Methods verification
To further validate the rationality of numerical results,
experimental measurement on characteristics of airflow velocity
and pressure is carried out in a room with the dimension
of 15,000 mm
×
8000 mm
×
4000 mm (length
×
width
×
height). A
white half-cylindrical FADS in penetration mode is hanged under a removable support with 4000 mm
×
1000 mm
×
2500 mm as
shown in Fig. 3. The length of FADS is 3400 mm, and the diameter
is 305 mm, the depth is 0.47 mm. The air is supplied into FADS by a
Kruger centrifugal fan. The supply air flow rate is changed by adjusting
the input frequency of a converter ranging from 0 to 50 Hz. The
pressure inside FADS is measured by six standard pitot tubes with
the interval distance of 300 mm, which are placed 100 mm away
from the porous fiber along the length direction. The experimental
data are collected with data acquisition system (Keitheley 2700).
The interval time of data acquisition is set to 3000 ms. Regarding the
air velocity, the magnitude is measured by a hot-wire anemometer
(Testo 425) with the measuring accuracy of
±0.03 m/s + 5% of
reading for the measuring range of 0–20 m/s, and the measuring
resolution of 0.01 m/s. During the experiment, a 250 standard
resistance is used to convert the current signal (4–20 mA) into the
voltage signal (1–5 V). Fig. 4 shows the layout of the measuring
points for the internal pressure and the air velocity close to FADS.