The maximum velocity and minimum static pressure occurs. I used total pressure, total temperature for the inlet of the plenum and fixed pressure at the outlet of the pipe. The parameter that becomes choked or limited is the fluid velocity. Compressible flow or gas dynamics is the branch of fluid mechanics that deals with flows having significant changes in fluid density. This is the best general reference on this subject i am aware of. An orifice meter is a device used for measuring the rate of fluid flow. The calculation of compressible flow through orifice plates at high dp critical flow appears to be carried out incorrectly in most instances. Chaplygin 19021 solved the subcritical compressible flowfleld of a 90 slot. Region c is the flow area through the orifice, which is also the confined annular wall jet region. Flow through an orifice university of texas at austin. Orifice meters, sometimes referred to as orifice fittings, satisfy most flow measurement applications and are the most common flow meter type in use today. In round numbers at ambient temperature, the compressibility affects volume by 0.
Restriction orifice plates and critical flow devices. By using a mechanical energy balance, compressible fluid flow in unchoked conditions. Simultaneous oil, gas and water individual volumetric flow rate measurements at standard conditions respectively q o 0 exp, q g 0 exp and q w 0 exp were made at the separator outlets by using respectively turbine, orifice plate and magnetic flow meters. Effect of varying diameter of orifice on coefficient of discharge. The flow of compressible fluids through a constriction in a pipe is treated in chapter 6. Select a subscription plan and enable the full service. When a flowing fluid at a given pressure and temperature passes through a restriction such as the throat of a convergentdivergent nozzle or a valve in a pipe into a lower pressure environment the fluid. The quality is not great, but it is not bad either. Region b is the zone between the orifice plate and float, which has the maximum velocity and maximum pressure gradient in the whole flow field. The parameter that becomes choked or limited is the velocity. Consider an orifice plate placed in a pipe flow as shown in fig. Heat transfer of supercritical fluid flows and compressible. The orifice meter for measurement of flow of gases and liquids on. While all flows are compressible, flows are usually treated as being incompressible when the mach number the ratio of the speed of the flow to the speed of sound is less than 0.
On the flow of a compressible fluid through orifices. Restriction orifice sizing for compressible flow posted in industrial professionals. This will require solving simultaneous equations, since reynolds number is involved in eq. Would be happy to provide more data and details if desired. Consider gas flowing in a duct which varies in size. The beta or diameter ratios of concentric orifice plates range from 0. Discharge coefficients for compressible flow through smalldiameter orifices and convergent nozzles article pdf available in chemical engineering science 467. Orifice meters with supercritical compressible flow, r. I can scan for you if you cannot find in reference libraries.
Y has a minimum value corresponding to choked flow. If the flow is compressible, the density is a nonconstant function of the pressure, the temperature, phase, composition, etc. Use features like bookmarks, note taking and highlighting while reading orifice and venturi pipe flow meters. It uses the same principle as a venturi nozzle, namely bernoullis principle which says that there is a relationship between the pressure of the fluid and the velocity of the fluid. When a flowing fluid at a given pressure and temperature passes through a constriction such as the throat of a convergentdivergent nozzle or a valve in a pipe into a lower pressure environment the fluid. Modeling a flow meter with compressible flow pipeflo professional has certain limitations concerning the use of compressible fluids in a piping network. A restriction fulfilling the function of a primary converter, is installed in a pipeline and produces in it a local change of a flow section. Modeling choked flow through an orifice applied flow technology. In this chapter, the heat transfer between supercritical fluid flows and solid walls and that between compressible flows and solid walls is described. An orifice is an obstruction meter used to determine the flow rate of a fluid. The effects of fluid viscosity on the orifice rotameter. Keep in mind this orifice does not have a constant diameter. Orifice plate critical pressure ratio chemical process. Flow measurement of liquid, gas and steam according to the differential pressure principle has been recognised principle for very many years using orifice plates, venturi tubes and flow nozzles.
This report showed that mass flow rate is function of ratio of actual mass flow function to the limiting value. This article provides calculation methods for correlating design, flow rate and pressure loss as a fluid passes through a nozzle or orifice. I know the volume of fluid, the area squared of the orifice and the flow rate. The net effect is that it slows down your flow at your outlet. Flow through orifice plates in compressible fluid service at. Nozzles and orifices are often used to deliberately reduce pressure, restrict flow or to measure flow rate.
Lets go on to apply the knowledge of entropy to the flow of compressible fluids starting with isentropic flow. The pressure difference between section 1, with the full flow and section 2 at the throat, can then be used to measure the liquid flow rate, using equations developed earlier for the venturi meter and the flow nozzle. For liquid flow or gas flow kindle edition by bengtson, harlan h download it once and read it on your kindle device, pc, phones or tablets. Price new from used from hardcover, 1953 please retry hardcover. See all formats and editions hide other formats and editions. An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting. The flow is fed from a plenum through the orifice into a pipe. Cunningham, transactions of the asme, july latexman chemical 29 apr 19 14.
In his paper orifice meters with supercritical compressible flow, ref. An orifice meter is a conduit and a restriction to create a pressure drop. Calculate the beta ratio, reynolds number, discharge coefficient, mass and volumetric flow rate of a newtonian fluid through an orifice with a corner, 1d. When the velocity increases, the pressure decreases and vice versa. Orifice ports are accurately machin ed f or precision measur ements. As the flow approaches the critical regime local sonic condition, measurements diverge from the theoretical result. First, the physical fundamentals of supercritical fluids and compressible flows are explained. Asme or bs data are used with 90 orifice plates for flow meter applications and. Orifice plate sizing calculator pipe flow calculations.
Orifice meters with supercritical compressible flow by r. An orifice or a constriction in the piping will increase velocity at the constriction, but the pressure recovery afterwards when the gas travels past the restriction causes an overall reduction in pressure. For the orifice flow meter, the volumetric flow rate is. Download limit exceeded you have exceeded your daily download allowance. Discharge coefficients for compressible flow through small.
Fluid flow through an orifice physics stack exchange. With the additional measurement of void fraction, the slip. Calculation of flow through nozzles and orifices neutrium. Since it depends on the orifice and pipe diameters as well as the reynolds number, one will often find c f tabulated versus the ratio of orifice diameter to inlet diameter, sometimes defined as b. The concentric orifice plate flow meter has a sharp squareedged concentric bore that provides an almost pure line contact between the plate and the fluid, with negligible friction drag at the boundary. A new theory for the compressible flow through an orifice is presented which provides a significant advance over the approach currently employed.
The orifice meter, sometimes also called a head loss flow meter, is chosen most frequently because of its long history of use in many applications, versatility. When a fluid particle of some mass dm interacts with neighboring fluid particles via pressure forces, heat exchange, chemical reaction, etc. Flow through a large penstock such as used at a hydroelectric power plant can be measured by averaging the flow velocity over the entire area. When a fluid whether liquid or gaseous passes through the orifice, its pressure builds up slightly upstream of the orifice. Does an orifice plate reduce flow, pressure, or both. Each orifice plate has model number and orifice diameter stamped on tab for easy identification and selection. Tables for the basic orifice factor are presented in appendix c of this book. Flow through orifice plates in compressible fluid service. Switch between metric and imperial units in one click. A restriction in the pipe line creates a pressure drop if the fluid flows.
As shown in the figure, the jet narrows over a short distance beyond the orifice that is comparable with the jet diameter to form what is generally known as a vena contracta that is. Iso 5167 orifice plate flow meter excel spreadsheet. When a flowing fluid at a given pressure and temperature passes through a constriction such as the throat of a convergentdivergent nozzle or a valve in. An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. Model 5 720 calibrated orifice flow meters are desig ned for measurin g flows of air or g ases at pressures up to 100 psig and temperatures to 700 of. On the compressible flow through an orifice journal of. The most critical parts of the meter tube to inspect are the 5 to 7 diameters. The orifice meter for measurement of flow of gases and liquids hardcover 1953. Pressure drop control using multiple orifice system in. Compressible gas flow university of texas at austin. Pdf discharge coefficients for compressible flow through small. Flow through an orifice consider the situation, illustrated in figure 4. A little downstream of the orifice the flow reaches. The effect of a rounded plate is a matter of detail and will not be considered here.
I am investigating the effects of sound waves on the flow through an orifice. I need to place an ro in a nitrogen inerting line to a tank in the event a regulator fails. Measurement of the flow rates of liquids, gases and vapors with orifice meters has found wide use both in industrial and in scientific measurements. Effect of varying diameter of orifice on coefficient of. Oct 23, 2012 restriction orifice sizing for compressible flow posted in industrial professionals. The investigation concluded that measurements using orifice meters operating with wet gas flow are repeatable and reproducible. This purpose is accomplished in, essentially, two steps. No one seems to be offering the book online including asme. What would be the method to determine the pressure a non compressible fluid creates when forced though an orifice. In this case we will consider the flow to be adiabatic also, that is, with no heat transfer. More sensitive to flow disturbances at higher beta ratios than some meters.
Pdf discharge coefficients for compressible flow through. The article name is orifice meters with supercritical compressible flow. International organization of standards measurement of fluid flow by means of pressure differential devices inserted in circular crosssection conduits running full. Friends, does anyone have any suggestions or rulesofthumb from their experience when sizing restriction orifices in compressible flow. These are devices that have applications in flow measurement. It is on pages 625 through 638 of the july 1951 issue of transactions of the asme. The limits of the darcy weisbach equation pertaining to compressible fluids are covered on page 18 of the method of solution for pipeflo and elsewhere in this knowledge base.
Just like a control valve you pinch off the flow area, the velocity through that flow area sky rockets, increases your. For the orifice flow meter, the volumetric flow ra. As the flow approaches the critical regime local sonic condition, measurements diverge from the theoretical result due to the nononedimensionality of the flow. No such minimum value of y is provided for a square edge orifice indicating the limitations in using the crane method to evaluate choked flow through an orifice. Modeling a flow meter with compressible flow engineered. Because of the sudden contraction at the orifice and the subsequent sudden expansion after the orifice, the coefficient of discharge c for the orifice meter is much lower than. Orifice meters with supercritical compressible flow, rg cunningham asme, july 1951 perrys chemical engineering handbook 7th edn rh perry, dw green flow measurement engineering handbook, 3rd edn rw miller note. As shown in the figure, the jet narrows over a short distance beyond the orifice that is comparable with the jet diameter to form what. Jobson by making certain basic assumptions, the author has determined a theoretical expression for the contraction coefficient, c, appropriate to an orifice when transmitting a compressible fluid, either. This flow condition is often encountered on gas plants, compressor stations and pipelines where orifice plates are commonly used as a cheap and convenient way to regulate blowdown and pressurising rates. The flow coefficient c f is found from experiments and is tabulated in reference books. The subsonic and criticalflow regions for 16 orifice and nozzle flow elements with the following. The manufacturers should be contacted for detailed information. In order to investigate the effectiveness of an orifice system in producing pressure drops and the effect of compressibility on the pressure drop, computations using the massaveraged implicit navierstokes equations were applied to the axisymmetric pipe flows with the operating pressure ratio from 1.
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