Greenheck Fan QEM, QEP Performance Comparison Vs -Blade Wheels, Advantages of 12-Blade Wheels

Performance Comparison

9 vs. 12-Blade Wheels

Advantages of 12-Blade Wheels

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performance is adequate, recent industry trends have seen the emergence of 12-blade wheel designs where customers demand higher mechanical efficiency and lower sound levels.

Model QEM and QEP plenum fans feature a 12-blade aluminum airfoil construction wheel. As demonstrated in Figure 1, this 12-blade design meets customer needs by providing higher efficiency, lower sound levels as well as lower energy consumption.

Greenheck’s 12-blade wheel design features extruded aluminum blades up to and including size 49, while the largest sizes utilize laser cut, die-

formed aluminum blades. The two performance examples below demonstrate the superior performance of the 12-blade design.

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8IFFM	RPM	#SBLF	Motor	Static	LwA
Type		HP	HP Size	Eff.
#MBEF	2607	7.76	10		96
#MBEF	2400	6.37			90

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8IFFM	RPM	#SBLF	Motor	Static	LwA
Type		HP	HP Size	Eff.
#MBEF	1469	26.9	30		96
#MBEF	1416	23.9			92

Air Performance

Figure 1 plots the fan performance and efficiency of two fans running at the same rpm. Increased wheel efficiency allows the 12-bladed fan to produce more airflow while using less energy.

Sound Performance

Figures 2 and 3 show the inlet and outlet sound spectrums for the size 33 unit used in the above performance comparison.

Lower Sound Power (LwA)

The overall A-weighted sound power levels for identical performance requirements show that the 12-bladed wheel design is quieter.

Easy to Attenuate

High sound power levels in the first and second octave bands are difficult to attenuate. The 12-bladed wheel generates less low frequency sound power.

Improved Sound Quality

A sound spectrum with a dominant tone can be annoying to a listener. Greenheck’s 12-bladed wheel provides balanced sound power levels across the octave bands. This results in sound that is pleasing to the listener.

Air Performance Comparison

Size 33 @ 1400 RPM

		9-Blade Wheel			RPM
		12-Blade Wheel			Efficiency
	8									80%
wg)	7									70%
	6									60%
(in.	5									50%
Pressure
	4									40%
Static	3									30%
	2								20%
	1									10%
	0									0%
	0	5	10	15	20	25	30	35

Volume (cfm x 1000)

Figure 1

Inlet Sound Comparison - Size 33

9-Blade Wheel 12-Blade Wheel

(dB)	100
	90
Power
	80
Sound
	70
	1	2	3	4	5	6	7	8	LwA

Octave Band

Figure 2

Outlet Sound Comparison - Size 33

9-Blade Wheel 12-Blade Wheel

(dB)	100
	90
Power
	80
Sound
	70
	1	2	3	4	5	6	7	8	LwA

Octave Band

Figure 3

Static Efficiency

3