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Q12PE
Expert-verifiedThe main uptake air duct of a forced air gas heater is 0.300 m in diameter. What is the average speed of air in the duct if it carries a volume equal to that of the house’s interior every 15 min? The inside volume of the house is equivalent to a rectangular solid 13.0 m wide by 20.0 m long by 2.75 m high.
The average air speed in duct is \({\bf{10}}{\bf{.33}}\;{\bf{m/s}}\).
Given Data:
The diameter of air duct is \(d = 0.3\;{\rm{m}}\)
The time to fill the room by gas is \(t = 15\;\min = 900\,{\rm{s}}\)
The size of house is \(V = 13\;{\rm{m}} \times 20\;{\rm{m}} \times 2.75\;{\rm{m}}\)
The average speed of air in duct is found by dividing the volume of house by time and area of air duct.
The area of the air duct is given as:
\(A = \frac{\pi }{4}{d^2}\)
Substitute all the values in the above equation.
\(\begin{aligned}A &= \frac{\pi }{4}{\left( {0.3\;{\rm{m}}} \right)^2}\\A &= 0.071\;{{\rm{m}}^2}\end{aligned}\)
The average air speed in duct is given as:
\(v = \frac{V}{{A \cdot t}}\)
Substitute all the values in the above equation.
\(\begin{aligned}v &= \frac{{\left( {13\;{\rm{m}} \times 20\;{\rm{m}} \times 2.75\;{\rm{m}}} \right)}}{{\left( {0.071\;{{\rm{m}}^2}} \right)\left( {900\;{\rm{s}}} \right)}}\\v &= 10.33\;{\rm{m}}/{\rm{s}}\end{aligned}\)
Therefore, the average air speed in duct is \(10.33\;{\rm{m}}/{\rm{s}}\).
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