AIRFOIL FANS - Aerovent

Piezometer Ring (Airflow Measuring System)
A piezometer ring is available on model CAE fans,
as well as other Aerovent housed and plenum fans,
as part of an airflow measuring system, based on
the principle of a flow nozzle. The inlet cone of the
fan is used as the flow nozzle. The flow can be calculated
by measuring the pressure drop through the
inlet cone. No tubes or sensors are inserted in the
high velocity airstream which could obstruct airflow.
The system, consists of a piezometer ring mounted
at the throat and a static pressure tap mounted on
the face of the inlet cone. A differential pressure
transducer and digital display can also be provided.
The pressure drop is measured from the tap located
on the face of the inlet cone to the piezometer ring
in the throat. The inlet tap is connected to the highpressure
side of the transducer and the piezometer
ring is connected to the low-pressure side.
Based on Aerovent laboratory tests, the system was
determined to be accurate within +/-5%.
Flow Measurement System
Piezometer Ring
Mounted at Throat
of Inlet Cone
NOTE: Aerovent does not recommend placement of
flow measuring probes inside the fan inlet cone in the
path of airflow. These devices create disturbances
and unpredictable performance losses. Aerovent will
not be responsible for loss of performance due to
such devices.
Performance Correction
for Temperature & Altitude
The performance tables in this catalog are based
on fans handling standard air at a density of 0.075
pounds per cubic foot. This is equivalent to air at
70°F at sea level (29.92" Hg barometric pressure).
When specified performance is at a density different
than standard, it must be converted to the
equivalent standard conditions before the fan can be
selected from the performance tables. The equivalent
standard conditions can be calculated by using the
Temperature and Altitude Density Ratios shown in the
table below.
Temperature and Altitude Density Ratios
AIR
TEMP
°F
ALTITUDE IN FEET ABOVE SEA LEVEL
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 20000
BAROMETRIC PRESSURE IN INCHES OF MERCURY
29.92 28.86 27.82 26.82 25.84 24.90 23.98 23.09 22.22 21.39 20.58 16.89
–50 1.293 1.247 1.201 1.159 1.116 1.076 1.036 0.997 0.960 0.924 0.889 0.729
0 1.152 1.111 1.071 1.032 0.995 0.959 0.923 0.889 0.856 0.824 0.792 0.650
50 1.039 1.003 0.967 0.932 0.897 0.864 0.833 0.801 0.772 0.743 0.715 0.586
70 1.000 0.964 0.930 0.896 0.864 0.832 0.801 0.772 0.743 0.714 0.688 0.564
100 0.946 0.912 0.880 0.848 0.818 0.787 0.758 0.730 0.703 0.676 0.651 0.534
150 0.869 0.838 0.808 0.770 0.751 0.723 0.696 0.671 0.646 0.620 0.598 0.490
200 0.803 0.774 0.747 0.720 0.694 0.668 0.643 0.620 0.596 0.573 0.552 0.453
250 0.747 0.720 0.694 0.669 0.645 0.622 0.598 0.576 0.555 0.533 0.514 0.421
300 0.697 0.672 0.648 0.624 0.604 0.580 0.558 0.538 0.518 0.498 0.480 0.393
350 0.654 0.631 0.608 0.586 0.565 0.544 0.524 0.505 0.486 0.467 0.450 0.369
400 0.616 0.594 0.573 0.552 0.532 0.513 0.493 0.476 0.458 0.440 0.424 0.347
450 0.582 0.561 0.542 0.522 0.503 0.484 0.466 0.449 0.433 0.416 0.401 0.328
500 0.552 0.532 0.513 0.495 0.477 0.459 0.442 0.426 0.410 0.394 0.380 0.311
550 0.525 0.506 0.488 0.470 0.454 0.437 0.421 0.405 0.390 0.375 0.361 0.296
600 0.500 0.482 0.465 0.448 0.432 0.416 0.400 0.386 0.372 0.352 0.344 0.282
650 0.477 0.460 0.444 0.427 0.412 0.397 0.382 0.368 0.354 0.341 0.328 0.269
700 0.457 0.441 0.425 0.410 0.395 0.380 0.366 0.353 0.340 0.326 0.315 0.258
750 0.439 0.423 0.407 0.393 0.379 0.365 0.351 0.338 0.326 0.313 0.303 0.248
800 0.420 0.404 0.389 0.375 0.362 0.350 0.336 0.323 0.311 0.300 0.290 0.237
850 0.404 0.391 0.376 0.363 0.349 0.336 0.324 0.312 0.300 0.289 0.279 0.228
900 0.389 0.376 0.363 0.349 0.336 0.324 0.312 0.300 0.289 0.279 0.268 0.220
950 0.376 0.363 0.350 0.337 0.325 0.313 0.301 0.290 0.279 0.269 0.259 0.212
1000 0.363 0.350 0.338 0.325 0.314 0.302 0.291 0.280 0.270 0.259 0.250 0.205
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