The New COMEFRI Plenum Wheel:

The New
COMEFRI
Plenum Wheel:
NPA
AL
NPA PLENUM FAN
AL
UNPARALLELED FLEXIBILITY:
- DIFFERENT MOTOR SIZES ON THE SAME FRAME
- ONE STRUCTURE FOR THREE IMPELLER TYPES
NPA
NPL
A WELDED STRUCTURE TO
ACHIEVE VERY LOW VIBRATION
LEVELS AS DEMANDED BY THE
RELEVANT ISO STANDARDS .
TE
NPA PLENUM FAN
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NPA PLENUM FAN
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NPA PLENUM FAN
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NPA PLENUM FAN
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NPA PLENUM FAN
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NPA PLENUM FANS
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NPA PLENUM FAN
Wheel Performance .
@ 1500 rpm
2 000
Static Pressuree [Pa]
1 500
1 000
NPA 710
500
NPL 710
0
0
5000
10000
15000
20000
Air Volume [m3/h]
AL
25000
30000
35000
40000
NPA PLENUM FAN
Wheel Performance .
@ 1500 rpm
100
Static efficiency %
90
80
70
60
NPA 710
50
NPL 710
40
0
5000
10000
15000
20000
Air Volume [m3/h]
AL
25000
30000
35000
NPA PLENUM FANS
The new NPA wheel is therefore capable of
delivering higher air volumes than the
corresponding size NPL fan, whilst maintaining
very high efficiency levels.
levels In turn,
turn significant
improvements are obtained in acoustic
performance through the utilisation of Airfoil
performance,
blades.
NPA is therefore a perfect choice for
acoustically sensitive projects.
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NPA PLENUM FANS
Focusing
F
i on this
thi aspect,
t let’s
l t’ now consider
id a
typical Air Handling Unit manufacturer’s
requirement:
i
t
- Delivered
D li
d air
i volume:
l
20 000 m3/h
20,000
3/h
- Static pressure : 1400 Pa
- Air temperature: 20 °C
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NPA PLENUM FAN
2 000
Requested performance:
V = 20000 m3/h
P = 1400 Pa st.
Static Pressure [Pa]
1 500
1 000
500
NPA 710 @1437 rpm
NPL 710 @ 1494 rpm
0
0
5000
10000
15000
20000
25000
Delivered Air Volume [m3/h]
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30000
35000
40000
NPA PLENUM FAN
Requested Performance:
V = 20.000 m3/h
P = 1400 Pa st.
100
90
80
Static efficiency
y%
70
60
50
40
NPA 710 @ 1437 rpm
30
NPL 710 @ 1494 rpm
20
10
0
0
5000
10000
15000
20000
Delivered Air Volume [m3/h]
AL
25000
30000
35000
NPA PLENUM FAN
Required performance:
V = 20.000 m3/h
P = 1400 Pa st.
102
Sound P
Power level at Ou
utlet [ dB(A)]
100
98
96
94
92
NPA 710 @ 1437 rpm
90
NPL 710 @ 1494 rpm
88
0
5000
10000
15000
20000
25000
Delivered Air Volume [cmh]
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30000
35000
40000
NPA PLENUM FAN
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NPA PLENUM FAN
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NPA PLENUM FANS
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NPA PLENUM FANS
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NPA PLENUM FANS
Fan Efficiency (continued)
Between a small (250 mm) and a larger (1400 mm)
diameter impeller, the results show differences of up to 6 8 points in maximum efficiency.
The same impeller, when running at maximum allowable
p
and when running
g at 33% of max speed,
p , can show
speed
differences of up to 4 points on the measured efficiency.
These two effects combined, can result in over 10 points
difference.
AL
NPA PLENUM FANS
Fan Efficiency (continued)
Other manufacturers
Oth
f t
ttend
d tto d
declare
l
th
the same llevell off
efficiency on their complete fan range and choose to say
nothing about the relationship between size, efficiency
and speed.
AL
NPA PLENUM FANS
DIN 24 166 standard
d d has
h the
h following
f ll i maximum
i
d i i
deviations,
f
for
each “class of tolerance”:
Parameter
Limit of deviation for:
Class 1
Class 2
Volume flow rate, V
+/- 2,5 %
+/- 5 %
Pressure increase, 'p
+/- 2,5 %
+/- 5 %
Power, P
+3%
+8%
Efficiency , K
-2%
-5%
Sound Power Level , Lw (A-weighted)
+ 3 dB
+ 4 dB
All published COMEFRI performance data are in line with Class 1
tolerance.
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NPA PLENUM FANS
Noise
Another important aspect is the published fan noise data.
The majority of fan noise is generated by the wheel and its main
contributory factor is the ‘blade tone’, or ‘tonal noise’, at a well
defined
spectrum position
(the
so-called “blade
passing
fi
ii
(
“
i frequency”).
f
”)
Blade passing frequency = (z x n)/60
Where:
z = number of blades
n = wheel revolutions,
revolutions per minute
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NPA PLENUM FANS
Noise (continued)
(
)
Therefore,
Th
f
it is
i absolutely
b l t l vital
it l that
th t tonal
t
l noise
i be
b
considered to enable an accurate calculation of
th ambient
the
bi t noise
i level
l l !!
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NPA PLENUM FANS
Noise (continued)
(
)
This graph represents the difference between octave
band
ba
d spectrums,
spect u s, w
with
t aand
dw
without
t out Tonal
o a No
Noise,
se,
calculated for a blade tone of 250 Hz:
105
100
95
88
84
85
95
90
93
93
88
90
85
90
84
85
81
85
77
81
75
77
125
250
500
{Hz]
1000
2000
4000
8000
AL
98
Total
Noise
value [dB]
4 dB of
difference on the
total value,
th twice
t i
more than
the level !!!
80
75
70
70
63
102
100
93
90
80
105
Octave band Values
[dB]
100
Without Tonal Noise
With Tonal Noise
NPA PLENUM FANS
Noise (continued)
Some manufacturers, however, publish their sound data
without the tonal noise included.
This approach is misleading, so that other manufacturers
often prefer to clarify their published data by stating;
... “without removing the blade frequency”, or
“the octave band spectrum includes blade frequency”!!!
COMEFRI consistently publishes the full noise
levels, blade frequency included.
AL
NPA PLENUM FANS
Choose the winner !!!
AL