Question

The minimum fresh air requirement of a residential building is specified to be 0.35 air changes per hour (ASHRAE, Standard 62, 1989). That is, 35 percent of the entire air contained in a residence should be replaced by fresh outdoor air every hour. If the ventilation requirement of a 2.7-m-high, 200-m2 residence is to be met entirely by a fan, determine the flow capacity in L/min of the fan that needs to be installed. Also determine the minimum diameter of the duct if the average air velocity is not to exceed 5.5 m/s. The flow capacity is determined to be L/min. The minimum diameter of the duct is determined to be m.

Answer 1

Answer:

a) The flow capacity of the fan is 3150 L/min

d) the minimum diameter is 0.11 m

Explanation:

given data:

A = area of residence = 200 m²

h = height of building = 2.7 m

Percentage of air that must be replaced by fresh air is 35%

v = velocity of air in the duct = 5.5 m/s

a) The volume of the entire building is:

$Volume=2.7*200=540m^{3}$

The flow capacity of the fan is equal to:

$Flow=\frac{0.35*540}{60} =3.15m^{3} /min$

$Flow=3.15\frac{m^{3} }{min} *\frac{1000L}{1m^{3} } =3150L/min$

b) The volume flow rate of fresh air is equal to:

$Flow=\frac{\pi *d^{2} }{4} V\\d=\sqrt{\frac{4*Flow}{\pi V} } =\sqrt{\frac{4*3.15}{\pi *5.5*60} } =0.11m$