Rapporten från etapp 1 - BeBo

Pressure Drop (Pa)
120
100
80
60
40
20
Small Duct vs Large Duct
0
0 2 4 6 8 10 12
Air Flow (liters per sec)
Figure 7. Duct area comparison at Length 3
Discussion:
Small Duct Large Duct
Table 2 Laboratory Sound Tests
Air Flow Octave Frequency Decibels
~7 l/s A 125 Hz 42 dB
~7 l/s A 250 Hz 42 dB
~7 l/s A 500 Hz 42 dB
~12 l/s A 125 Hz 42 dB
~12 l/s A 250 Hz 42 dB
~12 l/s A 500 Hz 42 dB
Upon observing the results, several points can be made. With Figure 1, the small area
duct results, the pressure drop at seven liters per second air flow is most interesting. This
air flow is required for proper ventilation as these ducts will be used as radial ducts
stemming from a larger area duct. The air speed measurement is approximately 0,9
meters per second theoretically, but the observed value is a bit to the left of the curve.
This is due to the placement of the air speed instrument which is set before the fan and
before all the air silencing equipment. It is believed that the speed was slightly reduced in
the ducts after passing through all the equipment, as well; air speed readings were
averaged over the length of time with possible recording errors.
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