Trane TRG-TRC013-EN manual Determining Fan Airflow, Velocity Pressure Pv = Pt - P s

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Determining Fan Airflow

Velocity Pressure (Pv) = Pt – P s

Velocity (V) = Constant ⋅ √ Pρ v

Airflow = Velocity ⋅ Fan Outlet Area

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[t
q			/ q
	/ u	/4 [t	ρ/2
rp“r		/ q
2
px
P—
p
■	c—	/ F 84:; x”4 R8] j=848 –– R8] —
■	b	/ F 846 x”4 R8] j;64A –– R8] —
■	et“—rx	/ F _ – P = 2.45 – 2.0 = 0.45 in. H8O [11.4 mm H8O or 119
	Pa]

■Fan outlet area (A) = 1.28 ft8 [0.12 m8]

■Fan speed = 1,100 rpm (revolutions per minute)

■Air density (ρ) at standard air conditions = 0.0749 lb/ft9 [1.204 kg/m9]

Proceeding with the calculations,
	V = 1,096	P	0.45
		-----= 1,096	-----------------= 2,686 fpm (ft/min)
		ρ	0.0749
	Airflow = V ⋅ A = 2,686 ⋅ 1.28 = 3,438 cfm (ft9/min)
	V = 1.414	P	119
		-----= 1.414	--------------= 14.06 m/s
		ρ	1.204
	Airflow = V ⋅ A = 14.06 ⋅ 0.12 = 1.69 m9/s

It is determined that at this point, the fan, operating at 1,100 rpm, is delivering 3,438 cfm [1.69 m9/s] against 2 in. H8O [491 Pa] of static pressure.

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