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3 years ago

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A hair dryer is basically a duct of constant diameter in which a few layers of electric resistors are placed. A small fan pulls

the air in and forces it through the resistors where it is heated. If the density of air is 1.18 kg/m3 at the inlet and 1.05 kg/m3 at the exit, determine the percent increase in the velocity of air as it flows through the hair dryer.

1 answer:

nikitadnepr [17]3 years ago

4 0

Answer:

the percent increase in the velocity of air as it flows through the dryer is 12%

Explanation:

given data

density of air ρ = 1.18 kg/m³

density of air ρ' = 1.05 kg/m³

solution

we know there is only one inlet and exit

so

ρ × A × v = ρ' × A × v' ........................1

put here value and we get

$\frac{v'}{v} = \frac{\rho }{\rho '}$

$\frac{v'}{v} = \frac{1.18}{1.05}$

$\frac{v'}{v}$ = 1.12

so the percent increase in the velocity of air as it flows through the dryer is 12%

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$F_{drag}= F_{thrust}$

We can now replace $F_{thrust} with F_{drag}$ in the above equation.

Therefore, $F_{thrust}$ = $\frac{1}{2}$ × CρAv²

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Substituting our data from above; we have:

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$F_{thrust}$ = 110,990N

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3 years ago