Orifice Plate Calculator Pressure drop Calculations

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Orifice plate calculator pressure drop calculation

Orifice plate pressure drop calculator is used for flow rate measuring in pipe systems. With orifice plate, pressure drop

is created. Based on the magnitude of pressure drop, flow rate can be calculated. The pressure drop calculation

formula for the pipe is explained in more detail below .Practical for larger tube diameters and for dirty fluid where other

methods are impractical.

Measure pressure drop from position 1 to position 2 and calculate flow rate and more with this easy to use flow

calculator .Pressure drop formula calculation is published. It can be used as liquid, gas or air flow meter and the

results can be checked against the textbook formula to gain confidence in using this easy to use orifice plate pressure

drop /flow rate calculation . Flow rate can be expressed in metric or imperial units.

(requires Java Runtime Environment http://java.com/en/download/index.jsp )

Explanation of used values

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Orifice Plate Calculator Pressure drop Calculations http://www.flowmeterdirectory.com/flowmeter_orifice_calc.html

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D1

D2

p1

p2

p1 - p2

ni

mi

T

rho

R

kappa

diameter of tube

throat diameter

upstream pressure

downstream pressure

pressure drop through orifice

kinematic viscosity

dynamic viscosity

upstream temperature

upstream density

gas constant

isentropic coefficient

Resulting values

Q

G

V1

V2

ReD

e

C

volumetric flow rate

mass flow rate

upstream velocity

throat velocity

upstream Reynolds number

expansion coefficient

coefficient of discharge

Theory

Calculation of flow rate using orifice plate calculator is for incompressible flow, based on the Bernoulli principle:

where is:

p - pressure

rho - density

V - velocity

g - gravitational constant (9.81 m/s2)

z - geodetic height

Assumption that pressure lost is negligible (pressure drop is obvious and included with coefficient of discharge which is

introduced bellow):

and:

and if velocities substituted with flow rate:

where is: Q - volumetric flow rate

D - diametar

Pressure drop through the orifice because of velocity increase can be calculated as follows:

or:

Expressing flow rate from the previous equation leads to:

Substituting:

flow rate can be determined as:

where is:

C - coefficient of discharge

e - expansion coefficient

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2 de 4 22/01/2011 10:07

Coefficient of discharge can be calculated using following equation (ISO):

where is:

beta - diameter relation D2/D1

ReD - Reynolds number which can be calculated as follows:

where is:

ni - kinematic viscosity

mi - dynamic viscosity

L1 and L2 are functions on tap type and it is:

L1=L2=0 for corner taps

L1=1 L2=0.47 for D & D/2 taps

L1=L2=0.0254/D D[m] for 1" taps

Expansion coefficient e can be calculated (for gases only):

where is:

kappa - isentropic coefficient; kappa = 1.4 for air and other two atom gas molecules

Other values are calculated using following equations:

mass flow:

velocities:

If flowing fluid is gas, then it is considered as incompressible and ideal. Equation for ideal gas:

can be used for calculation of temperature T:

as well as density rho:

where R is gas constant (R=287 J/kgK for air).

Appliance

Orifice plate calculator can be used for both liquids and gases. Fluid is considered as incompressible, so density (rho)

and temperature (T) are constant through tube. Also, gas is considered as ideal.

Units of measure are both in SI and English system.

Orifice plate calculator can be used for calculation of:

volumetric flow - Q

mass flow - G

velocity on inlet, bigger diameter - V1

velocity on smaller diameter - V2

Reynolds number on bigger diameter - ReD

For calculation of those values, necessary values for input are:

inlet, bigger diameter - D1


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smaller diameter - D2

inlet pressure - p1

either pressure on smaller diameter - p2, or pressure drop p1-p2

either kinematic viscosity - ni, or dynamic viscosity - mi

for gases only:

either temperature - T, or density - rho

gas constant - R

for liquids:

density - rho

Beside four values (Q, G, V1, V2), which calculation is main purpose of calculator, values that are not defined by user

are determined in process of calculation (for example: if pressure p1 and temperature T are specified for gas flow -

value for rho is calculated together with four main values (Q, G, V1, V2)). Also necessery coeffients: expansion - e and

discharge - C are calculated and results are shown.

Orifice plates and metering runs are popular because of

low cost . Orifice plates combined with differential

pressure transmitters are now commonly supplied as

complete flow measurement packages.

Multiport pressure transmitter manifold valves gives

options to operators for e.g to isolate , equalize and

vent the differential pressure transmitter. Orifice plates

and differential pressure measurement devices are

used to measure the flow of fluids such as steam, air,

gas and water. In natural gas transmission a familiar

type of orifice plate is the senior orifice plate. This

special design allows operators to remove and inspect

the orifice plate during normal pipeline operation. A

metering run, flow straightener may have to be installed

to correct the flow profile in custody transfer

applications or orifice plate applications that require

higher accuracy.


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Documents

Orifice Plate Calculator Pressure drop Calculations