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.

Answer 1

We know that

`A=200m^2\\h=2.7m\\\upsilon= 5.5m/s\\\%_(air) = 35%`

So, the volume of the entire building is

`V=2.7*200 = 540m^3`

The flow capacity of the fan

`\dot{V} = (0.35*540)/(60)`

`\dot{V} = 3.15m^3/min`

As
`1L=10^(-3)m^3,`

`\dot{V}=3150L/min`

For the other part we know

`\dot{V}=(\pi d^2)/(4)V`

The diameter is,

`d=\sqrt{\frac{4\dot{V}}{\pi V}}`

`d=\sqrt{(4*3.15)/(\pi* 5.5* 60)}`

**Note 60 is for the minutes

`d= 0.1101m`