Question

A desktop computer is to be cooled by a fan whose flow rate is 0.30 m^3/min. Determine the mass flow rate of air through the fan at an elevation of 3400 m where the air density is 0.7 kg/m^3. Also, if the average velocity of air is not to exceed 95 m/min. Determine the minimum diameter of the fan.

Answer 1

Answer 1: mass flow rate = 0.21kg/min

Step-by-step explanation:

Mass flow rate = volumetric flow rate x density of air at that elevation

M = 0.3m3/min x 0. 7kg/m3 = 0.21kg/min

Answer 2: min diameter of fan = 0.063m

Explanation: the velocity V must not exceed 95m/min,

Using Q = AV

A is the surface area of the fan

Q = 0.3m3/min, from above

A = Q/V = 0.3/95 = 0.003157m2

But A = (¶d^2)/4

d^2 = 4A/¶ = 4 x 0.003157/3.142

d^2 = 0.004019

d = 0.063m