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8 Secondary Ventilation
You are asked to calculate:
(a) Pressure losses due to all resistances in the system,
(b) Power loss due to all these resistances,
(c) Velocity pressure at the fan outlet, and
(d) Fan power.
You may simplify by assuming that there are no airflow leaks along the length of
the system and that the fan and duct diameters are equivalent.
The following equations will be of use:
Shock loss resistance:
R sh =
X sh ρ
2 A 2
Friction resistance:
R f r =
K 1.2 L O
A 3
where
O: Perimeter of the duct cross section.
Solution
(a)
1st Since there are no leaks, the flow rate at the inlet of the duct is equal to the flow
rate at the outlet, i.e. the continuity equation can be applied. That is:
A 1 v 1 = A 2 v 2
8 Secondary Ventilation
You are asked to calculate:
(a) Pressure losses due to all resistances in the system,
(b) Power loss due to all these resistances,
(c) Velocity pressure at the fan outlet, and
(d) Fan power.
You may simplify by assuming that there are no airflow leaks along the length of
the system and that the fan and duct diameters are equivalent.
The following equations will be of use:
Shock loss resistance:
R sh =
X sh ρ
2 A 2
Friction resistance:
R f r =
K 1.2 L O
A 3
where
O: Perimeter of the duct cross section.
Solution
(a)
1st Since there are no leaks, the flow rate at the inlet of the duct is equal to the flow
rate at the outlet, i.e. the continuity equation can be applied. That is:
A 1 v 1 = A 2 v 2