Hydrodynamics behaviour of a fluid flow in micro-venturi

2012 ◽  
Vol 90 (1) ◽  
pp. 83-89 ◽  
Author(s):  
A.M. Maqableh ◽  
S.A. Ammourah ◽  
A.F. Khadrawi ◽  
M.A. Al-Nimr ◽  
A.C. Benim
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Axial Velocity ◽  
Pressure Loss ◽  
Discharge Coefficient ◽  
Diameter Ratio ◽  
The Other ◽  
Hydrodynamic Behaviour ◽  
Velocity Jump ◽  
Net Pressure

Hydrodynamic behaviour of a fluid flow in micro-venturi is investigated numerically taking into account the effect of the Knudsen number (Kn), diameter ratio (β), and Reynolds number (Re). It is found that the velocity jump in the throat of the venturi increases with increasing Re. The axial velocity takes its maximum values at the narrowest section, and these values increase with decreasing Kn. Also, it is found that the dimensionless pressure distribution and the net pressure loss increase as Kn decreases while pressure attains its maximum values at the entrance section. On the other hand, it is observed that increasing Kn and decreasing β cause the discharge coefficient to decrease.

INVESTIGATION ON HEAT TRANSFER ENHANCEMENT IN A CORRUGATED FIN-AND-TUBE COMPACT HEAT EXCHANGER

2016 ◽  
Vol 78 (10-2) ◽  
Author(s):  
Ahmadali Gholami ◽  
Mazlan A. Wahid ◽  
Hussein A. Mohammed ◽  
A. Saat ◽  
M. Y. M. Fairus ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Loss ◽  
Boundary Layer Separation ◽  
Performance Criteria ◽  
Recirculation Region ◽  
Moderate Pressure ◽  
Compact Heat Exchangers ◽  
Heat Transfer Augmentation

Heat transfer augmentation and pressure loss penalty in the fin-and-tube compact heat exchangers (FTCHEs) with the corrugated shape as a special form of the fin are numerically investigated to improve heat transfer performance criteria in low Reynolds numbers. The corrugated fin as the newly design of fin pattern is presented in this study. The influence of applying corrugated design adjustments on the thermal and hydraulic characteristics of air flow are analyzed on the in-line tube arrangements. The performance of air-side heat transfer and fluid flow is investigated by numerical simulation for Reynolds number ranging from Re = 400 to 800 based on the tube collar diameter, with the corresponding frontal air velocity ranging from 0.35 to 0.72 m/s. The outcomes of simulation revealed that the corrugated fin could significantly improve the heat transfer augmentation of the FTCHEs with a moderate pressure loss penalty. The computational results indicated that some eddies were developed behind the fluted domain of corrugated finwhich produce some disruptions to fluid flow and enhance heat transfer compared with plain fin. The corrugated form of fins could enhance the thermal mixing of the fluid, delay the boundary layer separation, and reduce the size of the wake and the recirculation region behind tubes compared with the conventional form of the fin at the range of Reynolds number used in this study. In addition, the results showed that the average Nusselt number for the FTCHE with corrugated fin increased by 7.05–10.0% over the baseline case and the corresponding pressure loss decreased by 5.0–6.2%.

Pressure Drop, Air Entrainment and Moments of the Axial Velocity in the Laminar-Turbulent Transition Jet Flow in Domestic Gas Injectors

2021 ◽  
Author(s):  
William Alexander Carrillo Ibañez ◽  
Márcio Demétrio ◽  
Amir Oliveira ◽  
Fernando Pereira
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Axial Velocity ◽  
Energy Flow ◽  
Discharge Coefficient ◽  
Mixing Layer ◽  
Air Entrainment ◽  
Flow Rates ◽  
Free Jet ◽  
Internal Mixing

Abstract This works aims at characterizing the flow in the outlet of three gas injectors used in atmospheric burners and developing correlations for the discharge coefficient, air entrainment, momentum and energy flow rates. These devices have millimeter sized orifices, a cup-like region at the injector outlet and the flow occurs in the transition from the laminar to the fully turbulent regimes. The pressure drop was measured and correlated as a function of the orifice Reynolds number for the three injectors. The correlations are able to predict the discharge coefficient within ± 5% deviation from the measurements in the range 90 < Re < 4400. The axial velocity and turbulent intensity were measured at the outlet of the injectors using a hot-wire anemometer at the orifice Reynolds number of 3060, which is typical of the applications. The measurements were compared to CFD solutions using the gamma - Re-theta RANS transition model in the STAR-CCM+ commercial package. The results indicate the strong influence of the shape of the outlet cup-like region of the injectors in the development of an internal mixing layer and the external mixing layer in the free jet. The momentum and energy flow rates for the injector model with the largest cup are reduced to 50% and 21%, respectively, of the simplest gas injector. However, the gas jet in this injector carries 28% of the stoichiometric air before leaving the cup. These aspects must be taken into account in the preliminary design of atmospheric burners.

scholarly journals Flow "reflexion" and " refraction" on perforated wall

2019 ◽  
Vol 213 ◽  
pp. 02085
Author(s):  
Vaclav Tesař
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Cross Section ◽  
Oblique Impact ◽  
The Other ◽  
Perforated Wall ◽  
Spatially Periodic ◽  
Oval Cross Section ◽  
The Impact

This article presents some results accumulated by author during investigation of an oblique impact of fluid flow on a wall consisting of a spatially periodic rods of very simple oval cross section. The flowfield in the vicinity of the impact is quite complex and strongly Reynolds -number dependent. A part of the jet downstream from the impact is “reflected” from the wall — while the rest, which passes through the empty spaces between the cascade members, leaves the other wall side in what appears to be “refraction” direction.

Analysis of Transitional Flow in Tube Based on PIV

2014 ◽  
Vol 574 ◽  
pp. 485-488
Author(s):  
Jun Wang ◽  
Guang Sheng Du ◽  
Yong Hui Liu
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Flow Field ◽  
Velocity Distribution ◽  
Axial Velocity ◽  
Transitional Flow ◽  
Experimental Result ◽  
Fluid Field ◽  
Normal Speed

In order to get the situation of transitional flow in tube, we tested the fluid field by PIV experiment and acquired the velocity distribution of the flow field at different Reynolds number (Re=2400 and Re=3000). At the same time the structure and characteristics of the flow field were obtained. The experimental result shows that the change of axial velocity in boundary layer is not obvious at low Reynolds number, the fluctuation of axial velocity appears and normal speed changes a little in mainstream area. With the increase of Reynolds number the axial velocity both in boundary layer and mainstream area change obviously, pulsation of the normal speed increases, the state of fluid flow gradually evolves from laminar to transitional flow.

Length Efficiency of the Etoile Flow Straightener: Numerical Experimentation

2011 ◽  
Author(s):  
Boualem Laribi ◽  
Abdelkader Youcefi ◽  
Elhacene Matene
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Velocity Profile ◽  
Cross Section ◽  
Circular Cross Section ◽  
The Other ◽  
Flow Parameters ◽  
Numerical Experimentation ◽  
Valve Position ◽  
Turbulence Intensity Profile

This article presents a numerical investigation of the development and the establishment of the flow in the presence of the Etoile flow straightener recommended in ISO 5167 (ISO 5167. Measurement of fluid flow by means of orifice plates, nozzles and venture plates inserted in circular cross-section conduits running full, 2003). The objective of this study is to examine the effectiveness length of the Etoile flow straightener, recommended by ISO 5167 with length of two pipe diameters, on the development and the establishment of the flow. The flow is produced by air in a 100mm pipe diameter and 40D of length with a Reynolds number of 2.5×105. The disturbance is a valve maintained at 100% and 50% open. The flow parameters examined are velocity profile, turbulence intensity profile, and the gyration of the fluid. Several measuring stations upstream and downstream of the unit are done. The code CFD Fluent is used for this simulation. The results obtained are compared according to directives of the standard ISO 5167. However, they show that for position valve 100% open the various lengths of the Etoile flow straightener do not present differences for the three flow parameters. On the other hand, for the valve position 50% open, the Etoile flow straightener with 2D length which presents the best performances according the standard.

Numerical Study of Inlet and Geometry Effects on Discharge Coefficients for Liquid Jet Emanating From a Plain-Orifice Atomizer

2002 ◽  
Vol 18 (3) ◽  
pp. 153-161 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Discharge Coefficient ◽  
Numerical Study ◽  
Surface Force ◽  
Diameter Ratio ◽  
The Body ◽  
Liquid Jet ◽  
Discharge Coefficients ◽  
Geometry Effects

AbstractA computational model for flow in a plain-orifice atomizer is established to examine the inlet and geometry effects on discharge coefficients. The volume of fluid (VOF) method with finite volume formulation was employed to capture the liquid/gas interface. A continuum Surface Force (CSF) model was adopted to model the surface tension. The body-fitted coordinate system was used to facilitate the configuration of the atomizer. The influences of the inlet chamfer angle, the orifice length/diameter ratio, the Reynolds number, and the inlet turbulence intensity are analyzed. It is found that the optimum discharge coefficient occurs at a chamfer angle of about 50°. The discharge coefficient at first increases with the increase in the orifice length/diameter ratio and then it decreases. The discharge coefficient increases with the increase in the Reynolds number up to Re = 40000, after which it remains sensibly constant. The influence of the inlet turbulence intensity on discharge coefficient is not significant, especially for a longer orifice.

Fluid Flow in Perforated Pipes

1975 ◽  
Vol 17 (6) ◽  
pp. 338-347 ◽  
Author(s):  
B. J. Bailey
Keyword(s):  
Fluid Flow ◽  
Discharge Coefficient ◽  
Static Pressure ◽  
Pipe Wall ◽  
Air Flow ◽  
Diameter Ratio ◽  
Friction Loss ◽  
Flow Through ◽  
Good Agreement ◽  
Air Discharge

Values of the discharge coefficient for air flow through single holes in a pipe wall, and for the angle of efflux are reported. The variation of static pressure along tubular polyethylene air ducts with a maximum length-to-diameter ratio of 250 containing pairs of diametrically opposed holes has been measured. This information was used with data on friction loss to determine values for the coefficient of static pressure regain. It was possible to predict variations in static pressure and air discharge along uniformly perforated ducts which were in good agreement with those observed experimentally.

The Quadrant Edge Orifice—A Fluid Meter for Low Reynolds Numbers

1960 ◽  
Vol 82 (3) ◽  
pp. 729-733 ◽  
Author(s):  
M. Bogema ◽  
P. L. Monkmeyer
Keyword(s):  
Reynolds Number ◽  
Discharge Coefficient ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Roughness Effects ◽  
Low Reynolds Numbers ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Number Flow ◽  
Low Reynolds

Tests have been conducted to determine the usefulness of the quadrant edge orifice as a fluid-metering device for low Reynolds number flow. As a result of numerous laboratory tests to determine the behavior of the discharge coefficient with changing Reynolds number, the following are discussed: The range of constant discharge coefficient, reproducibility of orifice plates, diameter ratio effects, upstream roughness effects, reinstallation effects, and effects of pressure tap location.

scholarly journals A review of single-phase pressure drop characteristics microchannels with bends

2021 ◽  
Vol 12 (1) ◽  
pp. 38-44
Author(s):  
Endro Junianto ◽  
Jooned Hendrarsakti
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Single Phase ◽  
Flow Characteristics ◽  
Fluid Flows ◽  
The Other ◽  
Fluid Flow Characteristics ◽  
Phase Pressure ◽  
Comprehensive Study

Microfluidic use in various innovative research, many fields aimed at developing an application device related to handling fluid flows in miniature scale systems. On the other hand, on the use of micro-devices for fluid flow the existence of bends cannot be avoided. This research aims to make a comprehensive study of fluid flow characteristics through a microchannel with several possible bends. This study was conducted by comparing Reynolds number versus pressure drop in a serpentine microchannel to gain bends loss coefficient. The result showed that the fluid flow with Re 100 did not affect the pressure drop, but on the Reynolds number above that, the pressure drop was increased along with the appears of vortices in the outer and inner walls around the channel bends which causes an increase in an additional pressure drop. The other finding shows that the reduction in diameter bend tube can increase the pressure drop.

Friction factor calculation for turbulent flow in annulus with temperature effects

2019 ◽  
Vol 30 (7) ◽  
pp. 3755-3763
Author(s):  
Mehmet Sorgun ◽  
Erman Ulker
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Pressure Loss ◽  
Diameter Ratio ◽  
Pipe Diameter ◽  
Fluid Temperature ◽  
Flow Loop ◽  
Content Type ◽  
Pipe Rotation ◽  
Factor Equation

Purpose The purpose of this paper is to present a new friction factor equation for practical use, including fluid temperature, pipe diameter ratio and inner pipe rotation effects. Design/methodology/approach A friction factor relationship is developed by applying Buckingham’s Theorem of dimensional analysis. Then, the formula is calibrated using experimental data conducted at Izmir Katip Celebi University flow loop. Moreover, the effects of fluid temperature, inner pipe rotation and pipe diameter ratio on friction factor are investigated experimentally. Findings Satisfactory agreements are obtained between proposed formula and experiments. The experimental results indicate that major variable parameters affecting friction factor is Reynolds number. Pipe rotation has negligible effect on friction factor at high Reynolds number. Prandtl number is one of the important parameters affecting the friction factor. Moreover, as the pipe diameter ratio is decreased, friction factor increases. Originality/value Determining fluid behavior of fluids under high temperature is especially important for deep wells during drilling. Temperature drastically changes fluid properties and flow characteristics in wells. These changes have a remarkable effect on pressure losses. However, since the temperature is considered constant in the calculation of the pressure loss, problems can be encountered in most systems. Friction factor is one of the important parameters for determining pressure loss in closed conduits. The originality of this work is to propose a new friction factor equation for practical use, including fluid temperature, pipe diameter ratio and inner pipe rotation effects.

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