Viscosity Influence on the Flow Coefficient to Small Orifices

The Canadian Journal of Chemical Engineering, 1999

An investigation has been carried out to evaluate the two-phase pressure drop for gas-non-Newtonian liquid flow across orifices. The method of dimensional analysis was used to correlate the experimental data. The correlation developed predicts the two-phase frictional pressure drop across the orifices with acceptable statistical accuracy.

Engineering Research Journal - Faculty of Engineering (Shoubra)

One of the most important factors to be studied carefully is the discharge coefficient "Cd" through the orifices, which reflects the efficiency of the flow and plays an important role in the design of hydraulic units. The purpose of this paper is to investigate experimentally the effect of changing orifice thickness on the discharge coefficient for water flow through different orifice shapes and comparing each other. To achieve this goal, four orifices shapes were used: circular, square, equilateral triangle and rectangular, five different thicknesses (9.25, 7.5, 6.75, 4 and 2 mm) were tested. It should be noted that the tests were conducted on four different values of the pressure heads affecting the center of the hole: (35, 40, 45 and 50 cm). Bernoulli's equation was used as a theoretical basis for calculating the discharge coefficient. The results of the study demonstrated that the changing in the thickness of the orifice affects the coefficient of discharge. The coefficient of discharge gradually decreases when the ratio (orifice thickness "t"/orifice equivalent diameter "d") increases, with the fixity of both the orifice area and the vertical pressure head located above the center of the orifice. In all the analytical comparisons made in this study it was observed that circular orifices give the highest values of the coefficient of discharge compared to all other shapes followed by equilateral triangular orifices and then square orifices and finally it was observed that rectangular orifices give the lowest values of the coefficient of discharge.

Journal of Hydraulic Research, 2022

Orifice flows were used as water clocks since the Antiquity up to the 16-th century. Today orifices and nozzles are used for measuring discharges. Most works were conducted with steady flow conditions and there is little information on the unsteady flow pattern. In this study, the writers describe an experimental investigation of an unsteady orifice flow discharging vertically. The study was conducted in a large-size facility with a rectangular orifice (0.75-m by 0.07-m) discharging up to 1.2 m 3 in about 10 seconds. The study presents new information on the unsteady flow patterns, the discharge capacity and the velocity field in the reservoir. The results are compared with ''classical'' orifice flow results. RÉSUMÉ Les écoulements dans les orifices ont été utilises comme horloges à eau depuis l'Antiquité jusqu'au 16 ième siècle. De nos jours les orifices et les ajutages sont utilisés pour les mesures de débit. La plupart des travaux ont été menés en écoulement permanent et l'on manque d'information sur les configurations non permanentes. Dans cet article, les auteurs décrivent l'étude expérimentale d'un écoulement instationnaire débitant verticalement par un orifice. Les essais ont été faits dans une installation de grande taille avec un orifice rectangulaire (0.75 m sur 0.07 m), évacuant jusqu'à 1.2 m 3 en 10 secondes environ. L'étude présente des informations nouvelles sur les configurations de l'écoulement instationnaire, la coefficient de débit et le champ de vitesse dans le réservoir. Les résultats sont comparés avec les résultats ''classiques'' des écoulements dans les orifices.

Flow Measurement and Instrumentation, 1990

Experimental work has been performed in an effort to gain a better understanding of the flow field inside orifice flowmeters and the pressure field generated on the walls of the pipe and orifice plate. As a part of a larger study, extensive wall pressure measurements have been made on the pipe wall from four pipe diameters upstream of the orifice plate to six pipe diameters downstream, as well as on both the upstream and downstream faces of the orifice plate. These measurements were performed for Reynolds numbers of 54 700; 91 I00 and 122800; for beta ratios of O.50 and 0.75 with air as the working fluid. An adjustable swirl plate was installed, which was used to impart varying amounts of swirl into the flow upstream of the orifice plate. For each swirl case, Pitot and static pressure probes were used to characterize the upstream flow field while the pipe wall and orifice plate surface pressures were measured.

Flow Measurement and Instrumentation, 1994

The effects of upstream velocity profile on the performance of orifice flowmeters were studied. Non-swirling maldistributed axial velocity profiles were obtained using a concentric pipe flow conditioner. Orifice flowmeters with/3 ratios of 0.43, 0.50, 0.60, 0.70 and 0.75 were installed downstream of the flow conditioner and operated at a Reynolds number of 54 700 in a 50.4 cm pipe. Increasing the flow along the centreline of the pipe decreased the pressure drop across the orifice plate, resulting in increased discharge coefficients. The opposite was observed as the flow along the pipe centreline was decreased. The errors increased with increasing/3 ratio. A swirl generator was installed upstream of the/3 = 0.43 and 0.50 orifice plates. The swirl produced effects opposite to the axial velocity. The change in discharge coefficient increased with decreasing /3 ratio.

Water, 2019

The traditional orifice discharge formula used to estimate the flow rate through a leak opening at a pipe wall often produces inaccurate results. This paper reports an original experimental study in which the influence of orifice-to-pipe diameter ratio on leakage flow rate was investigated for several internal/external flow conditions and orifice holes with different shapes. The results revealed that orifice-to-pipe diameter ratio (or pipe wall curvature) indeed influenced the leakage flow, with the discharge coefficient (C d) presenting a wide variation (0.60-0.85). As the orifice-to-pipe diameter ratio decreased, the values of C d systematically decreased from about 12% to 3%. Overall, the values of C d also decreased with β (ratio of pressure head differential at the orifice to wall thickness), as observed in previous studies. On the other hand, orifice shape, main pipe flow velocity, and external medium (water or air) all had a secondary effect on C d. The results obtained in the present study not only demonstrated that orifice-to-pipe diameter ratio affects the outflow, but also that real scale pipes may exhibit a relevant deviation of C d from the classical range (0.61-0.67) reported in the literature.

Revista Brasileira de Engenharia Agrícola e Ambiental, 2021

This study aimed to evaluate three methodologies for orifice-plate water-flow estimation by quantifying errors in the flow determinations to propose an appropriate measurement range for each evaluated condition. Two orifice-plate models (nominal diameters of 100 and 150 mm) with 50% restriction in the flow section were evaluated. In the theoretical equations, the discharge coefficient was obtained using the Reader-Harris/Gallagher equation (Method 1) and approximated from experimental data using the angular coefficient of a zero-intercept straight line (Method 2). The recommended measurement ranges for errors that were lower than 5% for the 100 and 150 mm plates were 30 to 65 m3 h-1 and 70 to 130 m3 h-1 using the theoretical equation and 20 to 65 m3 h-1 and 40 to 130 m3 h-1 using the empirical equation, respectively. The Reader-Harris/Gallagher equation (Method 1) adequately estimated the discharge coefficient of the orifice plates; however, the use of empirical equations (Method 3)...

Experimental Thermal and Fluid Science, 2015

ABSTRACT The dimensionless pressure drop was measured for six micro-orifices with diameters of 150 μm, 300 μm and 600 μm, and thickness ratios between 1.87 and 6.93. The experiments were carried out with water for orifice Reynolds number between 6000 and 25,000, thus extending the range covered in previous researches in turbulent flow conditions. The dimensionless pressure drop was found to be a weak decreasing function of the Reynolds number, and was found to be unaffected by the micro-orifice diameter ratio or thickness ratio. The static pressure profiles measured immediately downstream of the micro-orifices were flat, indicating that the vena contracta is located within the micro-orifice. A new prediction method for the dimensionless pressure drop in micro-orifices at high Reynolds number was developed using available data.

Ultrasound in Medicine & Biology, 1997

An accurate and reliable method of regurgitant flow calculation is currently unavailable. The goal of thii study was to define a new general method of flow calculation for orifices of different aspect ratios. The success of the method relies on matching the imaged flow field distribution obtained by color ilow mapping (CFM) to a three-dimensional (3D) numerical Bow field distribution of known geometry. The flow field in three orillces of identical cross-sectional area with aspect ratios of 1 (circular), 2 and 4 (elliptical) was evaluated by: (a) CFM, (b) 3D echocardiographic imaging, and (c) 3D finite element modeling (FEM). The orifice shape and size were accurately estimated by 3D echocardiographic imaging. FEM showed that the normalized centerline velocity profile of the flow field depends on the orilice aspect ratio. CFM provided a good description of the centerline profile for each case. For a given distance from the orifice center, the equivelocity contour surface area increases with increasing aspect ratio. A simple flow calculation scheme was developed to calculate regurgitant flow independent of orifice shape. This improved method showed better results than previous studies and may prove to be advantageous when analyzing in viva flow fields with complex geometries. 0 1997 World Federation for Ultrasound in Medicine & Biology.

2019

The main parameter of the orifice hole diameter was designed according to the range of throttle diameter ratio which gave the required discharge coefficient. The discharge coefficient is determined by difference diameter ratios. The value of discharge coefficient is 0.958 occurred at throttle diameter ratio 0.5. The throttle hole diameter is 80 mm. The flow analysis is done numerically using ANSYS 17.0, computational fluid dynamics. The flow velocity was analyzed in the upstream and downstream of the orifice meter. The downstream velocity of non-standard orifice meter is 2.5% greater than that of standard orifice meter. The differential pressure is 515.379 Pa in standard orifice.