A ventilation duct must convey 2 000 m of air per hour. The cross section of the duct is rectangular, 1 000 mm x 500. Determine the average air velocity as well as the mass flos rate if the air density is 1,2 kg/m3

0.6672 kg/s

Explanation:

Q = Volume of air = 2000 m³/h = 2000/3600 = 0.556 m³/s

Length of duct = 1000 mm = 1 m

Breadth of duct = 500 mm = 0.5 m

ρ = Density of air = 1.2 kg/m³

A = Cross-sectional area = 1*0.5 = 0.5 m²

V = Average air velocity

a) Q = AV

⇒V = Q/A

⇒V = 0.556/0.5 = 1.112 m/s

b) Mass flow rate = ρ*A*V

⇒Mass flow rate = 1.2*0.5*1.112

∴ Mass flow rate is 0.6672 kg/s