What is the flow rate of air in cfm in a rectangular duct with dimensions 1 ft x
ID: 717767 • Letter: W
Question
What is the flow rate of air in cfm in a rectangular duct with dimensions 1 ft x 3 ft, with a flow velocity of 35 ft/sec? What is the mass flow rate of air in the above duct, at 1 atm pressure and 320°F? Air is flowing in a duct with diameter 1 m and velocity 15 m/sec, at 175°C and 1 atm. What is the mass flow rate of air in kg/hr? The concentration of NO in a stack is 38 g/m3. The stack gas exits at a velocity of 20 m/sec, and the stack has an inside diameter of 75 cm. What is the NO emission rate in kg/hr? The SO2 concentration in a stack is 600 ppm, the stack diameter is 10 ft, and the gas flow rate is 40 ft/sec. The gas temperature and pressure are 450°F and 1 atm. Determine the SO2 mass flow rate in lb/hr. In an industrial operation, a ventilation air stream (1000 cfm, 100°F) passes through a paint drying oven. Toluene (MW-92) evaporates into the air stream at a rate of 0.25 lb/min from a painted surface. Determine the concentration of toluene in the air stream lumetric Flow Rate Conversions . Air flows through a duct at a rate of 10 l/min at 1 atm and 25°C. If the air is heated to 200°C (still at 1 atmosphere pressure), what is the new flow rate?Explanation / Answer
Ans 1
Area of rectangular duct = 1 ft x 3 ft = 3 ft2
Velocity = 35 ft/s
Volumetric flow rate = area x velocity
= 3 ft2 x 35 ft/s x 60s/min
= 6300 ft3/min = 6300 cfm
Ans 2
Pressure P = 1 atm
Temperature T = 320°F
T(K) = (T(F) + 459.67) x (5/9)
= (320 + 459.67) x (5/9)
= 433.15 K
Density of air = pressure x Molecular weight / R x T
= 1 atm x 28.97 g/mol / 0.0821 L-atm/mol-K x 433.15 K
= 0.8146 g/L x 1kg/1000g x 1000L/m3
= 0.8146 kg/m3 x 2.205 lb/kg x (1m/3.2808ft)3
= 0.05087 lb/ft3
Mass flow rate = density x Volumetric flow rate
= 0.05087 lb/ft3 x 6300 ft3/min
= 320.46 lb/min
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