User Manual
9
Determining Flow from your Laminar Flow Element
Calibration
Curve/Table
The curve/table of each LFE is normalized to standard conditions listed by multiplying the calibration
data points by the ratio
of:
Therefore, you should NOT read the flow rate directly from the curve/table unless your flow
temperature
and
pressure are identical to the standard conditions.
The
following steps must be taken to
determine flow rate at flowing conditions other than standard.
1. Measure and correct to 4ºC and if
necessary,
the DP across the LFE.
2. Measure and record the inlet
temperature (always)
and absolute line pressure (for
s tandard or mass flow rates). Convert both values to absolute units.
3. Follow the AIR FLOW or GAS OTHER THAN
AIR
guidelines below
Model 50MK10 All Other Models
Air Flow
Select the proper flow
curve/table
for the LFE
being
used.
Standard Volumetric Flow Rate
1)
To obtain standard volumetric flow rate if inlet
pres
sure and
temperature
are other than
29.92"
Hg
absolute and 70ºF, respectively, find the flow rate (Q) that corresponds to the corrected DP.
Multiply Q
by
temperature/viscosity and pressure corrections shown on charts A-32422 and
A-31031, respectively, to
bring
flow to standard conditions of 29.92" Hg and
70ºF.
2)
At flowing
conditions
of
70'F
and 29.92" Hg,
read
curve directly in standard volumetric
flow rate.
Flow, Q
Flow, Q
0 1 2 3 4
Differential Pressure,
Inch of Water @ 4ºC
Flow, Q
0 1 2 3 4
Differential Pressure,
Inch of Water @ 4ºC
4 5 6 7 8