Question

A smoking lounge is to accommodate 19 heavy smokers. The minimum fresh air requirement for smoking lounges is specified to be 30 L/s per person (ASHRAE, Standard 62, 1989). Determine the minimum required flow rate of fresh air that needs to be supplied to the lounge and the diameter of the duct if the air velocity is not to exceed 8 m/s. (Round the final answers to two and three decimal places, respectively.) The minimum required flow rate of fresh air that needs to be supplied to the lounge is m3/s. The diameter of the duct if the air velocity is not to exceed 8 m/s is m.

Answer 1

Answer 1: minimum required flow rate of fresh air is 0.57 m^3/ses

Explanation: since the minimum requirement per person is 30 L/sec

Converting to m^3 it becomes

30/1000 = 0.03 m^3/sec

For 19 heavy smoker we will require

19 * 0.03 = 0.57m^3/sec

Answer 2: diameter of the duct will be 0.3m

Explanation: since flow rate is

Q =0.57m^3/sec

Also

Q = AV (continuity equation)

Where A is the duct area and V is the velocity of air flow in m/sec

0.57m^3/sec = A * 8m/sec

A = 0.57/8 = 0.071m^2

Area of the duct is that of a circle

A = 3.142 *(d^2 ÷4)

d^2 = (0.017 * 4)/3.142 = 0.09

d is square root of 0.09

d = 0.3m