Rosemount Model 8800C Vortex Flowmeter
3-8
Density Ratio
Density Ratio is used to convert actual volumetric flow to standard
volumetric flow rates based on the following equations:
Calculate Density Ratio
Calculate Density Ratio will calculate the density ratio (shown
above) based on user entered process and base conditions.
Operating Conditions
T
f
= absolute temperature at actual (flowing) conditions in degrees
Rankine or Kelvin. (The transmitter will convert from degrees
Fahrenheit or degrees Celsius to degrees Rankine or Kelvin
respectively.)
P
f
= absolute pressure at actual (flowing) conditions psia or KPa
absolute. (The transmitter will convert from psi, bar, kg/sqcm, kpa, or
mpa to psi or kpa for calculation. Note that pressure values must be
absolute.)
Z
f
= compressibility at actual (flowing) conditions (dimensionless)
Base Conditions
T
b
= absolute temperature at standard (base) conditions degrees Rankine
or Kelvin. (The transmitter will convert from degrees Fahrenheit or
degrees Celsius to degrees Rankine or Kelvin respectively.)
P
b
= absolute pressure at standard (base) conditions psia or KPa
absolute. (The transmitter will convert from psi, bar, kg/sqcm, kpa, or mpa
to psi or kpa for calculation. Note that pressure values must be absolute.)
Z
b
= compressibility at standard (base) conditions (dimensionless)
Example
Configure the Model 8800C to display flow in standard cubic feet per
minute (SCFM). (Fluid is hydrogen flowing at conditions of 170 °F and
100 psia.) Assume base conditions of 59 °F and 14.696 psia.)
HART Comm. 1, 3, 3, 3, 2
HART Comm. 1, 3, 3, 3, 3
HART Comm. 1, 3, 3, 3, 3, 1
HART Comm. 1, 3, 3, 3, 3, 2
Conversion factor
density at actual (flowing) conditions
density at s dard (base)tan conditions
------------------------------------------------------------------------------------------------------------=
Conversion factor
T
b
P
f
Z
b
T
f
P
b
Z
f
----- --------------- -----------=
Conversion factor
518.57 °R 100 psia
1.0006
629.67 °R 14.7 psia
1.0036
----- --------------- ----------------------- --------------- --------------- ---------- 5.587==
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