Orifice Coefficient Research Articles

Gravity driven counterflow through an open door in a sealed room

Flow measurements using tracer gas techniques were made on the exterior doorway of a test house for indoor-outdoor temperature differences of 0.5–45 K. The time for door opening and closing was constant at 3.75 s, and fully open hold time varied from 0.5 s to 120 s. Predictions of a variable density steady flow model were in good agreement with the measurements when adjustments were made for the time-varying size of the opening and for the effect of cross-stream mixing between the incoming and outgoing air streams. The flow rate is shown to be governed by an effective density very close to the average of inflow and outflow densities, and the control condition at the doorway is fixed by the jet-like behavior of the inflow stream. Dependence of cross-stream mixing on interfacial stability caused the orifice and coefficient to increase from 0.4 to 0.6 as temperature difference increased. This varying orifice coefficient is well represented by the combination of a discharge coefficient for streamline contraction combined with a mixing coefficient which accounts for mixing between the inflow and outflow.

The API/GPA Orifice-Plate Data Base

API and the Gas Processors Assoc. (GPA) have completed a four-year, $1.4 million program to develop a new archival data base for flange tapped orifice coefficients. This paper describes this project and the results to date.

Characteristics of a countercurrent reciprocating plate bubble column. I. Holdup, pressure drop and bubble diameter

AbstractThe hydrodynamics of countercurrent air/water flow in a 5 cm diameter reciprocating plate bubble column have been studied; the plates contained 14 mm diameter perforations and had a fractional open area of 0.57. The ranges of superficial velocities of air and water were respectively 0‐0.99 cm/s and 0‐3.95 cm/s. The stroke was in most cases 4.5 cm and the reciprocation frequency was in the range 0–5 Hz.The pressure drops were measured in the absence of reciprocation for single phase and two phase flow conditions. Pressure fluctuations and time‐averaged pressure drops were measured with plate reciprocation under single and two‐phase conditions. The results were described in terms of the simple quasi‐steady state model; the effective orifice coefficients of the perforations were within the range 0.4 to 0.97 depending on the reciprocation conditions.The Sauter mean diameters of the bubbles decreased with agitation; they were about twice the values predicted from an earlier correlation developed for liquid‐liquid systems. The gas holdups were also substantially greater than predicted from correlations based on liquid‐liquid systems. Both these effects were explained as due to the tendency for bubbles to cluster in the plate region.

Doorway flow induced by a propane fire

A series of full-scale steady-state experiments was conducted to study the high temperature fire-induced flows through doorway openings connecting a burn room to a second room containing a hot gas layer. A propane diffusion burner served as the energy source. Fire strength and doorway width were varied. Measurements included two-dimensional velocity and temperature profiles within the opening and vertical gas temperature profiles within the rooms. Opening mass flows were determined from the opening data. These mass flows are explained in terms of a static pressure model based on actual gas temperature profiles in the two rooms and an orifice coefficient of 0.68. It is also shown that the simple relationship between mass flow rate through the opening, M a , and ventilation parameter, WH 3 2 (W, opening width; H, opening height) holds even when the opening is in the wall between two rooms. The proportionality constant for this simple relationship may depend on the configuration.

A Comparison Between Orifice and Flow Nozzle Laboratory Data and Published Coefficients

Prediction of orifice and flow nozzle coefficients from their dimensions is a matter of major concern. In the mid 1930’s, laboratory flow coefficient data were obtained for flange top orifices and for the ASME flow nozzle. The working equations and tolerances developed from these data provide the basis for AGA Report Nos. (2,3), Fluid Meters, and ISO R541. Recent statistical evaluation of these data indicated that the tolerance should be at least twice the published values. This paper presents a considerable body of previously unpublished precision flow calibration data on orifices and flow nozzles. The significant difference between these data and the original 1980 data is that they were obtained on devices not constructed for a controlled laboratory test program. The majority of these devices were not manufactured by Foxboro but were purchased by the user from different manufacturers and were flow calibrated at Foxboro for high accuracy measurement applications. Data plate dimensions were used in all calculations, and conformity to ASME code requirements was the responsibility of the manufacturer. These data are compared point-by-point to the ASME and other proposed equations. These results indicate that a tolerance of ±0.7 percent for nozzles and ±0.5 percent or less for orifice plates is possible using a regression analysis equation. This compares to the ±2.0 percent and ±1 percent tolerance on previously published data. These data also point up the need for further work to bring the coefficient equations into line for pipe sizes less than 4 in. and for pipe sizes 24 in. and larger, as well as for beta ratios greater than 0.7.

The Measurement and Effects of Edge Sharpness on the Flow Coefficients of Standard Orifices

An investigation of the lead foil impression technique of determining orifice edge-sharpness and the resultant effects on orifice coefficient of the rounding of the square-edge as determined by water calibration are discussed. The data to date are encouraging and correlate well with similiar work done originally in Germany and more recently in England.

Formulation of Equations for Orifice Coefficients

Research Papers Formulation of Equations for Orifice Coefficients H. S. Bean H. S. Bean National Bureau of Standards, Sedona, Ariz Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information H. S. Bean National Bureau of Standards, Sedona, Ariz J. Basic Eng. Jun 1971, 93(2): 97-98 (2 pages) https://doi.org/10.1115/1.3425244 Published Online: June 1, 1971 Article history Received: July 30, 1970 Online: October 27, 2010

Precise Measurement of Differential Pressure When Calibrating a Head Class Flow Meter

When flow calibrating a head class meter to establish its discharge coefficient, measurement of the fluctuating differential pressure has caused the largest uncertainty. With conventional techniques, the reported precision of determining discharge coefficients may range from ±0.1 percent to ±0.3 percent. Improved precision and accuracy in the measurement of differential pressure can be achieved by the Null Balance Integration (NBI) instrumentation system reported in this paper. Using this system the obtainable precision ranges from ±0.02 percent to ±0.04 percent. The system provides accurate determination of the average value of the fluctuating differential pressure signal by establishing a constant, predetermined reference differential. The fluctuating differential pressure, developed by the primary element, is continuously compared to this reference differential pressure. The difference is a secondary analog signal, which includes the fluctuation of the measurement signal plus whatever average difference exists between the measured and reference signals. This secondary difference signal is integrated electronically for the calibrating period. The total is divided by the calibrating time and the resultant average difference is algebraically added to the value of the reference signal. The result is an accurate average value of the measured signal during the calibration period. Orifice coefficient data is presented using the NBI System combined with a high accuracy static-weigh/time system. The spread in coefficients was ±.022 percent.

Hydrodynamic Studies Of Tide Gauges

When tide gauges of the float and well type are situated such that there is a flow past them, an error is introduced into their readings as a result of the flow. The hydrodynamics of the flow are considered and a relationship is developed for the well orifice pressure coefficient Cp , in terms of a Reynolds number, Froude number and two geometric ratios. The relationship is investigated by model test on various tidewell end-shapes and orifice configuration. The Cp value and hence expected changes in level in the well are compared. The types giving least error from this effect are found to be the shrouded cone and the standard American gauge. Concern is shown regarding the magnitude of this error and several alternatives for eliminating it are suggested.

Local shell‐side heat transfer coefficients and pressure drop in a tubular heat exchanger with orifice baffles

AbstractBy means of a moveable sensing probe previously described2 local shell‐side heat transfer coefficients and friction losses were measured on a model tubular heat exchanger containing orifice baffles. The heat exchanger shell was 6‐in. nominal I.D. and 45 in. in length and contained four tubes in triangular arrangement passing through orifice baffles. Baffle hole diameters of 1‐/16, 1–2/16, 1–3/16, and 1–5/16 in. and baffle spacings of 4.0 and 9.0 in. were studied. Data were taken at several air flow rates for each of the four baffle hole diameters.The average heat transfer coefficient for the region between two central baffles was correlated with an empirical equation based on only two baffle spacings.An increase in the baffle‐to‐tube clearance caused a decrease in heat transfer. An increase in the baffle spacing also resulted in a decrease in heat transfer. Four flow zones in the baffle space are postulated from the analysis of Nusselt number distribution along the tube. The heat transfer characteristics in each of the four flow zones were analyzed in terms of the mechanism of the fluid flow.The pressure‐drop data were correlated in terms of an annular orifice coefficient of discharge and an orifice‐pressure‐drop function. As a result of this study a method was developed by which one can predict the average of the local coefficients at the baffle position from the knowledge of pressure drop across a single baffle.

Use of momentum balance in calibrating orifices for flow of gases

AbstractA method of determining the absolute calibration of a gas‐flow orifice without the use of gas holders or any comparative device is described. The method is based on the application of the momentum balance, as well as the energy balance, to the flow of the gas. The application requires the measurement of pressures on the face of the orifice in addition to the usual pressure‐drop measurements along the axis of flow.Orifice coefficients determined by the force‐momentum principle are shown to agree within an average deviation of 1.4% with those determined by other standard techniques. Also the application of the force‐momentum principle demonstrates clearly why orifice coefficients are much less than unity.

Discharge coefficients through perforated plates at reynolds numbers of 400 to 3,000

AbstractThe correlation of Kolodzie and Van Winkle (3) for predicting dry plate orifice coefficients through perforated plates originally covering a Reynolds number range of 2000 to 20,000 has been extended to apply to Reynolds numbers as low as 400. The correlation applies to column diameters ranging from 3 to 15 in.

Heat Transfer and Fluid Friction During Flow Across Banks of Tubes—VI: The Effect of Internal Leakages Within Segmentally Baffled Exchangers

Abstract An experimental study has been made of the leakage past segmental baffles within tubular heat exchangers with no fouling. Orifice coefficients are given which will permit calculation of the amount of leakage if the pressure difference across the baffle is known. For the case of turbulent flow of the main stream in the exchanger, the effect of internal leakage upon pressure drop and heat transfer is shown by comparing experimental results from exchangers with known internal clearances with the results from an exchanger with no internal clearances. Internal clearances comparable to those encountered in commercial practice were found to lower the heat-transfer coefficient to around 55 per cent and the pressure drop to around 30 per cent of the values without internal leakage. Graphs are presented which will aid in estimating the reduction in pressure drop and heat transfer resulting from internal leakages.

Discharge coefficients through perforated plates

AbstractThe design variables that affect the pressure drop across dry perforated plates were determined and correlated. Average orifice coefficients were calculated for the perforated plates by using a modified form of the single‐orifice flow equation.The variables which affected the orifice coefficients were found to be the hole diameter, hole pitch, plate thickness, fraction of the plate covered by the perforated area, and a Reynolds number based on the hole diameter. The orifice coefficients have been correlated with these variables in dimensionless groupings.The correlation presented covers a practicable range of variables for which the pressure drop may be predicted in design.

Notes on Some Recently Published Experiments on Orifice Meters

Abstract Dr. Buckingham presents a procedure for plotting orifice coefficient data which results in straight lines over a considerable range of conditions. By relating the slopes and intercepts of these lines to size ratio and the Reynolds number parameters, it is possible to represent the coefficients for a wide range of sizes and rates by two linear equations. By applying this procedure to several available sets of data he has determined the limits of applicability of the equations. Furthermore, he shows that the mechanical finish of the orifice-plate surface and orifice edge affect both the slope and intercept of the lines resulting from the initial plottings.

Orifice Coefficients for Reynolds Numbers from 4 to 50,000

Abstract The sharp-edged orifice meter is standardized in shape and application by The American Society of Mechanical Engineers (1, 2) and by the International Standards Association (3). With sufficient precision and care in fabrication of the orifice and metering section, and with standard techniques of use, the accepted coefficients as listed in the codes may be used within prescribed metering accuracy tolerance over the Reynolds number range of the standardization. Many applications arise for use of the orifices in the Reynolds-number range below that of the present standards. Calibration results in the “low” Reynolds-number range are available in the literature as obtained by numerous investigators. These were assembled to produce, if possible, standard coefficients for the Reynolds-number range of 4 to 50,000 (based on the pipe diameter) and for orifice-to-pipe diameter ratios of 0.1 to 0.8.

Closure to “Discussion of ‘Orifice and Flow Coefficients in Pulsating Flow’” (1952, Trans. ASME, 74, pp. 928–929)

Closure to “Discussion of ‘Orifice and Flow Coefficients in Pulsating Flow’” (1952, Trans. ASME, 74, pp. 928–929)

Discussion: “Orifice and Flow Coefficients in Pulsating Flow” (Hall, N. A., 1952, Trans. ASME, 74, pp. 925–928)

Discussion: “Orifice and Flow Coefficients in Pulsating Flow” (Hall, N. A., 1952, Trans. ASME, 74, pp. 925–928)

Orifice and Flow Coefficients in Pulsating Flow

Abstract The flow equations pertaining to the behavior of a fluid passing through an orifice are set forth so as to relate the flow coefficient to the orifice configuration and to flow losses. The general nature of the flow coefficient is developed both for the case of instantaneous flow and pressure differences and for mean flow and pressure difference.

Orifice Discharge Coefficients in the Viscous-Flow Range

Abstract This paper covers the results obtained from calibrating two orifice assembly units for use in measuring lubricating-oil flow rates in aviation engines during flight. A brief summary of available published data on orifice coefficients in the viscous-flow range is included. In view of the limited amount of available published data of this type, it is suggested that the Fluid Meters Committee consider the need for publishing orifice-coefficient data in the viscous-flow range in the A.S.M.E. Fluid Meters Report.