field ◽  
Evaluation Method ◽  
Deep Understanding ◽  
Internal Flow ◽  
Tip Clearance ◽  
Optimized Design ◽  
Centrifugal Compressors ◽  
Design Modification ◽  
Operational Conditions ◽  
The Impact

Abstract A deep understanding of loss mechanisms inside a turbomachine is crucial for the design and analysis work. By quantifying the various losses generated from different flow mechanisms, a targeted optimization can be carried out on the blading design. In this paper an evaluation method for computational fluid dynamics simulations has been developed to quantify the loss generation based on entropy production in the flow field. A breakdown of losses caused by different mechanisms (such as skin friction, secondary flow, tip clearance vortex and shock waves) is achieved by separating the flow field into different zones. Each zone is defined by the flow physics rather than by geometrical locations or empirical correlations, which makes the method a more general approach and applicable to different machine types. The method has been applied to both subsonic and transonic centrifugal compressors, where internal flow is complex due to the Coriolis acceleration and the curvature effect. An evaluation of loss decomposition is obtained at various operational conditions. The impact of design modification is also assessed by applying the same analysis to an optimized design.

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