Experimental and Analytical Study of the Pressure Drop Across a Double-Outlet Vortex Chamber

2006 ◽  
Vol 129 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Ali M. Jawarneh ◽  
P. Sakaris ◽  
Georgios H. Vatistas
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Analytical Study ◽  
Pressure Coefficient ◽  
Vortex Chamber ◽  
Core Size ◽  
Chamber Length ◽  
The Core ◽  
Swirl Velocity ◽  
New Formulation

This paper presents experimental and analytical results concerning the pressure drop and the core size in vortex chambers. The new formulation is based on the conservation of mass and energy integral equations and takes into account the presence of two outlet ports. The diminishing vortex strength is introduced through the vortex decay factor. The influence of vortex chamber geometry, such as diameter ratio, aspect ratio, and Reynolds number, on the flow field have been examined and compared with the present experimental data. It is shown that the presence of the swirl velocity component makes the pressure drop across a vortex chamber significantly different than the familiar unidirectional pipe flow. When the chamber length is increased, the vortex diminishes under the action of friction, producing a weaker centrifugal force which leads to a further pressure drop. It is revealed that by increasing the Reynolds number, the cores expand resulting into a larger pressure coefficient. For a double-outlet chamber where the flow is divided into two streams, the last parameter is found to be less than that of a single-outlet.

Experimental Study: Effects of the Annulus’ Center Body End Shape on the Performance of Low Mach Number Air-Air Ejector With Entraining Diffuser

2013 ◽  
Author(s):  
A. Namet-Allah ◽  
A. M. Birk
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Nozzle Exit ◽  
Pressure Coefficient ◽  
Back Pressure ◽  
Low Mach Number ◽  
The Core ◽  
Swirl Angle ◽  
Air Ejector ◽  
Center Body

In the present paper, an experimental investigation of the performance of a low mach number round straight air-air ejector with a 4-ring entraining diffuser is reported. The ejector system was mounted on an annular flow wind tunnel. Based on the hydraulic diameter and average velocity and temperature at the nozzle exit, the tunnel provides cold flow at Mach 0.2 with a Reynolds number of 5.2×105 and hot flow at Mach 0.27 with a Reynolds number of 2.6×105. The end shape of the annulus’ center body has major effects on the core separation size and shape that strongly affects the ejector performance. The effects of the annulus’ center body with elliptical and square ends on the ejector pumping, wall static pressure distribution and back pressure were investigated under different flow temperatures and swirl angles: 0°, 10°, 20°, and 30°. These measurements were conducted at 129 mm standoff distance using two different nozzle exit diameters. It was found that for both nozzle exit diameters, using the annulus’ center body with a square end improved the total pumping ratio over its ratio with an elliptical end due to the flatness of the core separation at the nozzle exits. For all configurations tested, the maximum entrainment ratio was observed with 20° swirl angle and the back pressure coefficient decreased as swirl angle increased. Removing the elliptical end, creating the square shape, the flow has more space to spread after the annulus’ center body to give the higher centerline velocity which enhances the flow uniformity at the nozzle and diffuser exits.

The Application of the Integral Momentum Balance on the Pressure Drop of a Sudden Contraction

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Andreas Malcherek ◽  
Sebastian Müller
Keyword(s):  
Pressure Drop ◽  
Control Volume ◽  
Pressure Coefficient ◽  
Momentum Balance ◽  
Simple Analytical Expression ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Contraction Ratio ◽  
Sudden Contraction ◽  
New Formulation

Abstract A new approach based on the momentum balance to calculate the pressure drop in turbulent flow through sharp-edged axisymmetric sudden contractions is presented. The momentum balance needs the velocity as well as the pressure distributions on the boundaries of the control volume. These distributions are obtained by a series of numerical simulations with different settings for the discharge, as well as the contraction ratio. The numerical model itself is validated by the comparison of the simulated and measured pressure drops in a laboratory experiment at different positions. To get easily applicable hydraulic formulations for the pressure drop depending on the discharge and the contraction ratio, the missing momentum and pressure coefficients are determined from the simulated velocity and pressure distributions. Only the pressure coefficient shows a dependency on the contraction ratio. After fitting the dependency by a simple analytical expression, a new formulation for the hydraulics of a sharp-edged sudden contraction based solely on momentum balance was obtained. The comparison with own experimental results as well as the classical parameterization of Idelchik show in both cases very good agreement.

The evolution of an elliptic vortex ring

1981 ◽  
Vol 109 ◽  
pp. 189-216 ◽  
Author(s):  
M. R. Dhanak ◽  
B. DE Bernardinis
Keyword(s):  
Reynolds Number ◽  
Vortex Ring ◽  
Ideal Fluid ◽  
Vortex Rings ◽  
Core Size ◽  
Vorticity Distribution ◽  
The Core ◽  
Moderate Reynolds Number ◽  
Break Up

The evolution of a vortex ring in an ideal fluid under self-induction from a flat and elliptic configuration is followed numerically using the cut-off approximation (Crow 1970) for the velocity at the vortex. Calculations are presented for four different axes ratios of the initial ellipse. A particular choice is made for the core size and vorticity distribution in the core of the vortex ring. When the initial axes ratio is close to 1, the vortex ring oscillates periodically. The periodicity is lost as more eccentric cases are considered. For initial axes ratio 0·2, the calculations suggest a break-up of the ring through the core at one portion of the ring touching that at another, initially distant, portion of the ring.Results from quantitative experiments, conducted at moderate Reynolds number with the vortex rings produced by puffing air through elliptic orifices, are compared with the calculations. The agreement is fairly good and it is found that a vortex ring produced from an orifice of axes ratio 0·2 breaks up into two smaller rings. The relevance of the results to the vortex trail of an aircraft is discussed.

Eulerian Transformation of Vortex Amplifier Static Characteristics

1984 ◽  
Vol 106 (3) ◽  
pp. 236-239
Author(s):  
R. F. Boucher ◽  
E. E. Kitsios
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Ambient Air ◽  
Vortex Chamber ◽  
Data Transformations ◽  
Test Range ◽  
Pressure Losses ◽  
Outlet Pressure ◽  
Flow Through ◽  
Point Data

Tests with ambient air flow through a nominal 300 mm chamber diameter vortex amplifier demonstrate independence of Reynolds number over the test range. This permits data transformations based on constancy of Euler number at any working point. Data taken with constant control-to-outlet pressure drop are shown to produce characteristics for constant supply-to-outlet pressure drop which would be experimentally discontinuous. The independence of Reynolds number also suggests that pressure losses within the vortex chamber are relatively minor.

scholarly journals Geometrical Scaling of Antiresonant Hollow-Core Fibers for Mid-Infrared Beam Delivery

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 420
Author(s):  
Ang Deng ◽  
Wonkeun Chang
Keyword(s):  
Structural Parameters ◽  
Transmission Band ◽  
Confinement Loss ◽  
Hollow Core ◽  
Core Size ◽  
Core Diameter ◽  
Mid Infrared ◽  
The Core ◽  
Tubular Type ◽  
Beam Delivery

We numerically investigate the effect of scaling two key structural parameters in antiresonant hollow-core fibers—dielectric wall thickness of the cladding elements and core size—in view of low-loss mid-infrared beam delivery. We demonstrate that there exists an additional resonance-like loss peak in the long-wavelength limit of the first transmission band in antiresonant hollow-core fibers. We also find that the confinement loss in tubular-type hollow-core fibers depends strongly on the core size, where the degree of the dependence varies with the cladding tube size. The loss scales with the core diameter to the power of approximately −5.4 for commonly used tubular-type hollow-core fiber designs.

scholarly journals Parametric optimization of a stamped longitudinal vortex generator inside a circular tube of a solar water heater at low Reynolds numbers

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Felipe A. S. Silva ◽  
Luis Júnior ◽  
José Silva ◽  
Sandilya Kambampati ◽  
Leandro Salviano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Geometric Parameters ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Water

AbstractSolar Water Heater (SWH) has low efficiency and the performance of this type of device needs to be improved to provide useful and ecological sources of energy. The passive techniques of augmentation heat transfer are an effective strategy to increase the convective heat transfer coefficient without external equipment. In this way, recent investigations have been done to study the potential applications of different inserts including wire coils, vortex generators, and twisted tapes for several solar thermal applications. However, few researchers have investigated inserts in SWH which is useful in many sectors where the working fluid operates at moderate temperatures. The longitudinal vortex generators (LVG) have been applied to promote heat transfer enhancement with a low/moderate pressure drop penalty. Therefore, the present work investigated optimal geometric parameters of LVG to enhance the heat transfer for a SWH at low Reynolds number and laminar flow, using a 3D periodical numerical simulation based on the Finite Volume Method coupled to the Genetic Algorithm optimization method (NSGA-II). The LVG was stamped over a flat plate inserted inside a smooth tube operating under a typical residential application corresponding to Reynolds numbers of 300, 600, and 900. The geometric parameters of LGV were submitted to the optimization procedure which can find traditional LVG such as rectangular-winglet and delta-winglet or a mix of them. The results showed that the application of LGVs to enhance heat transfer is an effective passive technique. The different optimal shapes of the LVG for all Reynolds numbers evaluated improved more than 50% of heat transfer. The highest augmentation heat transfer of 62% is found for the Reynolds number 900. However, the best thermo-hydraulic efficiency value is found for the Reynolds number of 600 in which the heat transfer intensification represents 55% of the pressure drop penalty.

Pressure Drop Measurements for Air Flow Through Open-Cell Aluminum Foam

2004 ◽  
Author(s):  
Nihad Dukhan ◽  
Angel Alvarez
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Rate ◽  
Aluminum Foam ◽  
Flow Direction ◽  
The Other ◽  
Turbulent Regime ◽  
Thick Sample ◽  
Open Cell ◽  
Two Samples

Wind-tunnel pressure drop measurements for airflow through two samples of forty-pore-per-inch commercially available open-cell aluminum foam were undertaken. Each sample’s cross-sectional area perpendicular to the flow direction measured 10.16 cm by 24.13 cm. The thickness in the flow direction was 10.16 cm for one sample and 5.08 cm for the other. The flow rate ranged from 0.016 to 0.101 m3/s for the thick sample and from 0.025 to 0.134 m3/s for the other. The data were all in the fully turbulent regime. The pressure drop for both samples increased with increasing flow rate and followed a quadratic behavior. The permeability and the inertia coefficient showed some scatter with average values of 4.6 × 10−8 m2 and 2.9 × 10−8 m2, and 0.086 and 0.066 for the thick and the thin samples, respectively. The friction factor decayed with the Reynolds number and was weakly dependent on the Reynolds number for Reynolds number greater than 35.

scholarly journals Simulation approach on turbulent thermal performance factor of Al2O3-Cu/water hybrid nanofluid in circular and non-circular ducts

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Ing Jiat Kendrick Wong ◽  
Ngieng Tze Angnes Tiong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Hybrid Nanofluid ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
The Heat Transfer Coefficient

AbstractThis paper presents the numerical study of thermal performance factor of Al2O3-Cu/water hybrid nanofluid in circular and non-circular ducts (square and rectangular). Turbulent regime is studied with the Reynolds number ranges from 10000 to 100000. The heat transfer performance and flow behaviour of hybrid nanofluid are investigated, considering the nanofluid volume concentration between 0.1 and 2%. The thermal performance factor of hybrid nanofluid is evaluated in terms of performance evaluation criteria (PEC). This present numerical results are successfully validated with the data from the literature. The results indicate that the heat transfer coefficient and Nusselt number of Al2O3-Cu/water hybrid nanofluid are higher than those of Al2O3/water nanofluid and pure water. However, this heat transfer enhancement is achieved at the expense of an increased pressure drop. The heat transfer coefficient of 2% hybrid nanofluid is approximately 58.6% larger than the value of pure water at the Reynolds number of 10000. For the same concentration and Reynolds number, the pressure drop of hybrid nanofluid is 4.79 times higher than the pressure drop of water. The heat transfer performance is the best in the circular pipe compared to the non-circular ducts, but its pressure drop increment is also the largest. The hybrid nanofluid helps to improve the problem of low heat transfer characteristic in the non-circular ducts. In overall, the hybrid nanofluid flow in circular and non-circular ducts are reported to possess better thermal performance factor than that of water. The maximum attainable PEC is obtained by 2% hybrid nanofluid in the square duct at the Reynolds Number of 60000. This study can help to determine which geometry is efficient for the heat transfer application of hybrid nanofluid.

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